ML20136B625

Survey of Hydrogen Combustion Properties

ML20136B625
Person / Time
Site:	Three Mile Island
Issue date:	12/31/1959
From:	Belles F, Drell I LEWIS FLIGHT PROPULSION LABORATORY
To:
References
1383, NUDOCS 7909100036
Download: ML20136B625 (37)

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REPORT 1883 i i I

s SURVEY OF IIYDROCEN COMBUSTION i

PROPERTIES e

Ly IS 4 U.;U L. DilELL and l'ItANIC E. DELLES I

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l Lewis Flight l'ropulsion Laboratory t

Cleveland, Ohio

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i National Advisory Conunittee for Aeronautics fleadqua' rters, 151211 Street NW., Washington 25, D. C.

Createil by Act of Congress approved.Niarch 3,1013, for the supervision and direction of the scie of the problems of flight (U. S. Code, titto 50, ecc.151).

Its membership was increased from 12 to 15 by act O

approved.\\! arch 2,1000, and to 17 by act approved.Nfay 25,1048. The members are appointed by the President.

and servo as such without, compensation.

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.!1 JAuca II. DoouTTLz, Sc. D., Vice President. ShcIl Oil Company, CAairmas

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Leow Ano CanuncuAzt Ph. D, becretary, Smithsonian Institution, Vies CAoirman As.t.ux V. Amrix, Ph. D.. Director, Notional Ilureau of Standards.

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Pnxarux R. II Aanr.rr, D. Sc.

Ca4utta J. McCanrur, S. D., Chairman of the Board, Chance Vought Aircraf t, Inc.

i Drrozy W. Ilnons, Ph. D., President, Ilockeretter Ioatitute for hiedical Research.

D.,s Au> L. Purr, Lieutenant Cencral, United States Air Force, D. puty Chief of Stalt, Dcyclopment, Facuenscx C. CnAwrono, Sc. D., Chairman of the Board, Thompson Products, Inc.

JAusa T. Pys.z, A. D., Administrator of Civil Acronautica.

Wu,uaw V. DA Y 8, Ja., VICo Admiral, United States NQVy, Deputy Chief of Naval Operations (Air).

Weather Bureau.

Pact. D. FooTE, Ph. D., Asnintant Secretary of Defenne. Ite. Eo w A nn V. R CKEND ACKEn. Sr. D., Chalfman of the Doard, search and Engineering.

Eastem Air I.ines, Inc.

i Wst.pwoTow T. IIspse, Hear Admiral. United Staten Navy, Louis S. Rotneca:Lo, Ph. D., Under Secretary of Commerco f Assistant Cidet for Procurement, Dureau et Acronautica. /

Transportation.

Janous C. Ilunsasan, Sc.

D., Manachusetts Institute of Tuouan D. Wairs, Cencrat, United States Air Force, Chief of Technology.

Staff.

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IIcow L. Davosw, Pu. D., Director Jouw F. Vicronr, LL. D., Lecutin Secretary Janu W. Caows.ss, Ja., D. S., Anociate Director for lituarch Eowano 11. Cut Auenaux, hecutin oftar i

lismar J. E. nrio, D. Eng., Director, Langley Aeronautical Laboratory, Lang!cy Field, Va.

Suits J. DzFnancz, D. Eng., Director, Amca Aeronautical Laboratory, h!offett Field, Calit.

E'owano R. SuAar. Sc. D., Director, Lewis Tilght Propuk!on Laboratory, Clevela'od, Ohio i

Wattan C. W LuA us. D. B., Chief, Illgh. Speed Flight Station, Edwards, Calit.

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b REPORT 1383 SURVEY OF IIYDROGEN COMBUSTION PROPERTIES t I

Dy Is4 smaa: L. Due.Lt. and l'nm E. Di: Lou SU3lalARY nre of much scientific intercut. Of ihe conunon fuel-oxidant, The literature on the combustion propertin of hydrourn air syst em8, tho hydrogen-oxygen (or hydrogen-air) nyntem is

.isturen in eurtryed to provide a single aavrce of information probably the simplest, the onc nhout, which much of tho

<cful in reararch and dcrclopment work in whicA hydrogen i, chemistry is known, and thus the one about which there is irned. Data are presented on Jame temperature, burning the greatest, likelihood of learning more.

locity, quenching JAtance, fammahdity composition limita, The survey is not, meant to be historically complete or ex.

inimum apark ignition ent/Uy, flashback and blow o,ff hauntive, but, to cover the important. hasic materint. It, is mite, detonation properlica, esplosion limits, spontancoug ntninly concerned wit,h hydrogen-nir connbustion properties,.

nition, and t4s c4cmistry of hydrogen oeidation. The.vurrey bu t nomo da t n nreincluded for hydrogen-oxygen a nd hydrogen-

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not meant to be 46torically complete or c.cAnnatice but to oxygen-nitrogen systems. Thu combustion data prenented rce tAs basic material of importance for flight propulaion include observations on (1) linmo tempernt. orc, (2) hurning

,plications.

velocity, (:1) quenching distance, (4) finnunnhility limiin, 3

tac validity of reperimental metAuda is JAcuncd, and the (5) almrk ignition energy, (0) finmo sinbility, p) detonation to are aucued,whercrer pouib/r. Recommended ralucx for prolu s tics, and (8) explosion limit s, spontaneous ignition, and a combustion properties of hydrogen-air mistures arc prc.

the chemistry of hydrogen oxidntion. Values of the com-

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n ted. Some original material is also inclwled. /Mations hostion properties are given under stated conditions of tem.

Song rarious combustion properties of hydrogen are JA.

perature, presum, ami composition (and vessel sixo and ucd. Calcidated adiabatic flame temperatures are pec.

other specifications of the apparatui when significant). The uted for a pressure range from 0.01 to 100 almospheren and variation of each property with temperature, pressure, and initialtemperature range from 0* to 140Ga Kfor all pog.

emnposition is then diuuued if information is nynilabic.

de Aydrogen-air mixtures; and the cariation of upontancon,.

Experimental meth6ds and data are interpreted and evnhi.

i sition lag with temperature, pecuure, and composition based uted, and recomn cnded values arn given. llelutions among 14 4 reaction kinclics of hydrogen oeidation (4 treated various combustion properties of hydrogen are dincussed, oretically, Other original materini incitades calculated adiabatic llamo INTitODtlCTION temperatures over tho eptiro hydrogen-air composition rango The use of hydrogen as a possible fuel for aircraft and for prensures of 0.01 to 100 ainuwpheres and initial temper-4siles has been considered for a number of years (ref.1).

atures of O' to 1400* K, and a theoretical treatment, of tho dong the many problems associated with tho uso of this cifcets of temperature, pressure, and. composition on 6terial are those of oflicient, burning under a variety of spont.ancousjgnition lag based on the muction kinctics of iditions. In the rescarch and development, effort, that, hydrogen oxalation.

!! be necesanry beforo these problems can be fully solved, m mOLS would be useful to leave a singlo sourco of information on "

c, specific heat n't constant pressure many aspects of hydrogen combustion. Therefore, as c c.

p.oportionality constants i

o inrt, of tho fuminmental combustion work at the NACA c4(T) temperaturo-dopendent proportionality constant, wis laboratory, the liternt,uro was surveyed and the D

width of flamchohler sent, knowledge on hydrogen-air flames wus collected

.d dinmeter of burner tuho.

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d, quenching distanco A great dcol of literaturo exista because hydrogen has of ten E

nctivatim. energy, enl/molo n used as a fuelin combusbon research from the earliest F

Fanning it..: tion factor

, dica up t.o the present,. Ono reason for this has' been the g

boundary velocity gradient, (cm/sec)/cm

,dy availability of hydrogen in a fairly pure stato. Further-I spark ignition energy, millijoules

.re, its high burning velocity, wido flammnbility range, i

rato of initiation (ato of formation of OII

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6Q.. 70 80 90 Mycrogen en o.r, percent by volurne 14cmus 1.-Itclation between equivalence rauu and volume-percent hytirogen for hy! rnge i K,K, constania h,h,... rato constants for chemical renetions ignition Ing, see r length of rceirculation zone behind flameholder equivalence ratio, fuel.oxidnnt rutio divided b. L ~ stoichiometric fuel. oxidant c..tio (mixtur JM) molar concentration of all molecules other thnu compositionsin this paper are given as mole frco radients - ' .V, fuel concentration in unburned mixturo, mole-percent by volumo or ~as equivalence ratio cules/cm2 the relation between these units for hydrogen mnlc fraction of fuelin unburned mixturo air mixtures is shown in fig.1) renetion rate w prereure, atm

"y gas constan_t, enl/(mole)(*K) average reaction rato in flamo

? lc Reynolds number Subscripts: a condition a temperat uro, 'K 6 condition b } equilibrium adiabatic flume temperuure, 'K h blownli mum! mixture temperature. *lk. ignition Limo availablo behind slamebohler sec jb flashback l chnrncteristic igmtion time of mixture, nec g j,;,, b j avernge flow Vclocity nnu maximum i laminar burning velocity, em/.ee I T turbulent y, : empirical exponents I 300 300' K initial mixturo temrmrn' urn l

.? .g. st nytv or nvonoc.nx costutvrtox enoverren;s 3 n.A. TIE TDIPEnATUnl: i ohinined llame iemperatarc-of 229.L* K for ihe stnichiomet-One of the mo* important farlors that cluin:rlen/c aml oc m ure pentnt hydiogen) and 231S* K for iho olluence combnition behavior in any fuel-oxidant system is ".'"O*""d"*P""'""'"""*" M6 lu n ent hydrogenh ho Home temperature. Finme tempenit ure, ns n,cd here, d "'" "" I " "" ""' F I "' '" " '" " h " ' I"

• h""3 "'" "I h "" I' clers to llamen Imrning nl. consinnt pn5 sore with me ap.

' I" ". er to the Meher lan ner und was use+nini heennyo o erecinylo extennd bent louca or guin. Table I amt fianre 2 ice menanred ami eniculated f!nme tempenttureA for hydro-dus inherent amngng cRut of the line revernni techmquo en-nir n)ixtures reported sinco 1030; carlier dulu are not Calculated flamo tempenstures, accmmting for diencia- .maidered reliable. The datn are for a II""' ""' obtained with the uwnmpihms of an adiabatic 1.,' pres

• nre of 1 system inut of chemical equilibriuni umong nll species present,

'( tmo,.phero and an initial mixture tempernture of 25* C. in the Imnwd gas. The enicuhued valne,. are in error if The criterion of negligiblo heat loss mnken nny experi-these nemmptions are not justificil or if the thenoodynamic- .cninl monsuremcut very difficult. The vnlues of Passauer 'han used are inaccurnte. Good agiecment. hetween calcu-ef. 2, pp. 314 to 316 nmi 310) nro timaght to be low her,mso lated and mensured ihmic temperniurcs Inis been ohinined f .cy were ohinined with rather large thermocouples. For by a refined thermocouple meilmd (ref. 5) for very lenn mperatures.nhovo 2223* K, ho used a thermocouple mmlo i 1""l"me-nir fin mes. This tends to support the validity of the DAS-millimeter wirc. The hot, junction was pinced I calculated temperatures. limtever, varionoonrces of crror r illimeter abovo the cono tip of n flamo on n 4-millimeter exist in any method of measuring Hume temperature, and it limlrical burner, both with tuul without a split-llame tubo is m>t uhrnys clear just how coirections shonhl he upplied. mithcIls sepurntor) that enclosed the primary zone mot in reference 5 the errors were minimie.cd mni after the dated it from surroumling air. dntu were corrected as currfully as po-ibh, a measured Tho sodium D-line-reversal measurements of mrgnn umi tempemture of 1530* K was obtnined, compared with a me (ref. 3) were of an approximate nature; furthermore, enlculuted value of 1560* K. I?qunily good agreement ran- ,y were mndo at a position 4 millimeters above the tip of not he expected in every case, especially in richer mixtures inme on a 4.8 millimeter-nozzlo hunwr, which sulmittedly with houer fhimes. In short, it is not po%ible at presen t, ' y not be the locus of maximum temperature. The earlier to confirm the general validity of calculated flame empern- -revenial measurements of Jones, Lewis, and Sennma t ure by experiment. Therefore, the nttitudo of this report . 4) probably turnish tho'best experimental vnlues. They is that the eniculated tempernames arc valid, particularly for premixed huninar flames inrge enough so thnt. quenching ij j 4 g,,,g, j cdects nro not, significant. Premixed flames on smnll burn-l - calculoted c!% where there is appreciable heat,loh, diffusion flames, and (noer me enermocouse; j turbulent (htmes will normally fail to reach the full theoreti. l - - tioenmenrei one,mocouo:e; 1 1 d Wmum M@ l l - -- - CaoN n a asum 0 hne R um 2600 gen-a r danu' temlwrntures from tho I ,everso n 4 recent literature (refs. 3 and G to 10) vary con *iderably.

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In fact, tho difTerence between high and knv vaines for stoichi-M00 ~ - coicuicao in,s repon h ometric mixtures is 65* K (tahic 1), which is nhnost ns great ,/ N j j l ns tho range of experimeqtal temperatures. This spremt is [ 9,7 % l probably due to ditferences in thermodynande data and air l f,,h, D h h I l l l l .cmnposition assumed by various workers. The theoretical i g 4 l l values computed for this report, are 2387* K for the atnichi-j ometric mixture and 2403* K for the nuainunn temperaturo x 000_- !I 8 \\ Inix: ure.

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fl l th i l %{ b For hydrogen-oxygen flames under the nn.c initini con. l /lll l i 300 7 ih, tion, the thcoretical finme temperature for the stoichi-i ,O I 4L I I. ometric mixturo (GG.7 percent, hydrogen in og en) is uhout, l l[l/ / l khl is K (ref. G, p. 280, and rc.f.s. 3,11, and 12);ine maxiouun 30S0

• 00 practienlly tho same. Line-reversal measurements by l

if (e,, j j g-l Pothmann (quoted in ref.13) agree fairly avell wit h theoreti-k/ ! l' en't vulnes. These measurementa gave a maximum of 3123* 4oo K nt GG perecut, hydrogen; surpri3ingly, thi.s is higher than fl / / l l l l ) l the theoretical vaiuc. Lorie and Sherman (ref.13) reported i f (if l j j j l jg a lower temperat.ure,2033* K, by the same methml. Their

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reported muxinmm-temperaturo mixturo of <S perecu t, j l$ hydrogen in oxy;:en a widely lifierent from the calculated ,c n.,,3, l p l l l l result and from Pothmann's measurement,.

1. 0s is 25 a

4s a es n Hydf 0 gen en ett, percent by volume, Drect of mixture composition.-Figure 2 shows that tho ggg{ggg (jggg gpgppyggg7g ja obtidned With a sligbtly rieb

1 -Calculated and measured ftamo temperatures for hyttroeco, mixture.

istures. Pressure, I atmosphero; initi. I t<inscr: Mont of the curycs presented, inch.di. 0;..

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i++too"ent 4 ' !for W

s 6 f unt ou r m.1-NNI NN Al..usmonY Coath!PrTE FOn MHON AUTIG roximnicly :ll percem hpin. gen in air (c-1.nD. The ! Eject of pressure.~lL,ocin tion of the burneil gn i Je* etnip oII segularly on 1,.ith si h, of Ilm muunnon. f avored by reduced prenmes, so that, flame t em pei n t ure t emp..i nt m e hel..w 1:1n0* K me ohinineil n-the decreases n-prewure is decreased, llowever, the :sier of Ihe .ne onnhility limin. nre apien>ncheil. carcet depcials sirongly on the genernilevel of flame tempern-be t wo esperiment al eurves of l'ns aner, ol,i nined for open iures produced by n given niiu ure. Figurc 4 3. hows eniculated .cs ami for llames on a Smithells hm ner w ith t he primmy !!nme temperatures as a funelion of preuure for hydrogen- . enclo4cil, show an interesting effect: Tim pht-ilame nir inixt uses at initial temperatures of cosa, r,00*, and 1000* ner gave lower llame temperatures iloni the ordinary K. Nenr-stoichiometric mixtures show a > t rong dependence n burner'for rich mistores (abovo 32 percent hydrogenh of flame temperature on pres 3nre, while lenn and rich mix-m le behiwihat. concentration the reverne was foumi. Thus, tures hava litlie or no dependence..\\lixtures ihnt are quito two kins of linmea may not have comparable tempern-lean or rich have Anme temperatures ino low to enue much

• cxecpt, near 32 percent hydrogen. The differences dis 3ociation, thus, pressure has lis tic effect.

thought to be due to diffusion or induced mixing of Edse (ref.12, p. 30) presented a plot similar to figure 4 for r .ndary nir from the surrounding nimorphere inio the open a stoichiometric hyd rogen-osyeen mist ure. Tiu. calcula-te; thee.o cifectri wouhl teml to raisc temperatures for rich Lions covered presures from i to 100 atmospheres. .tures and to lowcr them for lean mixtures. .ccording to llyrno (ref.14), secondary oxygen does not 3 coo etrato to tho inner conc of a rich finme; however, it does j -$h @- [- .!4 F% , F l -b 9 .l r tho outer mantic, where it renets with excev fuel in Q.g' {.J.4_ n g'.n,o,y,n,.p ,__ g,.; F' . ma. a .nin rich llunsen flames (such as methanc-or propaq,e-nir 2soo p 4 y gj,;'a.44.j.19c1 P (M ;_J,12' M, Y+ bO h h [y"/o*"5 ; acn) nml rnisen tho temperature. IIen t, transfer then 1,., h es Iho temperature of ahe mixture burning in the inner -t--! ' w t h, T"i W[NM,ld'!.dUY.., ' j, i F-- e and incrensen the burning velocity, llou cver, llytne 2600 ,a no., 'l' rved littln effect of secondary oxygen on the size am! - -l Y,.d- '2s'g',E s i h I f f M pc (and conscriuently on the burning velocity) of a rich t ,yy L-1gMCg'5f 2400

rogen air flamo. IIo concimled that, in this case hydro.

r' - " -- - / -~# molecules aml'ntoms ditTuso nwny from the Anme futer 5 o oxygen travels inwant (wherens in most hydroenrl"'" 22co acs the reverno in t. rue); thus secondary burning occurs 4 @ gt[H 12?)' r ;)' F, ' i 11 , y .r, f 1'- L-" v. "r-f 20'co4. W..?,... r /[. a..[N.y.3 7. from tho inher cono niul can havo little cifect upon it. R 'h Y....,[./ V *y 3 C -- .% 73 , seeming discrepancy with the resulta of Passauer mav h. l +! x ~ - I I.'..~- Y..+,!) a.l. lu-"L L..,p,{]/ gF to the inct that, t.ho burning velocity of hydroecn is not as 4 . T-;..?p~; ; r'r. f. i, -. j'4.y l. g r- .;t-- M i i .cmlent, on temperature as is the burning veJocit y oi hydro-aons. In other wonts, the temperaturo did presumnble i 1800 $ $..._d.'l !;.-,'" ' L /. $ ' l-*9)-i /,-} 'do'7 ;-, I" I ' Q,# .l.M'.F. , but not enough to affect the burning velocity percepiihlE. 3 isoo)-/. O)C. h.j7.-te. isceguently, Lho conclusion of Pas >nuer (ref. 2) that rich E - ;, P-b %lf f.7 - a.. A r A g g.l,q lrogen f; amen.m tjto open air have lugher lhune tempeib c es than enclosed flames bernuso of nihnixing of nir may be -p,

• yi,

. ; vm ,4 g(,, 7 < ,y ; ~ - 64oo[rm h;f:q r -f,3 s y.i r rr

• I; I:, W' F 9 Y[Y,

a' .r-- '- i .'ffect of initial mixture temperature.-Theoretient mh- _g 91 L " FF TU T ' /' - N T~[1, ,b, [ II l' 4" ,.9[; re-1,,,. i n. Q ~* 7. 4 . tic erptilibrimn (Inmo temperatures were eniculated for 5 / / i i r, ,rM ious hydrogen-nir mixtures over n range of... l tempern-izoo n utia ,I/H I "~' $~._/ ' ' M H * ~! i! es from 0* to 1400* K. The resi. s nre shown in ligure 3. -F-7;-~ ~'l---l(o, L@r iy c,' FW re h mixtures nro shown by solid lines and lean-toetoichio- ,2 - qIn l.__ 80 % tric mixtures by dnsidd lines.. Except, for mistures near f,-, ry,..-,- L A, r.n, I. I ri ichiometric, the flamo tempernture increases abnost k. n- ."~ 4. C r W ! r. M T T N l-' i i.o l' Iv with initial tempernture. In very rich or !can mix- .d,pE j ]. 4-l -F -[.-H i h. soo en, where flamo temperatures nre low nnd there is little M,;,y ;.Q.j,H j ,ociation, finmo temperature increases degree for degree i 7J.. 4. ~.,...;.q....._ .g,. 4 " ^"*" -] ~" ,. s o,, v h m. ture tempernturc. As the composition approaches 6corff Q'@N-L 77"li i-N 9 ix 7,- f N ichiometric, however, dissociation becomes more impor-rm eh,.ii: n - t..-. Il - - - - u o c n. o m e t,. c - o .t and flamo temperaturo beconnes len64lep0!ntent oilllHlluI d@f di-M S g. d.j l. - , :n q.. 4 i.. r. sture tempernt,ure. j ', -.l-..H.-.._ l. H; 9 :Fp-1.i.,i $.N..7O.b.m._L lIq ', ! /nasnuer (ref. 2), using the ohler thermochenden! hua, re I T culitted a curVo for the stotchiometric mixture ihnt ni Zoo 4o0 600 uoo looo n200 soo ',i o .le Elmilar to the ono m. figuro 3. IIe obtamed approu-i n, no,,,,,,,,,,,,,,,,,,, 4,. x i l stely the same flamo temperaturo for an nitia temperaturo rsoun 3.-E.tteet of initial minuro temperaturo on calculated flamo 30()' h. ns that from the present calculation, but h.is curvo tumperature of hydrogen-uir mixturus. Preneure,1 i.unmgimre. 6 greater slope. --.w.m.w .e.

