Study Of Physicochemical Properties And Effect On Spray Performance Of Injector Deposit In GDI Engines

At present,for the automobile market,because of the stand out dynamic,fuel economy and emission,the share of GDI is more and more.But compared to the PFI engine,the injector of GDI engine is working in the harsh environment of combustion chamber,that makes the injector easily deposit with the working time increase.Once the injector has the deposit,it will make a worse effect on the engine performance.So the paper respectively carries out the research on the physicochemical properties and the effect on spray performance.That helps we understand the nature of deposit,enrich and develop the injector deposit formation mechanism.At the same time,that gives a theoretical basic to analysis why the engine combustion and emission become worse for the car.So the study has the significance of basic research.In the study of the deposit physicochemical properties,an equipment is developed to simulate the injector deposit.Then by the means of SEM,X-ray spectroscopy and FTIR,the paper respectively analyzes the simulation deposit and actual vehicle injector deposit.In the study on the spray performance,based on the schlieren theory,the paper builds a spray test to research the spray of the new injector,the coke injector and the washed injector which they are operated in the 6MPa,12 MPa,and 15 MPa.At last,the paper analyzes the spray angle,penetration distance and spray area by using the MATLAB.The results show,for the multi-nozzle injector every orifices deposit is very different.With regard to the simulation deposit,it is isolated granule in the internal hole,but it spreads along the external holes.By the analysis of the X-ray spectroscopy,it is showed that the actual vehicle injector deposit and the simulation deposit have the similar energy spectrum,the former contains C,O,Na,Mg,Al,Si,P,S,K,Ca,Cr,Mn,Zn,Fe and so on,the latter contains C,O,Na,P,S,K,Ca,Fe and so on.By the analysis of FTIR,it is showed that the actual vehicle injector deposit and the simulation deposit have the similar infrared spectrum.They have Hydroxyl functional groups,Methylene functional groups,Carbon-oxygen double bond functional group,Methyl functional group and Sulfur compounds functional groups.Differently,there are differences in content.For the effect on the spray performance with the deposit injector,it is showed that the spray penetration distance of deposit injector is longer or shorter than new injector,that is because of the spray inertial force and broken beams interaction,but the spray penetration distance of the washed injector is closed to the new injector.Regardless of any injection pressure,the spray angle of deposit injector is smaller than new injector,the spray angle of washed injector and new injector nearly has no difference.With the injection pressure increase,the rate of increase of the deposit injector spray angle is relatively small.But for the new injector,within a certain range of injection pressure,when injection pressure is increased,the rate of angle increase is also increased,then if the pressure exceeds rang,the rate of angle increase becomes small.For the spray area of deposit injector,it is all ways smaller than new injector,if the deposit is washed,the spray area will be closed to new injector.