Injector spray characteristics include atomization particle size, oil mist distribution, oil bundle direction, range and diffusion cone angle. These characteristics should be consistent with the requirements of the diesel combustion system to make the formation and combustion of the mixture perfect, and obtain higher power and thermal efficiency. Injector is divided into open and closed two. Open injector structure is simple, but poor atomization, rarely used. Closed-type fuel injector is widely used in various diesel engines. The intake of diesel engine in the intake stroke is pure air. At the end of the compression stroke, the fuel pressure of the diesel fuel pump is increased to over 10 MPa. The fuel is injected into the cylinder through the fuel injector to mix with the compressed hot air in a very short time to form a combustible gas mixture. As the diesel engine compression ratio is high (usually 16-22), so the end of the compression air pressure within the cylinder up to 3.5-4.5MPa, while the temperature up to 750-1000K (and gasoline mixture pressure at this time will be 0.6-1.2MPa , Temperature up to 600-700K), much higher than the auto-ignition temperature of diesel. Therefore, diesel injected into the cylinder, in a very short period of time after mixing with the air immediately after their own fire burning. Pressure inside the cylinder rapidly rose to 6-9MPa, the temperature also rose to 2000-2500K. Pushed by high-pressure gas, the piston moves downward and drives the crankshaft to rotate. The exhaust gas is also discharged into the atmosphere through the exhaust pipe.