'4 /. 8tJnvEY Or itYDnOGEN COMutlbTION PEOPEllTIES s Sooo i,i;,,;;;; r ' ~7 7 ' Flr ]-

!- li n,

Rich m..tw,es I ! 1 "r n ) l_ -- --- L.e e.,.. u.c,...,,e - l. i L, -LL!- r~, P. l ~ ~i~Fl l! rm, -- ; e o 7 2eook -- 1. I i - 1 i h-1 14 .n i t~, 4i J L r-~'l' 'i,. sw ++ l 1 I ta,nos m.o,,e ieme,oe,. l /d : l w r si i p i l. e zoo.is7 ~-- ~~ "- F ' / - ~,-d,, >, l r r,. icoo. n ,,A !il i-M

I

!l! l i ~ asco_,. l r c ,' w r--,l l l l !',',l,@ i : l a ca,i,,oieace -- l l, l i ? O L. # 1Y ll, l P, ~ .,- d.* [,o M, c"Y lj ._ v' s i i= ' j @l.- .3 [7 [h.l """1,l' y, -,l-' ~*l ~ ,.3400 [ '.. I i j i i.i l' l ll 1 +" l { q Q. I l j - T... . g,,j..- " i _,' ; j d ' Til t5 ,g ) F,, -r' ' 1 j l j$ 230o l l ts! I i g ; q -. 7 - ~ ~.~.~ % j .~~ - i, l

i. I 6- ~r - Ah b

20oo " = ) l l

• 3 ff

.' l I .4 l l l -ve~~-*~]t~ ~~~ f Ia .__ R A I,l*ll.'I l l,'l l - =I III IIi 1!I I 8 000 r y ~-I ~N _ _,'. _._ _ r--- i i i I I i i l--! I l !lI lll ! lk 6 t 4 II i l i i i St i i i r T-M-- n, I fi i Il' l ll ll l I l } I l{ j I l*l l 400 i > ~ 6 i t 4 i i t ii 6i Ii iii l I I i I i i I P t i 1 l _-._ uj-.L _, _!_.L_L-w _L j l j l ll j g $A - L-F - , i pot I I ' ' i on t i l !lil!1! II I I I I ' I I I I Il I lI i. I i I 12 oi .,a i so soo oi .i i to too,oi Pressu,e, F, o r m , so ico Fmunr. 4.-Effect of pre. core on calcidaini ll.u..e semieratorn of hyringen.nir mhturn. nmended flame temperatures.-In siew of the esper-1. difficultien in' measuring flame temperatures, n3 l<igure 0 ab.o dhistrates'how disociation depends on u cil ,mited rango of conditions over which measurements (htmo tempecature; the molo fraction.i of the main dissocin-en male,it is reconunended that, the calcolated values tion products, II,0, amt O!!, ps ak not far from the c<tuivn-eport, he used. These data are summarized in 6;ure,!cace ratio for inaximum finme temperature. The c<piivn-lence ratios for these foue maximums do not coincide, how-e flamo Lcmperature is plotted against hydrogen cation over the complete rmige of compo,ition. ever, because tho dissociaticm equilibria depcml on coneon-to nimospheric pressure curves for initial temin in-tration as well as on temperature. 0', 208.1 G', 600*,1000*, and 1400 K. In midition, 'or 0.01 and 100 nlmospheres were emnputed for IwnNING VE1.0 CITY mperatures of 20S.10*, 000*, and 1000* K. The i.e. nuuma m.ocrn oun for extremely incl rich mixtures and for high mperatures arc included for.usc in the consideration

• i;he huuinar burning velocity.is detined an d,e vcbecity at engina cycles and of flight conditions where inlet w hich unburned gas of given composition,, prennte, amt

ures are high.

temperature ihms into a llamo in a direction normni he tho hme surface. .1-gss composition.- The calculations of e<pdlibrima The normal direction is specified in order to flame temperaturen for this report ni3o prcevided mabe tmtning veke,'ty indepcmlent, of the, qcton! -hape of t he 11'nmn. The aim in measuring huninar burning ulueity the composition of the burned gas. The data nie is always to obtain a phpical constant for the mixture iloit table !!. Mole frnellons at, various pressurce, is frra of any cliects of econu try, external hent sonrec, or operatures, and mixturn compositions are given for sinka, and nntore of the flow. The burning velocity alundd eing atoms and molecules: 11, 0, N, Olf, NO, N:, al ll:0. Figure o is a plot of these data as a fune-he distinguished fcom the spatial anno speed, widch is simply

uivalence ratio for a pressure of I utmonphere and the grma npeed of a hme traveling through a mixture.

temperature of 208.1G' K. This figuro i4 presented Tablo III gives burning velocities for tho hydro;-n. air o ahmv the typical orders of magnitude of the stoichiometric mixture nud the mixture of maximum burning i velocity at atmospheric pressuro and room temperature. of various countituents in the burned gas. The tions rango from about 10-* to values approaching liesults of 18 investigations covering the years betwcon th0 ~ and 1956 nro rep n tod (rnfa. 2, "I, h, in,.oa u; t., m ' ~ g r---m r w ew.+ ---m>--,,...-gir.-- m--e.i-- "mai-.e-e.e., ir

m _ m ..m _m_. m .as-- . ~..,,,,.,,,,, i e 4 e.

• g, 1

MOMT j *141-~.N,\\T] 0,\\*,1 f,,g 9 y jgg (, g g..g. swo. J,..I. 4 q. .g........ .,, 9 { [ I .. ;-.. j.. p-.--...--. -.___...,J I e ' { . i i - . j........ ,..].. M '", m. i ? 4 I s 2000 g. l l Vi L i i sA v, n 1 I g .i ( f:l.. l :... - u y T---~~em ~p.- 5 i a.9.. ,t i i ...( . y;,, 6.I ~ h... ~, l'~ 6... N ,Qi. t 4 . l *,

l. d l 1

og ; "j " t-l h{ b ' a I- .. ;...;......g. l .t - in je 2600... i; - - -+... _ N. v,, i 1 ,... up... j "k k.. m i-r - i ...q...;1; ...... f,,. .n............. a. i .c g.., I, s - l"g- " } E....J :....j... .A t .1P i ino, r k g'%l\\"k O -g l "' --"\\ _' _j,, a d I 1.! T T # ta ip.' p : e. o .a c. 3{ -;_ _g ; -..- [ - '.Q .i., ..i i 1 g. _g. . ~.... 3 I. t.. t p I 8 .I e.... {.. s .)i G1\\ (" ~ TY y - - [ j .d.. 2200 ;], [

f. R % dib.

T }Ti k gY . *.~j ? l l L J.s l. / / ] \\] % \\ I-- l t ,.l.m M 5-ai -....d; \\.. ..g --l f. .l..... )...[,[ \\g. i... l. [. .y.- 1 p 9-k. l .j .[ g. [- ya .. a ...,!). t,

,(,;

,,,.g n.a e I, i ~'} .j -7 7p +~~T ' " ' - ~ - -

p

. I,, [,+ - -l, V. q' I i f -tN 's. mietect [

• y-I s-'.

1.- IL i [.I.;i.. [ lk l , j,,/l " 'y] u ' l o. s ] F~ I tDCI 0 l u t t, P g

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g 4,og y =r 4 T Op6/~ ~ ',,g,.f p;@- a r-j p. q. I'

..... [g,,

-p - ,,,}~ ' ~~r# %.t "..y - -- l ; y a.-..a. 1-i. :-, 4 --- p ;---- r[- - y g = s a co,..,_ p.3 I.. ,....( ,,,, ;.,,, ;; g l -.I 1600 y . J.'.....L. I !. L. j..,. l9'. 'i 'N. i ch i ~ ' ". .r. r.r.- I" + .6 ' - ' -~~ y r ] - 1 l .-?- 7 q ..t l ...j 3 ~p l .,g q 71 h; ?"*** r i.' f l,- l I -- f.,.., M y_"a.L.l.,. u : - "'"* 9 ..t.. .g' - ("n p""*- O l.. Tin . ~/:-~. y J3 Fi '7 44 [ 1r( 8 f.,4 - ' F.

• ~M - -

h -.,.. - 'l A. [ Cr/ T I) T] ~. j I-b iOOO F \\ ~"i

• h.~*--""I

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i. ) H

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.h.

g spa ~; m.p 7 .e.. , I j, j. p. Io . g p';' ' ..,3 'p 4 ~ -

7. :......

. j.,, o i .r. 2 L :. , g "-,H. - " y +, -.;. ,.c p....,;,. r-h h.. . r. .t , j., l.i {, p ;. j..~ 4 4 j g pp .,.*..m-" .,3 ,.,.I, g. 9 . h. i 3 _ I;'f; u jp. g y - --j t"-~ no ; A...'l- .F.

• ep J,

.:+r=..p i.. 4 -{- }: 7g'- -* r - 6. O..' .'. 1 l ' ." i e,..ny. J n..rr t,r, 'w > !,:-- S N a ;.. n 00;l qg n . r-m ' - P Ed 4 '. '.. ' i. y. .. :q .~. .i

.. i

...p... i. h-'p . q ...t.~. 4 n { i .-.a.. Y ", {h .g.... p - .,,.,,4;,, .: ;... i , [. , T" r".4 b a--- d. .p..' e ' ' f# 4 ' p" ' 'q.;. I..-.,,' : ,.p l-3,j 4.- i "l~"** l' "" " ", i! ' ' h' -.'--i( g' ' "T~ ~t4 T~I "' r }." d j 000 L I y b., i-a m p.- .)

a...

~,.r .a.. j i t-

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t,, b', - - - - 'i g y 9 -.,. l., ,6 4-. 'l'8-

a. I y ; 3. 6.r...,,,?

v.. a; i : i r-l,j..------.H L.. L a,; ;. g L 4...... a,rLl l. l,_ +. 3 p....---~.,... l,j, g--. - v ---- 'i .I .. }. :,. F[] *q-g: .'m . d... i J,- ,.. = . a

.:Lu..

-r q-. . i;.,..)\\.' e 9 k >b ..d : .g.- .J l

T"~~ f* r-l 2

i,r s Trr r,- 7 m t j9; 7 p,,4 p{ p.q..:.H.

k. p - -

q, NI._R'. ! ' 'p ga___ .2 .j a ,a _.1. _.,. t,.. A.. s.r- --._j .m .. :._c -L ) i. i I . i.- .e. j. 'h 4002

d....#

t--.-.'---,'..L'.....i...... ". I_.I..h."... _ ! "4 C l'T"~ W tr, "'! N - t-~ .y .. U -Q. L l l q J gt ....L

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1;

; J.

1.m.~.l. t ~~1* j-a -c ~ ..g.,,I. p j. ..... n.. . t. 4 ' '.* - -f-M-~I,.b. ,--a g 1 4: 3

; p y-4 ps 1

an. .r '. :. 7",I" - ; },;. I ' ~ .4..-- e... -tp M _. J i1 - '->4 t Iiw ....,.3 -t - + H g-~ n.),.I :. c. :, _I at s - j U d' ~ ."_l. i auqi.a .:. t. c ~ 'Ni-~ M M C[ ~~ r'- -. '. Li. E bb f.hi a;. k -b i ' f i, - { l-- ( {-d.-M~.M.1 '.. )'.E 2 .!.,Y.i ..ja. d h "l d. -. l' f s.74"a, L..,m.a..". 1.. U'y ".9. "II ...i d ac ,p mm p# 1-1r .m % e. .,i. ...:.: t:. !.. y. 3,,;. q,. 7 y get i n.g]7,4 r a% .2 7. 3 g..{. O 80 20 Jo N W 00 70 80 ^" ' ho ' " ion Hydrogen.n c,,t, aercetit by volume o' ' {1 .i. u. i.. i ..q_ Ecuum ni;.,a t,o, p Inn 5.~Summsry of ctrects of luidst tcrnperaturs, pra.wre mi m.i..nir, ., on calcuinkd ttame tempera 6ures of hydrogerunir smuures. ee r-- t --,-y --r 6. v v.r

a r . s s btJnVEY OF HYD!!OnLN CO.\\ tdt.".3 TION PROPERTIES 7 lCo - ,~ . m_ '.h t... -_.',. ~ i i i ii t -t r-l I I l 1 I ) I 50 -, 1 i g ' ' *" go- ~ ~ ~ ~ ~' ) g [ j j u u [* l I l 1 I l l l l i'/ l -. - 1 } I

i.,

I l l l l \\\\- 2 a ./. = i i t 3 - - -} i i{ - l_ _.. -. 4 - i i i j l -i i i i. l l I l / / l\\\\ ' i i I l l 1 I/ t/ // A I \\1 i 1N I I i i l / 7. /_/ O L i_ ! N i / '/ / J I IN I i i

/

/ i// I i i i I \\, t i i i .i.001

/

/._L_ l I c i + L! \\ / / i i 1 N \\ J-l -_/l I i I i i N _,i X \\ i , con; i i % g\\e ! I \\ l i / f .p od c]/ 2 /s p. 1 I. . */ W l 4 \\, l i j

*'c-

. coco, t l i i i o io 2D 3 TJ ~~ ~ ~, 3,0 ' 60/ 70 ~BO i f l l 1 Hy droge.r) irn Gir, percent by VOI 4fPe 90 iOo E ! t t i t i ! t ie ,i! O 1 8 I-f i. 2 3 4 6 8 iO 20 40 i 1._,L U { s Esc.cnce roho, e n; G.-Theoretical adiabatic flaeno compordtion for hyibugen air nuxtures. Prewrc,1 atinosphere; puu.a udu ur.;.eruper;nure, 205.1u' h". o O!Nh cc0 s b ltr ll N l he U ok % %I. a n$i N INln%*sllrnce N I a ChhfrNkIjIC " ii%e kII k &nt O 10 ltlk-g 0 Chatclier in ISSI tref. 28), have been omiued. hunted gu (ref. 20. Thr hen mellnni oi monsoring the l e values in inble III have a large sprnni for a quannt v wen of tho surface is not o clentiv delinco. s delined so na to be a physical constant. The hnrnmg itics ran;;c from 153 to 232 centimeters per eemni for in the bomb method used by Manion amt Millihen (re f.'

OicidOmetric ndxltire and frOin 200 tt> 32n refunneters

26) tho rndins of a spheriently expanding thune was recorded ceond for the n.ixture of maximum horning velocity.

as a imirlion of limo hy schlieren photography 4 ntidta-i nennsty, the prm,nre in thn homb was .crmore, the reported hydrogen concentrations for t he recon h.d. From num horning velocire vary Trmn 40 in M peicent vnnons well-founded thernudlynamic assum pt hnm !.orning ut i velocines nmy be calculated from both types of a..ta, and ., not all the work was donc under strictic comp.in.n'c dona, cince t he ambient pressure and temperature nini the ugreenu nt provides an interoni cocck of the. . viion 4 in t he bomb method there are no hc..i h.-es egree of saturnhon with water vapor diffried. I b,w - ~m ,ocenc the effects of these vnrinides are thought near t he base of a burner thune, and thune curv;.t. to be (cw cifects tant than the cifccis of the experimental n.cthod. ar'c unnunized by mnking me.e nrement s on flaan -

radin, of!aigo experimeninl mensurement of burning velocity on a n or nozzlo burner in essenco requires recc,rding an It is believed that, ihn data of re icm es a. in. Ja,.':,26, 1 image of some surface in the llame zone atol then

27. and 30 reprc-ent. the best vahic, of hunun;< s c.ordy for hydrogen.uir mixturca. Thes.

dag the aren of th( imrface or its inclinntion to the ccent. data. nod they un .\\ll the workers cited in tablo 111 used soloe funn of obtain..a by.sao fai on y e s peronco nd n un. pes. were nern! method, cAcept Manton and Ahl!iken (rel NJ. it. in not pu.hv at prescot to oo... n l. .n.,c a ...t io n as tho be.. Tieu efore, :1.. re i...n.er..! d oon.a .'(1 ' pherical COnstan volutna hornh. Both atep s is i !' ; d 'i: ' 'd! tt u re: .? a s i.c i e, a rm r !Octho.l nr,' *,.,cc* Le errOT. r,. , '." ' ' h i.t ouou liri d I W. %c 'a !. c i rvation A .,t

6 i

P fi a C. .i-

St?RvEY Ol H Ylih0 GEN COMIsUSTION PROPERTIES = 7 r'.::t. ( l i } IN2 l i ij._ i _ i 9 _q 1 i i .,/.. m._. i y .l i l 1 i x_7 I. _1_ I i [ f i .'I I i I i \\ I i i .) ,i 1 !M E i I J_. ) t I 3 3 j _ _..i I ~ g, ~ j 1 / ~ ~l\\ 1 i l iN a l I/ // /l i \\N I iN 1 j / / // I l \\ I t I i i _/l ' / / l\\ \\ L 1 l t }ooi / i i 1 !V \\ l .-l/'/ _/ i i ~ _I \\ i ~ l\\ \\1 ll /'~ l i K l \\ l X t i / I / I L T d! '\\ \\ i N0f

• O of_2fH l0 2

0 0 H .000019 g g ( :. --- Hycro yn.n as, percent by voh,me jg 3

gg l

I f f I i ! t i I t I ! l ! ! O 5 Q L; i l-I J l l I I }.d lj 6 ( l 8 2 3 '4'

• 6 3

10 20 40 Ccmon'nce rano, <p

Unx 0.-Theoretical actinlaatic tlamo compo4Gon for hyilrncer.tir naturem INc4'mre, t.htmo sphere

initial misture temperatu.% OUS.th* h' spatial llamo 8peeds, Slurling with the work of.\\luddrd 1 Ia Chatclier in 1881 (ref. 2S), have been muit ted.

' a llame surface with a temperature close lo t hat, of the tm-Imrned gas (ref. 20)..The host method of nmasoring the The values in table Ill have a large spreml for a quanthy aren of the surface is not so clearly ilefined. .t in defined so as to be a physical constant. The hutning ocitics rnnge from 153 to 232. centimeters per second for in iho bomb method uscq by.\\houun nini.\\liniken (cer; i stoichiometric mixture and from 200 to 320 centimeters

26) the rmlins of n spherically espanding thune was recorded second for the mixture of maximum hurning velocity.

as a fupction of timo by schlieren photography. Sim nh a-

thermore, the reported hydrogen concentrations for the nemudy,tlm prmure in the bomb m reennled. From simum horning velocity vmy frma 40 to 46 percent.

various wcu-founded thernmilvaamic assumptions harning vehicities may be calculated from both types of ihtta, aml 01 .rse, not all the work was donc under strictly comparable ditions, since the ambient pressure and temperature and { ihe ngreement, provides an internal check degree of naturation with water vapor ditiered. in the bomb method there"are no hent losses u.ch as oc Ihm-r, the cfrects of these varinbles nre thunght to be lew near the base of a burner thune, and finmn curvature cirects .ortant than the cliccts of the experimental method. are minimir.ed by making measureme'nf4 on thunes of largo

radius,

.n experimental mensurement, of burning velocity on a . son or non.lo burner in essenco requires recording an It is believed that, the data of references i 3,16,.% 21,26, cal image of somn surfaro in tho flame f.one and then 2', and 30 represent, the best values of horning vehicit'y foc wring the arca of the surface or its inclination to the hydrogen-air mixtures. These are cecent data, and they obinined by satisfactory es perimen tal t echni. pics. All the workers cited in tablo !!! used some form of were generni method, execpt.\\lanton and.\\liuiken (ref. 26), it is not possiblo at present. to choo e any singlo investig a mn ut,tho best. Therefore, tho reconanended burning velocaics used a spherical constant-volume bomb. Both ateps fur hydrogen. air mixtures at I atmosphero and about 300* K ao burner method are subject to error. At present, it initial temperatures are averages of tho values from theso ) ilieved that schlieren observation is best, ainec it gives. soven nources. i' The rocomm. nded maximum hurnim: ve'oc. 4 s.ms--r,o-.--a

s.

