IN-CYLINDER FLOW CORRELATIONS BETWEEN STEADY FLOW BENCH AND MOTORED ENGINE USING COMPUTATIONAL FLUID DYNAMICS

摘要

Intake port flow performance plays a substantial role in determining the volumetric efficiency and in-cylinder charge motion of a spark-ignited engine. Steady-state flow bench and motored engine flow CFD simulations were carried out to bridge these two approaches for the evaluation of port flow and charge motion (such as discharge coefficient, swirl/tumble ratios). A one dimensional block analytical model was used to mimic the downstream honeycomb in a flow bench experiment, which forced the flow motion in one direction. The intake port polar velocity profile and polar physical clearance profile were generated to evaluate the port performance based on local flow velocity and physical clearance in the valve-seat region. The measured data were taken from standard steady-state flow bench tests of an intake port. When using an appropriate mesh resolution near the walls, the steady-state flow bench simulation predicted that discharge coefficient and swirl/tumble index are in agreement with the measured data. It was reconfirmed that the predicted discharge coefficients and swirl/tumble index of steady flow bench simulations have a good correlation with those of motored engine flow simulations. The polar velocity inhomogeneity factor correlates well with the port discharge coefficient, swirl/tumble index. A port performance evaluation guideline was generated by taking advantage of steady flow bench and motored engine flow simulations and port polar velocity inhomogeneity factor.