The Working Principle of A Four-Stroke Diesel Engine

The work of the diesel engine is completed by the four processes of intake, compression, combustion expansion and exhaust, which constitute a working cycle. A diesel engine in which the piston takes four processes to complete a working cycle is called a four-stroke diesel engine.

Intake stroke:

The intake valve opens and the exhaust valve closes. Driven by the crankshaft and connecting rod, the piston moves from the top dead center to the bottom dead center, sucking fresh air into the cylinder, the piston reaches the bottom dead center, and the intake stroke ends.

Compression stroke:

The intake and exhaust valves are closed, the piston moves from the bottom dead center to the top dead center driven by the crankshaft and the connecting rod, and the air sucked into the cylinder is compressed into high temperature and high pressure gas. When the piston reaches the top dead center, the compression stroke ends.

Power stroke:

After the compression stroke is over (the intake and exhaust valves are still closed), the fuel injector injects fuel into the cylinder. Under the action of high temperature and high pressure gas, the fuel is compressed and ignited, and huge energy is generated in the cylinder, which pushes the piston from the top to the stop. When the point moves to the bottom dead center, the crankshaft flywheel group stores and outputs energy. When the piston reaches the bottom dead center, the power stroke ends.

Exhaust Stroke:

The intake valve is closed and the exhaust valve is opened. Driven by the crankshaft and connecting rod, the piston moves from the bottom dead center to the top dead center, and the exhaust gas after combustion in the cylinder is discharged. When the piston reaches the top dead center, the exhaust stroke ends. In the four strokes of intake, compression, power and exhaust, only the power stroke generates energy, and the other three strokes are completed by the inertia of the crankshaft and flywheel.