The fuel injector is a precision device with very high machining accuracy, which requires a large dynamic flow range, strong anti clogging and anti pollution capabilities, and good atomization performance. The fuel injector receives the injection pulse signal sent by the ECU and accurately controls the fuel injection amount.

The spray characteristics of the fuel injector include atomization particle size, fuel spray distribution, fuel spray direction, range and diffusion cone angle. These characteristics should meet the requirements of the diesel engine combustion system to achieve perfect mixture formation and combustion, as well as high power and thermal efficiency.

The electronically controlled fuel injector is the most critical and complex component in the common rail system, and it is also the most difficult component in design and manufacturing. The ECU controls the opening and closing of the solenoid valve to inject fuel from the high-pressure fuel rail into the combustion chamber at the optimal injection timing, quantity, and rate. In order to achieve effective fuel injection starting point and precise fuel injection quantity, the common rail system adopts a dedicated fuel injector with a hydraulic servo system and electronic control components (solenoid valves).

The fuel injector is composed of a hole type fuel injector similar to traditional fuel injectors, a hydraulic servo system (control piston, control orifice, etc.), a solenoid valve, etc.

The diesel engine fuel injection system atomizes the fuel and distributes it in the combustion chamber to mix with air.

It mainly consists of a fuel injector and an injector body, and its installation position and angle on the cylinder head depend on the design of the combustion chamber.

There are two types of fuel injectors: open and closed. Open fuel injectors have a simple structure, but poor atomization is rarely used. Closed fuel injectors are widely used in various diesel engines. The diesel engine draws in pure air during the intake stroke. At the end of the compression stroke, diesel fuel is injected into the cylinder through the fuel injection pump to increase the oil pressure to over 100MPa, and then mixed with compressed high-temperature air in a short period of time to form a combustible mixture. As the compression ratio of diesel engine is high (generally 16-22), the air pressure in the cylinder at the end of compression can reach 3.5-4.5MPa, and the temperature can reach 750-1000K (while the mixture pressure of gasoline engine at this time will be 0.6-1.2MPa, and the temperature can reach 600-700K), which is much higher than the Autoignition temperature of diesel. Therefore, after being injected into the cylinder, diesel immediately ignites and burns on its own after mixing with air for a short period of time. The air pressure inside the cylinder rapidly rises to 6-9MPa, and the temperature also rises to 2000-2500K. Under the pressure of high-pressure gas, the piston moves downward and drives the crankshaft to rotate to do work, and the exhaust gas is also discharged into the atmosphere through the exhaust pipe.

[1] The ordinary diesel engine is driven by the engine camshaft and uses a high-pressure oil pump to deliver diesel to the fuel chambers of each cylinder. This fuel supply method needs to vary with the engine speed, and cannot achieve the optimal fuel supply at various speeds.

The common rail injection fuel supply system consists of a high-pressure oil pump, a common fuel supply pipe, an injector, an electronic control unit (ECU), and some pipeline pressure sensors. Each fuel injector in the system is connected to the common fuel supply pipe through its own high-pressure oil pipe, and the common fuel supply pipe plays a hydraulic pressure storage role on the fuel injector.

During operation, the high-pressure oil pump delivers fuel to the common fuel supply pipe under high pressure. The high-pressure oil pump, pressure sensor, and ECU form a closed-loop operation, achieving precise control of the oil pressure inside the common fuel supply pipe, completely changing the phenomenon of fuel supply pressure changing with engine speed. Its main characteristics include the following three aspects:

1. The injection timing and fuel metering are completely separated, and the injection pressure and injection process are controlled by the ECU in a timely manner.

2. The fuel injection pressure, starting point, and duration of each cylinder can be adjusted based on the working condition of the engine, in order to pursue the best control point for fuel injection.

3. It can achieve high fuel injection pressure and achieve pre injection of diesel fuel.

Compared to gasoline engines, diesel engines have a lower fuel consumption rate (average 30% lower than gasoline engines) and lower diesel prices, resulting in better fuel economy; At the same time, the speed of diesel engines is generally lower than that of gasoline engines, and the torque is larger than that of gasoline engines. However, due to its high quality and high noise during operation, manufacturing and

High maintenance costs and lower emissions compared to gasoline engines. But with the development of modern technology, these shortcomings of diesel engines are gradually being overcome.