The fuel used in a diesel engine is diesel, due to the large viscosity of diesel, and poor evaporation, it is impossible to form a mixture with the air outside the cylinder through the carburetor, therefore, the diesel engine adopts the method of high-pressure injection. This method is at the end of the compression stroke, the diesel fuel is sprayed into the cylinder in a mist by the injector, and the particles of the diesel mist heated by high-pressure air quickly evaporate and vaporize, and directly form a mixture with the air in the cylinder and spontaneously ignite. The fuel injection system of the diesel generator set is the core component of the diesel engine, and its performance is directly related to the reliability and durability of the diesel engine. At present, the fuel injection system of diesel engines mainly has two forms: mechanical and electronic.
The advantages of mechanical fuel injection systems are simple structure, reliability and durable, easy maintenance, and the ability to adapt to various working conditions and environments. However, its fuel injection control precision and response speed are relatively low, which is not conducive to the performance of the diesel engine and energy saving and emission reduction. Compared to mechanical fuel injection systems, electronic fuel injection systems are more complex, but their performance and reliability have also been significantly improved. At present, more and more diesel generator sets have adopted electronic fuel injection systems, such as high-end engines launched by Weichai Power. In addition, some traditional diesel engine manufacturers have also increased the development and application of electronic fuel injection systems to meet market and customer needs.
It can be seen from the above that the diesel fuel injection system is generally composed of fuel supply, air supply, mixture formation, and speed regulation. There are several forms commonly used at present.
1.In-line oil pump and nozzle system
This system is a common form of modern diesel engine, which includes a fuel tank, low-pressure oil pipe, oil pump, fuel filter, in-line fuel injection pump, high-pressure oil pipe, fuel injector, and governor. The fuel supplied to the injector is measured, timed, pressurized, and controlled by a diesel fuel injection pump. The injector is a spring-loaded, hydraulically operated valve that is inserted into the combustion chamber. Although it comes in many forms, its basic role is to atomize the fuel injected into the cylinder. The governor is generally a mechanical fly hammer, which can be installed in the pump body or a separate housing attached to the main fuel injection pump body. The governor is used to control the fuel supply of the diesel engine, to change the engine speed.
2.Pressure time system
The system is manufactured by Cummins Engine Company and is used in Cummins diesel engines. This system, sometimes called the nozzle system, consists of the following components.
Gear pump
The gear pump pumps fuel from the tank through the system oil circuit to the pump nozzle and also provides fuel to lubricate the governor and other working parts in the main pump body
Pump nozzle
The pump nozzle is operated by the camshaft of the diesel engine through a push rod and a rocker arm. The fuel is supplied to the pump nozzle from the fuel channel in the cylinder head, and the fuel must first flow through a small nozzle before entering the pump nozzle. The nozzle is replaceable and selected for a specific fuel supply so that the pump nozzle can be applied to many different models of Cummins diesel engines. Each cylinder uses a pump nozzle. After the fuel flows into the pump nozzle and fills the oil chamber, the fuel is injected into the cylinder when the pump nozzle presses down under the action of the camshaft
Throttle
The throttle is controlled by the operator, which controls the flow and pressure of fuel to the pump nozzle. The throttle is a simple knob with holes that fit inside the pump body. As the knob rotates, the degree of alignment between the knob hole and the fuel channel in the housing changes, thereby adjusting the flow and pressure of the fuel
Governor
The flyweight governor installed in the main pump body can control the maximum fuel pressure to prevent excessive fuel supply of the diesel engine and control the fuel supply to prevent excessive speed of the diesel engine.
It is a small and compact system designed for small and medium-power diesel engines and is used in a wide range of diesel models. The system is composed of a rotor-type fuel injection pump, oil supply line, fuel filter, fuel injector, high-pressure oil pipe, oil return device, and governor. Its main components have many roles. This type of pump usually has one or two pump oil plungers, which carry the fuel pump to the distributor and then distribute the fuel to the various cylinders, and the pump also controls the fuel metering and injection timing. According to the use of the diesel engine, the governor can be the mechanical fly hammer or hydraulic. High-pressure tubing, fuel injectors, fuel filters, etc. are the same as in-line oil pump systems.
Summary
The fuel injection system of diesel generator sets mainly has two forms: mechanical and electronic. The mechanical fuel injection system is simple in structure, reliable and durable, and easy to maintain, but its performance and injection control accuracy are low.
The electronic fuel injection system has higher injection control accuracy and response speed, which can better play the performance of the diesel engine, but also can achieve more accurate fuel consumption control and emission control. With the continuous progress of technology and the continuous expansion of application fields, electronic fuel injection systems will become one of the mainstream choices for diesel generator sets in the future. If you have any questions, you can contact us, we can provide you with professional answers and products.