Investigation into hydrocarbon emissions from crevice and oil film during cold start and idling periods in a spark ignition engine

Abstract

In order to understand better the process of hydrocarbon formation and the effect of the top-land crevice and the oil layer of the cylinder liner on unburned hydrocarbons during cold start and idling periods, the temperature of the piston top-land and liner was measured. Based on the measured results, the amount of unburned hydrocarbons from the crevice and liner has been predicted. It was found that the temperature of the piston top-land and cylinder liner took about 150-200 s to reach its equilibrium state as the engine started up. The concentration of hydrocarbons from the top-land crevice and from the oil layer will be reduced to 40 and 75 per cent of its initial value respectively. It is considered that a reduction in piston thermal capacity can reduce the total unburned hydrocarbons during this transient period owing to quick minimization of the top-land crevice volume and rapid increase in mixture temperature in the crevice region.