Computation and Validation of In-Cylinder Flow Field, Swirl and Flow Coefficients for a Naturally Aspirated Single Cylinder Diesel Engine 2016-28-0018

The present work is concerned with the computation of in-cylinder flow field of a naturally aspirated single cylinder diesel engine using 3D CFD methods. Flow in the intake port and across the valve and subsequent in-cylinder flow is simulated for different valve lift conditions. The in-cylinder flow field is thoroughly analyzed for the flow asymmetry, number of vortices and swirling motion. Predicted velocity field at 20 mm and 92 mm sections from the cylinder head is compared with those obtained from the experiments. Doppler global velocimetry has been used to measure the velocity vectors at the two earlier identified sections for vale lifts of 2, 4, 6, 8 and 9 mm. The development of flow in the longitudinal and transverse directions is studied from the measured velocity vectors. The evolution of the global in-cylinder flow structure with respect to the lift is presented. The flow structure and their development at different lift conditions in-turn determines the actual swirling motion at the end of suction stroke. Further to the above analysis, flow and swirl coefficients are calculated from the computed flow field solutions using Bernoulli’s equation. Flow and swirl coefficients for the cylinder head have also been measured at steady state test bench. It is observed that the predicted flow coefficients are with in the 5% variation of the measured values. However the deviation between the predictions and measurements for the swirl coefficients is about 5 to 25%. The reasons for higher deviation of the swirl coefficient are discussed.