• 'e e.

hEPORT 13x1-Na'r10 Nan Anvi3onY co.\\DttrTEE FOR At?h0NAUTICS 36 g g-~r --{- t i - l 2000 T-'s

---

~t

' ~r - g j 4 i W r ence i e ,.i. Ecuivoier<e ref.o, y Reference l l .. q.._ _.. o io a o o g, 4, i g l j o 26 o to,3.75 i 27 30 ~ ~ o e 320 y a o

o i g5 (Moumum owen.ng 1

.l y,,oca,eg ) o I j .I i.e9 (Mos.mun uning 2 ,p i i j i woca,eo i/ I I l 5000 -l-, l-l 280 i = L--- i -, ) ,0g L.j g_,. f ,*]g- - 1 / f\\ r j 1 l } l j 1/ j ---t - P-g g l l { y l f } 240 l } 600 ~-- 1 '= ,, l l l l f l t;* r

• /-- !

i g l j i ,; 4oo ![ .. /. 2% i I / l l Y i / l l' l c 9 / 2 .'m/// I I i60 j - + - - - - i / l I l i /l ^ ! l l 200 g l l l l i 12C l l j r._ l i 8h 3o --"-- 40' to 60 10 100"- i i i i i ^ 200 400 600 000 Nydrogen in oir, percent by volume '^'m rnMure temperoture, To,,,( unt. 7.-Effnci of hydrogen concentration ou Imrnuig velontna of Prenure,1 atmosphere; unnal tensperature, Fu.an; s.--lQrert ofinitial temperainre un'inerbng veloviues of liydro-retrogen. air rnixturcs. io* K. gen-air noxturen. Pre aure, I atmu phcru. EJcci of initial nfixture temperature, igurc $ is a lo is 310 centimeters per second at about 43 percent .rogen (p= 1.8). The stoichiometric burning velocitia urithmic plot of burning velocit y agains initial n mpe:mE". w a larger spremt than tho maximum inarning velonnes rm. several mixnires. The solid lines with syminds are ilata a the same sources and range from 103 to 232 centimetels from referenco 30. The da.shed line represents t he nnuinnon secoml, with an nyerngo of 215 centimeters per seemul-burning velocitics of Pas.sauer (ref. 2;, which are considered o burning velocity changes very rapidly with hydrogen less reliabic than the m'bre recent data. h appears from centrntion nenr stoichiometric, the wido range of values Ggnm 3 that the mixter'o of maxinnun hmning velocity is least sensitive to changes.in initial tetyperainre. The a ho expected. following erpiation expreses the relation between initial Ject of mixture composition.-Figure 7 :.hown t y pical , of burning velocity against hydrogen concentration tempenoure and maximum burning velocity over the rango a from four recent. investigations (refs.10, 2ri, 27, nin! of temperatures given: As aircruly stated, tho stia.simum occurs nene a u-enL hydrogen conecut rntion; the curves fall oli smoot hly U,,,,,,,go.0! ras Tl, u2 (1) either side. 'It shonhl ho noted that the ma sinnun The exponent on T. is considerably less lo hvdrogen nir dng velocity occuni in a mixture richer tium either the hiometric mixtnre or the mnximum.llame.innperature mixtures than for hydrocarbon-inr mixtures. For example, Discrepancies agnong results of various worhers exprewing some of the data of reirremi 32 m the form of ure. eituation (1) gives temperaturo dependencies of (G. .u of~ mo quito largo on a percentago hasis, especially for about Tl," and Tpu for n-heptune and i.sooetane, re pec- 'nres rich of the maximum burning-velocity mixture. Lisely. aes not seem possible to account for these differences at Eject of pressure.-.\\ lea <urements of burning s elocity ent. irning-velocity measurements cannot b-extended too at prennres other than anno phene are ihlhenit; ilus is opennity truo for reiluced pres

o the lean sido of stoichiometric. 13ca.uw of prefer-ditlientties aro reflected in large discrepancies in the thaa sun 3 Tin-nin rinn ntn!

.I diffusiion effects, tho tip of a burner' flamo may open a mixtures Jenner than 17 percent hydrwen bef. 31), i of the few workers who havo stnilicil hydrogen-nir n.ixt

n. 'erme.- 17 reports nearly constant burnin:: veloe;iv at a stream of mixturo may escapo tho &mo r.one wahout.

.ot.! prmi.vs from 1 to 4 atmo.,phera Mu

burned.

.+

V e hl'lLVld (H' H ilthe ml.N dlM ht'hTI(IN l'lWl'IULTJlu 0 '} t t 6 e.- + ' .. y I*.to' d.-, A t 4 +4.. --:"....~. +.4.4..... .,6 ,,g. .........i..y-

n. o.. a. "ff,t...

e. m,.

e.-

• + i l.

....6..~i.o g. ."q...."..,.......1

aa

-i.ri., t. 6-t. H. 4 s.9..,. 1 t- .. ;... 6,. - i.. l 'g e 6 ..t.,j.; .,. j, I. .o o ,lI ,i. ~. &9 4-.. !. p. e n.* . i_.t i _ +.,n n., t- -.i ..,i 4,.i. (i}. 4 4-.6, e .-4 ...,..i.....l..+..,... 6.,,.. g t. .....o .. i ...a..._ p, 1. 41 ..a,. e.. ,.a . n.,. o. .. e. .........r... ..I b..u i t .,i.. .o ... i,., .,o. !...,.,,i, d. . n,.,., I .. i 2 6..., o. -,....i i. gj.. gei. ..t,... , i ..i o-1 ni,.on,... t M i !?n C.. 3 r, ....r.- ... +...

r

......I..p .l0. H.i,.I ':.:

I H;.j b

@i,lV1.L i M

,;oi:

- l1 ,i. p.. j i .:.1: g i: 1.,,, m i m!:!,:: L i g 4 .-p.,, .,i. ' E l '. 8 I I 1l. . i..s.,...!l ...} t. ' i a i e i.8 4.

t. I,i

) 4.g ., i..,ee d i .., e t,i. ..e o 6 j .e. ~ -iid --i s . 9. I ). l .. Il j a. ..(.e. l..f. ll,l,) 4,.. 1 -4 ., i ,i.l,.6 w t ."-i-L... 16 l e i e ti i, .6 6,. 16,6..... . a.. 4. ..e. i..q i I~~* i. e n i i ,i ...i. i,. !h44 1 .r. i; i,i

o..i..,.

i ........ r. .q q.,.. . q....,. - 6 6. i,.,, pi.. ,i p p, u ..i i .,........ !.~ g.. ... 4 v..- ~,. s ,ni e. p. s e io:. t . }.4 6g, m .h g t I, 13 ,,a ,..i... g L ' ' '.. ll .i.. - g ..g ' i ' t -4 a, .,.,,q. lj lb iie -r "]'.', *ril i - ' '.,'lll} 'dl l p

• +,_ -. y,. t, 1,.

.i. + " + ".". l -..l. +. i , n, j j .i . p lll .i t,-. ". ' . t o. r.. L e c. i 4 i i i.. ..i. 9 6 .Ll. ji' {I}I yl$ .I Uj [ lkd ih 'il: $ 'Ull';:i$:$ 'I h MN! ' IIl' '. $,p.... '. [!. i.l l.. I i.l. H 'l '.$_ _.' 11 @ hf 7 [.7 l ll ,f!! d.I;$i i '6 !. I ! ', Y % .i !.Z. A l l' ij il l ~ ..,_o '. 'f4:: .y .lT,. 6 c p i 5 M.,d!,.~i,i 7 ilh.kI:. p, 'I dl @i.I'.' ll ? T.l.:d.!.:.- [T [ l lli' ! l ! !. I.i,! 1 l j l ;a .., ! U. ! + li s ,,1 o i ,r .i ..i.........,, - + a 4 i 1., i .4 +.. ..o.. ,.j. pp ..p. 9 .~ E.i + - - - - + , 1 & of,tp + ,4... 4 .... p. !.. .. H.. i... i ,a 4+.,i61..; = .,,. + + ,p.o g.. 9,, t-.-H i. ..,4

i..

....H.. q ,.3.,.,,., ! .,. 6. I. s. 4,. .o... i 7n tp. ! .-.-,.4,* ..3.. i 3,. 4., .,. l, p. i.. '..h.+ -L... i .. p. 4 + 7.,.. e., ,. 4 0- ,_.t.. ). H.l - j , q, -.bm ~ +. g gp.,..o ....q.. . L4 O ." h...' F.. 9..... ..,. q. p - L . i f..". [' .. g....... i. ' h i..- ' '...".t.. ". "....f.- ). i.., + 6 ,p .....o.,. .t -- ~ l , e, . p% .. b. . j.. sig .,o .,. q n,,... ,.p. ,, p..., r. 9., o n . m n..L... g +v i .,n n e... o.... 4 + . p,. p. 4. ?, ,_.+.1 ij -;.p. '... ,,o ip,,. .p ...y. i..... p. j g, ., -,...g .L i..... i o ni p............,. i. 4 ,.,p,a. ....._. - 4 1 6 4, j. 4 {,,,i.,.,., .p n .. i. . q...p 4-*+ I I, 3-+ d

l. 4

,1 i .i.. pu .(o. p .+., +6 6 il.,t,.r..e -+->- i . 7 p. i. j ~ o w a. jg i' 1,.'+++.+,.+r+ Ho +t.+. H++tt-H4~- ,4,+ ) 4,.e*+__H3 . t i l + ' "...m.,4.-. ' e. r. ', .4 H. : *,,46 e is i

o..,. r..o l.... i. !

wo a + 3 1 +r =

• t*t"+

l i j i,i 9 )M-- ft'. ,u p,' ! l.. ".,, o... 4 ".. '. -...r'.".' ,.t,tl i, ,,,ii i, .e,. j

,3

..,i 4-6 r- ".. 't..' ,~ dM.N, M,. -w;...+, +, -r p, nn. J o. o...r-+.. r. 4.i.iI. ......o y.. 6 . (..

e. -b T U

'4 ' d, Ul1M fj. U di! l1 .:i 'i C l ,.:i ' L., ! ;j.,, j,l l'L,$! !jL ',, J " ! Mi..f, pi g.. 'fl ' ! kC j.. h r sc o +- '4 + 4 -,+.,,m.,

• r r+

Q-M, 4 e e,o.o ~ . + 0 , D.

t. r

.l. .r, + b.4., o,.. ., a.-.,H L. p.g, p, ,r p4 n,.,,, r i.u ,n.,e+i... 4-.~.., p. .,e,.,.. . +. +,, - ., +, .t n in a t ~af. i,,, ,c... q .m.. r.M..,- m,.....a.., 4,l q.e. -m-,-++, t .w' -+t-+-+. .m. y.. .j . +.... . Wpp., u a i. . u. o., .n,.... . -,.., a g ... 7,. ,,'C 20 40 uO w 00 200 400 000 uCO iOOO 8%f vence outn.nq moco y, vy. crq / urt. Frounu D.-Variation of prismure dele.ilence J burning s elocay n uh re(crence burning veiocity (ref. 26). 93 nimosphero and 140 centimeters per secomi u t.. I j data for all 'iniuures definial a singin curve. The curve, aosphero for a mixture with e4.78. l(clerence.m l which is reproduced from ref. cence 2G in figure 0, slunes . orts that tho burning velocity of a mixturo with #3.58 that the pres 3nre dependence of burning velocity is variablo reused when the presure was raised from 0.25 to 1.0 and depemla on tho ' reference Inirning velocit y.

Tims, nosphere, und reference 27 gives data showing the saine slow.lnirning mixtures ((1,.<50 cmkec) have a negativo nd between # of 1.10 and 1.00.

prevure exponent, and tw'nce U,, incrches as pre suro The datn of reference 2G nre probably most nearly right, decren=es; wherens for fast-burning mixt ures (Il.> 100 f nuso the 6pherient.homb technique is not. 3ubject to mn.c cuikec) thn reverne is true. In tho intermediain ra n go the important, sources of error that atreet resuhs obinmed j ( *.n.cmkec < //,.<100 cm/gec) there is no elfcet ot' presure. Other methods..Tloreove'r,

• n previously unan3pect ed

Figure 7 shows Ihat, hoth zero aiul positivd prenin esponent3

.ct, was discovered that, may explain some of the d~ j may in. expected for hydrogen-air inixtures, de,.aling oit pancies in pressure dependenco reported in the liter..ture. j i he fuel concentration: negative exponents slan.n,.ypear for is generally ngreed that. burning velocity is proportional. rich or very lenn tuixtures only, in any case, tho ! n p,s ver the preuure raised to smnn power. The disagreemem, onent should he small. .ccru the value nnd sign of tho exponent. Entun i.nd l The work of reference 27 agrees <poditalivel3 wahthatof !!iken (ref. 2G) studied many fucl--exygen-inert-ge reference 26 but shows pressure dependence io he non h h.rger. <tures with atmospheric, burning velocitics fron} S to '0I" figure 10 shows burning VAaeities front reierences.N nnd .timeters per second and determined z for each mixturo j S plotted logarithmically am..n3t prewure for foor s ich m the empirical relation cip o vulence ratios. Tho data from referen, c S wero obiuined by a Bunsen burner toin!.nrea methoo. nod..ao U..o** CJ,e a. lukeli lo avoid qtlenching clfect.s frOin tuominall burni r t ff %=. m hes. Tho straight, hnes obtnined support the n-an.puon >n theso values of x were plotted auind the d.ciesence 20 that the data foHow a relation like cipodem 4e ni. dng velocity Ug,. (tho valuo at, atmunn'a s o. .J); however, the nlopo x caru.3 s ainiondy betwri n a .i.'

~ - ~. f i Q 8 i 10 ', ut cirr tasa-xxrto.wu,.snvmour comurrzu von aznoxu:ncs .ind 0.2,*iG for crptivalence ratio, froin 1.10 to 1.9n. the 400" ~~] ~~ ~ l T~ tverage value being 0.23 (ref. 27), whern s figure 'J would l j. iredict n idppn of leu than 0.1. l ,l The* coupo of Ihe di=crepancy hetu een rcfetcoces *$ nud n le not komen. Reference 27 tries to resolve ilu <tue-thm 3 cot _ ~ 4_ .. - {--- [._; M' xith the nhl of certuin theoretical reintions among cionhos- ",,,,, ? ', g tion propchics, but the result is inconclusive

• One reln-j j 200 - ~', - o~T',,,,

~ i lon Indor.] the snudl pressure dependence of reference 26, } g f rhilo the uther favors tho larger depcmlence of reference 27. +--. 4 { in any cront, recent, work agrces that hurning velocity of 3 Fiome Reference iydrogen-fir anmen increascn with increuing prenu re. ?cndmg ftJrt.hcr cyldence,11, as suggested that n pressure y( [gg"' _y

• y

.xponent, of 0.10 may be used to estimate the pressure etfect m i or mixturen near the maximma buring velocity without l ausing too great an error. The suggested value is the nyer-i l .go of Ihone reported in references 2G and 2 4. 3 I l I 'Oh ---- g---- r l-ha runnus.o r nun.wmc vu.ocarr io A flamo in turbulent flow differs considernbly in appear-I .nce from a laminar flame. Both views with the naked cyo I'munu 11.-Cornpari.on of turbulent anit taininar burning velocitics i' ,nd timo cxponed photographs show the luminous zone a n '((' d'"""k *i""""' "" func u n rin w nra naiuivaknennuo, . rush-liko region, thin near the burner port, thicker toward ho top of the flame, and of more or less indefinito extent.

27) is included for comparison. As is generally observed, t ho turbulent, burning velocitics are higher llum the laminar Eauivaience Reference I

tuuler the same conditmos of temperature, prequre, and reno,, cmnposition. The turbulent burning velocities appear to [9] depend on pressure alittic more han do the luminnr,and as y o uo i,, -j n resuh. the extrnpolated turbulent lino crosses the esperi- -3.58 26 l i l. un'nul laminar line, it in very difficuh. to understand why l thi+ Abouhl be true; one suspect r thnte turbulent burning k j ) velocities based on a mean linme surface may have littlo ,p meaning nt, low pressures. Much work needs to be dono on aoo the nature of turbuleitt finmes beforo turbulent burning j i[- velocity can havo real meaning. At present, it is only pos. I .ibic to make the follmving <puditativo statement: For tho 3 , ', [o l. most part, turbulent, flames con ume mixturo more rapidly z than kunim.r dames; that is, the maximum flow velocity at i which the mixture end ho compleicly burned is larger for turbulent, llames than for huninnr llames. loo2 .4 A .6 - .0 a.o Preuvre, P, cun {Tlahu.s arc (picuched by ex ' asive low of hent of HClivo . nun in.-Ettert of pn+nn na hundng vclueny of indnmen nir particles or bot h, Lo ndjacent. walls. Ihnerim..nis ha ve 3hown namra. thnt Ihunes in a mixture of given temperature, pressure, und composition entmot pass through openings sinuller ihun soluo 1 is not. yet. known whether the flame brush represents a minimum siec. This sixn is the spienching diunnce. Its dckened renetion zone or a laminor lhune 1 hat has been actual magnitudo depends on ihe geomet ry; f..- instance, tho rinkled, distorted, and caused to lluctuate by the turhu-minimum diameter for n cylinder is, greater than the mini-nee. As a result, there is no lhune surface on which mum separation distance of parallel phues. The geomet rical. trning velocity mensurements shouhl obvim. sty be based, relations mnong quenching disinnees for ducts of various al it. is necessnry to choose monm nrldtrary nm inen. shapes have been worked out t heoretically nini agree <ptico The only turbulent burning velocitics-tiu.;. h.. v c been w ell with esperiment, (refs. 3.1 and E). ensured for hydrogen air flames nro given in refeience a L Effect of mixturo composaion.-In figure 12 quenching menn linmc surface was chosen in images of visihic !!ames, distnners (minimum separniion of parn!!cl plates) from refer- .d ito aren was measured. All mensurements were mudo enco 37 (pp. 40S to 412) nro plotted ngninst fuel concentra-i n 1.02 ccmimeter-diameter burner at a Reynobl3 number tion. The data were ohiained in connection with measure-3500, over a range of pressures from 0.30 to 0.75 atmos-ments of ignition energy. Tho. curves show minimum ,ere, and at an equivalenco ratio of 1.80. The data nro quenching distances at or near stoichiometrie composition. own in figuro 11; the Inminnr burning velocity curve (ref, The minimum quenching di<tance ni t ,a. e-- w

- --_ - _ _. -.- -.-~ ..r 4 t SURVEY OP 11Ynnoci;x costalwrloN Pnorc1rrins 11 'L.l ~.!' L ' C ' 7 I~' J C_,i ! ure iluto for ibree equivalence rntio-from reference 3S. Four l .a' _-p . l. --- l H _j -._h - h J...q. l c<oino, from work by Lewis and vc n Elbo (ref. :i7) for an g._- _.l,-H p ~ pivuh nce ratio of 1.0 are al3o included. It,is believed that, ' ' " - - ~~ ---~j-"1 I, , j ; the data of referenco 33 nro more nearly correct becauso of l the methud used (described in ref.10). A, l Pr n s,n. p. ,The straight h.ues m figure la shmv that .4 aim ,I _o.2 l f i d, o: P-* (3) l j i .33 / ,1.he prenure exponent z vnnes wa. h hydrogen concentration, r .2 -a -. / l j The ihita of referenco 33 givo tho following pressure depend-4- cocies: For g = 0. ~),.r= 1.051; for v= 1.0, z= 1.1h3; amt for I p = 2.0, z = 1.007. h; Effect of ternperature.-No data nro availablo on tho [

• i

/ ( J-i tcmperaturo dependence of quenching ilistance for hyilrogen- , p / .08 j I nir mixtures. llowever, it, muy be neumed tinit, the quench- .06 ""~i. I ing ilist ance decreases as the temperature of,1he luixturo (and Wydrogen a oir, $r$ent t>yYobme of the sudace) is rnised; in other >vords, the lhunes will bo i able to pass through nunuller openings. This sinsement is i i Ecboiencero6o,, inned both on theory (ref. 40) tunt on the behavior observed

• i for propanc-nir thunes (ref. 41).

