ML20043F651
| ML20043F651 | |
| Person / Time | |
|---|---|
| Issue date: | 02/12/2020 |
| From: | Office of the Chief Human Capital Officer, Woodard Corp |
| To: | |
| Gary Callaway | |
| Shared Package | |
| ML20043F634 | List:
|
| References | |
| Download: ML20043F651 (4) | |
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Emergency Diesel Generator Glossary of Selected Terms Used in this Course Rev 3/16 E1 of 4 USNRC HRTD APPENDIX E GLOSSARY OF TERMS Acceleration Rate of change in velocity of a moving object, often specified in feet /sec2 (in math, the second derivative of position).
Aftercooler/Intercooler Heat exchanger downstream from a blower, compressor, or turbocharger for reducing the temperature of the compressed air, thereby increasing its density. The denser air provides more oxygen, allowing complete combustion of an increased amount of fuel (thus, more power) and the lower temperature air charge into the cylinders helps cool valves and pistons.
ALCO Engine A 4-stroke cycle engine previously built by American Locomotive Company (now out of business). It powers EDG units at some nuclear power plants and is now manufactured and supported by Fairbanks Morse.
API Oil Classification - The American Petroleum Institute (API) designation for lubricating oil use ratings. Oils can be rated for multiple applications. Diesel engine oils are indicated by the letter C (compression ignition) plus a suffix letter, as follows:
CA - Light to moderate duty, normally aspirated engines with low sulfur fuels.
CB - Moderate duty, normally aspirated engines.
CC - Moderate to somewhat severe duty, turbocharged engines.
CD - Severe duty, turbocharged engines.
Atomization - Breaking up of liquids such as diesel fuel oil into a fine mist to allow the fuel to effectively mix with the combustion air charge. The size and distribution of the tiny fuel droplets is very important for efficient combustion, which affects both the engines power output and exhaust emissions.
Back Pressure The pressure existing in a fluid (gas or liquid) system resulting from its physical configuration. Exhaust gas back pressure, for example, is the result of the resistance of the exhaust piping, work done in the turbocharger, and resistance to flow through baffles in the silencer (muffler).
BDC Bottom dead center. This term is the opposite of Top Dead Center. It refers to the location of the piston head at its farthest point from the cylinder head, just before it reverses direction. In a 4-stroke cycle engine the end of the power stroke and the end of the intake stroke both occur at BDC.
Bendix - An electrically or mechanically engaged, spring-retractable turning gear, used primarily for engine starters. Originally this referred only to products of the Bendix Company but is becoming a generic term.
Blower A mechanical driven air pumping device which provides an increased mass flow of scavenging and combustion air to the cylinders of a diesel engine. Required for starting 2-stroke cycle diesel engines.
Brake Horsepower (BHP) a measure of net power developed at the crankshaft of a diesel engine as measured by a device called a Prony Brake Dynamometer. One brake horsepower is equal to 33,000 foot-pounds of work per minute.
Brake Mean Effective Pressure (BMEP)
A theoretical term that refers to the mean effective pressure acting on the piston that would produce its brake horsepower. Stress on the engine is proportional to BMEP.
Brake Specific Fuel Consumption (BSFC)
The quantity of fuel (in pounds) consumed per brake horsepower (BHP) developed by a diesel engine for a period of one hour. Its expressed as pounds fuel per BHP hour.
Emergency Diesel Generator Glossary of Selected Terms Used in this Course Rev 3/16 E2 of 4 USNRC HRTD Cetane Number A measure of the ignition quality of diesel fuel oil, a key factor for engine starting and step load acceptance. It involves measuring the ignition delay of fuel oil samples vs. a reference fuel.
Clearance Volume The volume of an engine cylinder with its piston at top dead center (TDC), assuming its a conventional 2-stroke or 4-stroke cycle configuration.
Compression Ratio The ratio of the cylinders maximum volume to its minimum volume, during a complete stroke. For a conventional 2 or 4-stroke configuration these occur at BDC and TDC, respectively.
