横流中空心锥形喷雾的扩散特性与影响因素

Droplet dispersion of hollow cone spray in gaseous crossflow:Characteristics and influencing factors

为了更好地理解和认识空心锥形喷雾射流与横向气流的掺混过程,基于可视化实验测量,针对空心锥形喷雾的初始雾化状态、喷射角度和雾化锥角以及横流速度等因素对空心锥形喷雾射流在横流中的扩散特性进行了系统分析。研究结果表明,随着横流速度的提高,流场中对称反旋涡对(CVP)结构变小,但其稳定性及产生的卷吸气流则是先增强而后减小;提高喷雾初始液滴的动量和数流率,均可以增大射流剪切层的贯穿深度和射流尾迹的伸展高度,同时使流场中CVP的涡量强度增大。基于实验测量结果,建立了空心锥形喷雾垂直入射横流条件下掺混流场液滴群CVP结构特征尺寸和剪切层轨迹的预测关联式。另外针对喷嘴雾化锥角和喷射角度的分析表明,当喷雾初始雾化状态相近时,随着雾化锥角的减小,流场中CVP的水平尺度减小但竖直方向尺度增大且结构更为稳定,同时喷雾液滴的贯穿深度增大;相比喷雾垂直于横流入射,当喷嘴以一定角度逆向横流入射时,CVP结构稳定性减弱,流场剪切层涡结构变大且剪切层区域液滴富集现象减弱,射流尾迹紊乱程度增加,反之,则流场剪切层涡拟序结构变小,射流尾迹现象减弱,CVP结构变小。

The influences of different factors on droplet dispersion of the hollow cone spray transversely injected into the crossflow are systematically investigated based on the experimental measurements.The research findings show that as the crossflow velocity increases,the Counter-rotating Vortex Pair(CVP)decreases in size with its stability first increasing and then decreasing.With the increase of Reynolds number and number flow rate of the spray droplets,the depth of the shear layer and the length of the spray wake structures as well as the droplet CVP vorticity increase.The quantitative correlations between the feature sizes of the droplet CVP and the trajectory of the droplet shear layer structure are developed based on the experimental data in terms of the relevant parameters.Furthermore,it is found that as the spray angle decreases,the CVP decreases in width,increases in height,and becomes more stable,and the depth of the spray penetration increases.Compared with the case of vertical injection of the spray,when the spray is injected obliquely against the crossflow,the shear layer vortex becomes larger and the spray wake structures more irregular;the stability of the CVP induced and droplet preferential accumulation on the shear layer are weakened;otherwise,the CVP and the shear layer vortices as well as the wake structures will become smaller.