.c 12.-1&ct of hystroacn concentration on quenching di.<tanco of hydrogen-air mixtune (dain from ref. 37). Effect of nature of quenching surface -No appreciablo ell.ect, of the unture of the surface on (picuch.mg distance has temperaturo is 0.003 centimeter. From data given by ever In en (munL In an attempt to observe a chnngo for man (ref. S), a value of 0.057 centimeter Inuy bo inter-hydrogen finmes, Friednnui (ref. 8) lined his apparatus with ' 2d for a stoichiometdc hydrogen-air mixturo. This di atinnen, which is an efGcient, entuly.st, for hydrogen atom er, obt.nined iman entirely different way (by the Unsh-cr coin hin:u ion. No elTect, was found for the hydrogen-technique), agrecs fairly'well with the value given by ovnen-nitmgen mixturo used. aco 37. Flame traps.-In the quenclu,ng distnuco experiments just, a stoichiometric hydrogen-oxygen mixture, Fricibunn's 'ik""ed, thero was no largo pressure gradb nt. driving tho .ndicato a quenching diatanco of 0.010 centimeter (ref. d"me inni hot gas, iuni the finme had io'propagato on its own r,is not, knoivn how close this would be to the minimum j *thr"ngh the nmstricted space. In practical operations th il""li"" id "It "" taveling ihmugh a. quij.c di,lierent. For exmnple, a thuno curvo. et of pressure.-Figuro 13 is a logarittunic ploi, of long duct filled with combusiihte mixturo hing distance for parallcl platos against, pressure. Tixco '"ay hnild up a inrgo pressun', and the Unino nmy Int iiriven ihtough a t;ap nr.rrower rium the quench, g distance. m 4 I- - i

• l Fhuno traps nro conunonly used to protect, nuch syatems.

1 i F,,e hyamenchon-n r mixes anc-mesh screen, are onen i I u _ _. 2 . L_,i n-d: hydmgeiphuucs -~~rn auncua to quench. howevcc, I and other meinods are neewary. i EcWvoience i I T 'ouo. The value of sintered me:n:s un thone irups was simlied in kf A 1 o.3 l l the work of referenci 42. These trups wero able in stop l '} 2r i m!I n _ w e w _ iria u. men.osygen mi m es.eeathes y ,,o j would ho eWn more cifective with hydtogen-nir thunes, j N t also Uhpurtant is tho fact that the nintered-metal traps enuso l L .j Skirl)bNIII'[ Y NiIN hIcbMlN 4 IohN. N. g % l I The results of reference 42 are repm ted in terms of tho i j N' N N i \\ N \\, limiting wit [0 presSores beloW W!dCh II c Irnp M E!i d! Ways blop 'i i i i1 7 h the ihune. A sintered bronzo disk OE inch tinck, with a h statisitcal particle sizn of 0.01375 inch.nni a pon,eay of 20.0 I i i L ^ 'i 1. I i I i \\id perceni, gave a limiting sure pre-ure of Inore than 1 nonos-pd) o } l l Ret,$e [~ i I nTe for stoiMomede hdmgemog gen unos Utk d i C correlation was fonml betw,en tinme-trap clicetwencas und j lo o za, } art e to) a- ! iN ponesity, but there was. gion in <!icchveness as :he di Il m _.1 l ( ... i.._ i.

i l l ul were m.nlu thicker. dr. cered oron u.a, moro cifective thnu a

m. u ca m inh m e,. / $,2, AkPreswre,P, cr'm The work of reioence C w a * esunin..y o;u :n e, n n 1 o B 6

• * -E.Tect of prm'uro on quench;ttg rting;co of hy uw n-air d b "W

1. '"Y"#

u. J .,,4. m. 4 ~ s -rx-- w w - - ~ 7-p

ltE PoltT i:Ni-.u i lo s u. sin t-o m i o\\lu t il ti. H an .\\ Eunut7 ir-il) sure way to de-ign u flume trnp for n given h silio.co-ait i.n io of about OJ't.u .oinpainl wnh a h a n lla m n.a hiin i stein is by nicans of tests on u full-enle nonlel .\\ u ool of hnm of ahoni vita for nio i h d o.nirbon fin l-The 3 ution: Tim e wintered di ks are funo 3toppm. and ines s eiy inch n h honi. 74 pein ni ni e e. i-al-o o m -ian.' ay tiot he effective uguinst detonntions (1)ennonion w a s e-mel3 ddferent f r om t ho-e im mo-t onlhmrv luel-Fi n n e al lhe transition of flumes to detonation-an <h-e n -cd in ligm e 2. n muy be seen ihai t he lean-and nrh-hnni llame later nection.) t em pe rn i u re-are nhon l i n in " ami 12nm K. i c-peci n - w hich are values much lower ihan iho e for hysinn aihon. FLA5thl AlllLITY Lt.\\llTS I tief. 44 t F.ecrtosi ngge i-ihai ihe-c cafect-in enhar in The rich ami lean fluimunhility limit.4 m c ihe inel.oneen- ' hydnigen an due in ihe Ingh concem ranon of act n e pan ich - .itions that. houinl the ilummable range ni a gis en h mpera-amt t heir Ingh umbilhy Iref 44 re and pressure. Mixtures containing more foci dum the Recommended limits at atmospb 9 temperature and pressure. .b shown by I'he data ndlected in reference 4:L -h limit. or less than the lean limit wdl mu.-n-iam a llame. o extensive survey of flammubility limit-wa-Joade for t he the various workers u ho have n-cil the accepted metluid esent work, since this had already been done h3 ( 'o u a n t aeree w oh one another quite well. It i therefore unnece-- .d Jones (ref. 43). ,ury ne make any further ure-sment of the data. The Flanunability limits should be physiem hemient con inni-j foHowing inhle gives reconnucinted damniahdity lunits for a fuel-oxidant combination and shouhl be free of uppurain- ; hydrogen ni nir ni alunspheric presure und about 3000 10 Jec ts. However, wall-quenching may have un cifect on .mmability limits. It was therefore desired to delav con- '~ ~ ~~ ~ ~ ~~ ~ ~ ~ ' leration of the subject until flame quenchine hmI been ! 9',',',',""fj'j.'y'",',';'L'g( , cussed. in air in t.he usual method of measuring flammulohiy hmiis j hean liich

f. 43), mixtures are ignited at one end of a inhe thai u

de enough to prechale quenching by nn ignaion -ource j

ong enough to ensure that it is noi the lindiine faenir.

l'imod inoi e non ( 'ohci e n t Hame

• on b L4 ie tube is quite long (about 4 ft) so thni dm oh-en er can soncone,y,n n,nni.

.tn smv the flamh does imleed propagaie un it-im o amt n l'"= ant pr opannun 'nu ' Li .t driven by excess ignition energy. If tin linme ir.ncl-e full length of the tube, the mixture i.4 con ideo d Ham-able. Various mixtures are tested until the Hanonabihn For hydnigen burning in pmc mygen the lean limit-ure nits are dehned. , ahom the same and behn e in the mune way u dnese for Effect of direction of propagation.-The llanunahuny ! hpin, gen in air. The rich limii for upw,ntd propagation i3 nits for most fuels vary, depending on dhether they are ma peicent t ref.Li3 h asured for upward-or downwnnLplupagatine lhones. Effect of mixture temperature.-The lla:nnuible range is cau3e convection assists finmes inachng upwnni. For widened by heuting the unborned mixinres. That is, the .tance, the lean and rich limits of methane nre: upwanh lean limit occurs at lower c.oncentrations and the rich limi

and 13.0 percent by vahnne in un : dow nwani. 5 s ami at hieher concen t ra tion, n-the mixt nre t empera t m e i. in-6 percent by vohune in air tref. m Fm hpinben un

,een-ed. The duia o(.Wlute (ref. 45) w hi. h me con nien d havior is different. The rich linui of h hoeco i-ihe. nn,i rehable by Cow ant nod. lone. nre ploiicd in fienre 14. 3 mo for both directions flame travel. 74 petrent by These are limits for downw uni pnepagation so that the h an .lume in air (ref. 43). The lean linni i alb ci"d.1"o luno-n.fer to cohereni dame-There i-a hncar change in .i in the usual way. It is 9.0 pe n vo i foi don ou ani ihe innit-woh nouure t empei.u nre. u nd t he sich hnut n opugation (ref,43 h wherens for opw nol poepa.no mn i h. n- .onn.u hai onn e -n ongh.alecied i han t he b an Fonn henn two lean limits., One o,f, hem n called t he hoot "I. I L and t he llume t empeat m e-of ligm e 5. n enn he -cen t hat t e herent finmes; it is 9 0 perceul (ref. 41 u m! i-d o lo ne-1 d,c ii. h hnm for au miume mm pe r a l m e-.n em - for n u s-n;ture that burn, completely. Lennei on u n e-dona n. on e-Inn ing a nemly con innt ihnoe iempeno m e of n hom h d niern a re -oll lann# l'. The lean-lindi lhone iempera t un is hiwer bol e noneoherent limit of 4.0 perceni 3 .mmable (ref. 44), but the thune is nnule up of -ep.n aied i non e unable; for T, -aon" I{. h i,1060* K ; nnd for T,, . ono* ihule-that slowly n-ccml the inho \\b 6 ;b d..- Knr itin: K, ihule-do ma con 4mne all t he incl. t hc3 i.a s - o Wen of mm neuents la niin n- .. u ed w it h for sa fet y. The nonenhm ent 'la ns - i-n d.c a na hic iado_m an ne o m. i m m ". '.. ' 11 ' ddnled in D onlla u n na hd n 3 b 'eW I II 'u - I h - ' ns l-a- the high diffusivity of hytlrocen' e a p p' a l ' arbon o n.

i- '

m ele t.c act ually con: ume a miuinv rn h. - ihi annemt o. a oneimo m the origmnl inixture (ref( 37 aini 83 o n n.2cn m.o r t re f.13 : TI.c i n h limb t-.ha r pi s.h..a V a-e oi i Flammable range. The Manunaloc i "e d " 6 Fmun l'" m the ence bet w een t he neh-and b1 n I t C 'ud) I' O n!o ' "U I I I epilonally w ide 4r hpho .pngan in Ier hv b "'b' a i I' 'pd i a- .c .6 I l ts -

Ht'h\\ M ist n s io.i n.nN e osliit.i n n rin o't.tri l L-l( '~ / K i. ] / \\t ii : , i i. / MN. l --. ~' Leon ffI ! ! ! I R,en /' l@d j j j j j j j h m. t t ~ ~ ' ~ ~ ~ ~ i i ! ! j j ' %.s ~ ' _3,l l N. s i i ! IIl, v t j to g(A l I l l= j g l l i \\.,Ntrogen l t I .I [. _. i 'NI c -,/ ) l l _. -.a l\\ l i V I ! e i

N

, ~, ,o- )- I l l /l l l _. _._...,- _... __ c u m s I l ~ e h; .l [l l l .t l 20-4-- l E I d'0 '_'0' !,,-.+i c . _ q._ [ l l l [' l ! ' s y -_l I j.- _ I I ).w__7_. - }__9 g _r I.. -,1 l l . l l ~f _, I I L / I ( i i 1 i i c )O l I I ' w._. y.- i f l I k [ l l l l l i 6 6 i ~ 'O ' T2 0 ~ 2 0 0' ". 0 70 ~ 8 10 70 72 74 76 78 8 u Hydrogen in air, percent by volume Caroon Sonnie or added neirogen n air, percent by vowme I L-Lifert of temperature on flaturnalnlit) lunit* of h3 61rogen li'.i n L li-flaininntnhiy limile of hydrogen in air filuted uith in air for downu ard propagation (ref. 54 l inirogen or rarbon thousie tref 131 e , --- ] , - q - - y, no mixture of hydrogen, uir, and can hon ihovnle 20, pagate dame if it contains less than 7..; perceni ou F'larne propogotion j thus takes rpore nitrngen than carinin dioshh. n, s oo.n.or d t i flatne propagabion, plesumuhly because of t he gre;ocr k _d._1'- I d - UP""' C"'""' pacity of the latter. Water vapor behas es a ppr ou. __-t,_.._ like carbon. dioxide, i ven though it is a ponloci ol .% L - d ? tion; the oxygen limit in this ca.e is aboui 7., I,cr. LL bo* L- ~ s 2000-i a.am ' a* ,/ j J _a i j 36 C (ref. 4:n ! _;\\pp2,, /,. _.. _ _ J j e diluents are much more effective than nu n,uen or 3 ,n i l \\ N-dioxide in reducing flanunahdity. ".iir i uniannng i k d r.'4.s403 /

.___.I.___,

4 .e 4 ~~ ' M ' %, j.W,/ _.trx! ~ e'yg ~,_ A r"c.1 icent methylbronnde or 39 percent dichlonnhilnoro. ,;oc - e cannot form flaminable mixtmes w it h hyilo,een ; ~ I~~I r 1_ I1. 7 Z'$ jy ). Such cornpounds muy interfere chenneully w oh [J,u j .r__.! _.1. J tion reactions und should not be con idered inegly 3 ,00 I Q[ ~~~ luents. Reference 43 warns that the resuh oht.nned i l e i '2 l' { 00 :.- { ethylbromide muy not apply in pun nee. hn a n,e 4 fY l j l l iixtures of tuethylbromido and air are them,els e, I ' ~h. \\

--.h..:Ja. /,,s ble with a sufficiently strong ignition sonrec.

I 9~- I ~ -.'7.,. .i r, c8 r .a w-of pressures below I atmosphere. Con a ni and 1 s' f 9 i f. 43) sununarized the hieratore on elleris of n doci d iC C' M ' [ T J i'"J ~^ ' ~] ott flatnittability Umits.,They oh,crted ilna ihe i; ~, 'de rallge narrowed

• us t he pre-3ute wn-l e. h n ed, ~ ' 22

~ ~ ~ ~ ~ ^ ly at first, and more rapidly below 200 or JUU nulh. 02 ] 1 ~- j - of mercury. A mittimum pressitte n n-lenched. 10.y k chich no Ipture propugut,ed a lhune. !! 6-o _4;_.y-4 _; 7.. ..z o now j r Q j. -7 that stu h t eiglttmy due to n.dl..g oen. h u.g \\- m a tlle scellots oin quenclung di lann 1 i,. u all. s. i t a effect at hne pre-sures I t ha In i n n.nnd i h.o., '4 q__f flunlinalnlity Illml" nguilthi ju c. us e - un sils a ni s. ( E UI[etatratioin and piew-ore-ho who h iln c ',,2 O 20 40 50 80 o g d. ---.intunce is equal to tite dintneter of ihe llaine t nhe o g, q,n ,n a,,, g,,cen, y,ow ne i ? 3'4 6 blO O 2 3 6'6 ier words, it uppeurs that the flanunalohty Imot an. [ y,w,,,c e ,a,,o,, ed at, teduced ple--m es and ihn t fl.one i an po.pca n g, u, ,,g ,,,,n,,,g,,u,,,,g,u,, ,,,,,,,,g,g,,,u. . cAtreinely low pre-suici If flee lhime tohe Ialue t-or uns' u. u n h m rn.u 101,.. h.on. o r, Ha. d o n s t,.q. d.e For esample, Gar ner nini l' ugh.ief Is '" e o f a i..m r.cn n.nn.: d.n u et r,c n n. n

y/ 14 ItEPoter im - o u n n a un :-.,in i inni n i t.L' run.wm >u t 7 n :- ilo r ea -. ihe volunic of the d ar h a rge. Furt hennos e. Iln. in65tuof 4 tyillinleters of mercuty for l13di opriru n s gen li.in o - n es 10-centimeter t ube, l're-uin ald3 t hi-i n nii u ouhi la h o aior3 men-m emems an made in qua- -m mai me, ontituw. ter atill lower pressure i with lun ger n i h. - a h o a-m pno ocal en e-ihe cas e usuaH3 una mg and uni 3 The preuure-concentrntion i.oundary for Ihune po paea-I.. i n holeni. Fmally, tin spark duranon may alicet the .n.rei innhd for igmoon No uorh is hmiu n in have . ion imposed by quenching in u ininicelar i nin - oh en u-et ul .or practical applications, Although . h d: hase m. h.cn oone on t he clicets of dow s elocuy. t m huh nce les el. necu measured for hydrogen-nir flamco. iluy mn3 bc.~n-and -paik durniion on igmtion energies of hydneeco-nir nus-unted from quenching distances. Figure 16 -in.u - c-i nnai cd inir. indice wit h pmpain -nir mist ure< in,w thai iem. urves for downward flame propugation m cyluntrical inhes non energ) merensen wah velocity ami turbulence mien-Hy - / rom 0.02 to 20 inches in diameter. The con e-une run-ni f. P.n. mni the same trends would no douhi appenr w ah - .igth.ldr.on.the quenching dist unees of iefereni e a.s i mca-- l inih ogen-sur mist ures. As to the effect of spark dunnion. ! for hpirono hon fuels, sparks lusting 100' to 100n min o-ared with parallel plates) tuultiplied hv u geomcuiral factoi t iflELfIcLJfi) to unn ert them tu quenching di-ianns foi ! -pa:nd :nve low er ignition energies than slower or fa 2 -ero ylindHeni tub s. Flames are expected to pnipngaic at L-n e fs. 49 and not. pressures na low as '2 to 3 mR1imeters of mercury in a un-on-h-The renutimng variables-composition, piessure, and irm-liameter tube (fig.16). Some of thecurvc3 are estended to perat ure-have been simbed and are discussed in the nest ich and lean mixtures to illustrate the probable helmvior as pm aeraphs. It is again poi Hed out that 'the smaH energn 3

he rich and lean finuunnbility limits are uppomched.

.\\ n ein d may not sullice for practical enses, but the nemh stimated curve is also included for upw ard pnepaganon of houhl apply. ioncoherent flames in lean mixtures in a '?-inch-diameter Effect of mixture composition.-Figure 17 is a ploi of ube. Although figuro 16 represents the best cuinnues that ieniiion energy in millijoules ngninst fuel concentrntion for an be made, it is emphasized that the curves for the larger mision s at atmospherie temperature and several pn, surer, ubo diameters were obtained from long ext rapointions of the iref. 37). The 1-atmosphere curve indicates a minimum lata of reference 38. energy of 0 019 miHijoule at aho*ut the stoichiometric inixiure Effect of pressures above 1 atmosphere.--The ph ri-of and nses steeply toward the lean and rich flanuunhility iigh pressurc on flanunability limits ure nni u cIl e-iahh he l., hmit. lly way of contrast, the ignition energy of n :n-l'he data survej,ed in reference 43 indicule t hai t he lla nunable u, nee is. narrowed h.v the first increase, in pre--un. p i hap, i)) 10_ljtr3qsjjheret; thereaf ter, t he ra nge n unnloalle 0-m- -- videned. In any event, the effecu appear to bc snndl. , ' - " ~ ~ ' ~ ~ _..i.~.,__" _ ~ ~ ~ - \\t pressures as In,gh as 100 atmosphere % theinnits me om ouch different from the atmospheric values. ' ~ ~ ~ ~ ~~ ~ "/ ' 2~"

• ~

SPARK IGNITION ENEltGY / r.j The modern method of measuring spark igninon energt s us designed mainly by Lewis umi von Elbe and i-ih<n-+d [ M%E5GG-95 ullV m reference 37. A measured annunn of clern n al l C 4 -b--- ~4 h -[Mf / ['. b - nergy in the form of a short-duration caparnani -pmLr : atroduced very rupidly into a miNhne vi unio pn~-me e m , \\ _ [/ / ./ cmperature, und composition und u dh a gn en clei innh-

• ~

l [ eparation. The smallest energy t hnt w ill igone t he no u nn- , found, und the urocess i.s t epenied no o t h. r. h. n o. h t-c -- / t' / '\\ r pucings to finul the gap for which the enrrey n irau Thi 3 . i,. \\, / lata are more reproducible if Ilje electrode, m e llanjed at il.c .ps with a dielectric materiul. Thenilo - pa. b. -~ N ./ ,ao uum ignition is equal to the quencinng ih,inno la u i.oni .\\ / on Elbe were the first to recognize the n n p.n in m i m he a /' oenching effect in such mensurements. l g The ignition-encryy da t a to be ih-. o-y the general ineihod juH de-cribro !i s %ent ideal condilouls ikoll an' Init lil ^i Ng ..ry t herefore, one <himhl not "un .L .und no:S t hesc i nminion- :n hi - W-nition s3 stems. For hut ance. ib. ",'. m so w o sWl -o l hn t il niny in-t h n IIn ii li-unt. ololi.unis t uliluon:h izo * ~ c 'l ~n t si n a 3

n. r.,,

..J s;4 4 e.,

MUn\\ hi ist !!) loo n.i.N t f ntal hTION PnOPEltTIE8 l,~, percent mixture of hydrogen in osygen is o on! unihpode tref. 37). and this is apparently not do-inninnnm of : h. E p. m s -e D' ignit on-enet gy-concentrallon curve. ~ ~ 4 \\- o Effect of pressure.-As the pre.% ore is imo n

