The high-pressure fuel pipe is the channel connecting the common rail pipe and the electronically controlled injector. It should have enough fuel flow to reduce the pressure drop when the fuel flows, and make the pressure fluctuation in the high-pressure pipeline system small, and can withstand the high pressure fuel. Shock effect, and the pressure in the common rail can be quickly built up when starting. The length of the high-pressure fuel pipes of each cylinder should be as equal as possible, so that each injector of the diesel engine has the same fuel injection pressure, thereby reducing the deviation of the fuel injection amount between the cylinders of the engine. Each high pressure fuel line should be as short as possible to minimize the pressure loss from the common rail to the fuel injector. The outer diameter of the high-pressure oil pipe of BOSCH company is 6mm and the inner diameter is 2.4mm. The outer diameter of the high-pressure oil pipe of Japan Denso company is 8mm and the inner diameter is 3mm.

The high pressure in the common rail cavity is directly used for injection, which can save the booster mechanism in the injector; and the high pressure in the common rail cavity is continuous, and the driving torque required by the high pressure oil pump is much smaller than that of the traditional oil pump.

Through the pressure regulating solenoid valve on the high-pressure oil pump, the oil pressure in the common rail cavity can be flexibly adjusted according to the engine load condition and the requirements of economy and emission, especially to optimize the low-speed performance of the engine.

The injection timing, injection quantity and injection rate are controlled by the solenoid valve on the injector, and the injection quantity of pre-injection and post-injection and the interval with the main injection can be flexibly adjusted under different working conditions.

The high pressure common rail system consists of five parts, namely high pressure oil pump, common rail cavity and high pressure oil pipe, fuel injector, electronic control unit, various sensors and actuators. The fuel supply pump pumps the fuel from the fuel tank into the fuel inlet of the high-pressure fuel pump. The high-pressure fuel pump driven by the engine pressurizes the fuel and sends it into the common rail cavity, and then the solenoid valve controls the fuel injectors of each cylinder to inject fuel at the corresponding time.

Before the main injection, the pre-injection injects a small part of the fuel into the cylinder, and pre-mixing or partial combustion occurs in the cylinder, which shortens the ignition delay period of the main injection. In this way, the in-cylinder pressure rise rate and peak pressure will be reduced, the engine operation will be more moderate, and the in-cylinder temperature will be reduced to reduce NOx emissions. Pre-injection also reduces the likelihood of misfire and improves the cold start performance of the common rail system.

At the beginning of the main injection, reducing the injection rate can also reduce the amount of oil injected into the cylinder during the ignition delay period. Increasing the injection rate in the middle of the main injection can shorten the injection time and thus the retarding period, so that the combustion is completed within the more effective crank angle range of the engine, which increases the output power, reduces fuel consumption, and reduces soot emissions. Quick fuel cut at the end of main injection can reduce incomplete combustion of fuel, reduce smoke and hydrocarbon emissions.