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Intervenor Exhibit I-D-70,consisting of Inst of Marine Engineers Transactions Jan 1966 Article, Development of Highly-Rated Medium-Speed Diesel Engine of 7,000-9,000 Horsepower for Marine Propulsion
	ML20100N610
Person / Time
Site:	Shoreham File:Long Island Lighting Company icon.png
Issue date:	09/12/1984
From:	Lowe W, Pope J; MIRRLEES NATIONAL, LTD.
To:	;
References
	OL-I-D-070, OL-I-D-70, NUDOCS 8412130260
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c* ,m. cc. o ......,r - 3,,,,,,,,, Ae l . <j,,.,.- i coeruta-Gtner - g.g, Reporter. a@ g-h y ,.= e 3 c .F F.f ~~ y m ~ .s TEE INSTITCTE OF YARINE ENGINEERS TR AN S ACTIONS l l I Vol. 78 No.. ) JANUARY 1966 8412130260 840912 PDR ADOCK 05000322 0 PDR ~ _ _ :_ _ _ c _1_ _ ', ~ - - ~ ~ - - r--~'

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L a T 1 l t pD 5 c a [ f The Development of a Highly-raidd Medium-speed Diesel Engine j of 7,000-9,000 Horsepower for Marine' Propulsion \\ b

3. A. POPE, D.Sc., Ph.D., Wh.Sc., M.I. Mech.E.* and W. LOWE, B.Sc., M.I. Mech.E.t s

~ The design considerations and development Jests are described which have resulted in k

the production of.the Atirrlaes-National K Aisior e.)gine, whkh has a current wu il

^ g raung of 3,000 to 7,500 b h.p. in 6 to IS-cylinder units, and a p ojected future rating cf 9,000 b.h.p. sn IS cylinders. The Atarrices K engine has been well establiar-ed for over 12 years, some 91.0 engines I' now being m service for powe generation and marine propulsion. Of these engines,250 are E ,L operating on heavy fuels with iscosities ranging from 200 to 4,600 seconds Redwod I, 8 j repr'.-seming over 650,000 horsep~ - Th> obrtive it the de :g an.d development of the E. M Maior engine ',ss been to it.cin. tM st scifir powu outp. t by 50 per cent and W the name time to maintain of to increa.: tl.. seety 8.ctors posseued ')y the original K engine. { These faaors, whic;. octu.nine the ability c' the engine to operate on residuel fuels with a - low maimmance and high availabHiry, tre..ussed mod the achievement of the ob.um is ilhastrated. C Component parts of the e..pne cre described in turn, with details of the methods of / E mearerement of pressure and tem;e.ture levels, air flow and wear rates in test rigs and in a pmtotype three-cyhnder engine xhich was equipped with special features, such as a cam-shaf t with variable timing. to Iaciliuu dnelopment work. f The test results obtamed on the first ;2-cyhnder KV hiaior enine are shown to confurn the perf ormance expreted from the rig and protorype engine 3 :sts. JNTaoprcitoN ,3,, In general, +be requiremenn of a marine propulsion engine i d p '/do-relial$. -ity; 3 are-

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\\ f a)o) low f tael consumption; {,,,,0.' ' i. 7 j gQ' = 6 the abibty to burn heavy fuels obtained in any part g y 4 ....< s u of the world; t + f L 1.2 b d) low lubricating oil consumption;

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, j iO-f = s o-d 1 s c' k t maimenuce requirements; f(.i.. yo P fn t mimuto space and weight in keeping with a) and c). 2 soj Q d j j q 1 2 j j t : j 1 : f 1 - ; ; j ~ JE 'C s 7 These reautrements are obvious but can only be achieved 4,cq y if certain basic principles in design are followed. The paper is

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J .O N'* divided imo sittions, each dealing with one asyet of design d@f D

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=- which aff ects these overall qualities. o,,,,f,,,,,,,,,,,,,,,,,,,,,,,,,,, t -m. - m-However, before detailing these defmite sections, some ,3,,%,,,,,000 %jpf ' e. obserystions must be made on the application for which the f gr engine is to be used and its suitability for that application. An Fic.1-Dirtribution of horsepower for ships oper 2,000 d.w.r. engine developing 7,000 to 9,000 b.b.p. in 18 c, linden would

on order in Grcar Britain i. Afarch 1965 M J.1 Wi$c ?

r-be ideal for tnedsum-speed marine propulsion since the power A range avanable would be from 3,000 h.p., in a single six-at 525 r.p.m., and M0 lb./sq. a.n., b.m.e.p., 465 h.p./c3% der der engine, to 18,000 h.p. with twin IS-cylinder engines. w uld be developed. The design of the K Atapr.ngme wasbased q ;. a.. - E-power tunge covers a large section of the marine market, ".a c ntinuous ratmg of 250 lb./sq. in., b.m.e.p., at 525 r.p.m., g;.., k ustrated in Fig.1, so that if conditions a) to f) can be giving $28 h.p./ cylinder, and the development programme was achieved a worthwhile market should crist for such an engine. planned to achieve tlus ratmg, using heavy fuel, in the three f,. y, % : y,4 4' The initial design study showed that the dimensions of the stages mendoried. Atirrices-National K engine (15-in. bore x Is-in. stroke) would At the present time, the K Aiator is relased for the com-y V'd fit this power range very well, if the new design embodied the mercial market at a rating of 200 lb./sq. in., b.m.e.p at 500 'Qc modern features resulting from research and development which rp.m., and development testmg for the second stage of 220 lb./ f .Q would enable high specific outputs to be obtained whilst retain-sq. in.,b.m.e.p., at 525 r.p.m. is well advanced. { f V j -- 2 . ing economy and reliability. At 500 r.p.m., and 200 lb./sq. in., . A causs-secti n of the engine, showmg its gengral construc-OQ = hm e.p., this size of engine would give 402 h.p./ cylinder' while tron, as shown an Fig. 2 and the details of the desigra will be dealt. ! h. # a ' i'

Research and Technical Director, Mirrlees National Ltd.

with in the following sections of the paper under the headings i Qut! Development Engineer, Mirrlees National Ltd. a) to f) t1 ready given. j4g ,h B.' 325 t gj j g g ~ 5 Swm" - s.

g The Development of a Ilighly-rated Medium-speed Diesel JDighte 1 1 e N 1 '. ,- :-r es u e('[ 4D # "3I"' 4 / - .M as: J %. h '* "' I ~~ " . .I [' t: .k U '. [} 2 E.'\\.p:x$ci' V . / ' - c. 3 ] sfr* hfp ';%iY.. ~.. d ~ 'k.'s h)[n-...G,95.f,., Q. l e ,. %.9 -[W ( ~T g,3-h ' J l gfT d 'l i.. -- .;3 ; t. D a)1 .= 4,yd&A 1 O su t;.g=.g:.,,:4

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4 The Development of a Hig0y-rated Medium-speed Diesel Engine 2 a) an.z.tstz.rrr

1) exhaust temperature af ter the valves should not exceed 820 deg. F. (440 deg. C) with uncooled valve seats and Gancral Considerations Experience in engineering has shown that one of tbe surest 930 deg. F. (500 deg. C) with cooled seats; methods of producing intsinsic reliabihty in a complex piece of

2) top piston ring groove temperature should not execed machinery, such as a Diesel engine, is in proceed by a process of 430 deg. F. (230 deg. C);

3 logical e.olution from one successful design to the next, taking

3) injector r ozz!c tip temperature should not execed 350 care that the critical parameters, proved in the original design, deg. F. (IS0 deg. C);

are maintained in the new design. From the authors' cA.erience

4) exhaust valve seat temperature should not exceed of continuous. duty Diesel engines, the critical parameters to 1,020 deg. F. (550 deg. C);

be 11y watched are:

5) lubricating oil consumpt:an should not exceed one per j

cent of fuel consumption at full load and if possible TAat.a I should, approach 0 5 per cent of full load fuel con-sumption;

6) cn bearings should be well witidn their load-carrying hiirtlees KV12 hiirrices KV12 h!ajor engine capacity;

) t!'c stressing of all components, both in fatigue and d / engine sta.ic leadiar: conditious, should be such that an ade-brs.n.ter 154 200 270 250 quate factor of safety exists. IL/sq.in. Ib./sq. in. Ib./sq. in. Ib./sq. tn. Seme of the more important design and performance b.m.c.p. b.m.e.p. b.m.e.p. 1.m.e.p. characteristics of the K Major engine are compared in Table I with those of the earlier and successful K engine, the comparison j r.p.m. showmg that safe values of the critical parameters have becu r.p r.p m. r.p maintained and, in many cases, improed. htoment ofinertia of bed-h!asimum internal coup!c, '31,430 31,430 plate (in.8) 18,650 31,430 Piston Design tons, ft. 210 2M 290 290 The control of top piston ring g'roove temperatures by cool-Ratio, mastmum couple ing the underside of the crown of the conventional single-piece + moment of mertia 00!!3 0 00S4 0 0092 0 0092 cast iron piston, used in the K engine, is acceptable up to a ratmg 5 of about 180 lb./so. in., b.m.e.p., using a cast iron having a Z sNr'g* g o.82 0 91 0 96 U.T.S. In the ring belt of 17 tons /sq. in., but,.sbove this load, hiaximum c)linder pres. high tensile thermal stresses are produced on tia inside waU of sure. Ib./sq. m. !,030 1,350 1,350 1.400* C)linder head stud stress, the piston behind the ring grooves. Far the K Major engine, m to-s/sq. in. 83 10 10 1 10 4* a two-piece construction has been developed, as illustrated in Fatigue strength of Fig. 3, wnich has a high-tensile ste-1 cruwn and a "Mcch.unte." g threads. tonstsq. m. 17 27 27 27 skirt. This cesign incorporates an inner load-carrying host, so that no pressure load is taken on the outer wall which cirries stre'ng h 0 49 0 37 0 375 0335' the rings, and the latter may be quite tain, thus reducing th: iir }{e stress in fact D b./sq. in. 262,000 205,000 215,000 225,000* heat-flow path to the piston rings and giving efficient oil coalm:; a ht sting load, Ib./ of the ring belt, as well as ensuring that the roots of the pisten sq.in. 814 1,234 1,275 1,330* g hiaximum permissible l bearicg load. Ib./sq. in. 1,500 2,500 2,500 2,500 l Ratio load / permissible _.t ~- Y-load 0 54 0 49 0 51 0 53* M, c_ *. ? ! 2 Large end bearing load, L_ ri 3 lb. 2,400 2,500 2,900 3,050' hiau/sq. in. perrmsuble n ~q g i mum b k. bearing load. Ib./sq. in. 2,700 5,000 5,000 5,000 / : 2 Ret o load / permissible load 0 69 0 56 0 53 0 61* p] g, x" C' 1 m. io L h:aximum stress in piston .. ' H .' T' + U.T.S. of mat: rial 0 44 0 33 0 35 0 36* }7 4 Top piston ring groove temperature, deg. C. 220 165 183 205* 4 a. Exhaust temperature at D eylinders, deg. F. 800 810 850 890* I i Air flow, Ib./b.h.p..hr. 13 3 13 8 13 9 13 7* l r Exhaust valve sent tens-perature, deC. C. 540 460 490 520' l[ j l Specific fuel consumption, I i l M, t l' lb./b.h.p..hr. 0336 0335 0336 0 340* I Lubricating oil coasump-F: l tion. Ib./b.h.p..hr. at [ l i fullload 0 0030 0 0020 0 0020 0 0018' c Weight of engine, Ib./

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44 30 26 23 g N T rea of piston, s 138 162 162 162 hianimum thrust pressure i on piston. lbJsq. in. 35 3 33 5 34 0 34 8* L L Depth of eylinder head,in. 11 75 13 5 13 5 13 5 3 .. Injector nonle tip temper- , f ature(fuclat 200 des.F.). deg. C 177 127 130 136' k' d ' I Inlet valve seat wear .h-Q d 0 0 0 0 8 8 factor 192 156 156 162* ~

Ettrapelatsd values F10. 3-Anembly of two-piece oil-cooled phton i

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y -q. The Developnient of a fligidy-rated klediuni-spen! Dici lhigine l g A. \\ f ring grooves tre stress-free. The piston crown is retained by si? -- - - - r r -- vivo four high-tensile studs which have rolled threads to give maxi-t s,,,{,T** 8 'l p l i Q mum fatigu; strength, and heat-resisting "11eli:oi!" inserts are 3 used to carry tne studs, thus further improving the fatigue so,-- d ----y .p-- -pro ) /l / 44 strength of the assembly and alur acting as a heat barrier for the v, s / i d, studs. Dise springs are fitted under the castle nuts to increase the +fff.. f /. .__foog y resilience of the assembly and to provide an accurate method of { e._ _ _. f b checking the correct pre-load of the studs, this being achieved by

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springs. Lubricating oil is fed, via a drilling in the connecting i,.l_ !_ ^//l/ 1 C, ?" measurement of the gap betwten the two retaining plates for the /

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,,o j l' i Q rod, through the piston pin and to the annulus chamber behind I + i j g/ i / j j the ring grooves, thmugh which it circulates at high velocity before meeting a transfer drilling to the inner chamber below the } /. ? i = - rtso ". piston crown, from where it finally passes down an integral drain j #* /' l*[ l [ drilling in the piston skirt. The retuming oil is collected in a cast l / n ,p l aluminium tray, supported from the engine column, and is fed .I I\\ i i through a flexible connexion to a sight-flow and temperature -l T.4,4ce / t indicator mounted adjacent to the crankcase door. p'=8** The thermally-inluced and pressure-induced stresses have l l l yo[0 l been thoroughly mvestigated in test rigs prior to tests in the 3 ,o e ffo poo ygo 0 t l prototype engme. Fig. 4 is a diagram of the thermal stress ng .,c.,,,e. ene,,,,,,,,,,,, a/s,.. l which is used to simulate the heat flow through the piston which L occurs in the engine, beat being supplied by electric immersion Fla. 5-Comparison of temperatures and stresses in 2 :, heaters using solder as the. medium for transferring the heat to s ntle-piece and true-piece piston designs 4 i the piston crown. Heat transfer through the piston rings is t, achieved by water-cooling the standard engine liner and oil-cool-extremely small. Fig. 5 shows the variation in thermal stress ( ~ ing of the piston internally is arranged in the same way as in the the piston wall and also the temperature in the region of the gi engine. Thermal stresses are measured by Budd self-temperature ring groove as a function of brake mean efIective pressure Q compens2ted strain gauges, having an overall size of lin. x fin., both the original single-piece piston and for the K Major tw so that the effect of the gauges on the heat transfer conditions is piece piston; Fig. 6 i'lustrates the temperature and stress distr ~ ^' d ,8 ,C Jphe s,e name hasaiato , Startermotor gypp y ?) \\ Aeaters reirm.eren k4 V fromponer v P, *=hh <,, ff=5k'2['fromposer supply 6sa aA/e ae/ters aw/r s $%,rpr suppl,,4 A . f. &~ BWf ..Y '; {' I mrA V tos >

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The Developntent of a highly-rated Mediwn-speed Diesel Engine bution in the crown cf the two-piece pistcen. The reduction in top I ring groove temperature by some 126 deg. F. (70 deg. C), l achieved by the new design, has made availabic a wide potential peo r o 34o for increase in r.iting in the future, before any limitation due to f w4os P s'N, ' s

1. 0 lubricating oil break-down is reached. The thermal and pressure doo) i NN stresses are quite modest for the s!cel crown,which has a U.T.S.

