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A group of cylinders.
Bank
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The diameter of the cylinder.
Bore
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Part of a diesel engine’s air intake system that serves to compress incoming fresh air for delivery to the cylinders for combustion.
Blower
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Lowest point of travel by the piston.
Bottom dead center (BDC)
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The amount of usable power delivered by the engine to the crankshaft.
Brake horsepower
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The volume remaining in the cylinder when the piston is at TDC.
Clearance volume
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The volume of space where the fuel air mixture is burned in a diesel engine. Is in the cylinder of the engine.
Combustion chamber
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A measure of how much an engine compresses the gasses in the engine’s cylinder. Mathematically, the sum of the displacement volume and clearance volume divided by the clearance volume.
Compression ratio
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Diesel engine component that connects the piston to the crankshaft.
Connecting rod
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The area around the crankshaft and crankshaft bearings.
Crankcase
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Diesel engine component that transforms the linear motion of the pistons into a rotational motion that is transmitted to the load.
Crankshaft
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The structure and rigid frame for a diesel engine’s cylinders that provides support for the crankshaft and crankshaft bearings. In a liquid-cooled diesel, also provides the structure and rigid frame for the engine’s coolant and oil passages.
Cylinder block
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Diesel engine component that provides the top seal for the cylinder bore or sleeve and is the structure that holds the exhaust valves, intake valves, and fuel injectors.
Cylinder head
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A type of engine that uses the internal combustion heat to ignite fuel to convert the energy stored in the chemical bonds of the fuel into useful mechanical energy
Diesel engine
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The total volume displaced by a piston during one stroke.
Displacement volume
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Order in which each of the cylinders in a multi-cylinder engine fires (power stroke).
Firing order
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Diesel engine component that is located on the end of the crankshaft and is the mounting surface used to bolt the engine to the load.
Flywheel
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The power transmitted to the pistons by the gas in the cylinders and is mathematically calculated.
Indicated horsepower
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A diesel engine that has all of the cylinders in a row.
In-line engine
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The ratio of an engine’s brake horsepower and its indicated horsepower
Mechanical efficiency
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Diesel engine component that collects and stores the engine’s supply of lubricating oil.
Oil pan
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Diesel engine component that transforms the energy of the expanding gasses into mechanical energy.
Piston
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A slot in the cylinder wall located in the lower 1/3 of the bore.
Port
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The distance the piston travels from TDC to BDC, determined by the eccentricity of the crankshaft.
Stroke
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The highest point of travel by the piston.
Top dead center (TDC)
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The measure of the engine’s ability to apply the power it is generating to a rotating shaft.
Torque
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Engine component that is mechanically opened and closed to admit air or exhaust gasses as needed.
Valve
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The “slop” or “give” in the valve train before the cam actually starts to open the valve.
Valve lash
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Point at which the valve seals against the head.
Valve seat
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Explain how the ignition process occurs in a diesel engine.
Unlike a gasoline engine, a diesel engine does not require an ignition system. In a diesel engine, the fuel is injected into the cylinder as the piston comes to the top of its compression stroke. When fuel is injected, it vaporizes and ignites due to the heat created by the compression of air in the cylinder.
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Explain how a diesel engine converts the chemical energy stored in the diesel fuel into mechanical energy
In a diesel engine, the fuel is injected into the cylinder as the piston comes to the top of its compression stroke.When fuel is injected, it vaporizes and ignites due to the heat created by the compression of air in the cylinder.
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Explain the operation of a 4-cycle diesel engine to include when the following
events occur during a cycle:
a. Intake
b. Compression
c. Fuel injection
d. Power
e. Exhaust
- Intake - the piston passes TDC, the intake valve(s) open and the fresh air is admitted into the cylinder, the exhaust valve is still open for a few degrees to allow scavenging to occur.
- Compression - after the piston passes BDC the intake valve closes and the piston travels up to TDC (completion of the first crankshaft rotation). The air is heated by compression.
- Fuel injection - As the piston nears TDC on the compression stroke, the fuel is injected by the injectors and the fuel starts to burn, further heating the gasses in the cylinder.
- Power - the piston passes TDC and the expanding gasses force the piston down, rotating the crankshaft.
- Exhaust - as the piston passes BDC the exhaust valves open and the exhaust gasses start to flow out of the cylinder. This continues as the piston travels up to TDC, pumping the spent gasses out of the cylinder. At TDC the second crankshaft rotation is complete.
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- Explain the operation of a 2-cycle diesel engine, including when the following
events occur during a cycle:
a. Intake
b. Compression
c. Fuel injection
d. Power
e. Exhaust
- Intake - the piston is near BDC and exhaust is in progress. The intake valve or ports open and the fresh air is forced in. The exhaust valves or ports are closed and intake continues.
- Compression - after both the exhaust and intake valves (or ports) are closed, the piston travels up towards TDC. The fresh air is heated by the compression.
- Fuel injection - near TDC the fuel is injected by the injectors and the fuel starts to burn, further heating the gasses in the cylinder.
- Power - the piston passes TDC and the expanding gasses force the piston down, rotating the crankshaft.
- Exhaust - as the piston approaches BDC the exhaust valves or ports open and the exhaust gasses start to flow out of the cylinder (completion of one crankshaft rotation).
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Describe how the mechanical-hydraulic governor on a diesel engine controls engine speed.
The governor controls the fuel rack position through a combined action of the hydraulic piston and a set of mechanical flyweights.
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List five protective alarms usually found on mid-sized and larger diesel engines.
- Overspeed Device
- Water Jacket
- Exhaust
- Low Lube Oil
- High Crankcase
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