링간 틈새체적에서의 가스유동이 UHC배출물에 미치는 영향

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 and numerically investigated. The ultimate goal of this study was to reduce the level of UHC emission by minimizing the blow-up of the unburned gases trapped in 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 the expansion stroke and the early period of the exhaust stroke though the engraved grooves on the lower part of the cylinder wall. The extraction of the mixture form the inter-ring crevice resulted in significant reductions of UHC emission over a range of speeds and loads, without any losses of efficiency and power. A physical model for predicting the gas flow into and from the inter-ring crevice was also adopted to simulate the effect of the grooves on the lower part of cylinder wall. The calculated results agreed well with the measurements and could explain the mechanism of UHC emission reduction achieved with the grooved cylinder liners. This consistency has confirmed the importance of the inter-ring crevice on UHC emission in an SI engine.