Effects of port shape on steady flow characteristics in an SI engine with semi-wedge combustion chamber (3) - Comparison of evaluation method and position -

This paper reports on the third study worldwide on the steady flow characteristics considering the port shape in an SI engine with a semi-wedge combustion chamber. The evaluation methods of the impulse swirl meter (ISM) and the particle image velocimetry (PIV) are compared. A straight port and a helical port were applied to the combustion chamber and the swirl was evaluated with ISM and PIV from 1.75B, (1.75 times the bore position apart from the bottom of head), to 6.00B positions. The comparison showed that the ISM evaluation was higher than the PIV, and the ISM evaluation decreases as the measuring position shifts downstream regardless of the shape of the port. The decrease in the helical port was larger than that of the straight one. PIV evaluation also slightly increases to 3.00B regardless of port shape, and then decreases. However, as the evaluation position shifts downstream, the ISM assessment is significantly reduced though the decrease in the PIV assessment is relatively small, thereby reducing the difference between the two assessments. The significant reduction in swirl according to the assessment location in the ISM method is due to the increase in wall friction and the overestimation due to the assumption of the ISM evaluation in the upstream being resolved downstream by the flow development. When considering the steady flow characteristics and the flow of the actual engine at the same time, the position of 5.00-6.00B is suitable for consistent evaluation.