Study on uniflow scavenging system parameters of opposed-piston two-stroke gasoline engine

The scavenging process of the uniflow scavenging system of an opposed-piston two-stroke (OP2S) gasoline engine was analyzed to obtain a wide range of structure and operating parameters that influence scavenging process, including intake port radial angle, intake and exhaust port heights, circular utilization and operating speed. A 1-D (one-dimensional) simulation model was built based on the GT-Power to study the influence of the intake and exhaust port heights and circular utilization on the scavenging process, and three-level orthogonal simulations were made to optimize the flow areas of the intake and exhaust ports. At the same time, a 3-D (three-dimensional) CFD (computational fluid dynamics) model was built based on the AVL-FIRE, and the intake port radial angle was investigated and optimized. The influence of the intake and exhaust port heights and circular utilization on scavenging efficiency, delivery ratio and correlation coefficient were obtained from the orthogonal experimental analysis. On one hand a suitable intake port radial angle can promote stratified distribution of exhaust gas and fresh charge in the scavenging process; on the other hand too big an intake port radial angle can also increase the flow resistance, resulting in lower scavenging efficiency. The intake port radial angle of 15 degrees leads to the maximum scavenging and trapping efficiencies.