Effects Of Injection Strategy And Fuel Property On Combustion And Particle Emission Characteristics Of Gasoline Direct Injection Engine

Particulate matter emissions from ground transportation is one of the main sources of atmospheric particulate matter pollution.Gasoline direct injection engines can improve fuel economy and power performance,but at the same time emits high particle emission.The study of control parameters and fuel properties effects in the particulate emissions of gasoline direct injection engine has become one important content in the research field of the engine.In this paper,a gasoline direct injection engine is tested with DMS500 fast particle analyzer to study the particle size distribution,quantity,oxidization and particle phase polycyclic aromatic hydrocarbons(PAHs)emissions and other characteristics.The different injection parameters have been examined to evaluate the effects on engine combustion and particulate emission characteristics.The fuel injection strategy is optimized to reduce particulate matter emission,and gasoline with different aromatics content is tested.Compared with different fuel injection parameters,such as the injection timing,injection pressure,the two-stage injection,the research results show that there exists an optimal condition for particle emission points,which is different from best engine combustion point.With increase of injection pressure,particle number decreases.The split injection increases the particulate emissions compared to the single injection,and with the increase of the split injection,the number of particles increased,the nucleation mode transfer to the accumulation mode.As the split injection duration extends,the number of particles increases.Particle optimization based on the model can reduce particulate emissions effectively.The number of particulate matter in engine start-up process is very high,and the number of particles at cold start is higher than that of warm-up engine,and the proportion of nucleation mode particles in the starting phase is higher than that in accumulation mode particles.The number of particulate matters increases with the increased the fuel-to-air equivalence ratio,and increases with the delay of the first stage injection timing,and then increases with the delay of the second injection end time.The exhaust gas temperature decreases with the delay of the first injection timing and the delay of the second injection end time.Low coolant temperature at low load deteriorate the engine combustion process.With the increased coolant temperature,the number of engine exhaust particulate decreases.By adjusting the injection timing at low cooling water temperature conditions,the particulate matter emission can be partially optimized and the particulate emissions of the vehicle can be further reduced.The number of particulate matter increases with increase of aromatic content,and the influence of aromatics on PM emissions is obvious at high water temperature conditions.Reducing low-carbon number in aromatic hydrocarbons is effective in particulate matter emission reduction.With the increase of load and the decrease of coolant temperature,the maximum mass loss rate temperature of particles increased and the oxidation activity of particles decreased.The activation energy of soot produced by high aromatics gasoline is higher than that low aromatics gasoline,and the oxidation activity is low.The gasoline particle PAHs are mainly distributed in the four-ring,and low-aromatic gasoline can reduce the toxicity of PAHs in the particulate matter.