Research On High-pressure Oil Pump Control Strategy Of High Pressure Common Pressure Rail Diesel

High pressure common rail fuel injection system is one of the key technologies for energy saving and emission reduction of diesel engine.The use of pressure-time control system makes it more flexible.The precise control of the common rail pressure directly affects the fuel injection control,fuel atomization,fuel injection rate and injection pressure fluction.High pressure oil pump is the heart of the fuel injection system and the control strategy of high pressure oil pump directly affects the stability of rail pressure,which directly affect the fuel injection law and economic and emission performance in the working condition of engine.Because of the different requirement of rail pressure in different working condition of disel engine,it is important to research the contral strategy of the high pressure pump on different working conditions fot the rapid and accurate establishment of common rail pressure.Based on the former research of the high pressure common oil pump.This parper analysis and optimize the control strategy of high pressure pump of the GW2.8T engine in different working conditions and meet the control requirement of the high pressure pump in the way of simulation and experimental verification.The main content of this parper is as follows:First,using the one-dimensional fluid simulation software AMESim to build a detailed model of the key components of the fuel imjection system,with emphasis on the analysis and verification of the fuel metering valve and injector.Second,designing the fuel metering valve colsed loop system of the high pressure common rail dieseil engine and corresponding control scheme and flow according to conditions of the srarting,idle speed,steady state and acceleration and deceleration conditons.Based on calculating the parameters of plunger leakage of high pressure pump and return oil during injection,using Matlab/Simulink to build the whole control system model inchuding state machine,open loop feedforward control module,PID module,feedback module,limit module,traffic duty module and so on.In the cosimulation of AMESim and Matlab,the data of rail pressure of fuel supply system in different engine speeds can meet the requirements.Third,this paper makes a detailed study on the control requirements,difficulities and control strategies of the high pressure oil pump of the disel engine in the different conditions.The control of high pressure oil pump in the starting process is the most important,including open loop and closed loop.This papers divided the start conditions into two part.In the towing period,this paper studied the influence on rail pressure establisment caused by the pressure and speed of first injection and detemined the opening time and opening size of high pressure pump.In the starting period,this paper studied the influence on rail pressure caused by open loop flow,control method and method of setting target rail pressure.The data showed that the rail pressure can be improved to 40 MPa in 0.8s before sptating and can maintained stable.In starting condition,the rail pressure can be improved to 60 MPa from 40 MPa in 0.5s with overshoot no more than 6MPa.In the idle condition,it makes fluctuation of rail pressure small by making use of the method of stabilizing the target rail pressure,optimizing establishment of rail pressure in strating conditions and PID with differential filter.The data showed that the rail pressure can maintained stable before idle conditions with overshoor no more that 3MPa.In the conventional condition,the experimental show that the rail pressure can meet the requirements of stability.The data showed that the fluctuation can be controlled within 3MPa.In transient condition,this paper use hybird control method with open and closed loop.Experiments show that both the rail pressure and traget rail pressure can keep good stability and responsiveness.In rapid acceleration,the rail pressure can rise 30 MPa in 3s and in the rapid deceleration,the rail pressure can fall 30 MPa in 2.3s with overshoot no more than 3.8MPa.the rail pressure can change steeply at first then flatly.Engine can transit to conventional conditions smoothly.The paper proved the feasibility of the control strategy by the wat of motheod resrearch and experimental verification and optimized the performance of the engine under different working conditions.