液滴高速撞击低温壁面的动态特性及破碎机理研究

为研究液滴撞击低温壁面的动态行为，运用高速阴影法对韦伯数（We）在533～1630之间的单液滴撞击常温壁面（22 ℃）与低温壁面（?30～?10 ℃）进行可视化试验。试验结果表明:液滴以一定速度撞击低温壁面时，会发生即时破碎和冠状破碎，二次液滴飞溅明显；但液滴以相同速度撞击常温壁面时，未出现液滴破碎现象。随着壁面温度的降低，液滴撞壁破碎所需韦伯数减小。在壁面温度为?30 ℃时，液滴撞击铝合金板的破碎临界韦伯数降低至480左右；当We < 480时，即使壁面温度低于?30 ℃，液滴也不会发生撞壁破碎。当液滴撞击常温壁面时，液滴快速铺展，并且韦伯数越大，液滴铺展和回缩的速度越大，液滴的铺展因子越大。该研究可为液滴撞击低温壁面撞壁模型的建立提供参考。

Experimental study on spreading and breaking mechanism of droplet impinging on low temperature wall at high speed

In order to study the dynamic behavior of a droplet impinging on a low-temperature wall, a visualization test was carried out on a single droplet impinging on the normal temperature （22 ℃） and low temperature wall （?30 – ?10 ℃） with the Weber number between 533 and 1630 by the high speed shadowing method. The experimental results show that prompt splash and corona splash occurs when the droplet impinges on the low temperature wall at the certain speed, and the splashing of secondary droplet is obvious. However, when the droplet impinges on the normal temperature wall at the same speed, there is no droplet breakage phenomenon. With the decrease of the wall temperature, the Weber number required for the droplets to smash into the wall decreases. When the wall temperature is ?30 ℃, the critical Weber number of the droplet crashing into the aluminum plate decreases to about 480. When We < 480, even if the wall temperature is lower than ?30 ℃, the droplets would not smash into the wall. When the droplet hits the normal temperature wall, the droplet spreads out rapidly, and the larger the Weber number is, the greater the spread and retraction speed of the droplet is, and the larger the spreading factor of the droplet is. This study provides a reference for the establishment of the impingement model of the droplet impinging on the low temperature wall surface.