气口布置对进气涡流及扫气品质的影响

Effects of porting arrangements on intake swirl and scavenging performance

采用数值方法研究了气口布置对进气涡流及换气品质的影响,建立了缸内过程的三维瞬态数值模型,通过改变气口平射角引入进气涡流,根据归一化缸内二氧化碳质量分数评价扫气品质,对比了不同气口布置角度下的涡流比及扫气品质.结果表明:①改变气口平射角能够产生包括涡流在内的旋转流动,涡流持续到上止点附近,并近似为刚体涡;②进气涡流造成扫气过程中期短路损失,并使CO2聚集于旋转区域中心;③扫气口仰角变大或排气口沿旋转流动方向远离扫气口,能够抑制短路;扫气口平射角减小时,上止点附近的涡流比降低,短路损失增大.

Effects of porting arrangements on intake swirl and scavenging performance were investigated numerically.A three-dimensional transient numerical model was established for the in-cylinder processes.Intake swirl was introduced by changing port tangential inclinations and scavenging performance was evaluated by normalized carbon dioxide mass fraction.The intake swirl intensity and scavenging performance with different porting arrangements were compared.The results show：（1） Rotation flow including swirl can be generated by port tangential inclination arrangements,and the swirl approximates to solid-body swirl approaching the top dead center.（2） Intake swirl results in short-circuiting during the scavenge processes and a concentrated carbon dioxide central core.（3） The short-circuiting can be reduced by increasing the axial inclination of inlet ports or extending the distance between inlet and exhaust ports in the flow direction.Swirl intensity can be decreased by reducing scavenge port tangential inclinations,leading to increase of short-circuiting.