压力式螺旋型喷嘴二次雾化特性的试验研究

Experimental study on secondary atomization characteristics of pressure-type spiral nozzies

空气与液滴之间良好的接触是增湿室增湿换热的关键技术,因此有必要对喷嘴进行雾化特性试验研究。该研究选用工程上常用的压力式螺旋型喷嘴TF6进行雾化特性试验,TF6喷嘴雾化特性的研究包括喷嘴背压对雾化液滴尺寸的影响,分析距离TF6喷嘴下方不同位置各种液滴直径、比表面积、分布跨度值的变化。研究发现,雾化液滴的直径随喷雾压力的增大而减小,但喷雾压力有其临界范围。通过对距离喷嘴下方不同位置雾化特性的分析得到二次雾化的发生位置,该位置更有利于空气与液滴的热质交换。在二次雾化区内,利用最小二乘法拟合出喷嘴雾化液滴的经验关联式,整理成韦伯数和雷诺数的函数关系,可用来预测喷嘴出口粒子的直径。

The contact between air and droplets is key point to the heat exchange process in the humidification chamber. Therefore, it is necessary to study the atomization characteristics of nozzles. The present study investigates the atomization characteristics of the TF6 nozzle, which is a pressure-type spiral nozzle commonly used in engineering applications by experiments. The experimental study on the atomization characteristics of the TF6 nozzle includes an investigation on the effect of the nozzle backpressure on the dimensions of the atomized droplets and an analysis of the changes in the various types of diameters, specific surface areas and spans of the droplets at different locations below the TF6 nozzle. The results show that the diameters of the atomized droplets decrease with the increase of the spray pressure which has a critical range. The location of the secondary atomization is determined based on the analysis of the atomization characteristics at different locations below the nozzle. This location is more favorable for heat and mass exchange between the air and droplets. The least square method is used to fit the empirical correlation for the droplets atomized by the nozzle in the secondary atomization area. The empirical correlation is then converted to a functional relation of the Weber number and Reynolds number, which can be used to predict the particle diameters from the exit of the nozzle.