'N' a.,i.i, Ds N-_ (7, 03 of 60 tons /sq. in., st room temperature, so that the factors of j,,o safety are much increased over the original single-piece cast iron 's;',,O-]-{[,,p , c s ci c2f I-/ ol design. f,o,,, i i s t-1. \\ isoCL IQI lI t s 4 Connecting Rod % ~',l %,no The connecting rods are one-piece stampings with the large-end bearing housing obliquely spht at 30 degrees to the rod axis, I f,o and carry thin-wall tin-aluminium bearings. This construction I permits a cr.mk pin of maximum diameter, consistent with the frog,,. I withdrawal of the sonnecting rod through the cylinder bore. The optimization of tac connecting sch! proto-tions hancen a sisted - - mr.am,. e ,.e, t.,...f c l by rig tests in a full scale static rig, in which gas loads and ( )ce-earer,.e re,,ran,m .or. 9 e p,.r.wr c inertia loads are simulated by hydraulic pressure and the result-ing stresses measured by strain gauges attached to the connecting t ler.. re sem.. ecy,em rod. It was thus possible to reduce the weight of the connecting urau.i.em., syy,, Esc. 6-Tiro-piece piston cros:n ternpcratures and stresses rod by 15 per cent irom that of the original K rod so that,cren at / y, ~ f" ,f /. i L 're i gi j' \\ p, / - ~ ~ to u;h, 'ts a

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s s 14 ) ..i- .s, / )# ', ,c fm) / q,- q, \\ \\ 20 i,, b'/' IS /. o 39 M2 os 2/- s.. .,}// (b) (o) 'S[ m[T Sc s.052JJ / < 52]ll l' $$ 54 '/a SJ1 .ls$ 40 \\J 48 33 41 4 4 41 9 is sis b ds [* 45 y l 19 J4 J4 /y,./ \\/ ,1, y 25 /Jo

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33 ~. '24 33 2s as DI id) a) Nre stress (gas load) 19 Nre stress (inertia load) c) llackbone stress (gas les.D d) llackbone stress (inertia load) ) Fna. 7-un.snecting rod large-cnd stress distribution 329

+f The Developmenf of a Higidy-rated Mediwn-speed 1)icsei />give the increased speed and load, the connectin; rod stresses are lower Air Ports than in the original design. Fig. 7 s..ows the stresses in the largo Air Ihwv tests c.. ru K cslirider hec ewed that the pr. A end of the connecting rod under htmg pressure and inerna loaJ-sure drop m th inkt passages wm rnadc up as fohaw;- I Inkt passage up to vajvt 11 per cent TAnd II YCloCiry ChangC rouad valve seat 38 per cent Loss of velocity Mad at outlet 35 per cent Gauge No. l'osition I actor of safety interaction betwcen valves and cylinder wa!! II per cent I liott puiform radius 3S The large perceatage loss arou:id the valve seat indicat-19 Suppm iing rib 6-8 that optimization of the valve head profile and inlet passagt sha T,.E 33 Suppororic rib 57 in this region would be worth while, and the tests also show h ra us that a greater effective flow area could be made available by i 39 Bolt platform radius 44 creasing the valve lif t beyond the value of a quarter of val diameter at which the mirumum geometric area becomes constar Fig. 8 shows the increase in coefficient of discharge beyond t ing, arsd, in Table II, the safety factors at the most highly normal L/D ratio of 0 25 and the K Major valve lift was chos-F stressed points have been hsted. In determining these values, albwance has been made for factors which would affect the t ic h fatigue strength of the material, such as specimen size effect and j N Q,' \\ j surface decarburization where it exists, so that the resulting values indicate the worst conditions and show that the rod 2 design bas a large margin of safety. E - \\ cc VN ' J, - } N 1 ! Bearings f d ' Main and large-end bearings are thin-wall steel shells lined 7 y. )h I with tin-aluminium, the increase in bearing loads from the K [ j.h to the K Major being more than compensated by the improve- ,(,,,,, -f l J ment in fatigue strength of the bearing material. The actual and 0, 4 permissib!: bearing loads given in Table I illustrate the increased / ,/ factor of safety in the new engine, the Sgures given being the // conventional pressures obtained by dividing the maximum bear-10-d r/- / Jo* n a t ing load by the projected area of the bearing so that a simple / j' --45* aa r comparison can be raade. In the design of the K Major the more { /'/ 60* m

accurate methods of calculation, svhich have been made possible

4. or

/' by the use of computers, have been used to assess oil film thick-3 // 4 ness over the range of speeds and loads so that the true factor of e' y safety is even nigher than the simple comparison suggests. c A A positive disolacement lubricating oil pump is driven from o or os o.i a es M the fire end of the engine by a flexible drive and delivers oil had** "d a 4/D y through a 15-mieren full-flow Siter to the main oil gallery cast k in the bedplate. An oil-pressure regulating valve is fitted at the Fto. S-Flow characteristics of urives crith 30-degree, j engine plierv to ensure that engine oil pressure remains con- <fS-degree and 60-degree suts a stant, regardless of the degree of contamination of the filter, and 3 a pressure-safery valve at the pump delivery protects the pump in 2 the event of a complete blockage of the system. In addition to the to be 0 3 of the valve diameter, giving an increase in maximur 3 full-flow filter, ebout five per cent of the flow is bypassed and effecthe area of just oser five per cent. This, improvement i 3 filtered by small centrifuges mounted at the engine. TFis dual quite signi6eam when a,t is remembered that it is efIcctive over I filtration ensures that carbon and water particles are nmoved large valve opening period. from the lubricating oil and prevents the formation of sludge in The effect of varymg valve seat angle on flow characteristic the main filters. Tests have shown that a considerable increase in was also examined and Fig.,8 shows the characteristics ( filter hfe is achieved by this system. valves of the same throat area with seats at 30,45 and 60 degrec 0 The quantity of lubricatin; oil circulated through th: t the face of the valve. The 60-degree seat valve is clearl c engine has been determined af tcr thorough development tests to inferior to the other two, and the 30-degree seat is the best a j investigate the distribution of oil to main bearings, large-end small valve open ngs, whereas the 45-degree seat is best at larg ,g bearings, piston cooling and other requirements, and the oi! valve openings, while the advantage to be gamed by increasm-r quanterv ba bee t cher.n not only to lubr;cate bt e sho to :oel the valve lif t beyond L/D = 0 25 25 vahd for all v doe, of.ca j the main and large-end bearings, thus ensurmg that the fatigue ""8 '- I There are other factors to be cons 3, strength of the bearing material is maintained at its maximum angle which determine the relative men,idered m. choosing s X value. ts of 30 and 45-c' grc I seats, of which the most important is that of useful seat lite it b) 1OW FLTEI. CONSUMI'TtON service. Here, the conditions for inlet and exhaust valver :r The importance of adequate air flow in a high-powered quite different, and will be considered separately. j Diesel engine cannot be over-emphasized, the air delivered by the The mlet valve operates in a relatively unlubricated core. 3 turbocharger having to perform the duties of scavencine the tion at the seat so that seat wear, due to the relattve movement c, cylinder from the products of combustion and of cooling the the valve seating face against the face in the cylinder head, as ; ~ components in the combustion space region, as well as providing facto?, f the gas pressure, may be quite appreciable. '**"I t A " wen a high mass of trapped air for the combustion process. In recent was, der ved theoretically and its validity conSrmed b-a years the efforts of specialist turbocharger manufacturers to im-rig and engine tests from which the K Maior mlet valve heac h prove turbine and compressor efliciencies have made a substantial profile was determined to give the minimum practicable relativ< contribution to the success of the highly-rated Diesel engine, movement and hence mu, umum weartai. The " wear factor" s q and the erjgine manufacturer can play his part by ensuring the defined as: maximum utilizaticn of exhaust gas energy and by min mizing P,/.N. g, g,,,,. u. D' 3 flow losses in the porting and ducting. F,r = . b. cos P 2 3 330 e

The Development of a Highly-rated Medium-speed Diesel Engine coefficient of friction, rg where is = =

, p,

= snexarnum cylinder pressure;- P-engine speed; . *c valve disc riimmeter; D = ^ i seat angle; 8 = Young's modulus; E wear resistance factor (hardness number',; B = acat width; 'N m ~ ^~ = O distance from valve dise face to top of seat;

d t

. = l , W .[]n. heithtof valvedisccone. e = . It can be seen that a decrease in 8, or increase in t and o ' have the effect of reducing the " wear factor" and the K Major in-les valve head profile was designed from these considerations with i s a 30-degree seat angle and a stiff valve head. From experience on 5... . cther engines a wear factor of above 250 gi"es umatisfactory Eic %%DlII;;p ','l in service and a value of 200 is satisfactory. It will be seen from - Table I that the original K engine has a satisfactory value,which ..' 8 f is, conArmed by service experience, and the K Major has an even 1..;3 bigger safety margin. The criteria for the seat of the exhaust valve are quite V'- . different and will be disc assed later in the paper under the heading cf"licavy Fuel Operation". Pso. 9-Construction of teriaMe timing cam Valtre Timine formance for the engine speed and load range being considered. The influence of valve tammg on the exhaust, scavenge and Some results have been selected from the range of tests carried charging processes has been examined experimen,solly on a three-out on the three-cylinder engine to illustrate the way in which cylinder engin:, which was fitted with a special camshaft, m changes in timing can affect the power range over which mini-which the timmg of both opening and closing of t'se air and ex-mum fuel consumptionis achieved. - .haust valves, and of fuel injection were ws,dely variable. Fig. 9 In Fig.10, the performance of the tfiree-cylinder engine is is a pict: rial sketch of one of the variable timmg cams showing shown with all valve timings held constant except the point of the method by which the valve period as adrusted. Each cam as exhaust valve opening, the turbocharger match being changed ) made in two pieces which are able te rotate relative to each other tu r ive thc same tot. l eir flow. TI c vrtve tiraings were : when hydra.nl*c pressure as apphed between the cams and the E.V.O. E.V.C A.V.O. A.V.C shait Irom a hand pump. Release of the pressure then shrinks the to the shaft to give an interference fit and the two parts B D.$ T T. BD , cf cam are interlocked to form a bridge over which the cam l Ta. ming A 43 degrees 62 degrees 73 degrees 32 degrees i r roller can run without any discontinuity of profile.*Ihis Timing B 65 degrees 62 degrees 73 degrees 32 degrees 1 l method cf hydraulic rnounting allows the whole ecmposite cam Tanung C 75 degrees 62 degree 73 degrees 32 degrees to be rotated to any desired position, as well as permitting the t opening end closing flanks to be rotated relative tn each other. The left-hand curves of Fig.10 show the performance at 450 Engine tests have been carried out over a wide range of valve r.p.m., and since the engine did not have the ir. proved air flow I timings, re:ording overall engine performance and pressure dia-already described in the previous sub-section, th:: optimum fuel grams in the air inlet passages, engine cylinder and exhaust consumption occurs close to the original K rating of 150 lb./ passages, from which optimum com timings can be determined sq. in., b.m.e.p. As dt.: exhaust valve opening peint is advanced, f:r any engine speed and load condition. the position of minimum consumption moves further up the It will be appreciated that the optimization of valve sk.*ng b.m.c.p. scale. This point is more strikingly i'imtrated in th-is a complex operation and for a given set of timings it is 1. :es-right-hand curus of Fig.10 where fuel const:: crion is plotte. sary to match the injection equipment and the turbocharger per-against exhaust vahe opening point. At the lower rating of 140 0 42 . /,0Xr y f ,a EnAsest temperefore } l /' vel coasseisfien g* sicyanova j/ /, l or a c ep.*2oom/ syn, N 4 a +38 5 l lb eoo - " ~ ri l .o q ry.e r 9 D l soc y,M', oJd g(- /, O E" Y ~s* a 3 pa ,s g O_ e a Tasmg C 1------ a.00,p, s4.nlei o sa-5 x \\.! 8 seaswptsca ' a'7. W et e n ep *t40 nfor m. { s e 4 e Jd %-KQ*2,,. w jgef cons,,,, OJd %s ' - ^ ! '7-,;; - - -o,34 I oJ4 w,,,;- ,g.w I, C. I e os,1 ..l m_ ,,, ~ 00 100 - 12 0 ICO 90 0 la0 toO 40 So 60 PO aO aO s n er, eMm. Pome ettv0 Deveen aehave SDC. Fso.10-E(lect of odsenced exitanst selts opening point on performance 331

l The Derch>jmtent of a flighly-nited Mediwn-speed Diesci Engine )

n. in., b.m.e.p., the change in iuct consumpt:on is small but, tion calcul.itions confirmed by a wry sir ple tec,hnl ne i

