An Experimental Study on the Influences of the Width of Top Land Crevice and Operating Parameters o nExhaust Hydrocarbon Emissions in a Spark Ignition Engine

摘要

In this paper, the formation mechanisms of unburned hydrocarbons of a spark ignition engine, the thermodynamic parameters of the unburned mixture and the flame propagation behavior in top land crevice are investigated, the effects of the crevice widths, engine speeds, air-fuel ratios, and spark advance angles on engine exhaust hydrocarbons are studied, The effects of engine top land crevice width on power output and fuel economy are also analyzed. It is shown that the optimum engine top land crevice width is 0.32 mm(1.3 times the two wall quenching distance(, thus the flame can get into the bottomof the crvice and burns out lal of the accumulated hydrocarbons in it, consequently the engine exhaust hydrocarbons can be greatly recued by 35-50 cent with less penalty on engine power output and fuel economy(0.5approx1.5 per cent loss in power output and 1approx3 per cent increase in fuel consumption).