For an opposed piston (OP) engine the maximum and minimum volumes occur at ODC & IDC, respectively. See OP Engine.
Crankcase Explosion The over pressurization of a diesel engine crankcase when oil mist, fuel vapors, and oxygen in the engine crankcase are exposed to heat sufficient to cause ignition. The heat source could be a failed bearing, sparks from severe piston-cylinder scuffing, and / or piston blow-by (failed rings).
Droop In an engine governing system, the change in speed (RPM) the unit makes going from no-load to 100% rated load. Its normally expressed as a % of nominal RPM.
For those familiar with proportional control systems, Droop is synonymous with Offset.
DRU Digital Reference Unit, used to provide speed reference signals for later models of Woodward 2301A governors and some older governors. It can provide set points for idle, nominal RPM, and maximum speed, as well as ramp rates for getting up to speed (or back down to idle) gradually, during test, to minimize wear and tear on the engine. DRUs require input from a speed sensing device, typically an MPU.
Dynamometer A mechanical, electric, hydraulic, or other device used to indicate the power produced by a diesel engine by applying a braking action and measuring the developed torque.
Efficiency, Mechanical The ratio of the power output (BHPBrake Horsepower) of the engine compared to the indicated power input (IHPIndicated Horsepower).
Efficiency, Thermal The ratio of the heat equivalent of work output of a diesel engine compared to the thermal input provided by the fuel oil, measured over a period of time.
One horsepower is equal to 2545 BTU / hr.
Efficiency, Volumetric - In 4-stroke cycle, non-turbocharged engines, this indicates the engines ability to breath. It is the ratio of the mass of atmospheric air entering the cylinder compared to the mass of air that would be contained in a volume equal to the cylinder displacement.
EGA Governor Woodward electronic governor with hydraulic actuator.
EMD Engine - A 2-stroke cycle diesel engine originally built by the Electro-Motive Diesel division of General Motors. EMD, Inc. is now a subsidiary of Caterpillar, Inc.
Four-Stroke Cycle Engine A diesel engine that requires two engine revolutions for output power from each cylinder.
Frictional Horsepower (FHP) The portion of the indicated horsepower (IHP) developed by a diesel engine which is used to overcome the friction developed by the operation of the engine.
Governor A mechanical, hydraulic, electric, or combination device that controls engine speed by regulating the fuel input.
Emergency Diesel Generator Glossary of Selected Terms Used in this Course Rev 3/16 E3 of 4 USNRC HRTD GPM Gallons per minute.
Horsepower See definitions for Brake, Frictional, and Indicated Horsepower.
Ignition Delay The time period between the point when fuel begins to be injected into the cylinder of a diesel engine until combustion of the fuel actually begins.
Indicated Horsepower (IHP)
The calculated total power developed by a diesel engine. Its a function of the mean indicated effective pressure applied to the top of the piston, the area of the piston, the length of the stroke, and the power strokes / minute.
Isochronous Governing the operation of a diesel engine to maintain a constant speed irrespective of the load applied to the engine. Therefore, zero Droop.
Lubricating Oil Analysis See Spectrographic Lubricating Oil Analysis.
MOP - A motor operated potentiometer is used to vary voltage to a device. In some older models of diesel engine governors an MOP is used for speed control.
MPU - Magnetic pick-up coil, used in some EDG systems for engine speed sensing. By mounting close to the engine flywheel gear teeth, as each one passes by it changes the magnetic field, producing a pulse signal that the governor can translate into engine RPM and make fuel adjustment as needed.
OP Engine Fairbanks Morse Opposed Piston Engine. A 2-stroke cycle engine with two opposing pistons sharing each cylinder bore. Ports are used for intake and exhaust (no valves). The term BDC doesnt fit and is replaced by Outer Dead Center (ODC).
Likewise, TDC is replaced by Inner Dead Center (IDC).
Pielstick Engine One of several 4-stroke cycle engine families produced by Fairbanks Morse. Others include ALCO and MAN.