.. m Ib.hq. in., b.m.e.p., there is a madad reduction in fut! attaching strain gauges to the ena, e push rods. Fig. Le,. m j w:.umption as exhaust uhc opening is advanccJ. It must be typical push-rod stram race which charly mJicates the riatu e ~ .y.W. awed that this illustration is intended to be indicative only frequency of the vahe ;sar sysicm and confirms that there n d w; beneficial effects of carly exhaust valve openings. It is im-tendency for seWir.ition of the valve tram to c: cur. 4

nttunt that, at high b.m.e.p. ratings, good therm.d efheiency is j

.u.mtamed and in the 12. cylinder K Majer engine the mirumum Fuel Injcetion 3 f.r.1 consumption occurs at about 200 lb.hq. in., b.m.e.p., as To obtain a maximum rate of inicction, the fuel cams T . ustrated later in Fi;;.14, this result being achieved by improve-of a profile which ghes a constant plunger velocity during t tre.at in air flow and iuel inicetion. Fig.1I shows a lo.v-pressure injection period, and the correct matching of the injection equi r2 ,r,hr der and manifold diagram for the 12. cylinder engme at 240 ment was facilitated by the use of test rigs which enabled I in A4. in., b.m.e.p., and 500 r.p.m., and demonstrates the good injection characteristics to be determined and the design of t 'l v,c.engm; and adequate charging of the cylinder which has injection equipment to be very nearly finalized before engine t t tern obramed. As the development of the engine contmues to were started, only the confirmation of nozzle spray angle and t 1. .: ren higher ratings it will be necessary to more the specific fuel number and diam' eter of nozzle holes of a predetermined a e,mumption loop still f urther and the mdications from the three-rernaining for fmal decision from the performance of the engi ) s c.,hnder engme tests are that the advantages of earlier exhaust These test rigs enable a large number of permutations of f 't vahe opening will be realized at this stage. cam, pump plunger diameter, delivery valve design, no 8 design, etc., to be tested quickly and cheaply, using conventio 4 } /,vm Design methods of electronic indication of needle lif t, f uel line press } The increase in speed and loading, accompanied by fas:er and nozzle sac pressure. The latter has proved to be of consid j ,,yning and closing rates of the air and exhaust valves and the able importance in ensuring long life of injector nonles by nr..;rcawd lift stready described, would be expected to make much plaining the reason for over-rapid deterioration of nozzles in l " ' ' " " ~ -~ K engine under certain service conditions. This phenomen 1 was a difficult one to explain until, as a result of calcu!sti i l '#;\\ M. !* an.1 rig tests carried out by the fuel injection manufactu Jr ; 7 it was realized that a particular combination of load and s svo resulted in a hydrodynamic system in which there was a sud g a ra tre : d reI-j 5 o. \\ / needle closed, the time interval benveen the two events - .L 3 reduction in fuel pressure sn the nozzle sae just be.fo.e 2 4 c is ! ? m l !j of the order of a quarter of a rnillisecond. This resulted 9 f i en.~e.o..,,. A /,e penetration of gas from the cylinder into the nozzle sac duri T i l \\ the combustion proces, the hot gases impinging on the bott. p ':fo -.\\ r of the needle and esentually impairing its performance. In F l l V 13 this condition can M seen at (a) on the left, where the p. f ,s L _ I _..( sure in the nozzle sac has fallen down to a lovt level at a po-I 1 pll,$ j 16} degrees efter spiil closure an1 there is r period of o - i r degrec during which the needle i. 611 c'I sts seat and gas ~~ blow past it into the sac. The r:.t tests nmv ensure that } seating of the needle occurs before the sac pressure falls, 2 3 a._-,_;_ illustr.ited at (b) on the right of Fig.13. The value of . g roo iso soo iso Joo Jso 400 dso 500 sso doo preliminary rig work was confirmed by the performance ,1 duced in the 12-cylinder engine at a ver) early stage in l Psc. Il-Cylinder and manifold loro pressure diagrams at development running, many hours of " cut and try tests 210!b./sg. in., b.m.e.p., and 500 r.p.m. optimize injection equipment being saved. Fig.14 sho-preater dem:.nds'en the air and exhaust cams and follower gear. ~ I ter.vever, the design of cam profile, to optimize on rates of open-urtort urr in:: without exceeding established acceleration levels, has been i n.miderably facilitated by the use of computer calculation tech-N' nbues. The R Major air and exhaust cams are of polynomial sah-s*ia- -i. 1 pn. file, the mathematical analysis of the profile by computer its* re Jr a i u.h;ulations making selection of the most desirable curve a rela-(*- 7 t,vely s,imple procedure. The,behaviour of the valve gear zu,p. gg,p Q ne.- hatus n unde

r'innm; conditions, 'o deterr:me the degrac e,seo s,roo W

arni Inquency of sibration,has also been pro;rar.tmed and vibra-N minr m en,- y,oco. J g' i pacssvar { .,,. coo -.- i-- . i.-> s-i io s= .I os.s* n o - __ l A r0 An' push red A vc to,tce so, soc 1 o io do so ever m g,ooo-. -- -- - - M M PAE8N 4 Coo. - Eshaust push rod pg.s* _l 20.s* ] ..ooo - - g s o.- L t vo.

c. vc.

(*) O) 4" Psc.12-Push-rod strain at 200lb/sq. in., b.m.e p., Fic.13-inicetor necdle lift, nozzle gallery pressure and 500 r.p.m. and fuel linc pressure diagrams t 332

. The Derclopment of a Highly-rated Medium-speed Diesel Engine by the formation cf deposits on the valve seat, resulting from the soo ;- i-- l incombustib!c constituents of the fuel and largely from the com-bination of the sodium and vanadium salts present. As the seat l - -f,4< deposits build up, they prevent the valve from rnaking full con-W ./ i !E,wer re=A tact on its seat, thus reducing the degree of heat transfer and cos j V P"r'a#"8 f eventually aP/ wing tracking across the seat between the gaps in the deposits. The lef t-hand picture of Fig.15 shows such a con- ,A u dizion for an uncooled valve after 600 hours operation it ISO poo / l i l lb./sq. in., b.m.e.p., on a blended fuel of 300 seconds Redwood / l 1 viscosity with a three per cent sulphur content, SS p.p.m. t sodium and 100 p.p.m. vanadium. The beginning of erosion / ,---W* rme at eso rpm l

r,afer as s/4 re !

across the seat face between the deposits can be clearly seen 8'. Although the chemistry of the formation of these deposits is a most complex study, and is beyond the scope of this paper, ' ' ~ ' C"J 7 j l i \\. l I field experience and engine tests have shown quite clearly that i \\ l i the presence of sodium and vanadium is of great significance j rnd n prsetica' assessment of the temperature range in which i 0 38* \\-- derosits are likely to arihere tr> 'he setting face of the valve can 0 l ,spet,ric A.et I be made. Table III gives the melting point of possible deposit Ls [****#,'" l 4 constituents which are in the temperature range }vhich may 3 0J:= - ~.- l , jl appertam ac the seat region of an exhaust valve, as is shown m Fig.16, where the lef t-hand valve is of the normal uncooled I l i

I design corresponding to the left-hand illustration of Fig.15.

o.si -- - ----f 40 so tro too zoo, 240 zeo TAnte III ener,m/se. Fra.14-K and K Major per/prrnance cornparison Mciting romt Compound (deg. C.) I$ e perf rmance of the engine as compared with that of Nicket vanadate NiO. V;Os 900 h the eriginal K engine, f rom which it can be seen that the specific Sod um sulphate Na2SO4 880 i fuel consumption of the K Major engine is below 0 34 lb./b.h.p.- v04 . over a very wide range of power, i.e., from 140 lb./sq. in, to (n's"[ium Ns p50 lb./sq. an., b.m.e.p. The curve also shows that, in spite to Sodium pyrovanadate 2Na20.V O3 640 2 p sodium metavanadate Na VO 630 cf the meresse m, speed, from 450 to 514 r.p.m., and an increase m brake mean c'Tective pressure, frorn 150 lb./sq. in. to 200 Sodium vanady! vanadate (7.1$5) 0.V 04.5%Os 625 Na2 lb./sq. in. (i.e., a power increase of SG per cent) the same exhaust Sodium unadyt vanadste (5.I.1I) 2

cmperature as in the K engir,e has been maintained.

SNa20.V 04.IIV 0s $35 2 2 c) IrrAvY FUEL omtATIoM e operation of a Diesel engine on heavy fuel, the two From the Diesel engine designer,s point of view, it is suf-stems w ich normally deteriorate most rapidly are the injector ficient to accept that if the valve seat temperature can be kept nozz!cs and the exhaust valves, and the frequency of servicing of below about 1,020 deg. F. (550 deg. C), adhesion of any of tl.:se these two items is of predominating importance. In both cases components will not occur to any appreciable extent so that ra; J there is a athreshold" of temperature of the critical parts of the components so that, as ratmgs increase, the design of the com. build-up of the deposits wil not be possible. 'nte problem is thus quite different to that of the gas turbine engineer, who has ponent must be improved to mamrain safe operatmg temperature to consider the corrosive effect which occurs at higher tempera-levels. tures. Ilowever, the achievement of low valve seat temperatures at high outputs is not easy and calls for careful attention to Exhaust l' alt ><s Exhaust valve life with residual fuels is usually limited details of design and patient development engine testing to achieve the de red result. The three-cylinder prototype engine, shown in Fig.17, has been used for continuous testing on heavy ,-. -.[ fuelin the research laboratory for the past three years and more ",(] s y I $@*\\ l d \\, I sso-4oec. TE J I i Q 4oo-4sfc. @.1 't i I 5 d ? Q4so-soec. M 3' {.1 m G S @ soo-ssec. ( y. Q If A- .I sso-soec. 'N (} W W i /,. ~ N J, h:~:.r.M.4h Q soo-eso*c. f i w..q..; y 3 s a .w z .k: 4 %;$&;iW;a- &gdAY@3 i2:4T;. q; 'v. ~.. %.) fS.) s y* .1 ~ (a) gy ~~ - ~ - Fac,15-Cornparison of exhaust valve condi: ion Psa.16-Temperature distribution in exhaust valves ofter operation on heavy futt with uncooled and cooled cages 333

The Development of a Fighly-iated Mediwn-speed Diesci Engine M ' ' ~Sp. < y"- ::.ypssar* was prematurcly stopped at about the halfv.n state wb-inc '- -od g,-- valve condinon was not sate.f actory and, in ik l-'an ', vah e 'f N .j j j hm A7 f, as cmbhc3 w ere repl. iced in the en;.nic wrog, r.;-gran ng fo-N.c t, second mJ thirJ runs 5p.,cc e.3 nut permit a det.uleo report ri ? i l of the indivi,.A rem, but the resultm; K Maior exhavt va.- "J ,s { OV >,% ^I,/D. and c:;c dc3g,n v.ill h; described in detH' ta iii,ir.ae ih c r:...e ,4 C' -:. v J a ls ~~] ( . @ *j w hi,;h werc found to be i nportant. - 'ad M. n s Fig.18 shows the valve anJ cage and it can be e that a y, : , e ?,f g,Q ) Y,j s. g h t %g cooling passage is prm aid an the cage close to the va!vc sat ~- i... O , % j.[13. - The seat is rnade of a single piece of Stellite C, grooved to form I

m. 5, Y'3.,,.,6 p

the lower part of the coahng passage, and the upper pertion is t..' %r. ~. machmed in the valve cage which is a three per cent Cr-Mo steel [.3. t'.S ; q,* f. ', $*.*,3 3%.: i .6 b Y"Dr e :^-dh,'.;l a dr'h.i],:>rsh :h' weldmg. The Stelhte portion thus provides the facihty f castmg, the two being welded together by electron g imple b i:2't,% IJJf,.W ' ']. #s l rebuildm; of the se.at by oxy-gas deposition of Stelhte af ter a ,7 y m, N a long pcn d of tin. in service. The valve stem is of increased 'l Q. -d j.3, g%- 7 diameter and the valve of high-conductivity Cr-Ni-Si steel, to i o ' n. g 2 4. re e g g" .' POI" - - h.> t.W '1 - ce .~! 1 assist hear transfer from the head of the valve through the stem, i ',h'g:A .CC.~

""9 and the valve guide is also surrounded by a water-cooled space, 1 \\g g

?D p, f( ['%. "'}\\ T C' **..e...A [ b h Q ?' the coohn; water passing along a drilled passage f rom the top of h,j b .,ty cm., a., the cage direct to the annulus around the seat, then through a is.M h"4,J / M/3@*h-drilhng to the space around the guide and via another drilled 1.Me

y.,

D to the outlet at the top of the cage. The heat transfer f rom tne " X*5 $g,e m ', '.? e valve to the cooled guide is assisted by the close fit between the {jgfLQ*~,q e ja nf r' Q valve stem and guide, the previously mentioned development .[' '. P ' D l' % tests having shown that a diametral clearance of 0 012in, resulted .f a i l j(hb-!d ? ** in an uncooled guide temperature of 450 deg. F. s'B2 deg. C.) g C.) g3.; ,A ' M,';h h in its middle position, with rapid deterioration of the lubricant i t^ 3. ! /k 'A %... hT?F Q ~# W:. and the formation of hard carbon. Halving the e!carance reduced Y h

==Cd" 'MFN. '" k" the temperature to 380 deg. F. (193 deg. C.) end, nalvin;: it cgar f y.#,.

- <.,se-e-.;, g/*

g temperature down to 170 deg. F. (77 deg. C.), i.e., about 10 together with stem lubrication and guide coobng, brougnt t'- y,l, (4,.,- s% J / yi F. (6 deg. C.) higher than the cooling water temperature, v ^ no deterioration of lubricant and a guide wear rate of less ti.- 0 000$in. in the lirst thousand hours. Fw 17-Prototype three-cylinder development engine The valve is fitted with a rotator in the top suring carrier which helps mechanically to prevent br cl-up cf sea' deposits, tha. 60 c.sbaust valve and ca ;e design combinations hne been but its most important function is to. are an eveti temperatura rested, of duration 1,etween 300 and 1,300 hours caen to determine the effect of different factors in the design. A basic test duration distr bution around the y:Ac so the there is na local high-temperature region. The f. lubrication of the vahe gmde takes c,f 300 hours at 200 lb./sq. in, b.m.e.p., loadmg was chosen and advantage of this rotatio: using the vahr itse:f as a tim.rg valve seat condition as the m.nn pararreter, together with other device. Two flats nre provic..i on the valve spindle u n, e h period - features such as valve guide wear, was compared with a reference cally line up with oil ink and outlet drillin;< or the guide as desigr. which was maintained throughout. In many cases the test the valve rotates. The linear positioning of the slot. onh all m the oil to pass while the valve is open and thus the oi! spa:e 7' -G around the valve is only pressurized when the exhaust pul" C pressure is present in the yalve cage gas passan. it.e oil m i mg a:, 3c _ q- -m- ' ' q a seal agamst gas penetration up the stem and the exn.iust pres-u sure preventing leakage of oil from the guide. It was at first J y;j :: l~ "w-feared that a continuous oil suprsly to the guidt might result in excessive leakage of oil from the bottom of the guide, but this has

i S

!i M a-7 j!i Q, l 5.] y l-- Z? not proved to be the case and, in fact, the tendency is for the ): ?'

