What is a Diesel Generator Shaft Needle Injector?

The function of the diesel engine fuel supply and speed control system is to inject a certain amount of diesel with good atomization quality into the cylinder according to a certain injection pattern at a certain pressure within a certain speed range according to the working requirements of the diesel engine, and to quickly and well mix and burn it with compressed air. Its working condition has a significant impact on the power and economy of diesel engines.

The composition of the fuel supply and speed control system for the most widely used inline plunger fuel injection pump diesel engine. The inline plunger fuel injection pump is generally driven by the timing gear of the diesel engine crankshaft. The piston type fuel transfer pump fixed on the fuel injection pump body is driven by the camshaft of the fuel injection pump. When the diesel engine is working, the fuel transfer pump sucks out diesel from the diesel tank, removes the water in the diesel through the oil-water separator, filters out impurities in the diesel through the diesel filter, and then sends it to the fuel injection pump. After the diesel is pressurized and metered in the fuel injection pump, it is transported to the injector through the high-pressure fuel pipe, and finally injected into the combustion chamber through the injector. The front end of the fuel injection pump is equipped with a fuel injection advance device, and the rear end is integrated with the governor. The excess diesel supplied by the fuel pump and the return oil at the top of the fuel injector are returned to the diesel tank through the return pipe. On some small diesel engines, fuel pumps are often not installed and rely on gravity to supply fuel (the position of the diesel tank is higher than that of the fuel injection pump).

At present, small and medium-sized diesel engines often use closed injectors. When the closed injector is not spraying, the nozzle is closed by a needle valve compressed by a strong spring, separating the combustion chamber from the high-pressure oil chamber. Before injecting fuel into the combustion chamber, it is necessary to overcome the elastic force of the spring in order to open the needle valve. That is to say, the fuel needs to have a certain pressure to start injecting. This can ensure the quality of fuel atomization, quickly cut off the supply of fuel, and prevent fuel dripping. This is particularly important for low-speed and low load operation. Its main types are hole type and pin type.

Axial needle injectors are commonly used in swirl chamber and pre chamber diesel engines, and their working principle is similar to that of orifice injectors. Its structural feature is that the needle valve extends an inverted conical shaft needle below the sealing cone surface at the lower end. The axis needle extends outside the spray hole, creating a circular narrow slit in the spray hole. The size of the nozzle section and the angle and shape of the injection depend on the shape and lift of the shaft needle, so it is required that the shape of the shaft needle be processed very accurately. Most common axial needle fuel injectors have only one or two injection holes, with a diameter of generally 1-3mm. Due to the large diameter of the injection holes, the injection pressure is relatively low, usually between 10-13MPa, which is convenient for manufacturing and processing. At the same time, the axial needle moves back and forth in the injection holes to remove carbon deposits and improve work reliability.

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