Effect of exhaust gas recirculation(EGR) on combustion and emission of butanol/gasoline combined injection engine

N-butanol is a kind of biomass alcohol which can be produced by fermentation, and it is also a clean alternative fuel. The combustion and emissions characteristics of n-butanol/gasoline SI engine under different combined injection modes with the introduction of EGR was studied. N-butanol inlet injection plus gasoline in-cylinder direct injection is called N-GXDI; Gasoline inlet injection plus n-butanol in-cylinder direct injection is called G-NXDI. Through the analysis of combustion and emission performance under different EGR rates, injection modes and direct injection ratios (DIr), it is found that with the increase of DIr, cylinder temperature, pressure, and IMEP increase first and then decrease. Under the DIr = 50%, the combustion is more complete when the EGR rate is 5%. Under the same DIr, with the increase of EGR rate, CO emission decreased first and then increased, NOx emission opposite, THC emission increased. Under the same EGR rate, the total particle number of the two modes decreases first and then increases with the increase of DIr. The G-NXDI mode has advantages in combustion and primary emissions, while the N-GXDI mode has advantages in particulate emissions, suitable injection mode combined with EGR can greatly improve combustion and emission performance.