fuel injection

Common rail fuel injection systems only entered practical application in the mid-to-late 1990s. These electronic control systems can be divided into: accumulator-type electronic fuel injection systems, hydraulic turbocharged electronic fuel injection systems, and high-pressure common rail electronic fuel injection systems. High-pressure common rail systems can achieve functions that are impossible in traditional fuel injection systems. Their advantages include:

a. The injection pressure in the common rail system is flexibly adjustable, allowing for the determination of the optimal injection pressure for different operating conditions, thereby optimizing the overall performance of the diesel engine.

b. It allows for independent and flexible control of injection timing. Combined with high injection pressure (120MPa~200MPa), it can simultaneously control NOx and particulate matter (PM) within relatively low values to meet emission requirements.

c. Flexible control of injection rate variations allows for ideal injection patterns, easily achieving pre-injection and multiple injections, which reduces diesel engine NOx while ensuring excellent power and fuel economy.

d. Fuel injection is controlled by a solenoid valve, offering high control precision. Air bubbles and zero residual pressure are eliminated in the high-pressure fuel circuit. Therefore, within the diesel engine's operating range, the variation in cyclic fuel injection quantity is small, and uneven fuel supply to each cylinder is improved, thereby reducing engine vibration and emissions.

Due to these advantages, high-pressure common rail systems have attracted significant research attention from domestic and international diesel engine research institutions.

The design principle for the high-pressure fuel pump's fuel supply quantity is to ensure the combined requirements of the fuel injection quantity and control quantity under all conditions, as well as the fuel quantity changes during starting and acceleration. Since the injection pressure in the common rail system is independent of the fuel injection process, and injection timing is not guaranteed by the high-pressure fuel pump's cam, the high-pressure fuel pump's cam can be designed based on the principles of minimum peak torque, minimum contact stress, and maximum wear resistance.