Study On The Characteristics Of Exhaust Particulate Matter From Gasoline Direction Injection(GDI)engine

Gasoline direction injection (GDI) has the advantages of improving dynamic property and higher fuel economy of internal combustion engine.But there are significant differences in combustion mode between GDI engines and PFI engines,So the characteristics of particulate matter should be different,otherwise the smaller the particulate size is, more easily through the respiratory into the lungs, the bigger impact on the health of people. In order to deal with emission regulation standard and protect human health,a thorough and in-depth research on the characteristics of particulate matter from gasoline direct injection engine can improve GDI engine emission performance and provide the theory basis.In this paper, the research is mainly based on the type of 4G15 GDI engine for the characteristics of particulate matter using DMS 500 Fast Particulate Spectrometer manufactured by Cambustion, in order to set up and calibrate the test system, the research also includes the experiment on a PFI engine with 2L meeting the EUROâ…¢emission standards for the characteristics of particulate matter.The results of research in this paper are as follows:1,In GDI mode,While injection timing approaching TDC,nucleation(Dp between 5 and 10nm)mode in size distribution of number concentration shows the increasing trend, accumulation(Dp between 10 and 100nm)mode depicts exactly the opposite trendency;Both nucleation and accumulation mode show decreasing trend when A/F ratio gets bigger;While spark timing departs from TDC, nucleation mode has a increasing trendency,but spark timing has little impact on accumulation mode; While EGR ratio getting bigger,nucleation and accumulation mode in size distribution of number concentration shows the increasing trend; Both nucleation and accumulation mode show decreasing trend when rail pressure gets bigger;2, In GDI mode, number concentration of nucleation mode decreases greatly after TWC(Three Way Catalyst);but, number concentration of accumulation mode decreases slightly comparing with that of nucleation mode after TWC;3, In GDI mode, nucleation mode displays the opposite trend with accumulation mode in size distribution of number concentration while engine speed changes,nucleation mode with unimodal size distribution decreases gradually while engine load incereases; 4, In PFI mode, nucleation mode show relatively larger proportion in the distribution of number, surface area, mass concentration,and it has a increasing trend while engine speed and load,the reason is that the sulphate in fuel turn into SO₃ and getting more HC,the particulate matter has strong absorbability in sulfuric acid and HC because of enhancing the accumulation;5, In PFI mode, number concentration of nucleation mode decreases greatly after TWC and number concentration of accumulation mode increases greater after TWC than before TWC, because part of particulate in nucleation mode turn into accumulation mode after TWC.