Steady Flow Bench(l)에서 CI 엔진의 유동 특성 - SI Port와의 비교

In this study, the steady flow characteristics of 27 port opening cases in CI engines were evaluated and compared with existing SI results to determine the macroscopic characteristics and differences between two engines. For this purpose, the swirl ratios were evaluated from 1.75 B to 6.00 B, using an impulse swirl meter and a particle image veiocimetry. Then, die average of these values was calculated for each port and evaluation method so that changes in value can be analyzed, depending on the measurement location. Through this approach, the following results were obtained. Overall, the flow characteristics of the CI indicated less changes and remained consistent than SI, regardless of measurement location and method. Opening both ports simultaneously is very simitar to the case of opening the tangential port. In the ISM evaluation, swirl decreased toward the downstream for both CI and SI, and the decrease was greatest in the case of the opened helical port. In the PIV evaluation, the swir! of the CI decreased as it went downstream, but SI exhibited different characteristics, depending on the shape of the combustion chamber. Additionally, in the PIV evaluation, if the axial velocity is assumed to be proportional to the planar velocity, swirl was at its highest. In the CI, die value was closest to the ISM evaluation, whereas, in SI, it varied, depending on the shape of the combustion chamber and the port. When the PIV evaluation was at its highest in CI, TVO closely matched ISM, starting at 3.00 B, FVO was always lower than ISM and BVO matched well with ISM across the entire plane. Lastly, in the case of a pent roof combustion chamber in SI, the relative swirl ratio increased significantly as it went downstream. However, when a semi-wedge combustion chamber was adopted, the change in relative swirl ratio according to the measurement position was like that of CI.