Engines: Motive Power Types: Compression-ignition engine components

Basic diesel engine components	Diesel engine parts are usually heavier or more rugged than those of similar output gasoline engines. Their engine blocks and cylinder blocks are usually made of cast iron.
Diesel engine passages	In a diesel engine, just air enters the combustion chamber first. It is then highly compressed. Fuel is injected and ignites due to heat of the compressed air. That’s why diesels are called compression-ignition engines.
Diesel fuel delivery	Direct injection: fuel is injected directly into the combustion chamber. Indirect injection: fuel is sprayed into a smaller separate chamber in the cylinder head. A glow plug helps the combustion start.
Direct injection	Most valves in diesels are parallel to the centre-line of the engine. Small 4-stroke engines usually have 1 inlet and 1 exhaust valve per cylinder. Larger 4-stroke diesels may have 2 of each per cylinder.
Diesel valves & components	Valves in diesel engines are usually operated by a pushrod system. The camshaft is mounted in the engine block near the crankshaft. It keeps the valves working in sequence.
Diesel scavenging	Scavenging Uniflow - air flows towards top of the cylinder. Crossflow - air enters one side of cylinder, exhaust gases exit on the other. Loop - flows up in a loop across the top of the piston.
Crankshaft rotation	In a 2-stroke diesel engine, the camshaft and crankshaft must rotate at the same speed. So the gears driving them must be the same size.
Diesel crankshaft	In a 4-stroke cycle, only 1 stroke in 4 delivers energy. In a 2-stroke, it is only 1 stroke in 2. A flywheel stores this energy to help turn the crankshaft through the non-power strokes.
Diesel engine pistons	Clearance between the piston and its cylinder wall must be kept small. This is done by piston rings - expandable metal rings held in grooves in the side of the piston.