空心锥形喷雾与横流掺混特性研究

Study on Characteristics of Mixing of Hollow-Cone Spray and Crossflow

关键词:  空心锥形喷雾  横流  液滴扩散  CVP结构

Key words:  Hollow-cone spray  Crossflow  Droplet dispersion  CVP

摘要:

在空心锥形喷雾与横向气流掺混过程中，大尺度对称旋涡对CVP(Counter-Rotating Vortex Pair)是影响液滴扩散的主要机制，为了研究CVP结构的演变特性，本文开展了空心锥形喷雾与横向气流掺混过程的实验研究，采用PIV可视化技术对不同喷雾状态与横流速度下掺混流场中液滴的扩散与分布特性进行了测量。结果表明:CVP的卷吸夹带作用使雾化液滴主要分布在掺混流场中上部；初始雾化液滴动量较大时，CVP结构尺寸与涡心强度越大，有利于液滴的扩散；横流速度提高时，CVP结构位置上移，尺寸减小，掺混效果变差。采用涡心强度、涡心距与涡心高度三个参数来描述CVP结构强度特征，基于实验测量结果给出了CVP结构上述特征参数的关联式。在横流速度、喷嘴压力和初始雾化粒径3个变量中，初始雾化粒径对CVP结构影响最大，而喷嘴压力和横流速度的影响较小。

Abstract:

The CVP(Counter-Rotating Vortex Pair) structure which is caused by the interaction between the hollow-cone spray and the crossflow exerts great influence on spray droplet dispersion. In order to study the characteristics of the CVP evolution， experimental investigations on the mixing flow field of the hollow-cone spray in a crossflow were conducted. The dispersion and distribution of spray droplets in the mixing flow field with different spray and crossflow conditions were measured by PIV system. The results show that the entrainment effect of the CVP contributes atomization droplets to distributing in the upper of the mixing field. The larger initial momentum of droplets， the larger the CVP structure size and the vortex intensity and it is beneficial to the dispersion of the droplets. When the crossflow velocity increases， the CVP moves up and the CVP structure size decreases， consequently the mixing effect becomes worse. The intensity characteristic of the CVP is described by three parameters: vortex core strength， vortex center distance and vortex core height， the correlations of the characteristic parameters of the CVP are given based on the experimental results. In the three variables of the crossflow velocity， atomization pressure and initial droplet diameter， the initial droplet diameter has greater influence on the CVP structure， while the atomization pressure and the crossflow velocity have less effect.