What is the working cycle of the engine?

The working cycle of the engine includes four processes: intake, compression, work and exhaust. Simply put, the engine completes four working processes: intake, compression, work and exhaust in one working cycle.

When the intake valve is opened and the exhaust valve is closed, the piston moves from the top dead center to the bottom dead center, the volume of the cylinder above the piston increases, resulting in a vacuum degree, and the pressure in the cylinder drops below the intake pressure. Under the action of vacuum suction, gasoline atomized by carburetor or gasoline injection device is mixed with air to form combustible mixture, which is mixed through air inlet and air outlet. The intake process continues until the piston passes the bottom dead center and the intake valve closes. Then the upward piston begins to compress the gas.

The compression intake and exhaust valves are all closed, the combustible mixture in the cylinder is compressed, and the temperature and pressure of the mixture increase. Before the piston top dead center, the pressure of the combustible mixture rises to about 0.6-65438±0.2 MPa, and the temperature can reach 330-430℃.

When the power compression stroke is coming to an end, under the action of the high-pressure oil pump, diesel oil is injected into the combustion chamber of the cylinder through the injector at a high pressure of about 10MPa, and spontaneously ignites after being mixed with air in a short time. The gas pressure in the cylinder rises rapidly, with the maximum value of 5000-5000 kPa and the maximum temperature of 1800-2000 kKa.

The exhaust of diesel engine is basically the same as that of gasoline engine, but the exhaust temperature is lower than that of gasoline engine. Generally Tr=700-900K. For a single-cylinder engine, its speed is uneven, the engine is unstable and vibrates greatly. This is because only one of the four moves does work, and the other three moves consume energy to prepare for work. In order to solve this problem, the flywheel must have enough moment of inertia, which will lead to the increase of the mass and size of the whole engine.

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