影响直喷式柴油机挤流特征的几个因素

Some Factors Affecting Characteristics of Squish Flow in a D.I. Diesel Engine

对 3种不同结构燃烧室所对应的缸内流场进行了模拟研究 ,系统地分析了挤流的演变过程和柴油机转速、燃烧室结构、进气涡流对其特征的影响。在上止点前或后较大的曲轴转角范围内流场相似 ,逆挤流叠加于由气体惯性作用保持的环涡之上并集中于燃烧室边缘 ,燃烧室内速度和湍流度随柴油机转速和燃烧室缩口度同向变化。进气涡流是湍流生成的主要因素并使流场复杂化 ,随涡流和挤流相对强弱的变化 ,燃烧室内形成的环涡的个数。

The flow fields in three cylinders with different configurations of combustion chambers were numerically simulated. The evolution process of a squish flow, as well as the effects of diesel engine speed, configuration of combustion chamber, and the intake swirl on this process were analyzed. The flow field structure is similar in a certain range of crank angles before or after TDC. Reversed squish overlaps a vertical vortex retained by inertial force acting on it and mainly concentrates at the edge of the combustion chamber. Velocity and turbulence intensity in combustion chamber increase with engine speed and its throat narrowing ratio. Swirl plays an important role in generating turbulence and makes the flow field complicated. The number, revolution direction and intensity of vertical vortices in combustion chamber will be different depending on the relative intensities of the swirl and squish.