The Multi-cylinder Balancing Control Of Stratified Flame Ignition High Dilution Low Temperature Combustion In A Gasoline Engine

Represented by SI-CAI hybrid combustion,high dilution low temperature combustion's ignition and combustion process are extremely sensitive to boundary conditions.When applied to multi-cylinder engine,severe cylinder-to-cylinder variation is easy to generate.Thus its application is limited.In order to solve this problem,systematic research was conducted on the capability of main control parameters on cylinder-to-cylinder balancing control.And corresponding control strategy was put forward in this paper.Firstly,the high dilution low temperature combustion in a four-cylinder gasoline engine research platform,which is equipped with double VVT,external EGR and PFI/GDI double injection system,is established.The engine operation control and data acquisition is based on AUTOBOX and LABVIEW respectively.Then,the influence of PFI/DI injection control strategy combined the spark timing strategy on SI-CAI hybrid combustion was studied to explore the potential of injection strategy and ignition strategy for multi-cylinder balancing control.The results showed : SOI is not the best choice for individual cylinder CA50 balancing control because of its complexity effect on combustion,although it can been flexiblely controlled between cylinders.The increase of the ratio of direct injection(r DI)will greatly reduce the PRRmax with the deterioration of IMEP,while it has little influence on the combustion phasing.Compared with the homogeneous hybrid combustion,SFI can broaden the CA50 control window,improve the controllability of spark timing to combustion,which is benefit of individual cylinder CA50 control by spark timing.It can ensure the fuel economy in advance,while maintaining relatively small CCV and low PRRmax level.Based on the results of the control performance of PFI/GDI injection and ignition strategy on combustion,it can be concluded that the strategy put forward is effective and flexible in multi-cylinder IMEP and CA50 balance control.As a result,the multi-cylinder IMEP and CA50 balance strategy was put forward.In order to decrease the IMEP differences between cylinders,the PFI/GDI fuel injection proportion coordinated with the control strategy of Lambda in individual cylinder was put forward.Results of engine experiments showed that under the condition of 1500 r/min-3 bar,this strategy decreased the variations of IMEP between cylinders from 6.3% down to 2.4%.In order to decrease the CA50 differences between cylinders,CA50 mid-ranging balancing control strategy was put forward,which is based on individual cylinder ignition cooperated with IVC and eEGR control.Results of engine experiments showed that under the load of 1500 r/min-3.5 bar,this strategy can achieve CA50 balancing quickly and effectively,and prevent spark timing control into saturation.The each combustion stability has been improved effectively,and the IMEP variations between cylinders reduced from 6% to 4% by the joint balancing of IMEP and CA50 under the load of 1500 r/min-4.7 bar.In one word,for the SFI combustion multi-cylinder engine achieved by PFI/DI hybrid injection.The cylinder-to-cylinder variation of IMEP and CA50,due to its sensitive to boundary conditions,can be effectively restrained by the appropriate cooperate control of PFI/DI injection,spark timing as well as VVT and EGR.Hence the stability of continuous engine operation can be improved for the high dilution low temperature combustion multi-cylinder engine.