The effect of intake valve angle on in-cylinder flow during intake and compression process

Valve angle defined as the angle between a valve axis and a cylinder axis is one of the most important design factors that may have an influence on valve train design, cylinder head size, in-cylinder flow, etc. In particular, since valve angle cannot be altered during the development process once basic engine specification is determined at the initial concept design stage, the decision of a valve angle is an important process and the determined valve angle imposes restriction on the potential of the gasoline engine performance. In this study the effect of the valve angle on in-cylinder flows has been experimentally investigated using a PIV (Particle Image Velocimetry) technique. In-cylinder flows of two test engines that have different valve angles have been measured at four different horizontal and three different vertical planes during intake and compression processes. During the intake process, the result shows that the intake flow of the conventional engine in horizontal plane is more complicated than that of narrow angle engine and the flow in vertical plane is rapidly decayed at the end stage of intake process. The flow pattern of the narrow angle engine is well arranged in horizontal plane and the vertical component of the flow remains so high that forms large scale strong tumble flow. During the compression process, the flow pattern is well arranged compared with intake flows and basic tumble flow structures are maintained until the end of the compression stage regardless of the valve angle.