Research on Stratified Mixture Lean Burn of Opposed-Piston Two-Stroke Gasoline Engine

For the characteristics of small bore and long stroke for opposed-piston two-stroke gasoline engine, an asymmetric spray mode on exhaust and intake side was proposed in this paper and the spray direction was optimized with CFD AVL-Fire software to form the homogenous mixture in full load. The effect of two-stage injection strategy with different injection timing and injection ratio on mixture stratification and lean burn organization were simulated based on optimized spray direction. The results show that the increase of injection angle in intake side can improve uniformity index of mixture and the increase of injection angle in exhaust side can reduce fuel evaporation. The second injection ratio affects stratified mixture distribution and the second injection timing affects stratified mixture uniformity. When the injection angle in intake side is 30° and the injection angle in exhaust side is 15°, first injection timing at 220℃ A and the second injection timing at 270℃ A with 20% total fuel quantity finally lead to ideal in-cylinder mixture stratified distribution. In part load, stratified mixture distribution can shorten 30% time of flame developing period and shorten 15% time of rapid burning period compared with homogeneous mixture.