液滴撞击高温壁面的运动特性

Dynamics of Droplet Impacting onto Heated Surface

利用相界面追踪复合Level Set-VOF方法,综合考虑液滴蒸发传热及接触热阻作用,对单液滴撞击高温壁面运动及影响因素进行了研究.研究表明,由于液滴蒸发传热作用,液滴撞击高温壁面会发生Leidenfrost现象;撞击速度较小时,液滴撞壁后发生铺展反弹,随着撞击速度的增大,液滴撞壁后会发生破碎现象;壁面温度的升高利于液滴破碎发生;液滴初始直径的减小有利于液滴撞壁后的反弹,而液滴直径的增大有利于液滴撞壁后破碎.通过数值模拟,给出了一定条件下柴油液滴撞击高温壁面反弹及破碎的临界条件.

In this paper,in order to explore the dynamics of droplet and the influence factors when it impacts onto heated surface above the Leidenfrost temperature,a numerical model was developed using the coupled Level SetVOF method including evaporation heat transfer and contact resistance.The results show that Leidenfrost effect will occur when the droplet impacts on the heated surface because of its evaporation.The droplet with low velocity will levitate and bounce after impacting onto the heated surface,while the droplet with high velocity will breakup after impacting onto the heated surface.The high temperature of wall exerts a great influence on the breakup.The decrease of initial droplet diameter easily leads to the rebound phenomenon. While the increase of initial droplet diameter is likely to cause the spreading-breakup phenomenon.Finally,the critical conditions of rebound and breakup are summarized,respectively,by numerical simulation.