Experimental study on the secondary droplet formation mechanism when droplet impacting on superheated surface

When a droplet impacts a superheated surface, due to the different effects between wall superheat and the initial Weber number of the droplet, secondary droplets will be generated by different mechanisms due to the coupling effect of kinetics and temperatures, such as fracture, spray, atomization, and breakup. In this paper, a visual experimental study is conducted based on the effects when droplets impacting on the superheated wall. The wall temperature ranges from room temperature to 650 degrees C, and the droplet Weber number ranges from about 10 to 500. Based on the sequence images of droplets taken by a highspeed camera, three of four secondary droplet mechanisms (excluding fracture droplets) are presented and discussed in detail. Furthermore, the size and velocity distribution of the secondary droplets under different mechanisms are quantitatively analyzed through image processing. Finally, an edge-breaking model of the droplet with a high-temperature wall is proposed considering the evaporative momentum force near the triple-phase contact line, and it is in good agreement with the experimental results. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

In this paper, a visual experimental study is conducted to investigate the effects of droplets impacting on a superheated wall. The mechanisms of secondary droplet generation are discussed based on sequence images and the size and velocity distribution of the secondary droplets are analyzed through image processing. Furthermore, an edge-breaking model is proposed and validated with experimental results.