engine words.docx

A B C D E F G H I J K L M N O P R S T U V W

A

Absolute pressure. The pressure in pounds per square inch, psi, above absolute zero pressure, or perfect vacuum. A Bourdon or mercury gauge registers the difference between the pressure within a receiver and that of the outside atmosphere. At sea level and under standard barometric conditions, the atmospheric pressure is 14.7 psia. Tofind the absolute pressure, add 14.7 to the gauge reading in psig.
Absolute temperature. The temperature above absolute zero. If a Fahrenheit thermometer scale is used, absolute zero is Ч460 deg. To find the absolute temperature, add 460 to the Fahrenheit reading.
Accelerate. To increase the speed of movement, such as increasing the speed of a piston or flywheel.
Acceleration. The rate at which the speed of an object increases.
Adiabatic. From the Greek word meaning Уno pass through.Ф Adiabatic compression or expansion of a gas is accomplished without the loss or gain of heat through the cylinder walls.
Advance. Sometimes referred to as lead, or angle of advance, meaning the distance ahead of top or bottom (lead center of the piston as measured in degrees of crank travel.
Air cell. A small receptacle communicating with an engine cylinder into which some of the compressed air is forced, and from which air later flows back into the cylinder.
Air filter. A device for filtering the air, before it goes into the engine, to prevent particles of dust from entering the engine.
Air injection. The system of injecting fuel into the combustion chamber of a diesel engine by means of a blast of highly compressed air.
Airless injection. A general term describing all methods of injecting fuel without the use of compressed air.
Air starter. A system whereby an engine is turned over by admitting compressed air into the cylinders in order to initiate firing.
Aniline number. The lowest temperature at which equal parts of aniline and a sample of oil are completely miscible, or the temperature at which the mixture becomes turbid or cloudy.
Antechamber. Same as Precombustion chamber.
API. American Petroleum Institute.
API gravity. An arbitrary scale adopted by the American Petroleum Institute to designate the specific gravity of mineral oils. Diesel fuels range from 18 to 41 API.
Atmospheric pressure. The pressure of the atmosphere measured from absolute zero pressure. At sea level atmospheric pressure is 14.7 psi, decreasing as the altitude increases.
Atomize. To break up a liquid into extremely fine particles.
Axial. Parallel to the center line of a cylinder or shaft.
Axis. A center line. A line about which a body rotates or about which it is arranged.

B

Babbitt. A soft antifriction metal used to line bearings.
Bock pressure. The resistance to the normal flow of gases and liquids.
Bedplate. The lower part of the engine resting on the foundation.
Bore. The interior diameter of an engine or compressor cylinder.
Blow-by. Escape of gases from the engine cylinder into the crankcase because of unsatisfactory action of the piston rings.
Brake horsepower. The useful horsepower delivered by an engine that may be found by the use of a prony brake. Abbreviated bhp.
Brake mean effective pressure. The mean effective pressure, corresponding to the brake horsepower developed. Abbreviated bmep.
British thermal unit. The amount of heat needed to raise the temperature of one pound of water one degree Fahrenheit, from 68 to 69 F. Abbreviated Btu.
Burning. Commonly substituted for COMBUSTION, as late burning, meaning late or slow combustion.
By-pass. A passage which permits a liquid or gas to take a course other than that normally used.

