直喷式柴油机燃油撞壁特性及混合气形成研究

应用STAR-CD软件对燃油撞壁进行三维数值模拟,重点研究入射角度、环境压力和涡流比对撞壁特性和混合气形成的影响.结果表明,撞壁后燃油的二次雾化对燃油蒸发具有重要作用.随着壁面入射角度的增大,壁面油膜扩展面积增大,油膜从长叶形向扇形变化.随着环境压力的增高,燃油分布范围明显减小,但燃油堆积量和浓混合气的面积都会进一步减小,形成相对稀薄的混合气.涡流对燃油的影响主要发生在撞壁之后,随着涡流比的增大,形成大范围的稀混合气.涡流比过高,相邻油束的混合气将会发生干涉,造成燃烧质量下降.

Investigation on Characteristics of Fuel Impinging Wall and Mixture Forming in Diesel Engine

Fuel impinging on the wall was calculated by using STAR-CD with 3-D model. The emphases of investigation were the spray angle, environment pressure and swirl ratio affecting on the impinging and mixture forming. The results show that the secondary atomization after impinging is very important to the fuel evaporation. When spray angle increases, the area of film on the wall increases too. The shape changes from long-leaf form to sector. When environment pressure becomes higher, the distribution of fuel reduces obviously, and fuel deposit and rich mixture area decreases. Relative lean mixture is formed. The effect of swirl on the fuel happens after impinging wall. Along with swirl ratio increases, large-scale lean mixture formed, if swirl ratio is too higher, the mixture of adjoining sprays will be in collision with each other, which is disadvantageous for combustion.