横向热气流中单液滴剪切破碎特性研究

Experimental Investigations of Breakup Characteristic

关键词:  液滴破碎  雾化  热气流  喷雾  高速摄像机

Key words:  Droplet breakup  Atomization  Heated air flow  Sprays  High-speed cameras

摘要:

为了获得热气流中单液滴剪切破碎特性，采用高速摄像机对液滴变形、破碎过程进行了捕获。结果表明:液滴初始直径减小、气流温度增加，降低了液滴发生剪切破碎所需最小气动力；液滴破碎特征时间，随气动力增加呈线性递减变化趋势，且其值与变化梯度都随液滴初始直径增加而增大；液滴破碎区域面积、子液滴质量百分数随气动力增加呈先增加后减小的变化趋势，液滴初始直径增加，液滴破碎区域面积随之增加，而子液滴质量百分数则随之减小；剪切破碎锥角，随气动力增加呈线性减小的变化趋势；液滴破碎程度随液滴初始直径增加有明显改善； 标准离差率数学模型可以用于子液滴群空间分布均匀性方面的研究。

Abstract:

In order to obtain characteristics of single droplet deformation and breakage in a continuous and uniform heating air flow，the high-speed cameras was applied to measure single droplet deformation and breakage. Experimental results show that the reduction on original diameters of droplet and the increase on airflow temperature both could decrease the minimum requirements of aerodynamic force on the sheet-thinning breakup. The character time of droplet breakup has a negative relationship with the aerodynamics，while its value and change gradient are both positively associated with the original droplet diameter. The area of droplet breakup and the percentage of sub-droplet quality increase firstly but then change to decrease with the increase of aerodynamics. The area of droplet breakup increases as the increase of original diameters，but at the same time the percentage of sub-droplet quality decreases. The broken cone angle of sheet-thinning has a negative linear relationship with the aerodynamics. The level of droplet breakup is significantly improved as the increase of droplet original diameter. The standard deviation rate model can be applied on the study of the uniformity of sub-droplets space distribution.