• ihr een,:

-o-- .-o_ ,i d r s.. ci than energy increases rapidly, na show n by hguic I Ab N i 76 o though there nre too few points to dehm t he roi u - rhi-ch N r A i it uppeurs thut the minimum ocem s in ni In." In.nne iie r egardless of the pressure. The mismnom icminin encien

2. %. _ i, s _. u.. i~.c.

change by more than an order of magninnh m er ihe i n e-. ( c: ."-~~~[, M M,J~L __ 3 sure range studied. __ _< Q_ a. ^ T ' ~ - - - Y 4 Figure 18 is a logarithmic cross ploi of dain Inon tieme I i r 1 y \\h, for three equivalence ratios. Ahhough curus onehi hnu. ! i N 'M e been faired through the data mon closely, a line:o ichonin 'I~' ~ Y was assumed in order to show the averuge cirect of pic--m e. Nb \\ Thie effect is, approximately, 5 ch 9 ~ ~r b ~ Dh;F Ji od. _ u__ __ JT_p. -.- _ 4_ _.__. N \\g : \\. h p, 04- + - - - - ~ ~ ~ - - + - m - . _l e _. 4 i Data from reference 9 for stoichiometric mistuic, nre ;dso l I l meluded; the points are higher than tho3e (non reference :c 02; FTT ' 1 i and also show a greater pressure dependence. There e, iou i I ]~~sld l much scatter in both sets of data to define the slopes ofthe 4 0'l .2 Y~ d " - .6 lines very well, but in general the exponent i in ennut nm i i

• * > 8 ""

1 has a value of about 2. Una w 16 --Drect of pre ure on park n:nmon encno. Minimum ignition pressures are somentne3 s epoi ted for l ve>rious fuels. These pressures air ohinined wit h tiw.i cler. Irode spacings *And ocem' either because of quem lune cifrei' Ft.DI E M'AlW'l'Y or because of the limited spark energy armlable. In other words, it has not yet been shown that there is a n u h-ohn, low-pressure. h.aut below which ignition can neu, Fhunes are stahle hecuuse of interactions,unong the thanc* o, c o r flowever, minimum ignition pressmes use of nacoral s alue ilte dow. and nearby solid surfiiees. If a condition o.' i a i -t ahic dame I,or example, it is possible to ignite the musi In u o a hic sented on a hurner port or thuncholder is changed g.. flow vehteit v ), the thone may not rennnn -enied-hydrogen-air mixture down to o 010 ainnsphere h3 n-e of a .c \\\\. h hunn r. llameA, Unshback or blowotf muy occur: with n /ap 0.2S centimeter wide und b.tM junles of energv trel, Td i lhu n es on flamchohlers m ducts. only blowolf is usually en. .l'his is one of the cases mentioned pres inosly, m u hn h l . noniered, not flashback, ,t,he mecham.sma or stahibentnm l t he quenching effect, may he overpow ried by sollien.ni e,p es ' > fo l because the gap is less than the ipicochine ih tance ai the t wo kiluid of IhunW ale dd[erent ; t hpiefore t he dat a i pn-in'es less t han al out 0.2 at mosphere ih,g. n a r e sli-cuard sepa raiclv. Effect of temy arature. -Refe'rence .,2 ,onie m ilo onn 6 L A5n nat h 4%n nLow ot t ut nt us t.k t L a so:s 4ork found on the etreet of mixime iempeianne on -pa n, gnition energy. The authors state ilno t he fidlow m e wla- .I,he da-Munt ; uni Mon oir of lon act d.one-don holds, except perhaps at t empeia nn e-l~ t h.m ; r. N ac..o u i ina h3 Mn eraihem of Ilow s elocity m as the Inn o, r w.dl a-log Ix 1, T, , c,, P"mi "d o u t by 1.c u i a r n i u m 10 hc aer G. Ihn nei -n.hd. I rt y ila t a are, t herefore? u-nall3 correla t ed h3 pha t ing the l'he position of the minimum m em w-..I yno nin . nncal hoionhoy wh.cn3 ennh. n calc ol.a co I,o un ,,,n. in, a igninst fuel concentration sluf ted to leaner nost m e-as t h'c 'hnons ni da-hhack gn..or at blow olf g avama foci con. no n a non. The gnolients emperature was increased. The follow mg t able gn e, t he gnen by ihe follow mg es. aic hitn of reference 52 for stoichiomeine huboenn.nh n,W u.. pre--ion uvf. 53 ): e a pre-<ure of I ut nn.-phere: o Ik 'ib f lei f k. II

• elj as f.s.

as j . i r. F t ure.

• h Jonics

,,,4, ,gg.

g. g l

s 'l l '; ,I i

• !s

. 3 ,"a i s e

i nuoter iasa-.u i oiui. un t.-oin t o.st.sii rrLL > on ALno.uv iles Flashb ack. -Figure 19 shows the md3 dma h,in, i fo, 20% c,hback of laminar hydrogen-air burner liaine-y,y,lx, at ann"

1. g6/TITb

,cric temperature and pressure (ref. M L Uritical nomnian M 34 f ** C " locity gradients are plotted uguinst foci concen t ra non. - 27 fff/// solid curve represents flashbuck completel3 ihm the W lo* irner tube. The dashed curves refer to ene in wloch j' '. /, i e flames tilted and partly entered the inhe hefore finnih i

• 0 0

,/ ~ ' i3hing back. In these cases the borner wall w as po.- p,,.s so, p, .mably well heated, and thus quenching wa-n.duced and l "M-o"r ic flames were more prone to flush hnck; ron. cegnenil, for 3 iO 3 given mixture and burner dituneter n higher llow veloen t { '000; - .'_..r_ o i .oi required to prevent flashback, and ute s. w ns acconhneh t,. 1 ~ "O O' I cater. e The effects of reduced pressure on llushback of Innonar j 7 f .drogen-atr flames have recent) been studied ner. 271. In ~ _ //. .d ,_ _.i_ x, int. work tilted flames were considered to have flashed buck. 6 i !_ I -.,_i_' ~55 7 4000 L [,t [ 3 i- -~ -- - ~,* .en though they only partially entered the burner. Since 3 lted flames existed over a pressure range of only . I i a few f 5000r/ i 1 o f _-1 - ~ <

d. !imeters of mercury, little error wasi incun ed.

1,ieu re 3 i i shows curves of g,u. against fuel concentration for iwo 0 L _..__, _,_ _, _ j ggg

j. ij n_..

ff _..d ,I duced pressures; the atmospheric curve from Hgm e 19 _j j repeated for comparison. The maximum occur.s near ',) ; ; , ggg, 'j.. j percent hydrogen regardless of the pre,su re. The on essure dependence of gf..t for equivalence ratios from

u. !. _,

i i ,.a 95 to 2.25 can be expressed us follows (ref, 27): 10 24 2e .32 40 44 4e 52 56 H,arogen in air, percent by volume 9/a L c O" i%' 1/mino. 20.-Lifect of pre-ore on crit h al boundary velven y graih nt C '"'"""h""# """"""' All the data discussed were obtamed w ah a w nici- .oled burner. If the burner is not cooled. t he resnhs nic et reproducible and depend on the burner size and t he I l 2 8.OOOr- - -~ - ~ r - _,_'..."i-'-J 20.000. ]- t u 26.OOOr-+- 4 -; P 7 1 I. : ~- 4.. o.-. ~l ~ + ~* 'I--* . l l l 1, 7jp q} ]' y [ ~[+ M "~[T ~"'~j l u, 'it i 1 i i t t i I ' l ' ~'~' 18,000---* oome ter, d, W'I'TP T -]' ' { [l j ! I! J j-+ 7 } _.J[._,.Jl. _ ' .J } 24.000 j 0.452

r. 4_

~ t--~' ] ~ /T T ' j--- 7 T~ i i, i l j-. T-f / lg[ 2 2,000-- --' t-- j j i 1 -+- -9 g g - ;-.g FW-b- J' ', M f 1 20.000 Ym-j-d - ' "W' I4,000 .,-. J _ _a 2 2 n l l l / i2%i,( g j - i F ]u - -. j l i i i i i 4 u i I II l-l. L

• +

- -+- + M is.OOO -+ L-f ' d_ t 7 ' !_d 4 1P"5 W. 8 l I!jll \\@$ k '. ',00 i,- - :- - t, t-I j ot* -f, 1 12.000 - } lif fl l g\\A' l i o I 1 b m ~* t g t--- ,660 il h.ll-41 l ] l_l. ' " 1// '. / l ly 'I 1Q000~--.506 i. s; i [ - ! ) .452 ' Ficymore p ,4.000, .216 l C. t + 294 n - /. j . G39 ~ 4 e t W-l j l I f' ) 8000 i2OOO 7-- j j J._. _J i j j q q ./h --, w .-.4 f 1 6 000 ~ -v --I j!) l ' ;l }' [jj ,. )I ,. l\\ ,o j.,,l-l ll ,.o u 'yy,_ 's -q e.-,---. h' lih5 'f'W[N ), l* f._.-._ f4.-]?x fil 9

• o j

.r ,. s. /. j g, 2 000 ,l l 1 N/.}* i ' !f ft., l / i l t 7-i l i I .t a yyu j s i e Ai ~ - T T-i l i l ///jf } i j 'Jfr,.N ll 'i} t, t LI I 1 ' %'O 8 L 8 O -20 30 4'0 50 6 s. 4 10 15 20 25 30 35 40 45 50 b5 60 Hyo,c,qen in a., pm ent by w. a e om y.n in x, p< cent t:y a me I e,i n s 21 l'lfe<ct of pro -ure on. r u ir:tl li. o ndar s s i Lo a s t rmb. ot o.t RE lb-f'ht hbark of lannner b3 dri.c*.or l'an i. pre-.ure f ref.

• li fa l'a-Wat k of t u rho h ni h s d r..o,o.ir tLa o.

.of lI i

1 at'h\\ L) t o nildo n.l.N i< dint.lloN Pn O PEltTl La 17 .ckness aint material of the burner u nll. :suchcihes wen. Blo worf. -In hgure 22 the known dain for hh.n olf oi niied by Bollinger nini Edne for hydrogen-oy gen innim e-h pi n >een-;n r burner flames at a nnu< pherie pre--un ao

f. 55).

in,w n n-g,.., ploiicd againsi Inct concenirunon. The n on, Reference 34 extends the study of flashhnck ai inineni w a-doin. by s on Elbe and Ment cr t ref. >4 ), w ho n>rrelaico mures to turbulent flow. The critical homnian s eloi n s ihor dain in terms of u.., a-calculated by c< pia non ; idients for flashback gf..r were calenbaca h3 inenn-of ilm -unple equation for lannnar flow. Ilow ever, t he inuni-antion (6) by use of the appropriate frienon fa< tor in t hey took in t he t urbuleni flow reeime fell off t he enn e. ure 21 data from reference 34 for ihree pre--un~. ni e phined li w n-later hown by Wohl. IGpp, and Gazley tref. &n ainst mole percent of h drogen in air. Co m pa ri-o n of ihai all the data wouhl full nicely on u single curve if g.,, 3 ure 21 with figure 20 shows thut the s alues of un, calculated by the cormci expression, equauon un am w ere ich larger than those of ufu. but that the penk of t he li i-the lat ter curve that is reproduced in Ugure 22. For rves occur at about the same concentration. Reference a l honimu flow, equation (7) w as used; while for t urbulent > orts the following pressure dependence of gr..r: tion. ihe gradient was calculnied from e<p'ntion on m ihe followine funn: gre.r C F 0" c ggg3 Ap.g - y,,, 7 -- t11> ithin experimental error the exponent. the same n-d is it for laminar flames (eq. (8)). Therefore, the followme ! The daia cover only a linuted range of hydrogen concen-ation holds, regardless of pressure, burner diameter, and I t rations ghose lean to stoicinometric). Ilowever, on the np stuon: i basi, of work with other fuels, t he blowolf curve for open gy, horner thunes is expected to level off with inerensing equiv-g p 2.8 ilm l nh.nce ratio; at some rich equivalence ratio blowolf would -iop and wouhl be replaced by flame lifting (ref. 50). Tins is herd to explain why gf r sIould be uhnost three inne-i wonhi occur because of dilution of rich mixtures by ambieni large as gru.. Turbulent burning velocit ies are om i air. If ambient air is excluded, as in a Santhells burner, . ugh greater than laminar burning velocities to accomn ijn. hhiunif curve peaks at a concentration near that for equation (10).', Reference 34 tentatively conclude. t hat ma yonon hm ning velocity, just a, does the flashback enn e explanation lies in the penetration of the thune imo t he o.cc fies. m to 20. iiner sublayer at the burner wall and ihai the lhinn-Further burner blowolf dat a, ubinined ai reduced presure, iroaches the' wall more closely in t urbuleni t hen in lannom m huib lanunar and turbulent !!aw..are reponed in reference C 34 The-c data do not fii into a 3iinple correlation with 80coino3 h.onnlary velocity gradient such as the one shown in figure !---.' - I 22. lilowulf of-hydrogen-nir flames from burners is not 6000! I j fully understood, and the theoretical model (ref. a7), which MyN .. J lead-1o the concept of a critical boundary velociiy gradieni. i .. i 400o l l l l j i j B** " noiy have to be modified (re( 34). 4 l ll l al I . n' nu,w m r or cos ns,,m n. ou:s, uos, ru sioux.nso, 2000 py ll li l \\ l. Fhnoc hehl on hintf %nlic-in ducts owe their iabihiy 3 a n, no. mencohn,on zone behina on. nameinaaer. ni, - icoo +-- E Boo M I '"""*"F"' ""2 "I "S "l"I"' "*""0"""' sooI _.i k.p. MI 'I" d " I""E "* I ' I* " M " ' " ' 2"" " ' h"

• iN '" " U""
• 2 i

- p._L. t _. _ _ p.s ph,u olf occur 3 if the mam ircain flow s so fa-i ihai 1; ?, 400 - . H J- 0q

u. +.-

.m o uniinm i annot be achn.u d. The dou o 1o, n y I i l ,I t t i ? -+ - ' IT 'ai 4 hn h this nonlioon at ib depends on t he -ve and -ha pe h 200- "I f " ' " " U " ' " " ' I " ' ' "

• l " " " " "" P " " " "

+ l "j j ll l ainl i ompo-ition of t he incoming nnxture. 3 . + - - - - ul - . m u. h s oh uine fuci conn.nirution.againa a parann.n r of l \\lo-a Hainchohler blowulf data are corteh led on a single 9 g j ioo - m r e o - . p.Lv'. - - -- - tC-ni a n w r. empo o W e s pm-m -.di po-o n. .c y.. no an ,f I 2 0F + ,, er i. .a..a.o m.' ~. g } n i . i.. t. p......h h e o nr. ,e ~ 4 ,s y n,r.ce, m em *,,_. e 'O, j u. s.I' d s 'r .. ;o r l b .4 i re ' v f

14 nEPoirr im u t ins u. u n m.in i mut ro 1.c ain.u.aon t ne., The datu are mit given in ref. 57, Inm es er The u.a L on inon no.. n denonaion. The denionnor a n s e i hen nin anen which this panuncier i hused was donc ai s ed ui e.1 po - .o -es ci al i nne-t he spi ed of -oinni m it.e nulon neil m ai m e The effects of mixture tempeno mi w en noi -in.hed W h., ca - m onlinary thunes i hen .s. -mail pn~.m c ih op .ures. !)eZubay points out that the maximum s alue ohianied hn hon, i hi imbonn d to t he lau ncil gm. in a detonation t hen t he parameter is 11 times as grent s ery, on-nici a ble pn~-ni c n-e The ea'. ulnied ra tio or ns u.c. on -p n o n e n., maximum value for propane-air liainex no ef fect t h.o s cihmi-pic--nie in hind t he w u s e. m t he hui ned en-in ihnt abend t he much greater stability of hydrogen dume-oi ihe wase s Is for a -t oirinomet ne h3 hogen-oxygen Iteference 58, which deals with the clh rt-id t he domicier unsinn nod about la for a -i oicinomet ne h3d n eee n-m r _ of water-cooled cylindrical-rod fiumeinelder. fomni t h.o nin i u re iref. 37, p. on7 o Wnmer. t here is a o nmg con- ~ ihere are the following two separate regime-of Hamchohici s eet n e How of burned ga folk. wing the w as e. When such

~

tability: n pic,,ure w a ve meet s u n ob-t acle, the uwmentum of t he ! horned gns is added to the pn%nre effect, and very huye (1) Laminar-flame regime. The composition of t he mn-s ure burning in the recirculation zone behimi the lho ne-. force-nm e he eserted. _~ holder is affected by molecular diffu, ion. Since hydnigen The n asons for the inmsfonnation from onlinary hunnng .liffuses more readily than oxygen, in comrast to ulmost all to detonation are not fully umlerstood. In the usual laborn-onlinary fuels, small flameholders actuuHy stabilize hydn,- tory experiments the streogth of the igniti.on source nini the een flames to higher How velocities than do Inrger dame-diameter and surface roughness of the tube alicet the runup holders at a given lean equivalence ratio. distance (the distance from the igniter at wluch delonation (2) Turbulent-flame regime. At u Heynolds number neur occu rs h These variables m e, therefore, carefully conirolled. 104 the recirculation-zone shear region become. inrhulent. The Hume, ignited with n mininnd ignition source. musi l'he stability behavior of lean hydrogen thune3 reverses, u nd t ra vel a considerable dist ance in a sumoth tube before larger flameholders become more effective. Zuko-ki (ref.

18) concludes from an examination of the liieruture t hat for l 6cc mixtures near stoichiometric the blowolf velocuy for any j 7-I

\\ iuel varies appioximately as the square niot of t he thune-l

_J__,

- - f( }3 h1 l l l l aulder diameter in the turbulent-thune regune IH-ihua i ire not complebo enough to support t his concin-ion loi ihe acou - ---h -- 1 --: -pecific case of hydrogen-air dames; how e ver, l)cZuha3 % i I ~\\ l } [ j al tatement that U.. ecd *" for hyihogen thune-su ppon ed l hb l l m disks (ref. 59) is in general agreement wn h Zuho,h6 l l l l') Bio-on onclusion. l i i kkL l j These points are perhaps clarified by ligme _t. winch hows data adapt.ed from reference 55., h a ppe.n ed i hai ~ i D l j j i {l'l, l t he blowolf velocities and rod diameiers corre,pondine in [s { l o j ow Reynolds numbers could be correlated rouchly h3 the ; el l I l l I o parameter U../D-(Note the negn t is e d ia m ei n, ex- ,S l l l

1. 3 mnent, which ngrees with the discus ion ju-i gn,en i f ihr

' cor -- d -H 7 H p ( k{ g aminar-flame regime.) This parumeier w n, ace"nonele 4-- i B

Jotted against equivalence ratio. Sohd dnia ponna co r-

- rp, espond to flow velocities and rod diameiers -nch dun ( Boj j "q[-- 7t q" i+ j p pp q hp j !!r >10% and open data points correspond 1o tho-e -uch thai j g J_ j --- a- _!. L- !!r (10'. It is clear from figure 23 t hui t wo hh,w oif i un e-i. g so' \\ ire obtained. One is defined by poini-for winch //, im i i }

,,c

1 l.} _ _,__!_. _,_ l l i ~T y,[ _j __ md the other by points for,which //c < 10'. The fact that flamew wen stahihzed at ur3 h no mun a-i. j ence ratios (fig. 23) provides added proof t hut t he s een, ula. 3 l ~ l l 1 l ion zone is enriched by diffusion. The misinre* w ere iomogeneous and would not onlinarily be especied io sup. 'l - [j j d ~~~ - f ---] ,o r t combustion below the flununnhilit v limii foi.Ao>. % u.m lames (i. e., below e 0.24). c/ ,e done on the flamehohler stubihty of huhoeco-ao H.onn -?y Figure 23 also makes it clear ihai onn h wiu,, o n.an.- n. 3 o o he data are confined to lean mist ure-and -mail da on noion - 1 l l l l l l l l l sono d l'he difficulty is that the flames are esu cmely -iahic..u n i Peuci I ""'c 4 d arge air hundling (neilities un needed to po n '.de ih m - W h [^7 l nough to cause blowolf. iol - l l l ^ l '[ l 3 '5 gam g,,o,'C i 2 DETONATION PROPERTILS l i ra wh ne l i3.,,., tlnder certain conditions an unh na ry Hanw a.mener a h an t u hos.,. air no.n - m .on."-m.cor hrough a vessel filled with combusiihle nusiure can irans-i po. -ure rnon w an r-co,ioi o in.drwai ro i-a.o

stlo u or u s ni,ou.s e nu ors rtos elo u9.icrum l9 icionation occurs. For n stoichiometrn hph oern-oy een al o -how n. For h3 ib ogen-,or un u m es do,c :n c is. n,m uixture, for example. the finine must tiavel in i cm uncice-T.9.n peorot. nmi for hydn :.mn-oy gen unu ore-

1.. a n. i..o a a 25-millimeter tube at an initial pre--me of I.iuno-pin n l penrm.

