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运用CFD软件对小缸径柴油机三种燃烧室进行了两相喷雾碰壁过程的数值模拟,考察了不同燃烧室形状对碰壁后燃油沿壁面运动、蒸发过程的影响,并比较了近壁面区域燃油浓度和缸内速度场的分布情况.结果表明,燃烧室的几何尺寸对缸内流场有着重要影响,不同的燃烧室对碰壁处燃油堆积程度明显不同,φ℃A=380°时,B型燃烧室燃油堆积情况较A型与C型严重,这主要受凹坑内壁面不同曲率的影响.当活塞运行到φ℃A=390,°碰壁点移动到挤流唇时,进入挤流区的燃油受缸内逆挤流的影响,其发展形态存在很大差异,A型与B型燃烧室油束前锋略微翘起,将有助于避免与缸壁发生“淬冷”,降低未燃HC的排放.在φ℃A=400°时,活塞下行使三种燃烧室后期的流场涡团各异,并直接影响燃油蒸气的分布.
The CFD software was used to simulate the two-phase spray process of three small combustion chambers. The effects of different combustion chamber shapes on the movement and evaporation of the post-collision fuel along the wall were investigated. The results show that the geometry of the combustion chamber has an important influence on the flow field in the cylinder, and the accumulation of fuel in the collision wall is obviously different for different combustion chambers. When φ ° C A = 380 °, the combustion chamber of type B The fuel accumulation is more severe than Type A and C, which is mainly affected by the different curvatures of the inner walls of the pits. When the piston reaches φ ° C A = 390 °, and the wall of the collision point moves to the squeeze lip, the fuel entering the squeeze area is affected by the cylinder The influence of internal reverse squish flow is quite different. The forward and backward tilting of A and B combustors will help to avoid “quenching” with cylinder wall and reduce the emission of unburned HC. At φ ° C A = 400 °, the piston travels downstream in the three combustion chambers with different turbulence and directly affects the distribution of fuel vapor.