-- :M,,

leakage to be upwards as the retardation when the valve meets its seat is greater than the acceleration during opening and the anertis .Ig ! ' 1...,. ; i m. of the oil carries it upw:rds. This intermittent pie v. re hbrica-F ~- ';_J ' tion of the valve sicm nakes it possible to use a very small stem /

1. 9i 2

j i "l[ _', ' " ' -[{ guide bore clearance withcut any rish of valve sticking, and this fi .- Q. j Q g; In add.: ion, the danger of stem or guide bore corrosion at low j' helps the heat transfer from the valve to the water-cooled guide. l

l i

i o p,.; [s s load running conditions is avoided. H b' L Since the stem to guide clearance is important in the heat l C 'I 'f tmnsfer process, the reduction o. guide wear helps to maintain I' l l 1., (, L s p-low valve seat temperatures over a long perioct i-service, and g q f'

p!I many of the development tests were concerned wit's valve guide h,

[j, ;: I; l s. n material and valve rocker lever geometry to this end. The long . (i ,l l y;, jh-4Ip'll guide and tne small overhang of the valve head beyond the guide -.1 'l. will be noticed in the illustration and were found to be important t j '.p factors in reducing guide wear, as was the composition of the t i.. i 5Il special "Meehanite" iron which was finally used for the guide h flJ material. 1jt-L__lf_ :_j P -Q3 D -_. 0 sodium-conied and water.cooiea vaives were iested among ~ the many combinations but were found to effer no advantage over the design finally adoptcJ, mainly, it is thought, beenuse of Fac.18-AssemNy of cxhaust tolve and tvater-cooled cage the difliculty, with an internally-cooled valve, of providing cool-334

i The Development of a Highly-rated Mediwn-speed Diesel Engine Ing passages close enough to the actual seat of the valve. The Jeo-r- - - - usual methods of drilhng down the centre of the valve stem, t although successfully cochn the centre of the head, stillleave a j l / - -,C fairly high temperature at the seat, and in the case of the fee / internally water-cooled valve, the water connexions to the valve ef,, 1 are o difficult problem. G 6o'/ e right-hand valve of Fig.15 shows the results of this { eac I .t desSment, the valve having run for 900 hours at 200 lb./ c sa. m., b.m.e.p., on the same type of fuel as before. The good } ', s,C' = d[- - -*/ l / i condition of the seating face shows that no re-grinding is neces-i sary and the valve can operate for a much longer period without i '80 ' "" ,/ titention. The eorresponding temperature datribution in the z $5f@6 j valve head is shown in the right-hand illustration of Fig.16, and 1 the effcet of rating on exhaust valve seat temperature is given i i+ o-une g' M p d "' 30*' in Table I. 2 ev '

l The valve development tests also included investigations e

n!#y into the (flect of feel treatment on exhaust valve life and while ffo- - cco o :e fuel additive showed promise,in that the nature of the ulve I seat deposits was altered, it was not effective enough to justify its adoption. The principle of this additive was that other chemi-l } , p _.___. cals were added to the fuel so that the compounds, which were 4o ao rio /4o roo

40 28C fermed during combustion, would have higher melting points s a e p.a/se n than those listed in Table III. It seems likely that, with further d:velopment work by the additive manufacturers, there may be Flo.19-Inicetor no:zle tip temperaturcs cuith some tavantage to be gained in the future from this type of cooled and uncooled injectors additive. Water washing of the fuel, to remove the sodium con-tent, was found to be quite effective and the sodium could be re-for satisfactory operation. In Fig.19, the middle curve shows the duced from 90 p.p.m. to about half of this value without variation of nozzle tip temperature with load for the K Maior difficulty, engine tests showing that the washing had quite an engine, using an uncooled nozzle and distillate fucl, where the appreciable beneficial effect on the exhaust vahc seat condition. fuelitself has a considerab!c cooling effe:t, and there would be no As can be quickly calculated from Tab!c III the critical sodium / difficulty in operating an uncooled nonle on this type of fuel up tanadium ratics in the importan. temperature zone rsnge from to a load of about 250 lb./sq. in., b i t e.p. In the upper curve, 1:0 74 to '.:13 3, the lower melting point compounds being however, blended fuel of 300 secor4 Redwood I vhc9sity ass ' d with the latter end of the range, so that a reduction was used, with a fuel temperature of 160 deg. F. (71 deg. C) in content may tend to produce the compounds with the and it can be seen that the loss in cooling effect from the fuel has

!cw Iting points and, with particular iuel compositions, have limited the acceptable load level to a'oout ISO lb./sq. in., b.m.e.p., an undesirable ef!cet. Thus, with the wide variation in constitu-and with heavier, and hence hotter, fuels the load limit would be f ents in fuel from different parts of the world, it is difficult to much lower. A water-cooled nozzle is therefore necessary for l make a clear case for water washing of the fuel. high ratings on heavy fuel, and the lower curve shows the tip i temperature for a cooled nozzle using 1,000 seconds fuel at 200 InJcciors deg. F. (93 deg. C) with cooling water at 150 deg. F. (66 deg. C). Fuel injection nozzles, when operated at high tensperatures, It is important that the nozzle should not be over-cooled as cold tend to forra carbon around thb holes in the nozzles, kr:own as corrosion can occur at terr'peratures below 230 deg. F. (110 deg. " trumpeting", which may interfere with the injection spray par-C), but this is controlle,' by the water-circulation system which tern and reduce combustion efficiency, thus aggravating the tem-is separate from that of th engine-cooling water. Fig. 20 shows perature problem. For a time, the carbon formation d:velops the cooling system which is a closed circuit serving the injectors until the " trumpets"-become detached from the nozzle and a and water-cooled seat exhaust valve cages with a thermostatically l periodi: rise and fall of exhaust temperatures can often be seen controlled bypass around the heat exchanger and minimum as this occurs. The general trend of temperature, however,is up-volume in the system to ensure that correct operating tempera-Cards and conditions eventually level out at the top end of the tures are reached quickly. exhaust temperature cyclic range. In more extreme cases of high temperature, the needle seat may lose its hardness and the needle d) LUBRtCATING Ott CONSUMPTION rapidly hammers its way into the seat. The temperature at the The consumption of lubricating oil in a Diesel engine is nozzle tip can be measured by thermocouple and a temperature an important factor in maintenance costs and it is not always of about 356 deg. F. (180 deg. C) is considered to be the limit realized that, at a reasonable consumption rate of one per cent of cderst k / retter vehe sage, r-Prut rums,teoc a= p) w" e<r e < 3_~: 3 "h y,q. l, W ~ ~ l4

1. 1 88$_< --s G

U t <1 ~..... ((}, ETI&te Heat Rea esshanger ester n+ nerer r.>c C+M ^ O-D<F Psc. 20-Arrangement of injector and telt.e cage cooling system _ sw _

-d nam The Development of a Highly-rated Medmm-?pced Divyd Engine 4 !a f uel consumptian, a 4,000 h p. (nguic u ih burn a quantit) of Ib]sq. in. pre ourc netJed for the K Alajor engine, the resultir" 9 lubricating oil equivalent to it, sump c.ipacity in a lyrioJ nmun;um of Icss than 0 002 lb./h.h p -hr., bemn confirmt. M cd the order of 309 hours. Emphaus n ofica Iwi on larm periads in su 1.)-cslui&r engine during deselopment running. -4 betwcen oil changes which are utenJcJ by an engme uith a high -3 oil consumption, wherea, the relauve importance of oil con-Pnton Rme Qu1hty T sumpoori to oil change perioJ is around 30 to 1 The cost of Consntuit oil consumptian and low scar rat-are largei G nalern high-duty detergent oils is qmt appreciabic, so that an ucrendent on the qu.ihty of the piston rine f rom e p.unt i rii od consumption of one pcr cent of the f uct consumpaan icpsc-view of metallurgical structure as well o ascuracy of nw. g sents some:hing hke ten ptr cent of the f uel hill. Not ah of this f acture. Accurac3 and good finish ir. m.ouf auure can be assurc ? could be sa.cd, of course, but a reduction of 50 per cent in lubri-by conventional inspection met > J., and such methods com cm - j caring od consumption n equivalent to a five per cent saving on be extended to give som: indicanon of rnaterial quality, such a. the fuel bill, and would be well worth having from the pomt of by mensuring the permanent set of the ring at a given hud valu ; + above that re.luired to close the gap. A simple samp.e checkin 3 sicw of runmng costs m.thod on metallurgicil struerure was devised in which a smi .= piece of ring is clamped with its working face subjected to 3 '~ Puton Ring Dcsign To carry ot.t lubricating oil consumption tests in the rela-given load and resting on the surface of a ring of hner stor m tively short runnmg periods of 500 hours or so in the research The ring is then rotated at a standard speed for a fixed tirr. y laboratcry, it was necessary to develop an securate method of without lubrication and the weighi loss of the piece of rm measuring top-up rate and a system was devised, and has proved measured. Weight loss is used as a measure of the relatis _q resistance of the material and, although " rough an % very successf ul, whereby consumption can be measured consis-wear tently over successive two hour periods and plotted consecutively. ready", is found to co-relate well with the differences in micr-2 The runnmg-in period and the leselling-out to a steady con-structure of the ring material. Some typical resulta are give sumption can now be followed and it has been possible to obtain m Table IV, and illustrated in Fig. 22, and show that with 5 steady state results af ter a ' total test period of only 300 hours, same Brinell hardness, increasing amounts of free ferrite r 2 which allows much more latitu'de for testing variations on a ring progressively worse results and these are no: improved by n = pack than was previously the case. There is a large number of crease in phosphorus content within the amounts to comps.j detail pouits to be considered sue.h as liner finish, roundness, with mechanical strength requirementsW. j drainage an,the piston, etc., but the basic concept which has been .g.,gy established is to provide a parallel-faced chrome-plated top com-g pression ring, three taper-faced plain compression rings, a rela-

Hardncss, Weight j

tively mild scraper ring below the gudgeon pin, and a more severe scraper ring above the pin. This ensures that adequate Sample Structure HB loss. J No-E*- d lubrication is available around the body of the piston but that - r the minimum of oil is allowed to pass up into the combustion A Greativ undercooled graphite, d 2 space. The consistency of oil consumption measurement has cons'iderable free ferrite (cer ri-enabled some interesting facts to emerge, and Fig. 21 illustrate $ cast) 315 per cent. T.C., 0 83 -i one of these-the effect of the wall pressure of the scraper ring per cent P. 2l0 0 404 9 above the pin. The lef t-hand curve is fmm the threc-cylinder, B Some undercooled graphite, a g 15h bare prototy pe engme, and the right-hand curve from a hule free ferrite (centricast? i 4 3 20 per cent T.C., 0 40 per cent P. 210 0 185 d C Random uniform medium flake 9 C o--o is %,,n,,,l F.raphite, fully pearblic (sand. l l i l l casi) 3 45 per cent T.C., 0 55 E o ceo ; ----- -~ pf6.neage,- per cent P. 210 0 017 e) M AtNTENANCE { o oer -- 1 Engine running times between overhauls are depende l I upon the load, duty and running condition, and the precedc g t U sections have indicated the attention that hn beco paid to i = i _Q __ 4 __._ L _ f components which operate under the most arduous conditior 0 o oos - y ei o l j By reducing the critical temperatures of injector nonles and e 7 i l l l haust valve seats, so that when operatir, on heavy fuels the i i o oo..L i l 7 - -.i_ _ _ _ _, tempcratures are below the " threshold" values at which deterior 3 I l j tion becomes rapid, it has been the aim to achieve periods 9 L h__ _ _ p_J 2,000 to 3,000 hours before servicing of iniectors or exha! nil valves is neccssa y. Expcrience on the prototypc engme has 3 o _._. o to 4o so r .;o /20 A r.a ~., we .m. m/.m dicated tha. this ambition is by no means unreasonable tsut, 1 J course, true confirmation of success will only cor g 1 Fm. 21-Variation of lubricating oil consumptsor: irom the accumulation of service experiencc. Mainnenance ~4 saith scraper nng tuoll pressure other components would not be different frnm that establish 1 over many years, e.g., pisten removal annually, complete ov-7 completely different high-speed engine of 93-in. bore, the points haul every two years, the periods generally being dictated to s d i v marked being the stable lubricaung oil consumption achieved the enmenience of the operator rather than by the demands = af ter running periods of about 300 hours in each case. Both the engine. curves show the same trend of reducing oil consumption with j increased ring wall pressure and the tendener for the curves to f) sr' ACE AND WEIGifT level out at higher values of wall pressure. The value of wall In achieving high engine ratings reliably,.ae weight _ n pressure necessary to achieve a satisfactory consumption can hor epower, and space per horsepower, are natur dy reduced a d ~ be seen to be much higher for the smaller high-speed engmc the emphasis on reliabilitt for commercial mari se work nece: 41 than for the K Major engine, and in the case of the smaller tates a different approach' from that which would be appropri m engine it was necessary to use a spring-loaded conformable for naval work where light-weight constructions beco i scraper rmg to achiese the desired consumption. A convenoonal necessary but short life may be permitted. Sight should not j type of slotted scraper ring was adequate to provide the 50 lost of the importance of low fuel consumption in the conside f J k' 336 d

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1 i l'sa. 22-Contparison of piston rings oftcr : rear rig tests lion of ueight. A ship refue!!ing every 3,000 miles, for example, sq. in. Even butt welds must allow for discontinuity so that their at an ascrare speed of 15 knots, and having engines weighing taugue strength is only :'; 3 8 tons /sq. in., these values being for 34 lb./b.h.p., and a specific fuel consumptiop of 0 34 lb./b.h.p.- good quality welds, the strength of an imperfect wcld being of j hr.f would re-bunker an emeunt of fuel equivalent to twice the course, very low indeed. A good quality cast i.on has a fatigue wesght of the eng:nes. Thus a five per cent icduction in fuel strength of over 5 tons /sq. in., and as well as freedom from the l comumption would be equivalent to a ten per cent reduction in notch sensitivity, which so drastically reduces the fatigue strength rngine v.ci2ht in aJdition to the saving in fuct cost.. of a steel structure, cast iron has good internal damping properties In the design of the K.\\laior <ngine, cast iron his been used and also possesses the useful property of a diminishing E value as the main structural material and, in the authors' experience, with ircreased stress so that stress concentrations are consideraNy has snany advantages over fabricated steel designs. Few fabriented reduced and the snaterial tends to relieve itself of any excessive irructures are ab'.e to avoid fil'et welds in load-carry ng regions stresses. i pnd the latigue strength of such a weld is as low as = 12 tons / In keeping with the phileophy of designing for maximum D EMt W.-Ai[L -- p,N ~. Tant.z V

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Maximum continuous b.h.p./ cylinder 420 b.h.p. (426 cv) .c Lubricating oil int.:t temperature IS0 deg. F. (65 deg. C.) f ?*P .~.u.._ tL i -1 gr 4 Lubricating oil outlet temperature 165 deg. F. (74 deg. C.) '#~~ { p