.ince tbcse coni eninu mns an u itinn ih. i t.,,, ref. 37, p. 588). The rtump disinin e deen a-e-w h h on ica-- l inahihiy honi, not nll llanunnble mixt un~ nir acion..hh og pressure.

li

- no.1e,une io noie ihai ihe demnnin.n veloco s doc-mo In practical cases, however. the.c ih.-t ance-pinhably do, ba s e a pionounced pen k ai.-ome fa vored cipo s aicaci s.u io mt upply. Excess ignition energy may iend to ih n e ihe ; a honnne velocity doc.

lame, and rough walls muy enuse the ga-flow ne alo ad at ! li i-al-o noiew ort hy t hat deionut mn velocity depend-i to become turbulent. lloth factors u onhl icini io -honen inoch Ir-, on temperniure and pressure than ik,c, honnne he, distance for runup to detonation. Thn.,. one -hoohl not s eloch y This can he seen fnon the dain in inble IV orf. ount on a definite runup distance:it is safer to n--onn ihai ! 3 7, p. 5s.U. .\\ temperniure increase from p:P to 3W h I he possibility of detonation always esi3is if t he miu ore i, I ai constant pn.>sure neinnily causes a sligni dmp in den na-sithin the limits of detonability. How ever. i he on-ci of tion s elocity, perhaps beennse the density decreases. .\\ i ? letonation could be delayed by mukmg the inhe u nll, of no conu a nt t em perat u re the velocay a ppa ren t ly increase-coustically attenuating materinl, such n, pornos o n ci ed -low ly w it h pres.ure. The same conclusmn i3 reached in .ronze (ref. 60). The runup distance could he increased by r eference 02, w hich extends t he st udy of hydrogen-oxygen 4 much as a factor of 2. .inother safeiy device e, a smhlen miu nn, to a pressure of to atmospheres. The chance. ulergement in a duct. Reference 61 shows that deionaiion ab honeh consistent in direcimn. nre noi far ooiside the -aves traveling through stoichiomeine h dn.ern-o v eco espected error of ihe mensm ement. 3 iixtures in a 7-millimeter tube were trunsform-l to slow-EXPLUSION LIMITS. SPONTANEOllS IGNITION AND T}lt. ioving flames on passing an abrupt transinon to n larger tile 311STRY OF ff YDROGEN OXIDATION obe. However, if the larger tube were long enough. a new EXeLobloN LIMITS runsition to detonation wouhkub3cepu ntJy occur. Figure 24 shows detonation velocities in hydrogen-air and I Description of phenomenon.-When hented to lugh a ydrogen-oxygen mixtures plot ted againsi foci concentranon enonah iemperniure, a mixture of hydn, gen and oxidant ref. 37, pp. 585 and 586,). The linois of deionalnhi) may 4pontaneously ignite uher the hipse of some time called a n-3600,g l

j i

- mri -] 4 1 j i hise S :tece '"i T~l i r 1 l - p caen-i b ^* ~ 1000 ---,- 3400l: l l l iLimit of cefoncedity l l { l cogen P:eas,vm -- s 6 %c- - 2 .'~~% 4-m,oN- - 8 00 - - -- Hyamgen-cnmae l,, j {

i ; i,.

ongen

---

P amit * -

3200l I, t i i t i l l t-I - 60 5 ~- Myar00en- -e:o i-m --* -t casen pornso _ _ _.. _.r l l l l l l l l i CNJ.Ge 400-o Hydrogen-Petamm

---

t' -H' -

~ i i Cogeal l {'- j ~ ~ - o s progen.3 l So l l-I I i 10 74 / { caygen tenewa e~~-~~ j ' ~ / -" i 3000; ,---t-- i l l l l i i l ,i , l cir j l i i ' Nicmyn 7 +2 -! - 6 ee,$e. -- r, h; 7-

,0C - --

0 'Nmcen* l l + 1 i orgon t j / 2800l' ,pr~ crnr.oe ? aarn-i l I /' / C' 4 t. , ar e,cen - e ter I I f --'[ !My cm I [ ~ i i l 04a4r i i

2600 60 mr

, ; l l l I i l l l ! l t 1 2 e 7,4 - [ 'TC70 }2400 .."m j 7 i 3 e 2200 m d,~ -

• I b

*C " E * 'C S*" 3 g y,,, i l i i i l i 74 4 t-- o [4 \\ 2000 = i l ! _;, 7 I I l I i 1 e e. -// _i . eco. - / o00 ~ l[y ? s s '400r-. - +- -1 F t 1 3, ivo - :o V: -3 c %e s 1 [ .t' l l

d nemoni i s.:s ssions u. ua nous. o u u s i s i:1. n on u.m r. s i i n - ud.Inl 1 e I hr -lion hunneii w lig hic, ri.-.es s ;. n o'ignillolilag. Ihat wit h cert niil 41niil,situlie nl+ s n j n. l l l o t i s. '"li .li. is ni vewel aize, t he miunre muy fud n. igion.o a o m n. o. ninino -o n

n. mala ilic no u m e nin luonn o n in.h og. n 7.1. cni s met ri s c-ci innb are that would enuse ignition umler olhil..a n h e ion.

iso, n.

nu ihr

c. in ni honi n.

o the phenomenon of esplosion linuu ll

i. noi ni il" ninim.hh. ode minnnee ai ~. w ( ' s rui cd f rom +~, l o 117 n ovince of this report to give n shorough on wo of. s pin on unihincin-of metrur3 The mole h ui tion of no rocco in mito; this hus tmen dutw el4ewlwir te g.. o l

~7 In ih. 4ha no u nic r n 7.7.s i n he i n w n gn-e-m ilm enme icwent report the phenomenon in desentwa -on.c d.n a.u c amonni hai r innte.hilcieni. lhri-In nigon "an ' under iown, and some of the impoitant con.Inwon n-

n. I hr ihr -o me nunhisons ilo luim o insed io nl. oui t on nulle.

wmistry of hydmgen osidation are pic,cmed nmien of omicory. In eni hon.hos nic "mi ilm rifa i i- &nlwion limits nre.mensm ed in clo*cd s c-. l-ni s ci.u n cly o s ened, unit the econd lunn Lin cini i n 7,6 n ulh me t e n. of incowv. The specihr cihmi-of ilm-c nwi t g m.c., nic .w t_emperaturen junonlly 600* C or ic3,n The e mi n.n i . lun cr if t he partini prem,me-of h do gen niTil ou gen m ihe gs are reasonably long ut such temperniines, m fari. n-3 pointed out later, ignition Ings nn ciferinily mlunic nin onw. nie i ompar ed. inilwr ihn n ilm tot al pns,mn ( hi 2 Figure 25 in a colleenon of curren of esplo+nm Imno n-o ilu hn+.. nryon has no,peedic cifert, heran,c ilm pan nd ~ of h dn. gen uml n o gen toini 87, mdhnwirt, of tuction of taunperatuir and piessure (ref. 37) ('on idei po sin es 3 io salid curve, which in for n at9ichiomet rw h ub ogen-ou gen mei c o ry. Livigen uml cuihon ihoude hoth anince she isture in a spherient venel 7 4 centuncien m ihnmeno pai nal prewm e nt the second inmt, mtoigen, from s7, to 6:,

htly coated with patassium eldoride. Along n uu ncal nnthmeiers of meicory, nnd ny hon dioside, from x5 to 31 ic of constant, temperature there is at lin t no esplo-mo smilimeten, of nwicur3 in vww of the ven nonphrated l>chnuor of esplosum j

hen at some low prenure the tirnt esplouon lioni n inn Imd., leniis ami their senanivn3 to sm fare effects, id the mixture remains explowive with inciendog pos me i n n,w er quesinms on sa fe t y. For esnmple, the q uest ion itil the second limit is reached. Above t he pie,,m c of t he cond limit (which inerenars with incien*me tempcint mei wIwther i i< safe to heni a sinne mntme to a given tempeur .e mixture is nonexplosive and only undeigor-slow s encinm nu r shonhl be accompunwd hv n*siniement of t he pttwm e. g to the pre -ore of the third limit. At all Inghei po.-m e-s cwel <hnencier, uml sm face oniure. Even t hen, a t, nn. l espriinwnini doin wdl be funnd to on-a cr iemixLme nmaim expimave, hhcl3 that uns This eurve reihesents liinits in t he follon me -co-c lldain pe ncimal epm-iions denhog w n h incini i ononnen, and w n h cre taken at a series of tempernturm and. in-inni pic--m c. i he pico-e nus on c mnier. onsnin n uon. The dain m ligme 27, do no nnn e t han,et s cr3 npprosannte boundw along the 1000 onllimeter-of-mercure robni of he'ne 27, .e igention lap would increase mosc nuil moic inpolh n-I e n unsins or n uinm.rs oma nos .e temperature wan deciensed townol tr a, ,l.heu Inu-fer to the time frotn the instant ni whn h mixtm e r m. The comples behu s mr of esplo-mo honu hn-heen n-ed odneed into the hot vem,el unt d the esplo mn o.. m-ho n, c-inhh-h t he. dM ng.of ihe osidonon'of hs do.ern. The w temperature of the linut ihe Ings u onhi go up, cry inpnih roll nu s a not given hne, hoi mas he found m icfnence-m er '. i r t ' i n

7 nod n1 The hnsi, fuci a ihai ilm oudunon icm oon i

om a finite value at. n tempernime just l chum nwchnnnin, unh the hukogen aml feetively nn infinite valne at n t e m pei a n n e in-i mp o ponced, h3 n nu een anun- (H nod i > J nml t he hubos31 I cc onhi ni 1."' O. Since the system is closed, w hai walb hn ppro-r i nt below a critwn! tempn nttn e ihr w.c una .o r'n-d up d >ll a -. h.un nu nn .d diluted w ith pnninct a w nter).luol I bc-c clin b io. i p in i r, mso due to neccleration of the re.o non in ~ lbin mn.. uni ggg gg' - gi g lg I inin branching. Effects of variables on explosion linun..

1. s ph.-o m lu n n -

ll ti a di in 11 pend on the me of t he s ewel nini ilo n.n m c o' ilm 6 4lb t he his in nuliented by the dashed i m ic-m neme . ger the venel, t he* hnu.r the pw--m e of ihe thodlonn ti 11 4 01 11 111 he junction of the tin,t nini,ccond hono r ih-pla.d m gher temperaturca as the veuel is nuole nudici, Tione The i di onin al-ihnt anii the -ninone nw n-ouomi to I" " ' "' """ I"q n een 4 L n od U n dn dein d ol a h n h ie seconddimit curve, vreel me has litIle elfcci if t he iha nn - j ao

n. n. n.

.nmi.wr i7 The i ndiul-Ic.nl dn n ih m ihr .ico i L n luige (.,4 io lo em for t he duin -h"n n 3 N 1 k $ isii i"rh I ii

• i! i II * ' '

n. m ic ( I% k) S kii ni l' i'i 0n ! iil U 8!!l 00 # i' i + inonmyd, npecintl3 nenr the jom inn. o' On in - o i i ,a ag, m o, und hunn. Foi esain ple, ilus p u n n..n o .'o-h .. g... u. m po.,. m m o ; o. u i o, ntimeter fhe k ni ahoot 14M (' d t he o alb.u. mo .I n. r ..,o u.o,

1. 4

\\ ilo .I no e a , i .i nwmin t et ra..oi n n- -o n i ut enn i o ,hb..nic ., t e.1 u o b u.t s - o

3i nur in a s nuo..i.s i. e.u n - s in s eno n.u rn> .>l Tea %Un that hy drogen-oxy gen noslinv-are i a bic.i l n.nipat ed u iih t he ignition lug l#or esciy - p., n i m, ,y n ternperature, uvulion upp n niu, t here hould he a part icola r e s ph.-c.,. hain-breuking ilupown unother check on ihr espoo. nual hon, curw for a given hub oern mnon e, inca os n,. c cuso in ehnin carriers. H O, uinl Oli mu s he de-no3 nt -hap-aint malennl of con-irocinin The cinxe-n n chh,in .ey meet a wn11. This is the reuson for t he cu-n n. c oi .hmomnd m prn-oce. -ponnnn.on--ie m non d;n a .o, -o hrst e.xplosioti limit. It occurs ut powuic- -o hm t ha t, i.'.nal condinon-iconivnl a n nukin,u n di,i a nc. h on. t h. he uverage, a chain carrier striken ihe u nll herm e o ini-iin,n enn u t Thn. ilm rom ribniion-of t he varion-ea--pin -c nitful collision in the gas phase. lion co r. if t he u all a mi -in he c s en non-to t he -poninneou--iganion pn.n.-- are ets rather thun destroys the chain carner. ilm Innii h.n d i. r-inonie, even iln.ngh t he chemiriry o no donin ihr ~ r ed; this explains the dependence on surfnn. nanoe .nne a-n r ni ilm es plo,nin liinii,. kain carriers are alw destroy ed in the gn-pha,e The i n -m.nnui s. cs plo., ion limiis ni e det ernonni b3 t hc h. dunce hanism is probably as follows: h n u cen cinnn.lo cuking und -hinnehmg umi nd iinlependent ofinne 4poninnenus ignition. on the oiber lunnl. n u rute ~ 1"" ' h"' '""X '". nffcen d t o a grea ter or le-cr degin. by H + 0: +.1/

llO?M

.tv. , chu!"" breaking or chain branching, depending on the uppa-m se M is any molecule other than n chum enrner. 11 0;. ru tus, the preunre, and the temperature. e reactive, still can survive long einmgh in reach the ! Theoretical considerations.-The complexity of the chem-where it may be destroyed. The frequency of t hew i-iry of sponinneous ignition hus. led to nitempin to -implify tlw n o wc p i s. The general procedure i< to con.ider the e-body reections increases with increasing prenons I at some critical pressure they overcome the clunn pioi e,- a, a wl ole und to ignore the imliculual aeps of the ] .ching and thereby produce the second explodon honi. r""non nmchum3m: this type of appmuch has recently e the second limit is caused by gnephnw event. it i, hun icvmu ni in reference 04. For t he hydrogen-us3 gen ively insensitive to vessel factors; hot t heir n re,ome reaction one might hepe that the renetion rute conhl be ts when the wall is reflective tonani 110; and renu n-espie-ni in t he f ollowing Arrhenius form: the reaction zone. E .-[Il1101%p( //T) ae mixture again becomes explouve ni t he iloni linm. vio e the pressure *,ir so high thni Ifo; cannoi gei n, t he hefore reneting. It is likely thut the rencinm of lit )~ " l "'" "'" I "" d '" b.m bra-kets denoic molar concenn niion.) .e gas phase is .IL ira,.malde n,-umption is then made thai the iemtion "'""'"b in olnu1mnal t o t he ninenon run" HO + H.

H 0?ll iT 2

'M' 37). This reaction restores the clnno ennier h,-i in

ion (IV), and chain breaking can no longer overnnne I.""" "4 """""' M '""I U Id ' I"' I"U"*I"4 ' "I" U"" '""y be a branching.

o bi n n md. ds brief discussion explaius qualitutis ely the cd-tenn. plunion limits, but is not complete enough to esphiin all /s .letails of the observed effects, panicuhnly of -nrho e I"'"//T" I" k #" b., I ""d""' 'h" is. The arguments may be kununarie.nl by uanne explosion limits arise because of compeution in the gn-11 t he concentranons are converted io moleculn. per unn ut the wall between renetions that innetivate the chain s oinnm h3 means of ilm gain law, t he expected pn.3-ure ers H. O, and OH and those that perpet oaic t he enirmi-denen h;n, mar he found: mereuse their number. j:' jj j -(i+y) In /N-(e-y) In T -Con-t unt il7i - In r seospNcous,1c.u nos lation between spontaneous igniuon and explowon lun. -In the discussion of explosion limits, it is poinied oni IGponion # 17 > h.dds foi u given mist ure. the limit could be obtained from the varia tion of ieninon ILpudions OGs and 07) ure really little mose thun guides ith temperature at constant pressure. This unnhl be n (or handhne -poninneous-ignition dne.n; they show how to unnmrignition experiment. In othm u m d-io ite. -oh-u n h a i ca -m... bh espnimom m. - n -ignition t empera tures lie in th-i c/ >on n.

L

- oocin anc-lin i bei mon na pnn of in : a 2.. n > 1 /r of un cAphsion-limit curve such n- -hou o n, henn c. L..n. n- -h.pc on-tin s ahm /. //: he m c.ihe -h.pc y min..m general, modern work or, sponianconmeninon irmpri a-os emH a. ns aiion energv. Inn ilo value cannoi he rela ' cd (to w hich this review is limited) hun denh u n h i onor

n. ilo wn! i hennstry of t he procem u n hout innio ion-that give short ignition lags. Therefore. it hn heen !.-idn u non.

,ary to use flow tystems cather tlum the aanc. a.,cd Th. pn.cniure just dexribnl i, ninnut aU one c.n. Jo on ms used in the study of explo> ion limits, in w hi, h the ihcowncal gnonni, with most fuels. because the onnhn-non needed to admit mixture to the hot ve-ci heconm-h.ng . hcomt ry i-poorly understood. But hpinigen i-one of e

w w&, l u Jt 1 ,n. o,, 22 - @p nElolrr 13ha-xxitos.u. Anvimony camtrrrEE FOR AEnON.wr1CS % Mk 2h ' thojewfuels for which the chemistry is know n: t her ef ore ihe _.c: 3-2 thcaryjoffspontaneous ignition enn k clabosnted. Thi-i, ed TP EP donalithe following paragraphs, which give new inter preta-in iln.s equati n the terms c (T), k, and k. are all functions of i tionsfof.the effects of temperature, pressure, aml contenini, I '"* P"".a us e. H the temperature is held constant, tho varia-tion on spontaneous-ignition lags of hydrogen. I"E *

• P'"S " *"Y " *V"'"#"'"d' h """

h, 4

Res'ctions((I) to (IV) represent oIdy a imrt of the ioin!

'i"" d ',#"."*" hat case, takes the following form: lion C), m t me'chanism operative at the explosion limiin.' The em face chemistry,jia.left out altogether. But for a homogeneous g g, reictiiniunder' conditions where the walls are uniminulant 7 pi pf % 'i (i. e.7.atsreasonably high pressures), these equations may he sufficient,to'. describe the reaction. Ditterentiation of equation (26) with respect to pressuro ! = 'ThEo'rer?sll reaction rate w is the rate of formation of shows that the curve of 7 against P has either a maxirnum or wat.edMW.f a minimum at, the place whero $jg%y :_, w=d[H O]/dt P. g-I1m t271 g From, reaction (I),- mgn%f V - mq f 09) Differentiation a second time shows that at this value of P the .Mgr. ' d(H O]/di-kdHi][OH) second derivativo is negative. Therefore, the curve of r "3MW Afterf short induction period, the rate of water formation neninst P at constant temperatute should have a maximum. attains;a' steady state, and OH concentration becomes (ref. O'f course, the pressure at which the maximum occurs could 35, not. Le calculated unless the values of the constants were .h ^ , ((OH]- "$ remarks may also be made about the variation of I h(Hlhp},,ph (, ) f ignition lag with temperature at constant pressure. Equa-X, d.'$., i q$hf,M tion (17), derived from the simplified concepts discussed ekuations ('19) and (20) give, first, predicts a linear plot of in y against 1/T with a sloin: Qombining@h. range to show any effec'y taken over too sma 24W3 E/#. (Data are usuall h . d[H,Ol_ i t of tho other temperature-dependent. d8 2E (21) , term in equation (17).) Later in this report it is shown that. f$[h ;y.? w. $r g: $,, t 9 T k.[M) spontaneous-ignition data do co'nform to this simple relation, de $e Examination of equation (25) shows that, in order t!ntt the Jt is nagassumed, as before, that, the iguition lug is inver>cly linear relation. hold,' the second term inside the parentbeses propgrgional to the over-all rate (eq. (18)). The followi": should be'rchitively independent of temperature. Then, relagotua obtamed: a s.

