分层充气天然气发动机混合气形成的数值解析

Numerical analysis of the mixture formation in stratified charged natural gas engine

解析了渐缩形纵向直进气道发动机的进气过程 ,与实验结果对比验证了计算方法的可行性 .对渐缩形直进气道屋脊形燃烧室多点电喷天然气发动机混合气形成过程进行了解析 ,得到天然气 空气混合气在气缸内的速度场、空燃比分布等 ,探明了缸内纵向滚流的存在 .表明在纵向进气滚流作用下 ,压缩接近终了时 ,缸内混合气呈明显分层构造 ,在火花塞附近聚集较浓的可燃混合气 ,实现部分负荷工况下的稀薄燃烧 .

The intake process of a gradually contracting longitudinal straight inlet port engine was analyzed, the feasibility of this numerical calculation method was verified by comparison with the experimental results. The process of mixture formation was analyzed for a Multi-Point Injection (MPI) natural gas engine which has a gradually contracting straight inlet port and a pent-roof combustion chamber, the velocity field and the distribution of air/fuel ratios of natural gas-air mixture in cylinder were obtained, the existence of in-cylinder longitudinal vortex was proved up. It indicated that, at the end of compress stroke, the mixture in cylinder was stratified and the denser ignitable mixture was concentrated around the spark plug under the action of the longitudinal intake vortex, thus lean burning at part load could be realized.