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What is diesel high pressure common rail system?

diesel common rail system

In our world, there are hundreds of diesel engine manufacturers, each brand of diesel engine fuel, its fuel injection system is not only two kinds, one is mechanical fuel injection system, the other is electronically controlled fuel High pressure common rail injection system. The mechanical fuel injection system uses a traditional mechanical fuel pump, which is driven by a camshaft. The pressure of the fuel injection increases with the increase of engine speed and fuel injection. The diesel system has unstable atomization effect and cold start. Difficulties and other issues, but also unable to meet the increasingly stringent emission standards and the desire to reduce fuel consumption. Electronically controlled diesel high pressure common rail system. It has a higher injection pressure, better atomization, lower fuel consumption and cleaner emissions.

What is a high pressure common rail system?
The high-pressure common rail system refers to an oil supply method in which the injection pressure is generated and the injection process is completely separated from each other in a closed-loop system composed of a high-pressure oil pump, a pressure sensor, and an electronic control unit (ECU), and is previously driven by a camshaft. The diesel injection system is completely different. It is a high-pressure oil pump that delivers high-pressure fuel to the oil rail, and precise control is achieved by the oil pressure in the oil rail, so that the pressure of the high-pressure fuel pipe is independent of the engine speed, and the degree of change of the diesel fuel supply pressure with the engine speed can be greatly reduced.
High pressure common rail system
The diesel high pressure common rail injection system consists of a hydraulic system and an electronic control system. The hydraulic system is divided into a low pressure hydraulic system and a high pressure hydraulic system. The low pressure hydraulic system includes a fuel tank, an oil pump, a fuel filter and a low pressure oil pipe; the high pressure hydraulic system includes a high pressure pump, a high pressure oil rail, a fuel injector and a high pressure oil pipe; and an electronic control system (Electronic Diesel Control, EDC for short) includes a sensor , Electronic Control Unit (ECU), Actuator (including injector with solenoid valve, pressure control valve, glow plug control unit, boost pressure regulator, exhaust gas recirculation regulator, throttle valve, etc. ) and harness.
Among them, the injector, high-pressure pump, high-pressure fuel rail and electronic control unit are the four core components of the diesel common rail system.
An injector is a component that atomizes fuel and distributes it in the combustion chamber of the engine. The injection timing and duration of the common rail injector are accurately calculated by the electronic control unit to give a signal, which is then controlled by a solenoid valve.

The function of the high pressure pump is to compress the fuel from a low pressure state through a plunger to a high pressure state to meet the fuel injection pressure and fuel injection requirements of the system and the engine.

The function of the high-pressure rail is to store fuel, while suppressing pressure fluctuations caused by high-pressure pump oil supply and fuel injector injection to ensure system pressure stability. The high pressure rails are common to each cylinder and are the hallmark of the common rail system.

The electronic control unit is like the brain of the engine. It collects the operating parameters of the engine, combines the stored characteristic maps for calculation and processing, and transmits the signals to the actuators to realize the functions of engine operation control and fault diagnosis.

Working principle of high pressure common rail system
The electronic control unit accurately calculates the current required fuel injection amount according to various real-time parameters collected (vehicle speed, throttle opening, crankshaft speed, camshaft speed, rail pressure, etc.) (the amount of fuel injection depends on the rail pressure and The length of time the solenoid valve is opened, which in turn controls the opening and closing of the solenoid valve as an actuator, and the diesel fuel is injected into the cylinder to achieve optimum combustion under the current operating conditions.
The high pressure common rail system enables greater power, lower fuel consumption and cleaner emissions.

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