Effect of an inter-ring crevice on unburned hydrocarbon emissions in a spark-ignition engine

Abstract

The effect of the inter-ring crevice, the volume between the top and the second piston rings, on unburned hydrocarbon (UHC) emission was experimentally investigated. The ultimate goal of this study was to reduce the level of UHC emission by minimizing the effect of the inter-ring crevice. For this purpose, the unburned mixture trapped in the inter-ring crevice was extracted to the crankcase during the late period of expansion and the early period of the exhaust stroke through the engraved grooves on the lower part of the cylinder wall. The extraction of the mixture resulted in significant reductions in UHC emission by 23 per cent at maximum over a range of speeds (1250-3500 r/min) and loads (185-556 kPa, b.m.e.p.), without any losses of efficiency and power. This experimental study has confirmed the importance of the inter-ring crevice on UHC emission in a spark-ignition (SI) engine.