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-.N <EJ' Lubneating oil drain tank capacity 650 gal. (2,960 litres) t D,,,,.)Jg, ,%gdsA;y*- 5.n Fresh and salt water flow rates 5.5 gaLIb.h.p..hr at -c ' , %.M 8% 50ft. head (25 litres / T W sts/ 'd. N '.Nd%,, s;j.. "J",. ' cv.hr.) >. h"1 3 J fr jf Enginc cooling water inlet temperature 155 deg. F.(68 deg.C.) ,S .I'.),1 ri. ',2R.% d N;-e. T.i'.- e h. ,1 erp%"4 8%, *i k Engine coohng water outict temperature 170 deg. F. (77 deg. C.) ~"W,f.J'O k," r,%;*f , % M'; ) Exhaust temperature af ter turbocharger 400 lb./sq. (m.600 deg. F. 427 deg. C.) (.q '.. 8 8.4 7"7e. f.& M. Starting air preuvre 6 "'.* - :',' ;,.i%M.. r,W ' -rhp','.S"v.T.ntCG E! <j MM 8 Specific fuel consumption 0 335 lb./b.h.p hr. .4 k -V ~~ 6$hG*.YU2.d.)A...*iv A \\, M:19,;sihd$di6:,' (l.c.v. of I8,400 u II.t.u /1b.) "'Y U * * * "' . Pto. 23-Prototype Kl' Alajor 12-cylinder engine Taut.e VI-Powen RAsct No. of cylinders li.m.c.p. - -l l 12 l 16 18 lb./sq. sn. 6 l 8 l 9 m ( '2.h.D. output at 250 r.p.m. 200 1.200 1,600 1,800 2.400 3,200 3,600 L/ 250 1,500 2.000 2.230 3,000 4,000 4,500 II.h.p. output at 350 r.p.m. 200 1.650 2.240 2.520 3.360 4ASO 5.040 250 2,100 2.800 3.150 4,200 5,000 6,300 II.h p. output at 450 r.p.m. 200 2,160 2,880 3,240 4.320 5,760 6,4SO 250 2,700 3/00 4.050 5,400 7,20G S.100 f t.h.p. uutput at 525 r.p.m. 200 2.52o 3,360 3,750 5.040 6,720 7,560 250 e 3.150 4.200 4.720 6.300 M400 9.450 Overalllen;th of engme - 20ft. Din. 24ft. Oin. 26ft. Din. 24ft. 3in. 29ft.10in. 32ft. 7in. Oser.ill width of engine 7ft. 6in. 7ft.6in. Aft. 2in. l i ft. 7in. lift. Ilin. 11ft.Ilin. Usera!! height of engine l i ft. 6in. lift.6in. li ft. 6in. lift. llin. lift. llin. Ilft. Ilin. lleight abmc cranbh.ift C.I. Fit. 9v. Eft. %n. Eft. %n. Eft. 2in. Eft. 2in. Eft. 2in. Engmc ucight (dry) torw 33 44 48 65 35 95 337

= ll-Tise Development of a liighly-n ated Medium-speed Diesel Engine pso :-.. g4ao .....,.y.... et %< t Wt p/.. .,r _sw.t _-- y voo7.ro -- zon o I---lp, l o e I lose $~- N--oN no t 2s-fsso 7 L yl-- - f irpl ~~- :w ef.~-. t: I ,,OL soo 20 < - % D e lg,-(,,y/ r-*og .m e '%, = 5 f_u* '~W';:,( $j --.--- vroj ~ t so .g, - t- + ~ ~ ass 'soo .sso noo eso soo no i so r 200 Ar.Ar smM/n m. (a) (b) Psa. 24-KY binior angine performance characteristics [ L reliability and easy maintenence,the bedplate type of construction perience has shown to give reliable and trouble. free c,per: has been retained for the K Mejor engine and a useful facility There is little doubt that in the marine preguisson Aeld toer: has been added by the inclusion of a machined strip on the top considerable interest in the use of medium. speed Dicaci engui surface of the bed so that alignment of the engine can be quickly for higher powers than have hitherto been possible, and that wit and occurately checked, and crankshaft deAcxion measurements in the next few years engines of this type will he availabl,c, cover almest the whole range of power demands of Brin more easily interpreted. Fig. 23 shows the 12-cylinder KV Major on the test bed, shipping. from which the general construction and appearance of the .:CxNows.EnoutNys engine can be seen, and Tables V and VI give the specification for The authors wish to express their thanks to the Board the range of engines available at the current commercial rating of 200 lb./sq. in., b.m.e.p., and the future rating of 250 lb./sq. in, Mirrlees National Limited for permission to publish the infern, b.m.e.p, under normal temperature and pressure conditions tion contained in t'ais paper and acknowledge the assistar with sea water up to 75 deg. F. (24 deg. C.) to the charge air given by Bryce Berger Ltd. and by their collcagues in 1 o cooie,. com,n of data. CONCLUSIONS stEFERENCES The design and development c.f a highly-rated rnedium-1) DrNwts, R. A., and RADFoRD, J.M.196'.65 Symposium speed Diesel engine, to operate economically and reliably on Th rmal Loading of Diesel Engine -. Piston Strenes heavy fuels, has been described and it has been shown that, for T! coretical and Experirnental Development < the K Major engine the critical parts of the engine, which N:J.AfechE., Vol.179, Part 3C, p.19. and DENNIS, R. A.19 determine its reliabih,ty, have adequate safety margins for its 2) RAntono, J. M., WAt.t.ACF., W. B.,in the Development current rating 6f 200 lb./sq. in., b.m.e.p., and have ":ixperimental Techniques used a substantial increase in rating, to 250 lb./sq. in., potential for b.m.e.p., in Highly-rated Four-stroke Cycle Diesel Engines". Congi the future. The performance of the 12-cylinder prototype Internationale des Machines h Combustion (C.I.M.A.C.). engine, beyond the current commercial rating, is illustrated in 3) Gr,EN11ALCll, R. 1963-64 Symposium on Operating I Fig. 24, curve (a) snowing the performance at variab!: speed perience with High-duty Prime Movers "Turbochar; and curve (b) the performance at a constant speed of 514 Diesel Generating Plant Buming Residual Fuck in coniunction with Fig.14, show clearly Proc 1.MechE., Vol.178, Part 3K, p.74. r.p.m., and these, ides which are being made in the enormous str he Diesel 4) '.rt, J. A. June 1965 Edward Williams Lecture--"Thet. engine industry towards higher specific outputs without J. Cast Irons in Modern Diesel Engine Design". 7nt.l.B exceeding the temperature and pressure levels which past ex-Foundrymen, Vol. LVIII,p.207. i O 338

w 7 1 A w 1l= 1lic 5m = Discussion X@ -P Ma. R. Coox, M.Sc. (Alember of Council) said that, at the roots gave almost as great an increase. The degree of rolling ? present time, the manufacturers of medium-speed engines i.i lud b:en fo.'nd to be not very critical, but his Association was Great Eri*ain were taaking very strenuous efforts to extend their at prtsent i.nestigaririg more fully the opimum degree far =_ share of the marine market in propulsion machinery. The paper various sizes and pitches. He imagined that with the high-s. , therefore, timely and few who had read it would have tensile steel material used by the authors, the gain in fatigue failed to be impressed by the manner in which the authors and strengtis would not be so great as in the case of mild steel, but their col'eagues were applying the latest knowledge and re-it would be interesting if the authors would quote some figures. search techniques to the solution of the problems which arose Form-re!!ing could be a very cheap method of bolt product:on, y-- when such machinery was descloped to operate at high ratings particularly in small sizes. -ir on residual fuels. One could hardly doubt that success would The means adopted to ensure correct pre-loading of studs E attend their efIorts, although he suspected that the large direct-was to be commended since there was t2o doubt that the maiority drive Diesel wouM be about for quite a few years to come. of failures of dynamically-loaded bolts were due to fatigue ~ The histogram shown in Fig. I was interesting. It would caused by inadequate tightening. It was not ahvays appreciated P be noted that by far the largest horsepower on order at the that, with a properly-designed bolted connexion, fatigue failure m present time was between 9,000 and 21,000 s.h.p. per ship. was virtually impossible if the bolt was adequately pre-loaded. .t With the rnachinery described in the paper this implied the use The section in the paper dealing with' heavy fuel operation e of some 18 to 36 cylinders of 15 in. diameter each with two was, of course, of the greatest possibic interest, since a solution exhaust vahes, two inlet valves, together with tItc injection and of the difficult problems involved was essential if the medium-y'F, starting equipment. He said that he could not help wondering speed engine was to be able to compete with the direct-drive whether the modern reagoing engineer, who was perhaps not engine, which was so much less fastidiou> as to its diet. Here E quite so amenable to long and arduous hard work as his fore-again, the authors had given evidence of a careful scientific C bea + ould take kindly to the never-ending task of top-approach which shouki.-) a long way to ensure success. They .ove ing such a formidab!c number of cylinders. had commented on the pmsible use of fuel additives. One could ther point for thought was the eficct which such main. imagine this approach tving successful where fuel supplies of tenance requirernents would have upon the red"ction in constant composition were available, but this was seldom pos-engine-room staff now being. achieved with direct-drive sible in marine practice and the chances of obtaining a cheap y machinery bythe application of an increased degree of automatic additive,which was effective with a wide variety of fuels, seemed 3 control. He hoped that some superintendems would comment somewhat remote. The authors' approaca, by tackling the de- = .syr on these aspects later in the discussion. sign, was ecrtainly 11. right one. Their remarks on the TT He said that some years ago Dr. Pope had made a very drawbacks of water wamiag were also worth noting. thorough theoretical and experi'mentalinvestigation for the Dri-No reference had been made in this section to sump-oil 6 tish Shipbuilding Research Association into the causes of failure contamination when using heavy fuels. Presumably this must =E of pistons, liners and cylinder heads in rnatine oil engines, with occur to some degree in this trunk-piston design, and it would 5-results which had since been published in the Transactions of be useful if the authors were to give some information on the .g another Institution. He was not surprised, therefore, to see the procedure involved in maintaining the lubricating oil in a attention which the authors had given to thermal and pressure-sunable condition. .,.F induced stresses in the design of the two-piece, oil-cooled piston. Dr. Pope had, over the years, made many investigations into 7: Presumably, the piston temperatures shown in Fig. 6 were the properties of cast iron. Few were, therefore, more familiar Y measured on the actual engines and the rig used to check the with its strength and frailties. Sir Harry Ricardo had once K thermal stresses calculatcJ from these temperature incasure-referred to cast iron as "the material which served our fore-p ments. If so, he wondered whether good correlation w.is fathers so wcll for lamp posts and kitchn ranges" but he was g achiestd. It would be interesting to know how the temperature sure that Sir Harry would be the first to acknowled$c the advan-b. distribution in the stationary rig piston correlated with that on tages which the authors had enumerated. Its use as the main the engine. structural material in the K Major engine had much to com-g He said that he was interested to observe the use of rolled mend it, since weight was rarely of paramount importance in threads on the high-tensile steel studs used for securing the merchant ships. piston crown. Work by D.S.R.A. on the rolling of threads of On the subject of east imn, he said that it might be inferred . L-lars ild-steel bolts such as those used in the dynamically-from the data given in Table IV that centri-cast piston rings .EE jos mponengg of djrceg.dgjve Diesels, had shown very were inferior to sand-cast rings. He icit sure that this would ? stri improvements in fatigue strength. Reference to a paper

not be the authors' intention. Centri-cast rings had been widely

_g appearing m the Transactic... of the Institure four years agn employed with success. He took it that the authors' purpose g would show that form-rolling inercased the fatigue strength of had been sirnply to show that, with this type of material,under-large forged bohs made from mild steel some 2} to 3 times. cooling and consequent presence of free ferrite was most E when compared with cut-thread speciment. Rolling of thread uudesirable. The paper had touched in an interesting manner on'so h

Cook, R., and McClimor.t, W.1961. "The influmn of Screw m.,my aspects of Diesel design that to point to ornmissions Forming Me: hods on the Fatipe Strength or Large Ilohs".

mmht seem somewhat churlish. Ile wished, however, that the p w :. Ufu.E., Vol. 73, p. 417. authors had found it possible to touch on the subject of turbo-339 "e E.- ,,.~r +- .-,._._,,.-7.,7.,.,n ,w_ 7 7 - ,e .r.-,s m y % .re---- ~ V., ---(,,, .\\ L u.. a