.-:2 -

. hf f 2k, t cc (2S) c (T) 1 .= w .}d . Q 7.c[\\ ' % Since the factor e [T) expresses a chemical rate, it :..ay he hknaI;.M.' ' - 2 3; i the initiation reactions, which are lun[ ped nyuted to vary as up(-E/RT). The observed relation ra then follows. The advantage of this treatment a that it togetheiin'the term i, is fairly well understood (ref, r, fwuws nuention on the reaction whose activation energy is ph42%It 'they are introduced explicitly into the <imple uttuah named inun the plot of in r against 1/T; ihai s. tchema of reactiotis (I) to (IV), the calculatino-herome.verv "".' I"' "h"I "'I"III" ' I"" '"""' I""' " ' " ' h" P" P"#"' i"" "" complicated.; Fog the present purpose it is.uHirient to use clnan-breaking reaction. Physically, it is logical that tlas thejessure. dependence of'the rate of. initiation. and t hl is kng from explosion limit work to be at least as girat as Angkl be so in a spontaneous-ignition process. F mally, the expected dependence of,igmuon lug on hy dru-ded Therefore, it is asumed that gen concentration may be discussed. The approumate rela-sego.nd oi,p.,(ref. 3", p. 37). r iacPs 1 tion (eq. (28)) is used. Since c (T)is related to the chemical 4 WW raie exprmion for the ehnin-iniiia' tion proces. c/ Ti dep. oA ' M h h-i=c (TjP2 J m%pe not only on temperature but also on concentranon. th.ce ! a.:ain, the depemience cannot be stated explicitly heranse whe(e c (T) is a propor'.ionality consnua desemb ui on f tempgature.; The cone'entration [M], which refer-to any I ihe complete chemical mechanism has not been used. Ilow- ' eser, c.splosion' limit studies show that the raie of iniiinnon of 3 e:mlalecules of tlni mixture, is directly pnipm tional to h , thig ure and inversely proportional to the temperature: l increases strongly with increasin and depends hardly at all on oxygen concentration (ref. 37, Q,,Ma. p Q. [M]=c y (21)

p. 40). In fact, oxygen seems to be simply un inert diluem as s

&y bMP, far as chain initiation is concerned. Therefore, ignition log-WhenMuations (23) and (24) are combined with equation should decrease sharply with increading hydrogen concentra.. (22); the following expression is obtained: tion. age-. ,,.--,y_.,,--,_e w,y --e.s4

[(- SM', ,x SURVEY 01 !!YDmn.I'N t.nMDL'STION l*l OPERTIES ')'j i he Inain conclusions of the e'Xtended trentincut of pon. l g 4,gg gg,, g y,m, f,c n,,,,gn n,y 5 'ouS igidtlon of hydrogen hubed on real lenetion linvin* I ~' CN"" O *'0" 0"" C000"9 '""9% . be summarized as follows: ncostmc.ne ni con iant ._ _ o ic. on o.r, eo e6

6),

t,n,,,,1,,n to'

) The curve of Igmtton Ing agam, st prenun:

34 me,m to N ne 4 6 _ peraturo should show a maximum. ' To

• ) The observed linear dependence of la r on 1. T -how n s i q.".e,*"y'n if,

[ Ng the chain-initiation process is dominant in upontancon-tb Sod'um 69 ~ tion experiments. Activation cuegies derived hum,nch -- c stacniomac hn onygen) crsonae o sio,cn,ome,,c 93 soa.um 69 -~i 4 apply to the initiation process.

• 'Y9'")

20.000- .) Ignidon lags should decrease sharply with iiwreaWng { ~ iogen concentration and should show thtic, if any, gggg w

/,_'

-ndence on orygen concentratmn. coco,- ,urces of spontaneous ignition data.-The subject of the ooo, - -- - - i f .taneous ignition of hydrogen is a very old one. but much cr i UUU'~ se earlier work is only qualitative. The following puru- { ~ g=yr a __'. j .he consider the more recent work contained in references moo: to 68. Despite the extensive work on spontaneous //," ion, even the data from recent sources are strongly 4oop r,' ndent on apparatus. Therefore, data for a particular I t - f-, l T ication are best chosen from work done in a manner that E. 2oo 7 .nbleo the practical situation in' question. For this reason I g og; i eneral features of the experiments reported in references 5 [gm-i 68 are described here. } ,y

e cferences 65 and 66 report studies at hnver temperature

--p l fong ignition lags (0.1 to 10 sec), The delays were ihere. 2a mecoured direc,tly and re,fer to the time from the inanni i ,g _ ixing of hot st.rsams of hydrogen and oxidant to the in-9"- T E.E C t at, which flame appeared. References 67 nod weover 7' -/-- ~ taneous ignition temperatures high enough to give igni- '/ / delsys in the millisecond range. In these ruwe stable 2-o fronts were formed in the ducts, and the hip ucie cul-j / ed from th' known average flow velocity nod the dis. 42o 99c76 9$o~960 do~, 640 8;O s i from a zero-reaction point. to the fluse. The high

• "D"*"""*'""'*

ianeous ignit. ion temperatures are prohnbly not ihe only f"#"E 20.-Eticct of epontaneoushnition ternperature on henition of the short lugs reported in references 67 und 68; the l** nce of the flame may also have had an effect. j her sources of discrepanc'y are the degree of mixine and &conUng m equation (16) or (17), over-nll uctivatmn inethod of heating. In the work of reference d the enedes inne he nunpugd frmn the idoin+ of dose hnet ogen was injected into an airstream hen ted (und vitinted, , Valuco are H,,ted on ugure 26; dny runge Inun M m e Wo. ""I"rb pn in le. The niemjed theory pois netkudon enngies an' wn nH values for du,ns out that the reburning upstream. In the work of icference 65 the and air were hented separatelvi aml no special elfon clunn-noinuson nade to produce rapid mixing. 'In reference 66 ilm gn-e-I"'""""., The wide sprend pnihably menns ibat unrecog nved heated separately and rapidly mixed..\\nd in the wor k i ninoinn nial nuiuldes nHccied the nsnhs. 1 or esnmple, ference 68 a premised strealp was heated to a static J "'" U"I"'" ""' i"' "W "' kE""' W I""" " "'E "I V"" i crature below tb iiponta'neous-ignition t empet ui m e " '"I b"* N "" "* "'" h. I"I "" I""""""'"'"' "h"">pkne such duia in;.""unl same range ai, thow hen passed into a diffuser, where the increase in 3,tutw in -rature and pressure caused reaction to start. The '""n of du espannents in %, wing s3 stans. How an, t he enetion point in this case was arbitrarily cho4en na the P"'""" "I ". surface effect ni dn,s want bnh or suhum , g; ome inte iontme) how that 3u h clbrh nm3 nr3 wcH be '"'""?""'"' ret of temperature.-It hua ulready heen pointed "M " ""N nuple theory anticipales u lincur relatom heiween ito J.pp.r.>io n, "* { ""l"#'*'" thm of Ihe igtutum hig and the recept oral of 1in 1 menus ignition temperature. Figure 20 ouhen nom .a I U nhows that this relation does hold for duin of t uo { 3 4 .h 2 entore...nd a i+ ut mned tu hohl im ih. iho n ol....,. m i 4 nb well. Tids ihonir relation nl o sei rophn.e. 'i, 11.0, - -. f l.t ) E,0: t\\ly & n e

• w.-i uno m e n e with m. m,.0,od-t 'r e arl a

4.,rden..s n w,..d u,'.

y; g

gg, g igg

-]

t M ltEPonT land-NNiloN.sl. a us t onY coMMi r El; D>tt AEltON At"flW l00C ~ ~C ' _ l 8C- -- cc. 1 600 j h,- K..- j;i 40__ __y j i, p r -- g sponiceous, s 40C

l.,,'l' I

I. I '9""*" 600 I >(..._..._. i temper ciur e. l i l'il \\ l

• C I

20C N 2Cr - --t j t --. l l i ! '. \\ l \\ I I i l 1 l Ilt;]-- - \\ i i 4 I N i 80 - -- - -- \\ " ! - et- -t -- loc t .- -+ ii s to j y e/ -4 v I I \\ g 7C f ! *--- - - ~ .f. 6 I I Spontonews. Refv- ] g l _, l '9"'"" 1 I I T. 4C .e E 658 68 5 ' l l MC., t ernperoture' 4$, fi

• C m

t-- s l 649 66

l

- 20 i 3 i 3 I l a,p .+ { l l l N IC -- - 7, 7' N sycoj IL '.g' i '. _. _ _... 3 8 K ~ I\\ -, :' t - - ~ ~ - - 8: 6 i

x 6{

j x 4 [ -y i\\! { lI i i l l l l\\ ' - 4-r j l i 2 l l ~ ~ - - - - - - - - - - - - -. 3 'it 750 . l1l: ^d t ~~l 3 .4 6 .7 8 S {l I Pressure, /l orm il i 2 4 6 s

20.. _ _ 40. 60

? Hydrogen in car, percent by v6:wme l o.t ML h 4-P.dect of premuro on ignition lag of h.s drogen.uar nihtures tref. 07). Facenc 2*.-Effect of hydrogen concentration ou nonnon 1.ur ai atmospheric pre ure-in oNygen content, frota about 13 to 20 percent beennae of ihe Therefore, wall effects may affect the oh,crved io In nio n wide range of hydrogeii concentrations eovered. The data energy if they net to inhibit,one or inore of iire pn.cr.In.e l wonhi he expected.to deviate from a straiglu line if there very strotW effect of osygen concentruiion. (nher reactions. This is a subject that inn not bei n denh u n b m w eie n es nience comes from Dixon% esperiments tref. 6M, in w hn h spontaneous. ignition work, I h.s drogen was injected' into both air aml usygen nod the Effect of fuel concentration.-It w.e. concimled hom the theoretical considerations that ignition lag -honhi deco.nc .h,tlei ences in t he sponinncons-ignition tempeinon e w ei r with inerensing hydrogen concentrutn.n hni -In.nbl he unar onh P to r>* C for a 0.3.-ecoml ignition Ing lloih ci, er independent of oxygen concentranon..\\l olh os knun! no dann theiefore confirm the piedichun that ignun:n Ing -hould variation with ovEr-all fuel-hir rutio for carbon monosuh or I he independent of os\\ gen concenu ation. l methane und implicitly assumed timt tin, ie-nli hohl-f or Effect of pressure. -lbu h 1)isob oef. c.Jo und Slotho, very lean udstures of nuy fuel (ief. 07 h that in the tw o es. I tref. 67) sunlied the.ulfect of pres <nte on spontancon-igni- ' tion. $1nllins' data are plotted in figme 2N the em s es of periments in which hydrogen conevntranon was a-t ually l ieninon Ine neninsi preunre ni esupinnt poninneon-.ieniiinn known und w n4 varied, a -trong h3d n.e n, on.. n n ai e,n 2 ' '"P' ' "' U N' h a e nia s on oia-Thm. i r, - u 0iL prinlence wo* lound. Dnta ol n h n n.. .a..n o..- ' " ' ' " ' " " ""'" led t hroi s ni -po i.o s o o Shawn in figure 27 Ilot h esperno. m-lo.a. o, 1... ' a.. ignition Iny decit'ases WitIl iln M asn y,' hi ih.c. i.u n

I"

" ' I I " ' ' l "' " ' E-i a. I ""'I"3""'""""""'" "'""'P" "d ii.m over the range evvered. Ilow.'.: o, n l !.. noo a inri her den enses in p r e--n o i n o-c ihe n. .o.n..-. the dependence and the orders of nmeoiin.h of an I m.s I b s..n unted similar hcha s.n.i foi ino-inni o -..on.1 r;in. use entirely dilhtent m t hi two n, . i- '4 a a n. < oo o n on i n-o i n.n in,y, hat 6, a pi c- .o b c o-pin r e. t h" -ni s i o f - ;. "' o n - tm on'o. ame pont uncon41gmuon b :np i.o u: e - r. t Ti ce b,ive '.ce- .u.T - i o -n' 4 -u' 'h 'ha e. m n'n' 'n o i .( r l'- .i I i T o ' ' - n 3,.,,, .., c i-4 I ' 3 6

4 p a til'RVEY OF HYlsnOGEN s 'h tilit.w i juN PKU eEltTIE6

• ],*

romoting effect, of reduced prenure to begin. Fnriher-T[,)?"'d"!flPI"5"? ynenching d6taneca: the spontaneous-ignition temperu t ures ut w hich cm Rencoon rute i found 0.5-second lugs were in the range where Stolli"" i lugs of a few milliseconds, so again there was the k,mi h condsined with a tln.rmd burning. velocity equation i i i crepancy noted in figure 27, 13nrning velocity ec 3 (Henetion rnie)fl'runsport property} SAFEM CONalDERATioNo Q0) view of the many factors that affect ignition Ings und '"4"" aneous ignition temperatures and the wide discirp. U "'"I"E d """.Y ccRenetion rato al) T Quendung distance . in the results obtained, it is not powible to sinie itely safo limits of temperature and souking time for ' from thin approach, it was calculated (ref. 71) that the aver-2. . gen mixtures. However, it seems significant that the age renetion rate in a stoichiometric hydrogen air flame is large differences are found when one compares ex-um moles per liter per second. The average rates for hydro-e eats wit.h and without a stabilized flame, In both enrbnu fuels are very much lower. The,yalues reported in 5 20 and 27 the lags fotmd by Afullins und by Fonre icference 71 for propane-air and isooetane-air mixt ures are a flame present throughout the test.(refs. 67 und 08, 1.n4 and 0.24 moles per liter per second, respectively. tively) are in the millisecond range; those of all other rs were obtained from systems in which a llame wu l l l fl l[ dtially present and are about two orders of magnitude i i i 'fo",," mene.ng i r. Considering all the data, it is likely that, in the .t 2 somg ce of a flame, hydrogen-air mixtures at 1 atmosphere, veioca y. groo.ent amonce. l j flowing or static, may be held at temperatures up to 4

1. 9

( vi i 3 for at least I second. 26 54 i A l l 4.o o 10 g4 37 recent'. work at the Bureau of blines, minimum f I o 27 27 l meous-ilmition tem,pgIgtures _ _were measured for -r i gen-air mixtures d_iluted wit) wat.cr-_ vapor (ref. 70L -j 3~e - - - ; ihnmum spontaneousagmtmn temperut ure is the lowest y o[ j -rature at which'a mixture willignite in u closed upparn-f - -- - m i r en if allowed to soak for a very long time, and is there-I l /' I l l l I " _ ~ ~ ie came as an explosion limit temperature. R eference jf i j i orts minimum spontaneous-ignition temperatnre. from - g ' (no water. vapor) to 580'_.C (30 percent water vapor) % [o i I i s4 -~ ressure of 7.8 atmospheres... Other tests show ed ibni

1... 7 a o.

^ i .re has ittle effect hulm interval from 1 to 10 atmo*. !' &2 [ l .- n thTbasis of these and other data, refepute in t i mends that anyjeqnperature above 5Jy f he con 21 " 2.8 3.o 3.2 3.4 3.6 3.0 I a potential spordatgousygnition hntard for hmg d,'f y %# 1 g tunes at pressures nyar,.atupuhgrie. At low pre - with celtain sErfads, ignitimi'enn occur at tempein-as low as 340' C (fig. 25). ~f"" '" 2' Arl"""" he'" e"n"r""" """ I"da"" en for n.ohourn-RELATIONS AMONG COMBUSTION PitOPEstTit.s The very high reaction rath is the basic rea on for the combustion properties of hydrogen huse been di,- ""t""di,ng sigor of hydrogen liainen compnied w ith linnn.s "I h drornrhon ruels. Fh:me temperat ure-ure not much more or less individually, und the duin an. s alunide m 3 Wih1cnt. no thune temperatore ia not the driving force of the elves. However, there are also inierrelnimn+ nmong ; I of the properties Ihat should he pointed out.

Tin, la drohen renetion. Ily.lrogen in osidized by a free-radient inneo of these relations is twofold. Fn i,the3 muy

' h"i" '"echani-m. nini the snme i pn.hnhiy irne for hydro-d to estimate voids in the data on one pioperty fiom i r"8 hons at or near flame temperatures. It is <piite po-sible l ro,at the netivation energies of the individuni steps of the ih ble data on another. Second, there are rehaion, noion mechoni-m nre c.unpornble in both en** Ilow-burning velocity and <pienching dMum, f, o n, n chemical rate, in themes nmy bc. - n n.. n.. Th. J+ 'h~ n -h"" a o m.1 " n o f.n on - n H "I" ' oh el-u n n :le pidy ai nic o hy don ni n% ire significant in catuhlishing the volonwu n i.m.c-for combustion. ". d i l a - m m h n-lo -low ci ihan ihr .on.. - l 4 P ! 4 ". l' iMi h'n-u ilb lbe -iluple d[nlof hlr hi dlogen npd.. rt.A%1i k!;4cTio% k AT);n ihustioit properties in general depend in,t b on. hen.wel ' on, i s en d act n uiion i"ictgles ute witudur for ihe i n o ca-e4 1nd on t ransport p rove <-es. Pere di-f lo" 80ieht,pcenInte. t h erefo re, ihn hvdioven horn, -o j hew can, hower r. 'm 4.unbim d to gis..,pn ig u i., h.a - O D' r n m.e n i-n sesy -nnpn tuoict nie. ordy.m one or the w h.. '"in m * 'o n. -o.h ' na s now t wrra. > ou s wi ni s o s n.:

• e ; e..,d k s elocity gradu nt, bur ning v decity, and quench.

-l f heinb.1 ..d.e a gn'c. 4 %" r. 'n ,s, i , A,., ;.. y,.ren n. ,,r:n,, g r;.,, L 3 l ' a

r .M ILEPORT 13h3 NArlONAL AD\\ inolti CONIN!t'l TEE FOR AERONAt' TICS riste. Reference 72 extends this concept und hou ihat the usual experinnental error >. Results that depart w idely reaction rate in question is not compheuied by t he cil'ceis of f rom the correlation should he suspected; 3nch a departure transport procenes und that the folhming sciation hohb. for might result, for example, if burning velocity were measured flames of a given chemical family: ut low pressure without proper care to prevent, quenetting ef fect s. p2; Burning velocity and quenching di::tance.-Refe ence 71 yffney' points out that the product of burning velocity and quenching It had previously been shown tref. 711 thni hornine velocity, distance should be proportional to a transport propert y, quenching distance, and reaction rate are related a-follow s, inunely the apparent t'iermal conductivity (see eqs. (210 und (30)), for chemicall, simihir systems such na various : as implied by equation (31): h vdrocarbon-oxygen-nitrogen mixtures. I rom the defini

• l tion of apparent, thermal conductivity given in reference 71 l h, *

,.nn 5e5 it was predicted that the following relation shouhl hohl for: j 'uch systems: When equations (32) and (33) are combined, the folknung Ud,x[,T_, 3, is obtained: t P z(Ut 'm us) gie ye It was found that equation (35) holds very well for hydrocarbon-oxygen-nit rog'en thunes. But attempts to u pply Figure 29 is alogarithmic plot based on equation (34 ) for data nt Wwa Han3es , bnause no unount on hydrogen-air mixtures at 25 C and various presures. pa a ta n f udargecdnis I hydmgen concentration on ) Two sets of recent atmospherie-pressure burning-velvcitv the transport process. It was found empirically that the i data. (refs.10 and 26) were used t.o show the spread thas f 11 wing m dified relation fits the data fairly well: may be expected (in spite of wigh t he correlution is definite,. T,T, n, The line as drawn has a slope of 1.03 rather than 1.tr,s us U'

• 1-n,f.

predicted by equation (34). _ P Figure 29 may be used to estimate data on one of the properties ir[voh'ed if'the other tw o propertier. are know n. N""lleMPL IS """I" I"'re to justify equation (36) on theoreti- ! Aside from this practical purpose, the plot i3 valuable becan-e calgi unds. Figure 30 is a logarithmic plot made according l it shows that the theoretical ideus icinhng to c.iuanon a4, j ~~ [ ~ [ l f f [ ' ' '~~ ue probably correct; the same basic chemistry i4 mvolved l [ i i i / j a S~ in flashback, flame propagation, and flame quencinne. l . E I i i/ I The consistency shown when the results of varion., uniLen. are plotted in the form of figure 29 indie'ates t hat '.he du ta.u c ! .h? +!. ! 4 'o /o 1 I basically correct, even though there is some spread hom ihe j ] i t! p l l l / 'l l /! oI l' l 1rt. l i l l a.m,l.. p. 'ndo.c. i a,+ m. / cim vono,, . 9 C e cnm;

iwrc, i

l l. l / l l s 2--j ij l j oistance c, .eicca. 4 i o 10 0.50 to 4 CC 37 i t h'I. o !I f. I ' J ? 3e 03 o0.5 2.00 1 -~- l l l l,l t-l ll a m.i i, + 1 -

• 10 0 i

i., '

o i t ii } l . l e 8Qi ~7---__.. O/- ---+~t----- - - +, + t-4 c. ~' ' ~ ~ ' ' " ~ u. 60I-- - 1 4- + i 4 J I* n 8~ t...._ -i - % j.. _ -{~p-- p-- g i y' 14 ~- i } y, j. j. ! l l, D -4 a -w _ _. ~,.. _. _. _., r-- m-I i +- -- -- ? C6m 40 -*-~t i o -h h -.___ !- __. I f I' l' iI l j H i i { l l i g--- ll,l, I l l i ! j 'o, l ll f l } f 04 -- yl m7 3 ,(

j j777 q 1

i E, o I

/

20 f ( /,i --- / ,1 j h l -:o. -" N wa

e w -

0 } w c, a W:mg 7 + I 7 .g. 10[ / 3*:% # '  % -' 4 ~ ' ' i o iO O S 'o 4 0 37 I SNN kh 37 i ! l -~ 3g t ,la 12405 2 ',I' --- l - b 2 6 L-60 20 40, 60. 80 iOO -c l gi ij i l u ij i, ; / d / npj .04 06 08 4 .i 4 6 i I Cvence; c stance, eg, :m ( p / W g, f Ficcaz 30.-Itrlation lxtween prodort of inn u Lu a.h m e - mi i ro.r u 31.-itelation bem een park ieninon ra re.s and qu.w hir.g burning velocity and transport paranieter.- of hpir... n ur o.nt:n.- i di-t ance (betw een parallel plate-i for hpiroerreair nmtur..

