汽膜对熔滴水力学碎化影响的数值模拟

在熔融物与冷却剂相互作用(FCI)过程中,熔滴的水力学碎化对于后续是否产生蒸汽爆炸以及爆炸的强弱程度有着重要影响。传统的熔滴水力学碎化数值研究通常只考虑液液直接接触的两相系统;而堆芯熔化后,熔融物温度在2 500K以上,熔融物周围会迅速产生汽膜,导致熔滴和冷却剂之间的传热和阻力特性发生改变。本文基于PLIC-VOF(piecewise linear interface construction-volume of fluid)界面跟踪方法对有汽膜存在的三相系统中的熔滴水力学碎化过程进行了数值研究,通过分析熔滴在有无汽膜和不同边界速度触发情况下碎化过程中的界面特性,发现熔滴碎化程度随Weber数的增加而加剧,汽膜对熔滴的水力学碎化存在一定的抑制作用。

Numerical Simulation on Effect of Vapor Film on Molten Droplet Hydrodynamic Fragmentation

In the process of the interaction between the melt and the coolant (FCI),the hydrodynamic fragmentation of the molten droplet has an important influence on whether the steam explosion will happen or not and how intense it will be thereafter.The traditional numerical study of molten droplet hydrodynamic fragmentation usually only considers the direct contact of the melt with the coolant,which is a two-phase system,without considering the existence of vapor film.However,the core melting temperature is above 2 500 K and vapor film can be rapidly generated around the melt,thus,the characteristics of heat transfer and flow resistance will be changed.In this paper,the numerical study was carried out on the molten droplet hydrodynamic fragmentation process with the presence of a vapor film using a three-phase system based on the PLIC-VOF (piecewise linear interface construction-volume of fluid) interface tracking method.Through analyzing the interfacial properties of the molten droplet in the process of fragmentation,it is found that the molten droplet fragmentations are more severe with the increase of Weber number and the vapor film has a negative effect on the hydrodynamic fragmentation.