Diesel engine has the advantages of large torque and good economic performance. There are many similarities of the diesel engine working process with gasoline engines, each cycle has intake compression power and exhaust stroke of four. However, due to the use of diesel fuel is diesel, its viscosity is larger than gasoline, not easy to evaporate, and its spontaneous combustion temperature is lower than gasoline, therefore, the formation of combustible mixture and ignition methods are different from gasoline engines. The main difference is that the mixture in the cylinder of the diesel engine is compressed, not ignited. When the diesel engine is working, the air entering the cylinder is compressed, and when the air in the cylinder is compressed to the end point, the temperature can reach 500-700 DEG C, and the pressure can reach 40— 50 atmospheric pressure.