A diesel engine refers to a heat engine that uses diesel as fuel and converts chemical energy into mechanical energy.

What is a diesel engine？

The working cycle of a diesel engine has many similarities with a gasoline engine, but the ignition method is different from a gasoline engine. The mixture in the cylinder of a diesel engine is compression-ignition, not spark ignition.

Advantages of diesel engine

·Greater torque can be produced under the same displacement.

·Good economic performance.

Disadvantages of diesel engine

·Larger volume than a gasoline engine.

·High working noise.

·The manufacturing cost is higher than that of a gasoline engine, and it is not easy to repair.

·Difficult to start in winter.

·More carbon smoke and particles (PM) emissions.

Working principle of diesel engine

By burning diesel in the cylinder to generate kinetic energy, the crankshaft connecting mechanism connected to the piston is driven by it, and the circular motion reciprocating around the crankshaft is outputted. The four-stroke diesel engine is composed of intake, compression, work, and exhaust strokes.

The intake stroke is driven by the piston from the top to the bottom stop by the crankshaft. At the same time, the intake valve is open and the exhaust valve is closed.

When the piston moves from the top stop to the bottom stop, the volume above the piston increases, the gas pressure in the cylinder decreases, and a certain degree of vacuum is formed.

Because the intake valve is open, the cylinder is in communication with the intake pipe, and fresh air is sucked into the cylinder.

When the piston moves to the bottom stop, the cylinder is filled with fresh air.

The compression stroke piston moves from the bottom stop to the top stop, the intake and exhaust valves are closed.

The crankshaft is driven to rotate under the action of the inertia force of the flywheel and other parts, and the piston is pushed upwards by the connecting rod. The gas volume in the cylinder gradually decreases, the gas is compressed, and the pressure and temperature in the cylinder rise sharply (the temperature reaches 600-700C°).

During the working stroke, the intake and exhaust valves are closed at the same time, the temperature and pressure in the cylinder rise sharply, and the temperature in the cylinder is much higher than the ignition point of the diesel. The fuel injector injects fuel into the cylinder, and the diesel and air mix and immediately self-ignite under high temperature and high pressure, pushing the piston downwards, and the crankshaft is driven to rotate by the connecting rod.

The exhaust stroke opens the exhaust valve, and the piston moves from the bottom stop to the top stop, and the exhaust gas is discharged from the cylinder with the upward movement of the piston.