Study of the Cycle-to-Cycle Variation of In-Cylinder Flow in a Motor Engine.

Abstract

An experimental study investigating cyclic variation of the internal air motion was made in a motor engine having a cup-in-piston combustion chamber. The engine used for this study had a transparent quartz liner and a transparent acryl piston. The continuous wave beam of a 4 watt argon ion laser was formed into a thin light sheet to define the measurement plane. The scattered light from the particles which were supplied to the intake air stream, were recorded by a NAC E-10 high-speed camera and the bulk flow fields inside the combustion chamber were measured at both planes parallel and vertical to the piston crown by means of an image processing technique. This study reveals for the first time the continuous cycle-resolved two-dimensional bulk flow fields inside the combustion chamber around the compression TDC. Also, comparison between cycle-resolved and ensemble-averaged flow patterns showed that ensemble-averaged flow patterns may become artificial ones if there exists a large effect of the cyclic variation. Moreover, by examining the rms of the cyclic variation component and the ratios of the rms to ensemble-averaged velocity with/without swirl conditions, it was found that the ratios of the rms to ensemble-averaged velocity can be used for evaluating the effect of the cyclic variation on the flow fields.