Pour Point The lowest temperature at which a fuel or lubricating oil will flow with relative ease.
Power, Apparent - The power apparently required to be supplied to or drawn from an AC system. Apparent power is measured in volt-amperes (VA), kilovolt-amperes (kVA),
or Megavolt-amperes (MVA).
Power, Reactive The amount of electrical power needed in AC machinery (motors, generators, and transformers) to create the magnetic fields and voltage induction that enables them to function. This power is measured in volt-amperes-reactive, or VARs. It produces no work and so is sometimes referred to as imaginary power.
Power, Real In an alternating current (AC) system this is the true electrical power that is converted to mechanical energy, such as a motor driving a pump. This power is customarily measured in kilowatts (kW).
Power Factor The ratio of Real Power to Apparent Power. It is a measure of the utilization of the input power of a system, or equipment. Generators are typically rated for a power factor of 80%.
PSIG Pounds-per-square-inch gauge.
Pyrometer An electrical temperature measuring device, usually connected to a thermocouple, used to measure high temperature such as diesel engine exhaust gas temperature.
Scavenging Intake air blowing out exhaust gases prior to providing combustion air for the next power stroke. Blowers and turbochargers provide scavenging air.
Emergency Diesel Generator Glossary of Selected Terms Used in this Course Rev 3/16 E4 of 4 USNRC HRTD Specific Gravity Ratio of the density of a substance, fuel, or lube oil to the density of water. Water has a specific gravity of 1.
Diesel fuel oil has a specific gravity less than 1, so it floats on water (the latter normally settling to the bottom of fuel tanks).
Specific Heat The amount of heat energy required to raise the temperature of 1 pound of a substance 1oF expressed in British thermal units, Btu (or BTU). The specific heat of water is 1 Btu per pound per oF.
Spectrographic Lubricating Oil Analysis A method of oil analysis where a sample of lubrication oil is taken from a diesel engine and burned in a special furnace. The light emitted by its combustion provides spectral indication of the type and quantity of wear metals and contaminants in the lube oil.
Results are logged and compared to previous data. Trends can indicate incipient or impending problems with the engine.
Supercharging Increases the mass flow of combustion air to the engine cylinders beyond that achieved by natural aspiration.
Turbochargers are engine exhaust-driven superchargers. Blowers for 2-stroke cycle engines are usually driven by the engine.
Turbochargers recover power that otherwise would be lost in the exhaust stream, primarily as heat.
TDC Top Dead Center. The opposite of Bottom Dead Center. It refers to location of the piston at its closest approach to the cylinder head, just before it reverses direction. In a 4-stroke cycle engine the end of the compression stroke and the end of the exhaust stroke both occur at TDC.
Thermocouple A temperature measuring device composed of two dissimilar metals joined at their ends. When heat is applied to the joint, a voltage is developed across the opened end and its magnitude gives temp.
Thermostat A device that senses the temperature of the engine coolant and causes a change in the rate or direction of coolant flow, to maintain the desired engine temperature.
Torsional Vibration Vibration caused by twisting of the crankshaft due to the cyclical production of power from each of the engine cylinders. This results in localized stresses that can cause crankshaft metal fatigue and possible failure, unless moderated by anti-resonant / torsional dampers.
Turbocharger A mechanical device, powered by thermal energy of the diesel engine exhaust gases, that incorporates a centrifugal compressor to increase the mass air flow to the engine cylinders. Increased air (oxygen) allows more fuel to be burned, thereby increasing engine power.
Two-Stroke Cycle Engine A diesel engine that requires one engine revolution for output power from each cylinder. In two-stroke cycle engines, camshaft speed is the same as crankshaft speed.
Viscosity A measure of the resistance to flow of lubricating and fuel oils. Viscosity is a function of temperature. As the temperature increases, the viscosity of the oil decreases (becomes thinner).
Viscosity Index (VI) The viscosity index of an oil indicates how the oil is affected by changes in temperatures. A high viscosity index indicates the oil experiences little change in viscosity as the temperature of the oil changes.