Dynamics Of Droplets Evaporation And Atomization In Solution Precursor Plasma Spray

Solution Precursor Plasma Spray(SPPS)is a promising technique to produce nanostructure coatings with high quality.In the present study,we study the flow field of plasma spray by nu-merical simulation.The multiphase flow is simulated by the CAB(Cascade Atomization and Drop Breakup)model and KH-RT(Kelvin-Helmholtz/Rayleigh-Taylor)model,respectively.We analyze the special flow region and complex evaporation and atomization performance of droplets.Also,parametric study is conducted with respect to coating quality.The main contents can be concluded as follows:(I)Comparing CAB and KH-RT model,we conclude that both models are commonly used in the prediction of atomization process.Then by using the two atomization models separately,we present the predicting results of atomization of a single water or ethanol droplet in the flow field of plasma spray.(II)We simulate both the axially spraying and radial spraying flow fields,and identify the existence of the hot region and the secondary breakup region.Besides,we discuss the variation in the position of the above two regions and the thermal behavior of droplets as well as the droplets SMD(Sauter mean diameter).(III)From the spatial distribution of axial velocity and temperature,we analyzed the pre-cursor droplets' behavior of evaporation and atomization,using water or ethanol as solvent,respec-tively.Meanwhile,we investigate how the hot region and the secondary breakup region influence the precursor droplets' size and distribution in the flow field of plasma gas.(IV)We analyze the key parameters to the coating quality,including solvent properties,the composition of plasma gas and the position of substrate.Basic principle of choosing and matching SPPS operating parameters and conditions are offered in this study.In the current work,we focus on the characteristics of droplets evaporation and atomization in SPPS by numerical simulation.Three aspects are covered:first,analyzing the momentum and heat distributions in the flow field of plasma gas;second,identifying the hot region and the secondary breakup region;at last,discussing how these two factors influence the droplets behavior of evaporation and atomization.Meanwhile,we demonstrate the key parameters influencing the coating quality,and give out helpful suggestions on how to match operating conditions of SPPS.