Deposition characteristics of free-falling water droplet on a substrate at a low temperature

It is known that icing on the blade in jet engine causes serious accidents in operation of airplane. Thus, anti-icing technology has been developed extensively. It is necessary to clarify the icing process and its deposition mechanism as providing the basic knowledge to develop the advanced technology. This study focuses on the deposition process of a single water droplet and the adhesion strength on aluminum alloy (A2017) substrate at low temperatures (-20°C and - 10°C). In addition, influences of surface roughness and thermal conductivity of substrate on the deposition process are investigated. As a result, it was shown that the deposit area and shape of the frozen droplet is strongly affected by impact energy. The deposit area of the frozen droplet was, moreover, decreased with increasing the surface roughness and thermal conductivity. Observation of the deposition process by a high-speed camera revealed that the shape of the frozen droplet depends on wave motion which is generated on a surface of the deposited water droplet. The deposition and frozen process of a water droplet was also discussed based on these results and a simple theoretical model. All the results indicated that the deposition and frozen process are significantly affected by heat conduction between a water droplet and a substrate. From the results of an adhesion strength test, the adhesion strength of the frozen droplet was estimated to be approximately 0.1 MPa regardless of substrate temperature. © 2020 2019 The Society of Materials Science, Japan