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The Dcyelojnneni of a liighly-rafed W.dtun-speed Diesel Dmine { With regard in Tarde I, the specifi air flow for the 250 4 I charging. Perhaps they might, at somelat:r date,imJ is powiofe sq.in, b.m.c.p. 3:xu cJ a diop compared with hv.ver h.m.e.p., a ~ to give a paper on their experiences in turbochargm*: up to the although ihn drop wa only a small one, he wauh! h,vc thou;;h 3 250 lb.hy.in. in b.m.c.p. which was involved in the third st.sge it desirable to go on increasing the specifi: air flow. ( ? of the development of the engine. Turning to the piston design, he said that the features but it sa it were, in many ways, those with which he agrecil, junk. Th { Costat4Nmx E. Tvxur.t.t., R.N. (hiember), in a contribution mentioned that it wJ) a sicCl Crown and a cast iron 3> read by Alt. T. P. Incrett, referred to the successful intro-steel crown probably had a higher coefficient of linear expar duction, by the author >* company, of an engme which he sion as compared with the cast iron. This meant that there we. i considered met both industrial and marin: necdt which so far some problems in its connexion, for instance, it must mal had only been filled by llntain's foreign competitors. As the life a little difficult for the scahng ring, between the tu su. hors had so rightly said, rehabihty was the main requirement portions. Cold clearance between piston crown and h y of a marme propulsion engine, and nobody who had read this a be increased. paper could f ail to be impressed by the systematic way in which Figs. 2,3 and 6 showect s. double line round the junk. Mirrless National had carried out the research and development wondered what this signified and whether it was some dev' work necessary to ensure that this engine would operate satis-to overcome the cold clearance problem. f actorily at the ratings envisaged. With regard to exhaust valves and operation on heavy fuc If the medium-speed geared Diesel engine was to compete the importance of losutg heat via the stems of the valvc: w ws.a the slow-runing direct-coupled engme, it was essential that In the paper the clearance w certainly to be considered. it should operate satisfactorily while burning heavy fuel, and mentioned as being of importance. The we 4r rate was obvious n was evident that the authors had talen very considerable kept down by the ingenious device of centinuous lubricatiu trouble and had expended a comparatively large sum of money and he said that he wou!J be interested to know what w ) in trying to ensure that this would be the case. There was. maximum allowable clearance of the stem to gMc nnd w ( however, one point which he. felt should have been mentioned sort of life the valve hadin this respect. Also,it appeared ..f in this respect, and that was the effect of various grades and composmons of lubricating oil on the problems associated with the guide could be renewed y g the burning of heavy fuel. There was little doubt that trunk-it was intended to be renewed. piston engmes called for careful selection of the lubricating oil He suggested that there wss an argument for not wa af sansfactory operation syith heavy fuel was,to be achieved. washing fuel, in that the deposits also p New types of,lubncatm; od and testing for qurhty and make-up blades, and turbochargers co 4 by the addat on of detergents, antpoxidants, and,alkabs could the sodium was allowed to remain in the On the question of cast iron or steel as the main structu have a profound eficct on the satisfactory operation of trunk-material, he said that steel had its ow p piston engmes while burnmg this type of fuel. The wrong type of lubricant, or one which had been allowed to deteriorate cures could be designed with low stresses u ncre we gy unduly, could giye rise te ring stickmg and crankshaft corro~ Atodern techniques of manufacutre and in:p j sian. Tne operatmg temperattyre of the od v.as also importar.t good quality wckts. Ilt said that surely greater reliabih.ty resulted from a des. af these defects were to be avoided. Perhaps the authors would in which the ma,or loads did not have to pass through a,o t like to remstk on the type of lubricating oil and its optimum 3 i between the crankcase and bedplate, and easy mamtenance L'* operr. ting temperature for this type of engine burni9g heavy i n t confined to the bedplate type of constru:rion. The princi fuel'He thought that the title of this paper was slightly mis-OI.a machmed stnp tited for checking alignment of,the en qtuckh was also med on endnes cf fahnrated design hav k leading. He could not rgree that the Alirrlxs K Alapr engine should be regarded as highlv rated when operating at the con-underslung crankshalts and light sumps mstead cf baseplate ditions given in the paper. I' his opinion ther: was considerable f n scope for further advances in b.m.e.p. These were important as In. !!. IL Gnasettr.t. said that he propmed to limit his they should give worthwhile reduction > in the cost per horsc-servations and comments to the iuct injection side of the pa Introduction of a rehab!: engine operating at these departing only for a moment in order t i fully! Condd.. endorse power. higher brake mean effective pressures would da much to increase authors' statement und:r a) Reliability: Gcnero f tiont", where they said that the surest method of produ the competitive power of this type of engine agfist its com-e petitors abroad and other types of prime mover. In this tech-intrirnic reliability was to proceed by a process of log nically competit vc world, the main object of any Diesel engine evolution from one successful design to the next, taking ? it, manufacturer must be consistently to uprate his engines in order that the critical parameters proved in the original design s to f:ive better value 'or monn. He must at the ssrne time retain the new dnign. This sta'erient d F U maintained in + thunderous applause f rom both engine manufa:turers and en rehability. e' Alany of those present would be aware that the Alinistry users, particularly marine engine users. ? of Technology had recently placed a contract with the Yarrow-The use of test to for fuel-injection equipment deve Li. Admiralty Resear:h Department to irwestigate the use of ment was, of course, felly appreciated and valuable data reg y medirm-speed geared Diesel engines as propulsion units for ing performarce and hfe of the equipment rnight be gai when applying resuhs obra y ocean-going merchant ships. "Dris surver was now almost However, care should be taken,igs to engine c N complete. He thought that it was true to 'say tha' the results u ~ from inicetion-equipment test r of this survey would give encouragerr.ent to those manufacturers injection into a pressurized medium was strictly sirw!st R of medium-speed Diesel engines who thought that the medium-wondered if this was done in the case where noni ga -.t speed Diesel had a future and could compete in rnany ships pressure was found to be lower than the prevailing gas with the slow-running d. rect-coupled engine. The report show-with a needle still open which permitted g entranec int a ed that every type of ship and trade must be treated on its nozzl gallery. The cure adopted, he ventua J to guess, w ' n h merits, but that a shipowner who failed to carry out a detailed lighten the reciprocating mass of the inicetor.H ceonomic survc3 into the possible use of medium-speed Diesel i.- engine;, as an ahernative to the slow-running direct-coupled their own fu:1-inicetion equipment for the.t medium-s engine, did so at his peril. Diesel engines, had always been protagonists of the low in y injector, i.e. having needle springs acting directI f upon

}

AIR. S. H. HEN $ttAt.t., II.Sc. (.\\lember) said that, as an needle without the intermediary of a push rod. Of course engine builder of medium-speed engines, he found that he was ring wr.s thus placeu into n somewhat uncomfortable pos on the side of Dr. Pope in a lot of the thing, he had said.' The (h it and spm), but unorthodM spring wire sections h paper, however, had been sery stimulating and he wouhl like with the space and chromium 4.:en wire with the ternpera to ask several questions abant it. .h ,g

Discussion ~. The "hfdrodynamic condition" referred to in the paper, (200 deg. C). He wondered if this had been obscrved by the he thought, wcs a spill v.ase rec: ding too fast,which the normal authors. He also asked for the velocity of the oil. oscillating system of the injector was incapab:e of following. A Turning to valves in cages, he said that one considerable stiffer spring might help in border-hne cases. A trick, imparted advantage of the cage was that it very much reduced the flux to him some time ago bv Alr. J. F. Alcock (and gratefully ack-from the valve seats to the cylinder head. Since the cylinder nowledged) was to watch for gas bubbles in the injector leak-off head was a complex casting, a large concentrated heat flow from connexion; should gas pass into the nozzle, it woulJ generally the valve via the seat was undesirable. In smaller engines, which pass through the cylindrical lapped part of the needle-nozzle did not have caged valves, this was a very common cause of bore causing lacquering of the lap fit and would finally appear cracking between the seats. He cited the paper of Mr. Fujita* in the leak-off pipe, wnere a plastic tube would facilitate ob-as an example of this. ' n. He said that, acting upon this recommendation, his Turning to valves,he said that he had noticed in the paper ny sometimes used development engineers as bubble that while the temperature of the seat had been reduced t>y the wat ers". cooled cage, the temperature difference between the ecmre of H: thought the authors should be cong.atulated on having the valve head and the sut was increased. This would increase such confidence in the precision of cathode ray oscillogram the thermal stresses, and the risk of seat cracking due to thermal interpretation. He had tried something similar and the result stress. He gathered that the idca of sodium ecoling had been had v ried between i degree and 2 degrees cam angle, dependmg discarua, but he thought it might be a useful idea, not from upon the thickness of the pencil pomt used and the condiuon the point of view of cooling the vahe rest, but of reducing the of the intecpreter. thermal stress. Of course, what the sodium-cooled valve did was He asked if the line pressures in Figs.13(a) and 13(b) to pass the flux back to the valve guide, but there it could be referred to full load conditions. If they did, they were remark. coped with quite well. . lie then referred to crankcase explosions. These were prac-r_bly low. Also, the dif!:rence between maximum line pressure and maximum gallery pressure was rather large, being 1,650 lb./ t cally non-existent in small engmes, but they did occur frorn sq.in. in Fig.13(a) and 1,S00 lb./sq.in. in Fig.13(b). He won. time to time in large engmes,and were extremely nasty thmgs. dered if the edge filter (which,af ter all, was the maior throttling it wuuld be vduible to have mformation on this subicer rmd to j component between line and gallery) could be respansible for know, from tbc paint of view uf safety, what the difference was i this pressure discrepancy. Wall friction could hardly account between the tri nk-piston and the crosshead engines. for it with the custo nary maximum flow velocities of about 90 m./s. DR. W. P. MANsrtELn was particularly interested in the Dealing with the crwer on.w.- fuel operation, he said authors' lubricating oil consumption tests which were b.iefly that he was intrigued by the statement that :he lack of cooling desenbed on paj;c 336 of the paperand to svhich Fig. 21 referred. ability of preheated fu:1 shou!J be responsib!c for high nozzle In,some investigations on this subject on smaller engine the tip temperatures. The fuct temperature given was 160 deg. F. Dntish Internal Combustion Engine Research Institute Ltd. had (71 deg. C.) for a blended fuel of 300 sec. Redwood 1 viscosity; tned increasing the oil pressure by reducing the area c f the gas cil, not prehtated, wou!d rea.h the nozzle, after passing b:a,4 st.rface of the ring, but thir had had little effect. Ilow-through the esmpresnve cycle of the fuel pump, not very much ever, changes of, wall pressure, made by sarying the t. dial cooier. He ventured to think that the hotter nozzle tip of the thickness of the rmg, had a marked effect. Ile said that it o auld h-fuel operated engine was more the result of the sk>wer be interesthe to i:aow by what :nethod the authors had uried bt. ,. of the heavy fue!, with a resulting larger heat rejection wall pressure, apart from the change to a spring-loaded rmg to, and heat absorption from, the nozzle. which was mentioned in the paper. He said that he understood that the mechanism of trumpe: f;rmatio's was a function of the lighter fractions of the blended MR. A. J. S. BAKER (Associate) said that the authors had hesy fuels boiling off in the nozzle sac and squeezir; the. vduced a remarkably full description of what could on!v be l heaner fr-tions out of the nozzle holcs where they carbonized. described as an exceptionally well developed engine. Of particu. l Carbonization temperatures were much higher than the mea. lar interest to people connected with lubrication research was I sured nozz!c tip remper:ture of 392 deg. F. (200 deg. C.). He the systematic work which had gone into piston development. said that he would be very grateful if the authors could provide This work 1..sd obviously paid off handsomely in the modest information about the precise location of the thermocouple on temperaturv, to clearly denoted in Fig. 6. It would be interest-the nozz!e tip. His company had m. s ared nozzle seat tem. mg to see far the really excellent fuel utihzation rates, i l peratures (the thermocouple being lor.nrJ within a millimetre indicated b..ie exceptional fuelconsumption rates, had centri-from the no221e seat) and temperatures obtained on one engine buted to th:: For instance, metal temperature compantons type, depending on engme ratmg, cylinder head design und fucI, taken at the same time as the variable valve timing tests described had reached 464 deg. F. (240 deg. C.). This surely indicated in Fig.10, right-hand side, would perhap.i illustrate this point. nozzle tip temperatures of a far higher order. These nozzles had Fig.10 itself suggested that an even broader area of mimmum been uncooled and made from heat-resisting nitriding steel specific fuel consumption might be po>>ible with automatw. illy-which maintained the seat hardness at clevatcJ temperatures, uried vWre timing. He wondered if the authors had comidered He said that he envied the authors : low maximum such a possibihty. cylirWr pressure of only 1,350 lb./sq.in. at 220 lb./sq.in. Looking at the Fig.10 data points for a constant b.m.e.p. b.m es. This should enable them to get away with an injector of 200 lb./sq.in., it appeared that a fairer mean curve would release pressure of only 2,500 lb./sq.in., resulting in a closing have a pronounced and steepening hog rather than the sag pressure of 1,720 lb./sq.in., thus still having a comfortable shown by the authors. He asked the authors to justify the mean rnargin availab!c above the maximum gas pressure. hne they had postulated. conclusion, he said that the paper would aheays have With regard to the important work which had been done ap of honour in his hydraulies department, having already to optimize fuel injection characteristics, it was interesting to sen 11 sUde rules into a semi heated condition. coniider the authors' needle lift /sae pressure relationship con-clu> ions, in the light of the modificatien which appearcJ to have .\\tR. J. F. Atcocx, O.B.E., B.A., s'id that the piston crown been carned out. App.nently the unhuJing value had been in-was described as high-tensi!e steel, which term covered a lot of creased ktween (a) an,J (b,) of 1,ig.13. Did the mahors attribute ~.'mpnsitions. It would be valuable to have either the thermal this faer to the rcJuction m mespient sceondary liftmg indicated conductivity or the composition. na the neeJMft diagram (h)? I're>umably the injection rate Fig. 6 showed a wet. side temperature of over 464 dec. F.

Fujita, II.1961. " Service Records rif Ahtsubishi Napuki Diesel (240 deg. C.). Ile said that it was a rough general rub.stut one Ui!. Type Engines and linprovements Made en the Engines". Tr.,,n.

was apt to get coking on the surface if one went our 392 deg. F. I. Mar.E., vol. 73, p. 37. 341 Lt - m

-n { The 1)erclojnnent of a flighly-rafed Alediuni-meed Diesel Engine A 4 1' had aho been increased and this had been accomrwJared by The engine referred to in eh paper h:.d twen develop: 1 4* permitting on increase of ncedle lif t. If this ucre the case, to run on heavy fuel oil. II.. w.u;;ht the authors would agrt 5 2,I might not needle-lif t increaws have to be clo>c! controlled in that the turbxharged f..r-stroke, trunk-piston engine c< a: 4* service operation, he asked. I.ikewise, the f uei-Ime prenure di.i-be troub!n..mc imus the paint of view of combust;o: 1 g gram (b) was presun.shir taken at the noule end of the fuct optrating at low loaJ, on heavy fuel, and fr..m y... ingures ! -; pipe. Ile wondered if it had been neccesary to tune the fuel pipe had seen for other enginc>, which showwt.: drop m cornpre,.'.- J i, 4 length t.: control the magnitude of the secondarv prewuie wave pressure, from 665 lb./sa.in.,at full Imd and speed, to 355 ; = sq.in., at 60 per cent speed and 22 ptr cent of full load, i-j E so as to eliminate secondary it.jection. [J Ile thought that th: general conclusion to be drawn from strongly suspectcJ that.hc relatively l ow compreswm prmu: 9 the fuct injection work wa, that cngines of comparatively low under those conditions was one of the prmeipal reason, f; ? "mf speed needed the same careful attention as high-speed engines. this. Whilst combustion might bequite satisf a: tory under tho h it would be very interesting to see a comparsmt irwestigation conditions, when the engine wt, new sad in hrst-claw conditio: 53 At m certain large-bore, slow-speed engines, having several nontes with the accumulation of wear of tmt only hners, but miectio q ] connec'ed to a sing!c fuel-pump clement. The results of the equipment, he thought that the low compression pressure trr m careful work cone by the authors in this direcuan were demon. certainly a contributory factor. He would be glad to have th zu I strated in Fig.14. Bv extracting data points from the fuel authors' comments on this. consumption loops, it 'was interesting to note that the fuelling medium-speed engines in ships, parucularly in va,rbocha On the question of the operatiers.'. control of tu -I hnes for both the K engine and the K Major at different speeds cw of tb 2 E were virtually identical. The fuelling lines, from around 50 lb./ inercase in the number of ship, with bridge control of th 3 sq.m., b.m.e.p., on the lowest curve, were unusual in their engines, he was convinced that the fuel iniection pump ra: linearity. Perhaps the authors could supply fuel consumptions position should be governed to some degree by the booster pre at very low loads whien would give a cleaier indication of the sure. A few years ago, in a certain cross-Ch.mnel ferry, whi: 3 3 likely f.rn.c.p. From the data published it was evident that this was propelled by two turbocharged Diesel engines under bridg 1 5 must be of a very low order and comparable to that obtained control, it vas found, a very short time after the ship had gon m j with the largest low-speed engines. This point might be worth it.to servi., that the engine crankcase oil had become very dirt f bringing out since it was fashior.able to quote mechanical indeed. The reason for this was soon discovered: the bride f efficiency for large two-stroke snarine engines, and for a given control of the engines had been operated en leaving harbour a a M f.m.e.p. this would generally favour the four-stroke engine with if it had been an engine room telegraph, with the result that th -]' its higher b.m.e.p. engines smoked like chimneys until the turbochargers had tim [ ____s He asked the authors to indicate whether the performance to catch up and provide enough air for clean combustion. Unde : curves were obtained with the fuel described at the top of page these conditions the oil soon became filled with fuel soot. In I 333, nd if not, he said that he would like them to give details, stru: tion to the master as to the correct rate at which to ineren -n He said that the water-c.nled, exhaust-valve cage and valve engh.e power soon cured the troub!c. He fe!r that wh:re tum i } totators had made a major untribution to operation with low. charged engines were installed in ships,,ome form of centa m. cost fuels. Presumably some pruvision had been made to prevent over the rate of increase of the delivery of fuel to the engia boiling in the small scat-cooling passages in the event of sudden was essential. ' l shut-down, as rnight be expected in main marine engine application. Mr. C C J. FRENCH asked a question concerninp therm. $ S Ile thought that the notes on lubriesting oil consumption stress. 'ihe thermal stress rig shown in Fig. 4 was interestin-T were very relevant, as was the investigation on oil control by and provided an ingenious method of investigating a problen j. the upper scraper ring. He asked the authors to elaborate on which was becoming more and more irr.portant as engine rating = = this by indicating the degree of control exerted by the other were increased. This rig was useful in that it was applicab! ill rings in the pack. For instance, could a reduction in radial to asymmetric bodies, as wc!! as to those that were bodies of revo 3 pressure of the upper scraper be tolerated by in:reasing the load lution. In this respect the two-piece piston shown in Fig. c g a on the lower one? appeared to be a body of revolution. Computer programme a r The rig described to evaluate piston-ring quality resembled were nn v available for calculating the the. mal stress of suel 1 a variety of test rings used for different purposes. Experience compon 9ts. He wondered whether the authors had tried i =g with these had indicated considerable scatter of wear results, check calculation to see whether th-,e was am sort of agreemen -i particularly at high rate of wear. Perhaps the authors could between the rig and a computer. His own rather limited experi ' mdicate the signihcance of the weight loss figures they had ence so far, with a computer approach, had been more valuabl< ut 3 quoted in Table IV. lic wondered whether they had observed a in showing sp limitations in the computer programme than ii ? pattern of related ring to bore wear rates for the different giving realistic piston thermal stresses, the problems bein; material combinations tested. Ilad any significant difTerences in largely the rather complex shape of pistons. 9 = = p;ston-ring groove and ring side wear rates been observed when Turning to the inlet-vahc wear, he said that he was gl. 1 = different irons were run in the steel piston crown? The authors that Dr. Pope, in his presentation, had elaborated on his wea - -2 had nat shown the re.etallurgy of the piston crown," bu* othe.- factor, which Mr. Frrneh had found some.vhat incomprea:n appheations of high-tensile steel had suggested tha; steels con-sible as it stood in the paper. Ile agreed that lack of lubrican d a taining appreciable nickel contents might produ:e increased wear was the main cause of heavy in.cr-valve and seat wear in turbe j rates in the presence of boundary lubrication. charged engines. It was most interesting that the authors hat found thickening the head of the valve so effective in reducin iji =* 5 Ma. J. A. CowotROY,11.Sc. (Member) said that, as the I; this wear. g g Maior engir.e had been developed specifically for marine pro. Touching on service experience, he said that two year y pulsion, he had been surprised that Fig. 24 did not show the previously a paper

