The normal incident impact phenomena and solidification of a liquid metal droplet onto a rigid substrate.

摘要

The normal incident impact and solidification phenomena of a liquid metal droplet onto a rigid substrate is investigated. A general fluid flow solver, which can model free surface flows and account for surface tension, is modified to incorporate a thermal energy equation to account for thermal effects including solidification.; Simulations are run that alter only one parameter at a time to determine the relative influence of that one parameter. The parameters investigated are divided into two categories: the process control cases {dollar}(vsb{lcub}o,{rcub}{dollar}T{dollar}sb{lcub}s,{rcub}dsb 0){dollar} and the material property cases {dollar}(Csb{lcub}p,{rcub}k,Delta H).{dollar} The process control variables have the most substantial effect on the spread factor. The importance of this observation is that the spread factor is more dependent on the values of the process control variables than the material chosen for the droplet.; A correlation between a new non-dimensional number, Holt number {dollar}Ho={lcub}rm Re{rcub} We Pesp2{lcub}(Tsb0-Tsb{lcub}mp{rcub})over(Tsb{lcub}mp{rcub}-Tsb{lcub}s{rcub}){rcub}{lcub}Delta Hover (Tsb{lcub}mp{rcub}-Tsb{lcub}s{rcub}) Csb{lcub}p{rcub}{rcub},{dollar} and the spread factor is developed, resulting in a correlation factor, R, of 0.98.; The numerical model correlates very well with the experimental data. The spread factor appears to follow a {dollar}ln(xsp{lcub}1/8{rcub}){dollar} law. Due to the limiting assumptions, the numerical model underestimates the spread factor. The overall absolute error ranges from 35% to 45% for the Ho numbers investigated.; Proposed enhancements are: allow the substrate to thermally interact with the droplet, incorporate thermal contact resistance, use variable thermal conductivity, and allow heat to be connected away from the droplet during the impact process.; A few of these enhancements are tested to verify their validity. The error is raised from 39% to 26% when using the thermal conductivity of the liquid. This shows the importance of variable thermal conductivity. Next, the error is further reduced to 12% and 4.3%, when thermal contact resistance is added to the code.; The experimental endeavors are documented. Three head prototypes: the thumper, the vertically actuated pumper, and the horizontally actuated pumper were made. The two main issues that prevented the perfection of the apparatus are the clogging of the head and the varying droplet size.