Study On The Characteristics Of Exhaust Particulate Matter From Dual Injection System Gasoline Engine

Huge vehicle ownership makes the energy and environmental issues become more serious,which puts forward the urgent requirement of automobile energy conservation and emissions reduction.The particulate matter mass and number of GDI engines are both limited by Euro 6 emission regulation.Dual injection system gasoline engine combines advantages of the GDI and PFI engine,it has strong power,low fuel consumption and low emissions.Major car companies and research institutions pay more and more attention to dual injection system gasoline engines.It is necessary to conduct a thorough research to the particulate emission characteristics of dual injection system engine.The author conducted an experiment in a dual injection system gasoline engine and DMS500 particle spectrometer was used to test particulate emission.The results show that:1)In the medium and small load,medium and low speed conditions,with the increase of engine speed,nucleation mode particles and accumulation mode particles number concentration decrease;with the increase of engine load,nucleation mode particles and accumulation mode particles number concentration show a trend of down first,then increase;with the decrease of the GDI injection ratio,the effect of speed and load on the particle number emission decreases.2)In the speed of 2000 r/min and 1500 r/min,BMEP = 0.2 MPa commonly used point,with the decrease of the GDI injection ratio,nucleation mode particles and accumulation mode particles number concentration show a trend of down first,then increase.When GDI injection ratio ranges from 100% to 60%,the falling speed of the exhaust particulate matter total number and mass concentration is fast,with GDI injection ratio decreases further,the falling speed of the exhaust particulate matter total number and mass concentration become slow,the particulate matter total number and mass concentration even have a small rise.There is a GDI injection ratio making the total number and mass of particle concentration reach its lowest point.The operation mode of the dual injection system can significantly reduce particulate emissions,in the commonly used point,the total number concentration reduces more than 94%,the total mass concentration decreases more than 99%.3)In the speed of 2000 r/min and 1500 r/min,BMEP = 0.2 MPa commonly used point,with the decrease of the GDI injection ratio THC concentration in tail gas changes little;while the CO concentration generally presents the tendency of decrease.The working condition 2000 r/min and 1500 r/min respectively have a biggest fell by 27%,40%.With the decrease of the GDI injection ratio,NOx concentration generally shows a trend of increase.The working condition 2000 r/min and 1500 r/min respectively have a biggest fell by 47%,51%.4)Ignition timing can affect the mixing time of fuel and air and combustion heat release in cylinder.With the delay of ignition timing,nucleation mode particles and accumulation mode particles number concentration show a trend of decrease.High injection pressure of GDI can promote the spray evaporation and mixture of fuel and air,thereby reducing nucleation mode particles and accumulation mode particles number emissions.When the injection timing of GDI is either too early or too late,it will affect the mixture of fuel and air.With the delay of injection time,nucleation mode particles and accumulation mode particles number concentration show a trend of down first,then increase.