C

Cam. A disk-like piece attached to a shaft, a portion of which is circular, the remainder (the УnoseФ) protruding beyond this circle. Cams are used to impart a desired motion to poppet valves.
Camshaft. The shaft which carries the various cams required for the operation of inlet, exhaust, fuel, and starting-air valves.
Cam follower. That part of the push rod that is in contact with the cam.
Carbon. One of the chemical elements which is the main constituent of liquid and solid fuels. Also the residual substance deposited in the combustion space and exhaust system of diesel engines when combustion of fuel oil is not complete.
Carbon dioxide. Gas composed of molecules made of one atom of carbon and two atoms of oxygen.
Carbon monoxide. Gas composed of molecules made up of one atom of carbon and one of oxygen. It is formed when combustion is not complete because of the absence of sufficient air.
Carbon residue. The carbon remaining after evaporating off the volatile portion of a fuel or lubricating oil by heating it in the absence of air under controlled test conditions. It is an indication of the amount of carbon that may be deposited in a diesel engine.
Centrifugal force. The force acting on all parts of a rotating body that tends to pull thorn away from time axis of rotation.
Cetane. A hydrocarbon used in testing the ignition quality of diesel fuels.
Cetane number. A percentage indicating the ignition quality of diesel fuels.
Cetene. A hydrocarbon used formerly infesting the ignition quality of diesel fuels.
Chamfer. A beveled corner.
Charge efficiency. The ratio of the weight of the charge actually taken in to the weight of the air at standard conditions corresponding to the piston displacement.
Check valve. A valve that permits the passage of a liquid or gas in one direction only. It stops, or checks, reverse flow.
Clearance. The space between a moving and a stationary part. Clearance must be provided between two surfaces to allow for lubrication and for expansion and contraction with a change of temperature.
Clearance volume. The volume of air or liquid remaining in the cylinder of an air compressor or a pump when the piston is nearest to the cylinder head.
Coefficient. A ratio; a factor or quantity that remains constant.
Combustion. The rapid oxidation, or combination, of a combustible such as carbon, hydrogen, or sulfur, with oxygen of air.
Combustion chamber. The space above the piston in which the fuel-air mixture starts to burn.
Common rail. A pipe or header from which branch lines lead to each of the fuel valves in the different cylinder heads of a diesel engine and in which fuel is carried at high pressure, ready for delivery to each separate cylinder when the fuel valve is opened by a cam.
Compression. The act or result of pressing a substance into a smaller space. One of the events of a combustion-engine cycle.
Compression ignition. Ignition of a fuel charge by the heat of the air in a cylinder, generated by compression of the air, as in the diesel engine.
Compression pressure. The pressure of the air charge at the end of the compression stroke.
Compression ratio. The ratio of the volume of the charge in the engine cylinder at the beginning of the compression stroke to that at the end of the stroke.
Compression relief. A device to reduce the compression in a cylinder and thus to make cranking easier.
Compression rings. Piston rings placed in the upper part of a piston to seal against loss of compression pressure and against gas blowing.
Compression stroke. The stroke of the piston during which the air charge in the cylinder is compressed by the piston movement.
Compressor. The air УpumpФ which furnishes compressed air for starting the engine, or for time injection of the fuel in an airЧinjection diesel engine.
Concentric. Having a common center.
Condensation. The process by which a substance changes from vapor to the liquid state.
Connecting rod. The engine part which connects the piston to the crankshaft. It changes reciprocating motion of the piston into rotary motion of the crankshaft or vice versa.
Connecting rod bearing. The bearing located in the large end of the connecting rod by which it is attached to the crankshaft.
Constant. A value or figure in a formula or equation which does not change, remains constant.
Constant-pressure combustion. Combustion of fuel in a cylinder at so slow a rate that there is no rise in cylinder pressure. The slow-speed airinjection diesel engine is a constant-pressure combustion engine.
Constant-volume combustion. Combustion in a cylinder so fast that there is no change in volume. Many high-speed diesel engines have practically constant-volume combustion.
Contraction. Becoming smaller in size. In metals and fluids a result of cooling or a lowering of temperature.
Cooling water. Water which is circulated through the jacket space of cylinders and cylinder heads to prevent excessive heating of these parts.
Crank. That part of the crankshaft, which is in the form of a crank and crank pin.
Crankcase. The middle part of the engine structure surrounding the working parts.
Crankcase subbase. The lower portion of the engine structure; the BEDPLATE.
Crankpin. That part of the crank to which the connecting rod is attached.
Crankshaft. That part of the engine which transmits the reciprocating motion of the pistons to the driven unit in the form of rotary motion. That part to which the connecting rods are attached.
Crankshaft cheek. The part J the crankshaft that connects the crankpin to the main crankshaft journal.
Crankshaft journal. The part of the crankshaft which rotates in the main bearings and transmits the torque developed by the engine.
Crankshaft web. The crankshaft cheek.
Critical speed. Speed at which the natural period of vibration of a shaft or her machine part is in synchronism with the power impulses.
Crosshead. The part of an engine to which are attached the piston pin with the connecting rod and the piston rod and which is supported on guides.
Crown. The top of an engine piston.
Crush. The amount by which a precision bearing is compressed to ensure good contact between the back of the bearing and the bore holding it.
Cycle. A series of events, operations, or movements that repeat themselves in a regular sequence
Cylinder. The cylindrical part of the engine in which the piston moves, and in which combustion takes place.
Cylinder block. A number of cylinders cast in one piece.
Cylinder bore. The inside diameter of an engine cylinder. Also the surface of the cylinder in which the piston slides or moves.
Cylinder head. The part which covers and seals the end of the cylinder and usually contains the valves.
Cylinder - head stud. Threaded round steel rod, one end of which screws into the cylinder block, the other being threaded to take a nut which holds the cylinder head in correct position.
Cylinder liner. A cylindrical lining that is inserted into the cylinder jacket or cylinder block and in which the piston slides.

