基于 EGR 分层的直喷汽油机进气道结构优化研究

摘要

In order to realize the EGR stratification of air‐fuel mixture surrounded by the exhaust gas and thick exhaust area distributed at the bottom of combustion chamber ,the flow field of tangential port and combined port by tangential port and hel‐ical port were simulated with the CFD FIRE software to research the potential of EGR stratification and the mechanism of EGR stratification was analyzed from the view of in‐cylinder gas flow based on a gasoline direct injection engine .The results indicate that the tangential port cannot realize the anticipated EGR stratification because the tumble flow weakens during the compres‐sion stroke .On the contrary ,the combined port has better stability and can realize about 10% gradient of EGR stratification by combining the adjustment of EGR phase .Accordingly ,the developed EGR stratification realizes the anticipated effect .%为了实现废气围绕在可燃混合气周围，并且废气较浓区域集中于燃烧室底部的 EGR分层形式，基于1台缸内直喷汽油机，利用CFD仿真软件Fire针对原机切向气道结构以及切向气道与螺旋气道相结合的气道形式进行了仿真，探究其实现预期EGR分层的潜力，并从缸内进气流场角度分析EGR分层机理。结果表明：原机切向气道由于滚流在压缩冲程中被大幅削弱，不能形成研究预期的EGR分层形式；采用切向气道与螺旋气道相结合的进气道结构形式可以使滚流在压缩冲程中具有较好的保持性，并结合EGR相位调整，实现了约10％的EGR分层梯度，EGR分层形式符合研究预期。