The structure and parameters of the injector determine the quality of the spray. The spray should match the shape of the combustion chamber to promote the formation of a combustible gas mixture. The head of the syringe is exposed to high temperature gas, and the working conditions are extremely harsh. The requirements for the injector mainly include: good guarantee, good atomization quality, reasonable shape of the oil beam: the beginning and end of the injection should be neat, and there should be no abnormal injection such as dripping and secondary injection.
1. The structure and working principle of the injector,
The main component of the injector is the needle valve coupler, which is composed of an electric needle valve and a needle valve body. Electric needle valve spring preload. When the oil pressure on the pressure-bearing cone of the injector exceeds the pre-tightening force of the injector spring, the needle valve opens, and the high-pressure fuel is sprayed from the injection hole.
In the atomizing cylinder, this fuel pressure is called the valve opening pressure. When the oil pressure acting on the pressure bearing cone of the injector needle valve is lower than the valve opening pressure, the needle valve is closed. The volume below the surface of the needle valve seal seat of the injector is called the volume of the pressure chamber. At the end of fuel injection, the needle valve seat is closed, but there is fuel in the pressure chamber. This part of the fuel evaporates at high temperature and enters the combustion chamber to burn without injection, so it does not burn. Completely, making economic and emission targets worse. Therefore, the volume of the pressure chamber should be as small as possible. For medium and low speed diesel engines with a high degree of reinforcement, cooling injectors are mostly used. This injector is in the needle valve body. Coolant passages are provided in the section for cooling, which is called internal cooling. Typically, fresh water or fuel oil is used as the coolant. Fresh water has high thermal conductivity and good cooling effect. Fuel cooling does not require special seals and the system is relatively simple. Currently, new large and medium-sized diesel engines are typically fuel-cooled.