D

Delivery stroke. The stroke of a pump during which the fluid in the pump is forced out of the cylinder.
Detonation. A violent uncontrolled burning of a fuel in the combustion chamber.
Diesel engine. A compression-ignition combustion engine first developed by Rudolf Diesel.
Distillation. Separation of the more volatile parts of a liquid from those less volatile by vaporization and subsequent condensation.
Distributor. A device which distributes and directs the flow of fuel or compressed air to the various cylinders of the engine in proper sequence.
Dribbling. Slow seeping of fuel oil from the nozzle tip after cutoff of the fuel.
Dynamometer. A device for determining the power of an engine.

E

Eccentric. A circle not having the same center as another circle within it. A device mounted off-center for converting rotary motion into reciprocating motion.
Efficiency. The ratio of output over input.
Electromotive force. The potential, or voltage, developed by a dynamo, battery, or thermocouple. Abbreviated emf.
Energy. Capacity for doing work.
Engine. A machine which produces power to do work, particularly one that converts heat into mechanical work.
Exhaust. The act of discharging gases from an engine after they have done work.
Exhaust cam. The cam that controls the operation of the exhaust valve.
Exhaust gases. Products of combustion which are discharged from the cylinder after doing work on the piston.
Exhaust manifold. The pipe that collects the burnt gases as they are expelled from the cylinders.
Exhaust pipe. Piping through which exhaust gases from an engine pass out to the atmosphere.
Exhaust pyrometer. An instrument used to measure the temperature of the exhaust, mostly by the small electric current developed at the junction of two dissimilar metals when exposed to heat.
Exhaust valve. The valve through which the burnt gases are allowed to pass out to the exhaust manifold.
Expansion period. The portion of the power stroke during which the combustion gases expand from the movement of the piston and thus do work.

F

Filter. A device to remove dirt and other impurities from air, oil, or water.
Fit. The desired positive or negative clearance between the surfaces of two machined engine parts.
Flash point. The temperature, degrees F, to which oil must be heated before the oil vapor over the oil will ignite when a small flame is passed across the surface of the oil.
Fluctuation. Variation in value, such as of pressure or velocity.
Flywheel. The wheel on the end of the crankshaft that gives the crankshaft momentum to carry the pistons through the compression stroke.
Foot pound. Unit in which, work is measured; it is equivalent to the work of raising one pound vertically a distance of one foot or of moving an object ore foot against a resistance of one pound. Abbreviated ft-lb.
Four-stroke engine. An engine operating on a cycle which is completed in four strokes, or two revolutions of the crankshaft.
Framing. The part of an engine between the cylinders and the bedplate; the crankcase.
Friction. The resistance to relative motion between two bodies in contact.
Friction horsepower. The power consumed within the engine from friction between its parts.
Fuel injector. The device which sprays the fuel into the cylinder.
Fuel knock. A noise produced in the cylinder of a diesel engine during combustion, usually when the fuel oil has a low ignition quality.
Fuel pump. The pump that delivers the fuel to the injector.
Fulcrum. The support on which a lever turns.

G

Gasket. Packing placed between two surfaces that must have a leakproof joint.
Glow plug. An electrical device used to heat fuel as it is injected in the cylinder for quick ignition and starting when the engine is cold.
Governor. A mechanism used to control the speed of an engine.

H

Heat. A form of energy.
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