Study of Morphology and Secondary Droplet Behaviors during Droplets Impacting on Static Hot Film

冷液滴/热液膜碰撞形态及二次液滴特性研究

School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an 710072, China

Received: 18 September 2019

Abstract

The phenomenon of droplet impacting on hot film exists widely in nature and engineering applications. Considering limitations in current researches, an experimental setup to record the process of droplets impacting on hot film was built in this paper. Lots of experiments have been done and then the transitional threshold was established to determine impingement outcomes. The number of secondary droplets and the temperature of the secondary droplet are investigated based on the experimental results. The results show that impingement outcomes can be determined by the splashing parameter provided in this paper. The number of secondary droplets increases with the splash parameter, the probability distribution function of secondary droplet diameters follows the Weibull distribution. The temperature of secondary droplets is close to the hot film and almost all secondary droplets' temperature is above 90% of the hot film.

摘要

冷液滴/热液膜碰撞现象广泛存在于工业应用中，而液滴与液膜间温度差异会影响到液滴/液膜碰撞形态及其二次液滴的特性。针对先前研究的不足，设计制造了冷液滴/热液膜碰撞试验装置并开展了大量冷液滴/热液膜碰撞试验，基于此获得了冷液滴与热液膜碰撞判断准则，建立了二次液数量、尺寸分布和温度与碰撞参数之间的无量纲关系。结果表明，冷液滴/热液膜碰撞后有碰并、冠状液膜成形及溅射3种形态，且3种形态可通过文中提出的判断准则辨识；二次液滴数量随着飞溅参数的增加而增加，二次液滴的无量纲直径分布在0~0.3的范围内且二次液滴尺寸概率密度分布为威布尔分布，二次液滴温度与液膜温度较为接近，二次液滴的温度均在液膜温度的90%以上，同时二次液滴的温度随着二次液滴无量纲直径的增加略有减小的趋势。