Effects Of MMT On The Characteristics Of PM Emissions From Gasoline Engines

With the booming development of the automobile industry in our country and the increasing of the vehicle ownership, it has brought great convenience to people's life, but has caused the urban atmospheric environment and air quality severe damage. Recently, with the deterioration of air quality, the particulate emissions from the vehicle become the focus of research. Improving the quality of the fuel can reduce vehicle emissions, which is an effective way to control particulate emissions and to improve air quality. The fuel additive has been used to ameliorate fuel specification. MMT is a kind of efficient and unleaded gasoline additive.But there is a dispute when using MMT. At present, most of the study of MMT focuses on the road experiment and the congestion of three way catalytic converter, but the research on the effect of MMT on vehicle particulate concentration emissions and the particle size distribution in different types of gasoline engines has not been reported.In view of this, the research on the effect of MMT on vehicle particle emissions has important implications.In this paper,the research is mainly based on two types of gasoline engines, including one PFI gasoline engine and one GDI engine, for the characteristics of particulate emissions with MMT using the DMS500 fast particulate spectrometer manufactured by Cambustion.The paper has analyzed the effect of MMT on the engine particle emissions, so as to provide theoretical foundation and scientific basis for adopting effective measures to control it.The specific research results are as follows:When burning gasoline fuels with different content of MMT, the exhaust particulates from PFI engine and GDI engine consist of two kinds of particulate,including nucleation mode and accumulation mode.The particulate emissions are of a triple peak distribution consisting of ultrafine particle, fine particle and large particle.When burning gasoline fuels containing MMT, the total number and mass concentration of particulate from PFI engine and GDI engine increase significantly. The addition of MMT has improved the proportion of the number concentration in ultrafine mode.In PFI mode, when burning gasoline fuel without MMT, particulate number concentration generally remains in the low level. When the content of MMT was fixed, the increase of engine load resulted a decrease in number concentration at part load. But there was a sharp increase in particle number concentration at full load. The relationship between particle number concentration and load is weakened as the increase of MMT concentration in gasoline.MMT has almost no effect on the engine output torque and the fuel consumption, and with the increase of MMT, the engine's exhaust temperature decrease slightly.After TWC, at different loads, while burning different kinds of gasoline fuels, there is a large decrease for the number concentration of fine particle and large particle and ultrafine particle number concentration declines less.The proportion of ultrafine particle increases after TWC. Particle mass concentration decreases an average by an order of magnitude. When the content of MMT was fixed, with the increase of the engine load, the catalytic efficiency of TWC on particulate number concentration firstly increases and then decreases, however, the catalytic efficiency of TWC on particulate mass concentration first decreases and then increases. At the same load, with the increase of MMT, the catalytic efficiency of TWC on particulate number concentration decreases and then the catalytic efficiency on mass concentration increases gradually.In GDI mode, the addition of MMT makes GDI engine particulate emissions significantly increase. At the light load and medium load, with the increase of MMT, number concentration of particulate increases.At high load, the particle number concentration is the lowest when burning gasoline fuel without MMT.Then with the increase of MMT, the particulate number concentration decreases gradually. At the light engine load, GDI engine particle mass concentration increase significantly with the increase of MMT, but at the medium load and the high load, the growth is not obvious.