Study On The Characteristics Of Combustion And Exhaust Particulate Matter From Turbocharged Gasoline Direction Injection Engine

Gasoline direction injection (GDI) engine with its excellent dynamic economyand transient response capability is becoming a major electric vehicle. But thedisadvantage of GDI engine is more exhaust particulate matter. As the gasoline isinjected into the cylinder, comparing to Port injection gasoline engine, the mixture hasshort mixing time, piston and cylinder wall wetting lead to exhaust particulate matter.Euro Ⅴ emission regulations for GDI engine particulate matter emissions proposedrequirements. With increasingly stringent emission regulations, we must study theGDI engine exhaust particulate matter emission. Compared to diesel engine, GDIengine particle’s diameter is smaller, mainly nanoscale particles. They have a largerdiameter than the surface, they can be adsorbed more toxic substances, greater hazardto human health. The author uses DMS500particle spectrometer on a turbochargedGDI engine to investigate experimentally.Firstly, I studied turbocharged GDI engine’s idling, starting and small speed,small load conditions. Experimental results are as follows, engine start instantly, moreparticulate matter emissions; particularly accumulation mode particle number is high.With the warm-up, accumulation mode particle number is gradually reduced. In hotIdle, exhaust particulate matter is mainly nuclear mode. Compared to cold idle,particle size and number are much smaller. In small and medium-speed small loadeach operating point, particle number not in the same order of magnitude. In themedium speed and medium load, particle number concentration is highest. The totalparticle number concentration is affected by the nuclear mode number concentration.With respect to the engine speed, more impact on the larger cylinder pressure and heatrelease rate by the engine load. the mixture’s combustion rate and cylindertemperature combined effect the particulate matter emissions.Secondly, I studied supercharger GDI gasoline engine’s particulate emissionsunder different control parameters. Experimental results are as follow, when using theconcentrated mixture, maximum cylinder pressure increases, the peak heat release rateincreases, burning rate becomes faster, maximum combustion temperature increases,post-combustion cylinder temperature decreases rapidly, post-combustion oxygencontent decreased, particulate matter emissions increases. Organizing the excess airratio slightly greater than1.0is in favor of improving the particulate matter emission.Early fuel injection produces piston and cylinder wall wetting, and leads toincomplete combustion, the particle number is high. Injection too late, oil and gas mixing time is shortened, the mixture mixed uneven, particulate matter emissionsincrease. Especially the nuclear mode particulate matter has large increase.Reasonable to optimize injection timing can reduce particulate matter emissions. Withthe ignition advanced, maximum cylinder pressure increases, the crank anglecorresponding to the peak cylinder pressure gradually approaches the top dead center,the combustion process accelerates, maximum combustion temperature increases, andthese factors lead to increased likelihood of soot generation. With the ignitionadvance angle increased, post-combustion cylinder temperature decreases rapidly,reduced oxide particles, ignition advanced, the mixture mixing time is shortened,locally concentrated area will be appeared in the cylinder, this will lead to increasedemissions of particulate matter too. Intake valve timing has greater impact on cylinderpeak pressure; different valve timing has a significant effect on the maximum cylindertemperature. Excessive cylinder residual gas makes combustion instability willultimately lead to increased emissions of particulate matter. Different valve overlapangle and different valve opening time can impact particle emissions; however, thereis an optimal value to from the lowest particulate matter emissions.