_ ~ _ - - j: i srnn y or ummmt:x t o.untwitox rnorrnTiss W iuation-(36) for various hydrogen-air mi.u me, ni re-numbers tref. N. liow ever, a complete flushbuch em te i. I and atmospheric pressures. Except for ilo ce poini-i n adalde. With the uid of the relations just des eloped, it i-equivalence ratio of 0.5 and pressures in,m n.2 io n. ! ihiwfore powible to estimate a coinplete blowoff curve, it 4phere, thero is little scatter. The chief use of figme :m ! -honhl he noted that the curve will apply only when Reynolds finding tho effect of initial mixture tempesaiore monber is high enough to give a fully turbulent shear layer on hing distance. This effect can be found by u-e on het ween the wee and the free stream Wr>109 ible data that show the effect of temperat ure on'hnrnne.- Since the proportionality constant in equation (41) is nukuunn. the following procedure is used: s t y. 6rk ignition energy and quenching distance.-l.cn o. and (1i From equation (40), a characieristic time t,

• is com-

~ Blbs first... pointed out that spark ignition energy nnd poicd for a given mixture for which the blowoff velocity hing distance yield a correlation line when plotted from a rod of a particular diameter has been measured. ithmically (ref. 37, p. 415). Figure 31 shows Such n (2) From equation (41), the following relation may then for hydrogen air mixtures at reduced and ainnispieric he expected to hold for other mixtures: ares.Urha line shown is a segment of a genend cor-on thati fita' data on many fuel-oxidant combinations (*"p.g g ag y,g"C o a range of four orders of magnitude in ignition energy. heoretical basis for the correlation is not wellimderst ood. Equations (40) and (42) are combined to give,the following shback7 velocity gradient and blowoff from flame, result: rsl-Studies by Zukoski and Alarble (refs. 73 and 74) b' 5.5 N,d!",jQ) (43, _ = (t* N.d!"h .dy indicate that the mechanism of flamehohling on VD bodies l depends on ignition time, provided that th" For hydrogeu-air flames at I atmosphere, the normuliza-region between the free stream and the flamehohler tion poiIt for computing t.* was chosen at p=0.6, D=0.254 is fully turbulent. The length of the wake in c%en-

,ich, and U. =5000 feet per second (ref. 58). The flashback independent of stream velocity; for cylindrical rod data are from reference 54 (see fig.19). The estimated holders,ithe data of reference 74 indicate that the blowolf curve is shown in figure 32. For comparison, the ing relation holds for a wide range of flow velocitice sanu procedure was followed for methane-air flames, using b;p".

fla3hhack data from reference 75 and blowoff data from -Constant = 5.5 w? > yD reference. 3. i - L and D sire in inches. The ignition time availuhic N!e 32 shows that the maximum predicted value of gases flowing alohg the shear region is C'M I"r hydrogen-air flames is mbre than an order of magnitude greater than that for methane-air flames. Tlus 8"1/U is -imdar to the result.of DcZuhuy, who fouml that the max. Uis in inches per second. If f is equal to or les, ihan imum value of flG coerefuting parameter for blowoff of racteristic value for the given mixture, blowulf will hydrogen-air flames at reduced pressure was 1I times greater because the gas cannot ignite and form a propagating than that for propane-air flan.es (ref. 57). Stability is ex.

then, equation (38) becomes

in.eied to remain high even in very rich mixtures. The few data points available ugree with the enlculated curves av 1 g % L4," ,4 3m a well us conhl be expectede.m view of the many upproximu-ining equations (37) and (39) yichis, for cyhndnenf. l 'tnin* involved. Aloreover, some of the points uetually ameholders, i 2a go-u_ J s, a,og e a.a L. = 5.5 - un. ,c w c. - = :. -. n --. ; _ - goo ition along the flameholder wake is know n to occur ni , a 4000 .,.Z.!L (.. _T:. Z T ~ ~~...__. : - perr ture close to flime tempe'rature Iref, 7-l).. Th ere. -'I ~ - - -

• 'is" '

t is reasonable to suppose that the procc-- one.d M - ~ --- ~ o r g .tg ~l-meous ignition at high temperature. It is nemned in l , cco_'. ; 2__ e _, _r;, _,_ __ riier discussion of spontaneous ignition that the ignit ion l 'q. .c _--__-t = ._I = '_ _, ._. f = inversely proportionn! to the renetion rate nod in .I the high temperature ut which iennno. .a. m- ^ I question may be taken as the average rnte of o.. 2 +n / ~ ~ ~ ~ + }89C '-- ' M r -_... .. m c. It has already heen pointed out that tL hwd t 4 q y gradient depends on average thane reni inn. r..o ~ o. umer shown by equation (32). Thus. it follow ihat E ~~--'~~~~_A-j J L"Z I i 8 le 20 26 32 '. B 4A a. ~...i.-......., .n the blowolf of hydrogen air fiume, fnno cybinh o ai-nm or.., rnsiemmi dau. meh um.d run e e 3, .,,, 32 .a. mehnhlers at utmo-pherie pre %ure hus e been ol noned .a ,u,s n, %.u nu L,iasm ut racrence. si und :. O tuntra at r lenn mixturea utid at low nnd interun At. Ibs S- .Y! .j

){ [ REPoltT 13%3 N s IlisN \\L \\b\\ IN SHY CoM Alf rTEE Fult AEltONAt TIC 6 = apply'to conditions where the sheur lu,s er ina s not he Inljy v I rinimmn Ita s mond. The yuencione of 1.an. mar op hulrocci. Third s nrimn on conihn-omn turbulent, and these points of cour.,e m.ol,I noi he e s p,+ i c,1 3 """- by shd surfaw-o to lie 00 tho curve. ( o. (llaitimoreb 19 89, pp.110- 120. According to equations (32) and (33), the I,lon off eun c Penn. John U. I.ean InHanim hdity Umit and Mininium spark could have been calculated equally well hr u-e of II J m kuinon Energy. Ind. and Eng. Chem., vul. 43, nu. 12, Dec. place of g ji'* The choice of y,. was arbits ary. n51. pp. 2865-2scs. "- 3"ru a-cr, llennan, and Pea e, Itubert N.: Burning Velvenic of j The effects of pressure on blowolf couhl be e-iinnue.l. d. m addition to present knowledge, the varintion of u nLe leem h ".'d'""""~^" ""'" " # ""' ^ "" 'h""' 8"" " 7 7 ' ""' 22 ' .Nuv. 20,1955, pp. 5500-5hos. ot.h pressure were known. Work is needed to est nbli.-h t h"

11. Banbulung.,

E. Die Flamun uge-chu indigkeit is t mion ar Eects of pressure on the flameholder wake. brennendeu Flammen. Die Naturninen chaf te,, Jahrg. 23, -) A final comment about the calculated blowoff curve: Tin. Ilef t 6,1919, pp.171-175: 200-213. 2 "rTects of compressibility are not really known, From tin.

12. Dise, Itudolf: Studies on Burner Flames of flydrogen-Oxygen uurn at Hip Pn-nret ch.

ep. 52-59, Wght Hr. 2 vork of reference 74, equation (37) n; pears to hold up lo Lab., WADC, Apr.1952. free-stream Mach numbers of about 0.7. Ilowever, th"

13. Lune, II. !!.. and sherman. G. W:; Flame Temperature-of peak value of U../VD in figure 32 implies ilnti the blowolf combu,ubio Ga.,-Oxygen Miunre!. Ind und Eng. Chem., u,1.

velocity would be sonic (1640 ft/,sec) for a llamelmkles only 25, no. 4, A pr.1933, pp. 401-409. tbout,0.01 inch in diameter. It is not clear how the present I h H.irne, John F.: The Inituence of Atmospheric Oxygen un Bunaen amn unh Synphnn UnternadonaD on Combusuun,The analysis might be modilled under such comlitions. n.iuiama & Wilkins Co. (Daltimore),1953, pp. 345-348 iUMMARY OF RECOMMENDED VALUES OF COMiiUSTION n Michelson, W. Ueber die normale Entrundung>geschwmdigkeit PROPERTIES nplosiver Ga8gemische. Ann. der Phys. und Chem., Bd. 37, 1889, pp.1-24. Table V presents a summary of recommended values of

16. Ebbelohde, L.,

und irofoa%, M.: Ober die En t zondun gsge. the various combustion properties of hydrogen-air mixtures. .cha indigkeit im Inneukegel der Umn.entiamme. Jour. Gasbel., The values listed are for standard conditions, a inesuR of Jahrg. 54 Nr. 5L Dec. 2W 1913, pp.1225-1232; 1253-1262.

17. Rheluhde,1,, und Kwuiker, E Zur Keuntnis des Innenkegels I atmosphere, and an initial temperature of about 25* C.

der flunsenflamme. Jour. Gubel., Jahrg. 59,1916, pp. 49-57; Wherever possib!c, data are given for both Ihe stoichiometric c5-6182* 98-10L mixture and the mixture showing the maximum (or minimuno n nonie, K., und sieding A.. Cher den Einflue, der Warmeein-t ruhl-veJue. The form of the pressure and temperature depcml. nog auf die Entrundung ge<hwmdigkeit der Ga,.e. Ga4 u.

nce is stated, if known. Since some of the munber-me Warf ach, Bd. 71,1928. pp. 673-677; 701-705, 731-734.

und M &McM t, Waher: We h undung ue-tverages or involve the judgment of the autlnus, referetu c-chu mdigken s ou b,a genn chen. Gas u. Wawerfach, !!d.,,3, .tre omitted from (able 1,. l p,;m, pp. 837-S42 871 878 9 0-890. U Curugha, John: New Method for Deiermining igninun Yelocit V of f.sEwls Fucar Paorchston LAIJoH atony ^ # ""d ""d U " "'" A '" "" ^ "*' M "" ' h I L V"' XIII' NArtonAL Anvlsorty Couulrrts ron 'Arnos At Tic.- nu.10, Det.1931, pp. 437-442. CLzvstAno, Oulo, Aprst Ri,1957

21. o,a hn, G,eorg: Der Zundsurgang m G.egemi <; hen.

Verlag it. Okinbourg, Munchen und lierlin,1934. REFERENCES

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735. Fourth Symposium (International) on Combustion, The Wil-

1. 12, Bernard, and von Elbe, Guenther: Combu tion, Flame amt ham. & Wilkma Co. (llaltimore),1953, pp. 75G-7G4; discunion Explosions of Games. Academic Press, Inc.,19?> l.

l by 10. A. DeZubay, p. 764. ' otter, A. E., Jr., and Berlad, A. L.: The Effect of Fuel Ts oc and i Sw Zukueki, Edward Edom: Fiame Stabilintion on Blutt Bodie. at Pressure on Flame Quenching. Sixth 8yinpu-ima ilournanm.ah l !.u u and Intermediate lleynolds Numbers. Hep. 20-75, Jet on Combustion,*Reinhold Pub. Corp,1957, pp. 27-3l.. Prop 1.ab, C. I. T., June 30, 1954. (Contract D A-04-495-krlad, Abraham L.: Flame Quenching by a Variabh-u idth Itn-OltD-18J tangular-Slot Burner as a Function of I're"o re fur Va rion - ; 54 Longueu, J. P. Flame Stahdization by Bluff Budies and Turbu-Propane-Oxygen-Nitrogen Mixt ures. NACA HM l.53 N 3n. i h nt Flames in Ducts. Fourth Sympu ium (laternationah on 1954. (See also Jour. Phys. Chem., vol. 55. nu.11, Nov.1954, l Combustwn, The WiUiams & WilkinwCo. (Baltimore),1953, pp. pp.1023-1026.) 90-97; discussion by E. A. DeZubay, p. 97. telles, Frank E., and Berlad, A. L.: Chain Breaking and liranciong l na Evans, Marjorie W., Gisen, Frank L, and Itiche-on, WiHiam E., in the Active-Particle Ddfusion Concept of Quunelung. NKA J r.: Lifects uf.Attennaung Malerials on DAunation Inducouu TN 3409,1955. Distances. Jour. Appl. Phys., vol. 2G, no. 9,.N pt.1955, pp. riedman, Raymond, and Johnston, W. C.: The %)l-yuem hme 1111-1113. of Laminar Flames as a Function of Pre,oure, Temperninre, and til la m, M. P Sur la propagation de l'onde explo,ive. Cornpt e. Air-Fuel Ratio. Jour. Appl. Phys., vol. 21, nu. x. Ane 1944' b ndus N. IE.n24, pp.1391-1390. pp.791-795. "2 U"' '"' C ^" 3'"I M*h,"""h* W. O Inhenn. of h nual Pn7 gerton, A. C., Everet t, A. J., and Muure, N P. M i..n r. d '" U"""""T* I" C"" d '" ' " h '" U " *"" UAh 4.'"*11, A nh.",""'"I ns Tech, Ma r. W5L AfetrJs as Flame Trapn. Fourtl 9mpo nnu iInionamn.a io. n+ Combustion, The Williams k Wi'km. Co. i hah nnon - tou pp 689-495. "1 H ""l" l u oud, C N, and Wilham>on, A. T.: The Iteat uun Be-i uwr.rd, H. T., and Jone*, G. W. Limit, of F!a n.noihihi s of i.e. 1" e"" IIMh"cen and oxyged. Clarendon Preu (Osford).1934f and Vapors. Bull. 503, Bur. Mine*,1952. ni br. 9,it.3: Thermal luintkin, with Particular iteference in gerton, Alfred C.: Limits of Inflananabihm Funnh s om in l heh Ti mpend on.. eclected Cumbu tion Prohh m-Vol.11. (Internatianah on Combu, tion, The % dhain. a uAe i hio n ru nn ht.' ei. Pnh. i t.unduni,195r., pp.115-133 (Baltimore),1953, p%4-13. n.. t w..rd. If F. Ignition Temperatures of Ga-e. "Com ent ne chite, Albert Greville: Limits fur the pi nna eai r o fI. T, d,, l.sp.rnneni-uf o h.. laici llarvid.ltades I mu n. Jour. Intlammable Gas-Air Mixtuna. Ill-The 1.sf. ri v: '! ' i-c ln in. 30e. (l.undun,, pt. II, J ul - Det,193 4, pp.1382-i ino. 3 tura on'the Limits. Jour. Chem. Soc. Tran- ' l.o od"m ' "I u,,g m,,n,n, l.1, Bruka n, itl R, and Butler, J. N.: 1.tf ee t of Con-n, CXXVII, pt 1,1925, pp. tJ2-684. j y,.,aruios, un Igninon Delap for Vanous Fuel-Osygen-Narugen .urgoyne, J. H., and Williams-Leir, G.: The Inibwin. "I hu om-s o s,,y,. .,, n,.v;,,,.d Tem p< rn t uraa. L' A C A T N aW 1"*4. I,u tibic Vapour, on t he I.mnt-of lot!.m.ma' u" g, j, g,,,g, g. ,i j i apour. m Au. Proc. Ituy. ovi h i ,,,g g,,,, gg _; g,. g, q .hdy 2h IM. pp 525-#i9 g,, g g ,g,,n ,,, g t h~, Frank E., Non,n. Durut h s M. .n / % i g, ,g ggggg yw g,,, g, t *re--ure Linui, of Pla no Pn,paea a. n of No - Int!nence of Wall Quenehmg. Inu a.m L-- i "" 4 " " ' " " ' " ' ' 'I"""'" '"'d'" no. 5, May 1954, nn.1010-1013 D'" nst, W C. and Po e A. Th P. m ' ' " P', t 1", gen-09 gen \\liuures Tre 1

• "I-

' U ' """ hi 1 -a, + m. c' lue .o .ii '934,pp 2g3-293. ( . i 1.., i h \\1 b of I d .M G3 J - r'., J r g. s,., n n e i i' h t. p.12.s * 'W ~.

_ -. _ ~. _ ary a f,A. 50 % ' arront 13sa unox.u. assunoin co.u.uirrts roit AsnosAcTies - g

70. Zr,betakis, 311chdel G.: Ite eurch on itw rinnon-o.a. :n. I 1.un..

1 Alti.l.1. -l!YDitou1%Allt FLA31E Tl:311*Mit ATt'ltle sion Hazardaof Ilydrogen.Wuter Vul. 3.An hoc. Ai( l p.r...ure.1 utin: imtial temperature, 2.7 C.) ' 3327 Tech liiformation Service L -n.o n. t 3 Aiona. Energy Comm., Sept. 4,1956. l l H3drogen ~1. Potter, A. E., Jr., and Herlad, A. L.: A Itciao.. 35 i n. n linri.u* i stoichi. ni Velocity and Quenching Distance. N W A T s.5% i ola.

umet rie

.L si. mannuin-

2. Berlad, A. L., sud Potter, A. E., Jr.:lletation of liom.dars V.h a s

% u e, a nd.i.,ie itefer. ! mi.sture minn ir m pera. Gradient for Flaah.back to Hurning Vel..cm >=nl yo. nrhno: j 'tj,ITj'[ ['['.l*T'y'j '"$r'[$^~ Distance. Cumbustion and Flame, s ul

1. n..

i. mr. 195~,

s olume. pp.127-128. iwreent 3 f3. Zukoski, Edward E., and alarble, Frank E. The Ih.h of W as. ,. Transition in the Process of Flame. isNiiuinon uo luutt Hodir' Em rin,e ed Combustion Researches and Iteviewe, ilunerworih..wi. l'uh. 1955, pp.167-180. i f 4. Zukoski, Edward E., and h!arble, Frank 1:. J ap. nnn-ni. Cun. l'a..aner, lii30 <>plit 3, 2 2203 2253 31 eerning the hiechanism of Flame Bluwutt from Itluir lio lic- [j""d,g,;l,;(g;,--l Proc., Gas Dynamies Sympo.ium (Aerutherruochem.a Nor t h-mu n i u3 i.....,,... 4 , 2293 2318

31. 0 western Univ.,1956, pp. 205-210.

31 organ and Kane,1953.- 3 1 2220

• 5. Harris, >!argaret E., Grumer, Ju eph, von Elim, uneniher. and Ms 7) l l.....

Lewis, Bernard: Burning Velocities, Quem hing, und stahihty Data on Nonturbulent Flames of 5f ethane ami l'rupan with Theatetical Oxygen and Nitrogen. Third Synuxn ium un comi u-oun ami L__ Flame and Explosion Phenomena. The William A Wilkm'. Co. I (Baltimore),1940, pp. 80-89. gund you h. 3

31. G j

~

76. Hutt, Vearl N., Gordon, Sanford, and hlorrell, Virginia i;.: urneral FnedminiCiEfl.~.~.C 8

53f5 '$. 20 ...... l j l afethod and Thermodynamic Tables fur Compuiut ion of - Fe n n. 1951............ 9 2345 Equilibrium Composition and Temperature of Chemical lle. j Aiurgan and Kane,1953. 3 2380 ...... I e actions. NACA Itep. 1037, 1951. (Super edn N A CA TN '" Odun and Wolfhard, 2113 and 2161.) 1953............... G 2373

17. Glatt, Leonard, Adams, Joan H. and John < tun. liernek L.

Huru n. er and Pease, i i 1955.~............ 10 2315 Thermodynamic Properties of the II,o 31oircule fruu 8preiro. scopio Data'. Tech. It'ep. 316-8, Cryogenic f.ah, Dept. Chem.. Tina n pun.. - ~... ~ ; 23S7 2403 30.9 Ohio State Dniv., June 1,1953. (Nas y Contruct Noonr-225 i s a.. g g W j I 4 S g 4 .t O i' ~ J

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c. Temperature dependence Itemarks g

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