Effect of intake port bend angle on flow field inside the cylinder of a DI diesel engine

This paper presents the computational fluid dynamics (CFD) modeling to study the effect of intake port bend angle on the flow field inside the cylinder of a direct injection (DI) diesel engine under motoring conditions. The flow characteristics of the engine are investigated under transient conditions. A single cylinder DI diesel engine with two direct intake ports whose outlet is tangential to the wall of the cylinder and two exhaust ports has been taken up for the study. Effect of intake port bend angle (200, 300, and 400) on the flow field inside the cylinder has been investigated at an engine speed of 1000 rpm. The pre-processor GAMBIT is used for model preparation and commercial computational fluid dynamics code STAR-CD has been used for solution of governing equations and post processing the results. CFD results during both intake and compression strokes have been compared with experimental results of Payri et-al [7, 8]. The predicted swirl ratio, radial velocity and turbulent intensity variations at different crank angles and at different locations are discussed. Distribution of velocity and turbulence intensity inside the cylinder is also discussed. It is observed that the intake ports with 20 degrees bend angle produce maximum swirl and also results in a slight decrease in volumetric efficiency compared to intake ports with 30 degrees and 40 degrees bend angles and there is no appreciable variation in turbulent intensity. Hence, for the better performance of a DI diesel engine, it is concluded that the intake ports with 20 degrees bend angle is most appropriate and CFD is an effective design tool to develop more efficient DI diesel engines.