Combustion Close-loop Control Of Diesel Engine Based On In-cylinder Pressure

With the further study of the high pressure common rail control system of diesel engine,the traditional open loop control can not cope with the combustion deterioration caused by uneven combustion.This article designs a closed loop control system on the TBD314V8 diesel engine.In this article,NI cylinder pressure sensor,angle sensor,data acquisition card and other hardware and LabVIEW software platform are used to build a cylinder pressure acquisition system.The cylinder pressure data is collected every 0.1° crank angle.The pure compression cylinder pressure curve is activated by the cylinder deactivation method,and the compression top dead center is calibrated in combination with the Z signal of the angle sensor,and the top dead center is corrected by the compression neutral line method.Based on the spectrum analysis of the cylinder pressure,the linear difference method performs filtering processing.The combustion analysis module calculates and analyzes the amount of work,heat transfer and internal energy change of each node based on the cylinder pressure per 0.1 °CA.The heat conservation formula can calculate the heat release.Then calculate the heat release rate curve,seek CA50,and calculate IMEP using cylinder pressure.Due to the large amount of data in the eight cylinders,real-time optimization is performed to ensure that the computer can withstand the calculation load.Based on LabVIEW,the dynamic link library function is communicated with the CAN line.The CAN card control program is programmed to convert the fuel injection parameters into CAN messages and periodically send them to the CAN bus.In CANape's built-in program node,the program reads the message on the CAN bus,converts it into the fuel quantity parameter modification quantity,and modifies the variable in the calibration parameter,and then sends it to the ECU to realize the modification of the subsequent cycle fuel injection parameter.The simulation model of TBD314V8 diesel engine is built in GT-Power.The inhomogeneity between cylinders is evaluated by two parameters of coefficient of variation and unevenness.When different injection advance angles and different injection quantities are explored,inhomogeneity changes of pressure,CA50 and IMEP is investigated.The feedback variables based on cylinder pressure were also evaluated.And CA50 and IMEP are selected as feedback variables.The simulation study on the in-cylinder combustion process with different injection angle and different injection quantity shows that the injection angle has a good linear relationship with CA50,which is suitable for the control variable of CA50 closed-loop controller,and the injection quantity has a good linear relationship with IMEP,which is suitable for the control variables of the IMEP closed-loop controller.The actual and target values of CA50 and IMEP are used as input quantities,through a PI integrator,the fuel injection angle adjustment and the fuel injection adjustment are used as the output amount.CA50 and IMEP are respectively designed a closed-loop controller to improve the inhomogeneity of the two.