The fuel injection system of diesel engines, as a key component of the engine, precisely controls the timing, quantity, and pressure of fuel injection, directly affecting the performance, fuel economy, and emission level of the engine. The common types of fuel injection systems for diesel engines are as follows:

In line plunger pump fuel injection system

Working principle: Relying on the reciprocating motion of the plunger in the plunger sleeve to achieve fuel pressurization and injection. When the plunger moves upward, the fuel is compressed and the pressure increases. After reaching a certain pressure, the injector needle valve is pushed open to inject fuel into the cylinder. Control the fuel injection quantity by adjusting the effective stroke of the plunger.

Features: Mature technology, relatively simple structure, easy maintenance, low cost, widely used in early diesel engines. However, its injection pressure is relatively low, and the injection accuracy and uniformity are poor, making it difficult to meet the requirements of modern engines for high performance and low emissions.

Distribution pump fuel injection system

Working principle: Using a distribution rotor, fuel is sequentially distributed to the injectors of each cylinder through the rotation of the rotor. Fuel is pressurized in the distribution pump and then distributed to the corresponding injectors for injection according to the engine's operating sequence.

Features: Compact structure, small size, light weight, low cost, and good fuel injection uniformity. However, the manufacturing accuracy of the distribution pump requires high precision and is also sensitive to the cleanliness of the fuel, resulting in a relatively short service life.

Common rail fuel injection system

Working principle: The common rail system stores high-pressure fuel generated by the high-pressure fuel pump in the common rail pipe, and the pressure inside the common rail pipe remains stable. The electronic control unit (ECU) precisely controls the injection timing, injection quantity, and injection pressure by controlling the solenoid valves of the fuel injectors based on the engine's operating conditions.

Features: High fuel injection pressure, up to 200MPa or more, capable of multiple injections, improving fuel atomization and combustion efficiency, and reducing emissions. It has good dynamic response characteristics and can quickly adjust fuel injection parameters according to the real-time operating conditions of the engine, improving the performance and fuel economy of the engine. But its system is complex, the cost is high, and the precision requirements for electronic control technology and sensors are also high.

Unit pump fuel injection system

Working principle: Each cylinder has an independent fuel injection pump, which is directly installed on the cylinder head and connected to the fuel injector. The fuel injection pump is driven by the camshaft and achieves fuel boost and injection by controlling the movement of the plunger.

Features: High injection pressure, able to meet the requirements of modern engines for high injection pressure. High fuel injection accuracy enables precise control of fuel injection quantity. The structure is relatively simple, with high reliability and easy maintenance. However, the installation and debugging of individual pumps are relatively complex, and there are certain requirements for the structural design of the engine.

Different types of diesel engine fuel injection systems have their own advantages and disadvantages. With the increasingly strict emission regulations and the continuous development of engine technology, the common rail fuel injection system is gradually becoming the mainstream fuel injection system due to its excellent performance. However, in some applications that require high cost and reliability, inline plunger pump fuel injection systems and distribution pump fuel injection systems still have a certain market share.