The working process of a diesel engine is actually the same as that of a gasoline engine. Each working cycle also undergoes four strokes of intake, compression, power, and exhaust.

The diesel engine inhales pure air during the intake stroke. When the compression stroke is nearing the end, the diesel oil is increased to more than 10MPa by the fuel injection pump, injected into the cylinder through the fuel injector, and mixed with the compressed high-temperature air in a very short time to form a combustible mixture. Due to the high compression ratio of diesel engines (generally 16-22), the air pressure in the cylinder can reach 3.5-4.5MPa at the end of compression, and the temperature is as high as 750-1000K (while the gas mixture pressure of gasoline engines at this time will be 0.6-1.2MPa , the temperature reaches 600-700K), which greatly exceeds the self-ignition temperature of diesel. Therefore, after the diesel fuel is injected into the cylinder, it will immediately ignite and burn itself after being mixed with the air in a very short time. The air pressure in the cylinder rapidly rose to 6-9MPa, and the temperature also rose to 2000-2500K. Driven by high-pressure gas, the piston moves downward and drives the crankshaft to rotate to perform work, and the exhaust gas is also discharged into the atmosphere through the exhaust pipe.

The oil supply system of ordinary diesel engines is driven by the engine camshaft, and the diesel oil is delivered to the fuel chambers of each cylinder by means of a high-pressure oil pump. This oil supply method should change with the change of the engine speed, and the optimal oil supply amount at various speeds cannot be achieved.

The common rail injection fuel supply system consists of high pressure fuel pump, common fuel supply pipe, fuel injector, electronic control unit (ECU) and some pipeline pressure sensors. Each fuel injector in the system is connected to the common fuel supply through its own high pressure fuel pipe The pipes are connected, and the common fuel supply pipe plays a hydraulic pressure accumulating role for the injector. When working, the high-pressure fuel pump delivers fuel to the public fuel supply pipe at high pressure, and the high-pressure fuel pump, pressure sensor and ECU form a closed-loop operation to precisely control the oil pressure in the public fuel supply pipe, completely changing the oil supply pressure that changes with the engine speed. Phenomenon. Its main features are as follows:

1. The fuel injection timing is completely separated from the fuel metering, and the fuel injection pressure and the fuel injection process are controlled by the ECU in time.

2. The fuel injection pressure of each cylinder, the starting point and duration of fuel injection can be adjusted according to the working conditions of the engine, so as to pursue the best control point of fuel injection.

3. It can achieve very high fuel injection pressure and can realize pre-injection of diesel.