had been presented, giving ustasis of sen-ic-2 performance plotted against speed on a propeller law basis. He experience on an engine of very similar size and rating. H m E

would particularly like to see the compression pressure included thought that everyone looked fonvard to the t:me when th- 'E in such a plot, because he had th: impression that many builders authors would be able to give co nparable details of exhaust 1 of marine Diesel engines overlooked the implications of the vahe hfe, cylinder-liner and cylincer rin : uvar on the K Maior 4 .i propeller law, which related pewer to speed in a ship, partieu. when operating on residual fuels. In this connexion, if th al ~8 '4 larly when applied to iurbocharged engines. If this law were authors were proved correct in their aim of up to 3,000 hour. Z assumed to be a cube law it meant that, if the engine was between servicing of inicetors ana exhaust vahes, this wouk 2 developirig full power at full speed, it was only regu red to be a most valuable step fonvard. 1 develop as little as 121 per ynt of that power, even at half 1 speed, and as ships not inficquently proceeded at speeds lower

lienshall, S. II., and Gallois, J.19t>4. "Scrrke performance cu sj

= M than full, this condition did occur now and then. S.E.M.T. l'ielstick Engines." Tea,n.1. Mar.E., Vol. 76, p.145. i 342 3 ]

A 4 Discussion 1 I Correspondence e 'tAl4NDT.R E. R. A1Ay, D.S.C., R.N. (Alember) wrote rhat e C r ission suitable for employing, say, two K Alajors to drive

lii, it was.::e ten years since the Pielstick PCI had begun to make a single propeller shaft, and whether their company proposed

_d ~ its signi!. cant contribution to the propulsion of ocean-gomg to nfler complete propulsion umts-engines and reduction A ships, and durm; the whole of this time it had been without gear. any effective medium-speed competitor. The K Alaior must now be judged by comparison with the Pielstick PC2, with Mn. G. H. Hecnts (Member) commented, m a wrnten con-which it would be in direct competition in every field. tribution, that the increase in power output should in no way Power for power, the British engine was rather larger and alarm prospective users, because even the ultimate aim of $28 heavier than its French compentor. In some apphcations this b.h.p./ cylinder, with 250 lb./sq.in., b.m.e.p., and 1,400 lb./ m wouli mt rrsiter very much. Commander Atay imagmed that sq. in., pea'c pressure, representea only 2 93 b.h.f../sq.;.,. of g the relative hrst cost of the two engines would be very signifi-piston crown-almost identical to the power per square mch g cant, assu.ning that the/ had equil ability to ban heavy fuel. on the crown of the Maybach engine with pistons of similar i The Picistick had never bcen a cheap engine and, in its PCI construction. form,its exhaust valve life on heavy fuel dk! not ahvays prove It would be interesting to know the cooling oil flow rate, is irnpressiv. Its popularity had stemmed from its introJucing (he suggested approximately Ib gal./b.h.p. hr.), since crown ] high-speed engine standards of accurney into the marine engine and ring life depended on adequate cooling and, in this respect. field, with a refreshing freedom from the very heavy mainten-the oil feed through the connecting roJ might prove to b: the 4 ance work that marine ent;ineers often c.sperienced on propulsion limiting factor. Gisen adequate cooling,it was known that this j engines, less ucl! made and inJifferently developed, fonn of piston would stand greater pourr per square inch of Over the last few years, the maior British medium-speed crown area, es shmvn in the two-stroke cycle Ruston and J Diesel firms had caught up the lecuay in standards of manu-Hornsby A.O. engir., when published figures showed over a facture, and aho had undertaken most impressive programmes $ b.h.p./sq. in. = uf detailed deselopment. It therefore seemed that the K Alajor ifis company's experience of materials for such piston would mcet international comretition successfully, uould extend crowns indicated that thermal fatigue tended to become the 3 the market gained by the K engine, and join the Fielstick in limiting factor and this depended principally on coefficient = p ing large merchant ships. of expansion and thermal conductivity. Had the authors con- ? mmander Alav noticed that the authors had made a sicered one of the high-nickcl a.loyt to irinimize tne effect of M rar mis!caJmg referen:e to short-life engines being per-high operating temperatures, or the high-conductivity copper F missible in naval work. This had never been so (except in chromium alluys? motor torpedo boatQ. Submarine engines were designed and A further aid to cooling was increasel valve overlap. Had j produced by the Admirahy between the two wars in an attempt the effect of this been explored with respect to piston crown to produce better-not lighter-engines than those arcilable frorn and piston ring temperatures? W industry at the time. Af ter the last war, the Admiralty worked The scraper ring urrangement permitted adequate lubri-F hard to persuade industry to adopt modern standards it, devel-cation of the skirt or crossher.1 length of the piston, but when 1 opment and manufacture of long-life engines up to 91-in. bore, cil control became a problem after extended service, there ? 2 but success was only achievej gradustly and at substantial might be a temptation to fit a highly lo:ded ring in tie skirt { public expense. groove, with possible risk of seizure. To avoid such possi-In Germany, before and after the war, and in France at the bilities, had the authors considered omitting the skirt-ring J 1 present day, engmes designed partly for naval purposes had met altogether and adjusting the upper scraper ring accordingly? i with uidespread comtr.ercial seceas. Thi> had come about It was noted that three taper-faced rings were fitted below I through recognition that naval and commercial requirements a parallel-faced, chrome-plated ring in the top groove. There could be designed into the same engine with advantage to all might be a tendency to blow-by during the initial running of - i concerned. the engine with this arrangement. Had blow-by readings been Possibly the most remarkab!c feature of the K Alajee was taken during test work and had any indications been noted? that it had achieved so much while retaining cast iren for frame An important factor in piston-ring material was compati-and bcdplate. Rigidity was essential to maintain bearing oil bility with cyhnder liners. Not all materials were suitable in I film gcumetry withm acceptab!c hmits and cast iron was about this respect, but might be metallurgically sound and, therefore, I ) twice as flexible as steel. A cast iron frame must have heavier of good quality. scant!;ngs than a steel frame, the cylmder centres must there. It was not surprising, therefore, that a randorn flake g fore be further apart, and bendmg moments increased in conse. graphite hon had given satisfaction in this size of engine. I quence. On the other hand, cast iron was cheaper than steel, With regard to cylinder liner material, was this also random an lopment of modern cot irons had done much to make flake graphite? How was the bore machined, and what type thi> rial rnore attractive. Fairbanks Morse had used cast iron of surface was produced? ex tei cly in their new large opposed. piston, medium-speed With regard to the outside diameter,was the liner free from engine. Other manufacturers were, the writer belicsed, using water side attack and what precautions teight be taken to deal ] steel for comparable engines and had also chosen the two-stroke, with this possibihty at the higher ratings? valve. in head arrangement. On the question of heat dissipation, was it known what l Soon,at least four of the e s alve-in-head two-stroke engines proportion of heat was transferred through the piston crown 1 (one of them ilritish' would be campeting with the K Alajor and to the cooling oil and through the piston rings to the cooling the Pielstick in the rapidly expanding world market for large water? 2 medium specJ engines. It w.u obvious from this paper that T Alittlee> had p?anncJ to secure their share of this market. Altt.1. H. Allt.tDN (Alember) wrote that it was stated, on Z lt would be interesting to know the authors' view on t.ans-page W, that to produ c a reliable machine one had to pro-

g

== ? 1

y The Developmenf of a Highly-rated lledimn-speed Diesel Engine ] ~, - =i ~ g-- p-i cred from one successful design to the next, tsking care that o 4.I

6 1

x ru,jer et,.irater critical parameters proved in the enginal design were main-4 tained in the next. l o mqfor early venee.*ar = + russo-reer acarw'*ir With regard to the critical parameter < shown in Table I, t 3[. __.j_-..- ? it was rather surprising to see that gudgeon pin, or small-end bearings, were not mentioned, as these beanngs could be g o., T.,. t -i i s } troublesome and also, on occasions, connecting rods had split 2 g g lengthwisc through concentrated eye loading. i \\ j ,\\ = { of { '(5 -. r Perhaps the authors would care to comment on th!s subject, t' and give details of the design of their renall-end bearing with a l J b' particular reference to the bush-whether it was floating or not f --and its material. j x. With regard to the pistoa design, as shown in Fig. 3, it g l -I would be interesting to have the authors' views on the im-d U [ portance of the distance from the crown to the top piston '~ l i f ring, and also further enlightenment on their statements that: i i ,N } a) heat resisting "helicoil" inserts were used to carry the studs 'e and that these acte 1 as a " heat barrier" for these studs; b) that i 2 r disc springs were fitted under the castle nuts on these studs to o d ia. n a 'e,y,,,, %, 8 5 increase the resilience of the assembly. Did this mean that they had accepted the fact that movement must take place between the piston crown and the body, and if so, did fretting take Fic. 25-Relation bettecen output /srect! colums and 2 place w;th ensuing leakal,e of oil across the jointing face? cylinder borr Wi.' further reference to Table I, it was noted that the maximum permissible b aring loads for the main bearings above, nor too much below, the lines marking the up and bottom ends, vere given as 2,500 and 5,000 lb./sq. in. of current design. Referer.e had been made to the use of small centrifuge --s 1 respectively. Some enlightenment as to how these limitations mounted at the engine for the bypass purification of the lubri j were arrived at would be of interest cating oil. A marme installation of more than 3,000 b.h.r q On page 336, under " Space and Weight", the authors would norrr' ally justify the use of a motor-driven centrifug .i made a good case for the cast iron engine, stating that few N fabricated structures were able to avoid fillet wc!ds in load. for the continuous purification of lubricating oil. Such a sys tem aho enabled the whole of the lubricating oil charge to b carrying regions, and that the fatigue strength of such welds purified in harbour at the end of each trip, a practice adopte t) might be as low as plus or minus 12 tons /sq. in., and that g by many owners. Commander Good asked the authors whethe 3 even butt welds had only a fatigue strength of plus or minus they considered that the enginc-mounted centrifuges,woul g 3 S tons /sq. in., compared with 5 tons /sq. in. for a good avoid the necessity for a separate motor-driven umt, particularl i .y quality cast iron. If these figures were correct, it was difficult in a heasy fuel burning instsilation, and, if so, could they gh 9 in t, understand why, apart from the saving in weight, so many an indication of the time af ter which cl aning o.' the t. nits wo.21 j, M other en;;ine builders had adopted tabr;cated designs, espec. be required. It was am,cd that provisior. wss made to ci ially as aho, in the event of damage resulting from the failure off the flow to ind*ndual centrifuges, to permit them to i 'g of a bottom-end bolt, a cast iron engine did not suffer distortion cleaned while the engine was running. 1 J and could usually be " patch" repaired, whereas the fabricated The attention which had been paid to the design of ti ? f structure was usually distorted and had to be renewed. f uel injectors and exhaust vahes was very wc!come. The mair It was noted that oil was used for piston coo!ing and lubri-tenance of these items probably representeJ the largest woi 'a .. M cation and in this connexion it would be interesting to know load for the ship's engineers. It was consulered that a pern if the author >.had any relatht figures on lubricating oil capac-of 5,000 hours between overhauls would not be an unreasonab } F ity (e.g. gal./h.p., in circuit) for the engines forming the aim for the exhaust valves. s [' subject of this paper, as compared with slow-speed, direct-Shipowners were becom,m m, ereasm, g?v concerned aboi drive Dieseb. the noise levels in engine rooms and this v.as reflected in t; ] Furthermore, in the case of direct-drive, tiow-speed engines m {i burning Leavy oil, it was found essential,on account of crank-l x x 4.M,,,,,,,,d l W case corrosion, to isolate the cylinder bottoms from the crank-a 6, + o g 4.,,,,,,,,,,,,,,,,,,, case---what precautions, beyond using an inhibited lubricant, g were being tal n to prevent such corrosion takmg place m 8 + g4.jo,f,,,,,,,g,,,,, i hM,i the engines produced by the authors' company. s' ^ l A in conclusion, he would be grateful if the autho, conid ?J -N ~ r-i h.N,,,,,

i briefly state why, in comparison with the builders < f large, 1

0 ? slaw-speed, direct-coupled engines, they had chosen to develop I

x the four-stroke cycle engine instead of the two stroke cycle l

engme. 7 s g l that, when a new engine design was introduced, it was natural h ,NQ*--l # I COMMANDER E. B. Goop, O.B.E., R.N. (Member) wrote a }L to compare its ratmg with those of compeutors. A true com-d j " parison of ratings should take into account many design M features, but an inNestion of the mechanical and thermal load. j ing problem' which the manufacturers had to mercome could wh.I be obtained from the output per cubic inch of swept volume W. and the output per square inch of piston area. These factors c f had been plotted against cylinder bore, for a number of modern a to i4 is n a q 4 turbocharged engine designs,in Figs. 25 and 26. The factors for the K Major engine had been plotted at .g esca of the development stages referred to in the paper and it Fsc. 26-Relation betsveen output / piston area and y could be seen that these ratings lay neither too adventurously cylinder bore l g P 344 4 ':n-a y ,. q, 3

