Modelling of nucleation in Impulse atomized undercooled droplets

摘要

Numerous previous researchers have used nucleation models as part of their simulation of droplet solidification. None of these have verified the nucleation portion of these models with experimental results. In this work, a heterogeneous nucleation model based on the classical nucleation theory was coupled with a thermal model of a falling droplet through a stagnant gas. The pre-exponential factor, which is usually unknown, was determined to obtain an undercooling similar to experimental results for a 196 mu m droplet solidified in helium. A stochastic element was added by using a cumulative density probability function, leading to a range of possible nucleation undercoolings and nucleation points. The primary and eutectic undercoolings as well as the number of nucleation points were then compared with additional experimental results of Al-Cu alloy droplets. Good agreement was found between the calculated and the experimental undercoolings. Modeling results also suggest the presence of one nucleation point in the majority of cases and are in agreement with experimental observations. (C) 2017 Elsevier B.V. All rights reserved.