【摘要】 用数值分析方法研究柴油机伞帘喷雾燃烧系统中的空气运动规律,探讨了缸内流场的演变过程、涡流与挤流的相互作用和燃烧室结构的影响,并比较了该燃烧系统与原机燃烧系统中的流场.计算基于任意拉格朗日-欧拉法,采用k-ε湍流模型.计算结果表明,在上止点前较大的曲轴转角范围内,纵剖面流场结构相似.无涡流时接近上止点的缸内纵剖面流场受挤流控制.挤流促进燃烧室中心线附近的空气运动;逆挤流主要发生在燃烧室边缘;涡流使流场复杂化,随着涡流强弱不同,缸内形成不同的流动图案;折转壁面间的过渡情况影响气流贴合壁面情况;伞帘喷雾燃烧系统的挤气面积远大于原机,因此前者的空气运动明显强于后者,较强逆挤流维持的时间长于后者.更多还原

【Abstract】 The air motion in umbrella-curtain spray (UCS) combustion system for diesel engine was studied using numerical analysis with the emphasis on the evolution of in-cylinder flow field, the interactions between swirl and squish and the effects of combustion chamber configuration. The flow field of UCS combustion system was compared with that of base combustion system. The computations are based on the Arbitrary Lagrangian-Eulerian (ALE) method and the k-ε turbulence model is employed. The results show that the flow field structures on longitudinal section are similar in a certain crank angle range before TDC. The in-cylinder flow field on longitudinal section near TDC is governed by squish in the absence of swirl and squish promotes the air motion in the vicinity of combustion chamber axis. The reversed squish is mainly concentrated at the edge of the combustion chamber. The swirl complicates the flow field. Different flow patterns in the chamber will be produced depending on the swirl intensity. The transitional condition between two turning walls influences the wall-fitness of air flow. The air motion in UCS combustion system is much stronger than that in base combustion system and the strong reversed squish lasts longer in the former than in the latter because the former has a far larger squish area than the latter.更多还原