Common rail technology refers to a closed-loop system consisting of a high-pressure oil pump, a pressure sensor and an ECU. The high-pressure oil pump delivers high-pressure fuel to the common fuel supply pipe. By accurately controlling the oil pressure in the common fuel supply pipe, the change in the fuel supply pressure of the diesel engine with the engine speed can be greatly reduced.
In automobile diesel engines, high-speed operation makes the diesel injection process take only a few thousandths of a second. Experiments have shown that the pressure at various locations in the high-pressure oil pipe varies with time and position during the injection process. Due to the compressibility of diesel and the pressure fluctuation of diesel in the high-pressure oil pipe, the actual injection state is quite different from the plunger fuel supply law specified by the injection pump. The pressure fluctuation in the oil pipe sometimes causes the pressure in the high-pressure oil pipe to rise again after the main injection, reaching the pressure that opens the needle valve of the injector, and reopening the closed needle valve to produce secondary injection. Since the secondary injection cannot be completely burned, the smoke and hydrocarbon (HC) emissions are increased, and the fuel consumption increases. In addition, the residual pressure in the high-pressure oil pipe will change after each injection cycle, which will cause unstable injection. The above phenomenon is easy to occur especially in the low-speed area. In severe cases, not only the injection is uneven, but also intermittent non-injection occurs. In order to solve the defect of fuel pressure change in diesel engines, modern diesel engines use a technology called "common rail".
Common rail technology refers to a fuel supply method that completely separates the generation of injection pressure and the injection process from each other in a closed-loop system composed of a high-pressure oil pump, a pressure sensor and an ECU. The high-pressure oil pump delivers high-pressure fuel to the common fuel supply pipe. By accurately controlling the oil pressure in the common fuel supply pipe, the pressure of the high-pressure oil pipe is independent of the engine speed, which can greatly reduce the change of the diesel engine fuel supply pressure with the engine speed, thereby reducing the defects of traditional diesel engines. The ECU controls the injection amount of the injector, and the injection amount depends on the pressure of the fuel rail (common fuel supply pipe) and the length of time the solenoid valve is open.
The turbocharger of the diesel engine has been introduced. As for the turbocharger intercooling technology, it is when the turbocharger compresses the fresh air and cools it through the mid-section cooler, and then flows to the cylinder combustion chamber through the intake manifold and intake valve. Effective intercooling technology can reduce the supercharging temperature to below 50℃, which helps to reduce exhaust emissions and improve fuel economy.
