摘要
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.
A CFD software （AVL FIRE） was used to study the spray/wall impingement and the twophase flow in small diesel engines with three different bowl shapes. The influence of different bowl shape on droplet movement along the wall after impingement and droplet evaporation have been investigated, and the distributions of near-wall fuel concentration and velocity field are compared. The simulation resuits show that combustion chamber geometry has important effect on flow distribution, and different bowl shape influences significantly fuel concentration near the impinged location. At ψ℃A=380°, type B bowl has more serious fuel accumulation than type A and C bowls, and this is mainly due to different bowl inner wall curvatures. When piston moves to ψ℃A=390°, the impingement location moves to the squish gap, and the fuel entering into squish area is developing differently with different bowl shapes. The spray penetration front in type A and B bowls has slight rise over the piston, and it helps to avoid the impingement on cold wall, therefore reduce HC emissions. At ψ℃A=400°, the piston downward movement generates big differences on swirl flow for these three combustion chambers, which directly influences the distribution of fuel vapor in cylinder.
出处
《江苏大学学报（自然科学版）》
EI
CAS
北大核心
2006年第4期314-319,共6页
Journal of Jiangsu University：Natural Science Edition
基金
国家自然科学基金资助项目(50376003)
关键词
柴油机
燃烧室
喷雾碰壁
CFD软件
两相流
排放
数值模拟
diesel engine
combustion chamber
spray/wall impingement
CFD software
two-phase flow
emission
numerical simulation