Discussion number of new. hips which had insulated control rooms. With With the advent of a new medium-speed Diesel engine,i: a mnzimutts cylinder pressure 25 per cent greater and a maxi-was inevitable that designers of naval machinery installations mum speed 18 per cent greater than its predecessor, the K must ask themselves whether this new engine was suitab!e fo-Major might be expectcJ to be considerably noisier. Ilowever, warships. In this respect, scetion f', on " Space and Weight" was it was possible that the many design changes which had been relevant and one could observe that cast iron, whilst it hatt made had at least partly counteracted the tendency to higher r.uny admirable properties, was not the best of materials for noise levels. It would be useful if the authors could provide shock. Perhaps the authors would like to comment on whether any comparative noise measurements for the K and K Major they intended to offer a naval version of this engine in du: engi course. e e e 4 V I 1 l (n) u../ 9 O e 345

4

e Authors' Replies caring m2ss in the injector was quite correct and,the K Ma' 1

Mr. Lou. (rep!ying to the verbal discussioni referred to in ector was of the low inertia type, as descnbcd by M Mr Cook's pcmt about 36 cyhnders being required for a ship Groschel. of 18,000 horsepower and said that the paper had tried to show fuel Ime press sres in Fig. O referred to full-! The that the power available from that number of cylmdcrs was now conditions and the authors considered the pressures levels a twice as grea, as it was a few years ago, with the same rehability the difference betwecn line-pressure and gal!:ry pressure to quite normalin their experience. and maintenance requirements, A comparison of piston-crown temperatures, measured in He agreed that the higher nozzle temperature for the u the engine using templugs, with the temperature distribution cooled micctor with heavy fuel, m Fig.19, was only partly d produced in the rig and by'an electrolytic anatogue showed that to the loss of cooimg from the fuel and was also a result of t. in the engine, crown temperatbres were ra her lower than those slower burnin; of the heavy fuel. The conclusion, however, w t produced in the rig and predicted by the analo:ue, while ring-unaltered that cooling of the nozzle was necessary with hea belt temperatures were slightly higher. Thn difference was fuel and tests had been carried out, which were too extensae attributed to the rather more efncient cooling of the underside be fully described in the paper, which shou cJ that the tip te. of the crown produced by the motion of the piston in the pcrature was dependent not only on engm; load, but also engine. The temperature distnbution was proportionately the fuel temperature, water flow quantity and water temperatu f same in both rig and engine, so that thermal stress measurements The therruocouple for these temperature mea >uicments u s located actually at the surf ace of the nozzle tip. should be of the right order. The authors' company did not use a ratio as high as the Mr. Mcock had asked for details of the composition

2) to 3 times increase m fatigue strength of rolled threads over the high-tensile steel piston crown. This was a 5's-ton ten E

cut threads, mentioned by Mr. Ccok. Thc3 used a value of 0 25 I per cent Cr-Mo steel and he would gladly send exact p I times the U.T.S. for rolled threads and 0125 times U.T.S.ticulars of the tratenal and of oil veloen a t; M r. Aleo, for rnachine-cut threads, giving a rrit% of 2 :1 ia f avour of He pointed out that the 464 deg. F. (240 deg C.) maxim' - temperature in Fig 6 was a bulk tempera:cre of the m. t;. i rolled threads for fatigue strength. Hoth Mr. Cook and Commander 'l yrrell had commented and that the surface temperature in cortact with the oil wo: on lubricatm; oil > for uu wnh hearf uel It was difheult to be be lower. There had been no signs of oil coking on the surf f 4 the deterioration of oil lubricartes because no oil precise about of the cooling chamber. critical ta choose the ri sp-cification defmtJ accurately the requirem;nts of a lubricant He agreed that it was very for Diesel cngmn. The typ: of oil found suit h:c for this engine maternak not only for the seat of the vah., but for the va a "goaf' Supp:cment I level uith a cune reasonable n> elf. The tr!ative coefT eien:> of expanwa of thea was alkahnity. The' authors useJ a maximum bulk oi: temperature of matuiah and their conductivity were most :mportam 170 deg F. 7 deg C.. but it must be remembercJ that thn "I he subjcct of crankcase csplosions v % a reneral on: imphed that there woulJ b; local higher temperatures m the confined particularly to the enginc un'cr discussion. I not engme of the order of 210 deg. F. (99 deg. CJ. I shomd that the engine was fitted with nplo> ion doors lie confirmcJ that a was not the mtention to imply that cent ri-cast rm;3 were necessarily mferior to sand-cast rings, company had expenenced one or two se or eight year >, of crankcaw explosions m other tyrw but the pomt shou!J be made that the quahty of the sron was engine where the cxplosion doors had uoikcJ satisfac wi!) - o 7 the rr.ct more dif3: ult to mamta:n m a etntn-cast nn; R-ferring to Dr. Mansfielfs question about Referrmg to Mr. Henshall's pomt about specific a;r flow, of varying the wall pressure of the piston rinp. he said ? Sc wrted 'ha' it " a= desiraSle to continue to incr-ase the specific th.s haJ been dont ioth t y ahenng the hearmg area of si gi 1-as rating in:ressed, althougn th+ esaapolated hgure smg and also by re-desigmng the ring. air flou { m Table I shou ed a small reduction Mr.11aker had suggested that there should be autem There had not tren anc problem with differential expan-timing on an engine. This was an attractne idea, partica! k-sion between the steel crown and the cast-iron p.stan body, t if combined with automatic timing of fuel inicetion, but probably because the intensise cochn produced a low tem-the interf aces, as could be seen in Fig. 6. The very difIicult to achieve. Il some simple and foolprool double line in Figs. 2, 3 and 6 represented a threaded portion doing this could be found it would k perature at He said that he could not justify the mean line for E [ uhich was used to establish the best crown drameter and was 200 b.m.e.p. data on the right-hand diagram of Fig.10 q a wcll-known development technique. measured points indicated the " hog", sug:ested by Mr. B The development engine had been run with vahc guide but he could no: explain why this should be so and hence y 4 diametral clearances as small as 0 00lin. to o 002in. with the a force-lubricated guide, anJ a clearance of 0 003in. to 0 00lm. mercly indicated the downward trend whic of greater significance. f had been arrived at for the fmal design Wear rates with the Referring to the injection diagrams, he said that the lubricated guide were extremely low nnd a hfe of 10.000 hours loading vohimc had been increascJ from (a: to (b) in Fi. was exp:etcJ before replacement o' the guide was necessary. Mr. Groschel had sounded a word of warning about fuel-and had a very strong effect on the tendency for s iniection The injection rate had also been iricrea*.ed an injection test rigs and the author > agreed generally with him. Rtgs were extremely unfu! if one was careful in interpretmg the already stated in the reply to Mr results The suggestion that th-problem o' back-flow of us of injector had been adopted The f uel line pressure measured hallway alang the iniection pipe in each casc an. f rom the cylmJer had been praented by reJucing the recipm-346

Authors' Replies .+ was near to that of a good s: eel. There ucre other advant:ges in inicction pipe kngth was the minimum posuble for the engine. Mr. Ilaker's renurks bout the Willan's lines were qtnte valid using cast iron. One knew that one could obtain good castings with c.t,t iron far the si/c of engine he was discussing and it and, in fact, the su elve-cylinder engine had shown a was an ca>y material to handle. Size for size, his experience had rnechanical efficiency of 93 per cent. The performance curves been that cast iron c.m out cheaper, therefore if one had a were obtained using disti!! ate fuel. material w hich was as good as another and was cheaper, one had The piston-ring pack, described in the paper, was dehler-to have a very good reason for not u'mg it. Ife could only see ately designed so that the scraper ring above the pin was more onc reason for precludmg its use and that was if weight were severe than the lower scraper ring. The authors considered it a predominating factor. However, when one considered the rest importmt to maintain an adequate 0:1 film over the body of the so that the lower scraper ring was only intended to cf the engine room equipment, the tankeranc and the fuel cess oil to prevent the upper ring becoming flooded. capacity, one would find that there was a difference of one or The weight lon igures, in Tab!c IV, were only significant in two per cent between a welded design and a cast iron design remo so that, for commercial shipping, this was a marginal comparison to one another as they were obtained from a rig running completely unlubricated anJ could not be related to co isideration. conditions in an engine cylmder. There had not been any He pointed out that with an in-line engine with an under-controlled tests to mcasure wear rates in the grooves of the slung crankshaft, one could have a very nice stress line pattern which, on the drawing board, Imked very attractwe and almost steel crown with piston rings of different irons. impossible to improve upon, but when one came to a "V" in tnswer to Mr. Cowderoy's question about compression pressures, he said that, at $25 r p.m. and full load, the cora-engine with side by side conne: tint; rods, so that the opposite pression pris.ute was 903 lb./sq.in., oming down linearly liners could not W in line with each other, the s rcs* pr. 6cen Dith horsepower to 3SO lb./sq.in., at 100 r.p.m., i.e., effectively did not look quite so elegant. He accepted that the cast iron bedplate was more difficult to design because the stress p. 'ern no load. The compression pressure, corresponding to the 60 was more complex, but once one had Jesigned it and got a per cent speed, 22 per cent load condition, quoted by Str. good design one was simply comparing onc good design with Cowderoy, was 430 lb.hq.in. He agreed with the contributor another. It was also a question of continuing from a well tried that low compression pressure, or rather compression tem-engine to the next generation, without departing from well-p.rature, could contribute to inferior combustion in a worn proven design principles. His company had now completed its engine ct low load. Air. Cowderoy's suggestion that marine' propulsion one thnusandth K engine and had over 300 of them in marme engines should be treated like lxomotive engines, from the point application. Over a third of the engines were running day of view of preventing the driver from accelerating too f ast, was and day out on heavy fuel, a good point. The necessity for the turbocharger to accrierate was ef ten overlooked when rapid increnes in load were called At:Tnons' RF.PtX TO WRITTEN CONTRIDUTtONS for,tnd it might well be necessary to apply the locomotise type The authors wrote that they entirely agreed w*th Com-of fuel rite control to marine engines. mander Alay's appreciation of the rapidly increasing demand In reply to Air. French,he said that the computer approach to pi n crown thermal stresses had betn to comtruct ar for 1. rge m:Jium-speed engines. They had delihemtely restr::ted the paper ta the dcvelopment of the K Alajor engine itself but electr nWo'lue which, as mentioned earlier, gave quite their company was certainly proposing to offer complete pro-good ement with the thermal rig. Work was currently in progress en a digital programme which would calculate stresses pulsion units for geared installations wi6 cither single or multi-directly, whereas the analogue only gate temperature distribu-engine inputs. rion from which stresses could be calculated. In reply to Air. Hughes, the authors wrote that the pister. The numerical value of the wear factor for inlet valves cooling-oil flow was 17 gallons /b.h.p.-hr. at the current ful!- obvi:usly applied to one's own engines, but a inanufacturer load rating. The cooling design was such that the operating could apply the formula to obtam values from his own engines. temperatures of the piston crown were well within the therr.u! In this connexion, he said that the experimental work, from fatigue limit of the stect used, as could be seen from the iso-which the wear factor was developed, was described fully in therms of Fig. 6. The work that had been carried out on the optimization of valve timing and combustion characteristics, referenc2 (2). which was described, had been aimed at obtaining the best Dr. Pope said that before the meeting closed he would like thermal cfEciency from the engine and not at reduction of t2 make cne or two comments about some generalitio which component temperature by seaven;c air cooling, w hich they con. sidercJ was a relatively inefncient method of controlhng com-had come up during the discussion. ponent temperatures. The temperature of the critical parts of II; said that they were getting to the stage in the med um. speed engine industry where the research and development the engine, such as exhaust-valve seat, injection nozzle, and top cflort ci the engine builders was outstripping the companent piston-ring groove,was controlled by direct cooling. As mentioned in the reply to alr. I!aker, the lower scraper fuilders, cnd he could foresee, in the not too d stant future. ring in the skirt was telatitely mild and the upper scraper more that engine deve;opment might well be held up because of severe to ensure adequate lubrication of the piston skirt. The bek cf blowers and injection equipment. He hopeJ the supply i jindustry would persevere with enthusiasm for the highly-rated taper-faced compression rings were an advantage in initial run-ning as they bedded in very quickly on a narrow circumferential medium-speed Diesel engine as rnuch as the engine builders band. Initial runaing-in had leen the subicct of a good deal 112 thought that the problem of the maintenance of of investigation on the test bed and the best results had been were. mcJit need Die <.cl engines in the marine world should be obtained with a ielatively rough liner surface, which was honed to a C.L.A. of shcut if%, the liner being a random flake judge jectisely. Obvioudy, en the medmm. speed engine one graphite iron, slightly sof ter than the piston-ring material. yts gomg to hac more parts, but there was a world of differ-Calculations of lin:r frequency and vibration amplitude 15.in. piston and handling a 30-in. pnce between handling a,hl were nnt just the number of parts, were included at the design stage to avoid the possibility of pist:n. The factors invoh but the way in which they cotdJ he manipulated and a sta-water-side attack. The heat divir.uion through the piston rings to the coolin;; water could not he directly measured in the tistical analysis of what were the major and minor faults. His engine because of the heat teceived directly by the liner from view was that if this analysis were carried out scientifically one hould find that the meJiurr.apeed engine could stand on its the combustion gaso. liy reproJueing temperatures and total heat ihr f ;n the rig, the proportion of heat flowing to the cool-nwn,acn with regard to muntenance. i~r ti; we alvut 75 per cent of the total and the heat to the With regard to cast iron, he said that each problem must be juJged en its merits.The fatit;ue strength of a goal cast iron finer was 25 per cent. 347 /}}

ML20100N610

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