| The fuel injection of the diesel high pressure common rail system adopts the pressure-time control way,and the accuracy and flexibility of the fuel injection control play a key role in improving the engine’s power,economy and emissions.However,excellent rail pressure control is an important guarantee for precise injection control,so the rail pressure control of high pressure common rail systems is very important.Based on the principle of high-pressure common rail system,this paper derives the relevant mathematical model of rail pressure control,builds the corresponding rail pressure control model in Simulink environment,and carries out co-simulation with the physical model of high-pressure common rail system built by AMESim to test the rail pressure control performance of the control model under different working conditions of diesel engine.Its main work mainly includes:1)Deriving mathematical equations related to rail pressure control.Through in-depth analysis of the physical structure of high-pressure common rail system,the control equation of the entire system and the main components is established based on relevant theoretical knowledge.For the high-pressure oil pump,the motion law of the plunger and the driving power equation are derived;for the precise position control of the metering valve,the temperature rise correction equation of the solenoid coil is derived;and for the rail pressure control of high pressure common system,the demand flow calculation equation of the rail pressure-metering valve(Me Un)is derived.2)Applying Simulink software to build a rail pressure control system model.According to the rail pressure-metering valve(Me Un)demand flow calculation equation and the temperature rise correction equation of the metering valve solenoid coil,the rail pressure control state machine module,the metering valve demand flow calculation module and the metering valve position precise control module are designed.3)Using AMESim software to establish the physical model of the high pressure common rail fuel injection system.In the AMESim environment,the physical model is established according to the physical structure of the high-pressure common rail system,replacing the high-pressure common rail oil pump test bench and as the controlled model of the rail pressure control model.4)Testing the influence of the control model on the rail pressure under different working conditions of the diesel engine.Through the co-simulation of AMESim and Simulink,under the different working conditions of the diesel engine(starting condition,idle working condition,normal working condition and transient working condition,etc.),the influence of diesel universal characteristics of common working conditions on the rail pressure control strategy is tested.The simulation results show that during the start-up process,the rail pressure control model can reasonably calculate the demand flow of the Me Un,make the metering valve fully open,rapidly raise the rail pressure to the initial injection fuel pressure and idle target pressure,such as the time spent on rail pressure rising from 0.1MPa to 79.2MPa is less than 1.25s;In idle condition,even if the speed of diesel engine fluctuates(± 30r/min),the rail pressure control remains stable,the steady-state rail pressure fluctuates is within ± 1MPa,and there is no overshoot in the transitional condition;In normal condition,the rail pressure transition between each working point is smooth,and the steady-state rail pressure fluctuates regularly up and down centered on the target rail pressure,its fluctuation can be controlled within ±(35)P(descending absolute value of rail pressure when Cycle fuel supply is injected through singleinjection in a cylinder),such as 20 mm3 fuel injection,(35)P=2.5 MPa;In transient conditions,the actual rail pressure can closely follow the trend of target rail pressure change to meet the demand of diesel engine for rail pressure change under acceleration and deceleration conditions. |
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