Effects of tumble and swirl flows on turbulence scale near top dead centre in a four-valve spark ignition engine

Abstract

The in-cylinder flowfield and the turbulence scale at the ignition timing play an important role in enhancing the propagation speed of the initial flame and the engine combustion. The aim of this work is to investigate the effect of tumble and swirl flows on the turbulence scale near the top dead centre in a four-valve spark ignition (SI) engine by an experimental method. In this study, various flowfields such as tumble and swirl flows were generated by intake flow control valves. For investigation of the flowfields, the single-frame particle tracking velocimeter (PTV) and the twocolour particle image velocimeter (PIV) techniques were developed to clarify the in-cylinder flow pattern during the intake stroke and the turbulence intensity near the spark plug during the compression stroke respectively. In addition, the flame propagation was visualized by an ICCD camera, and its images were analysed to compare the flowfields. From these experimental results, the effects of tumble and swirl flows on the turbulence scale and the flame propagation speed were clarified.