噴孔流道曲率變化與表面親疏水性對噴射液滴行為影響之研究

Abstract

本文中我們透過數值模擬來探討一噴孔片透過壓電材料的形變振動，將液體噴射而出的模型，所使用的計算軟體為商業化計算流體力學軟體CFD-ACE+。我們透過給予不同液固接觸角的邊界條件來模擬液固界面的不同親疏水性，再利用流體體積-片段線性界面重建法來作液氣界面的時變追蹤，分析不同噴孔渠道曲率在不同邊界條件的情形下，對液滴噴射行為、衛星液滴個數與殘液的影響。 研究結果顯示流道曲率會影響液滴的飛行速度、斷裂時間、主液滴體積、衛星液滴與黏滯區域等。噴孔孔徑變大會降低液滴飛行速度，增加液滴的體積。提高噴孔片振幅或是提高振動頻率代表輸入能量增加，因此液滴飛行速度提高，減少主液滴的體積，降低斷裂時間，但是會帶有較多細碎的衛星液滴。接觸角方面，接觸角上升表示固液界面的作用力下降，因此阻力下降使得飛行速度上升，斷裂時間由親水表面略為上升，至疏水表面下降許多，主液滴體積則會下降。

A model which is a droplet on the nuzzle plate liked to a nozzle plate injects due to the vibration had been simulated. By different curvature of the flow channel, giving different amplitude, contact angle, and frequency of the nozzle plate we can observe the behavior of the droplet injection in the simulation. In this simulation, we use time-dependent VOF method to track the interface between gas and liquid and re-build the interface to observe the injection behavior of the droplet graphically. The simulation code we use in this article is the commercial CFD software CFD-ACE+. The results show that curvature of the flow channel will affect the velocity, breakup time, volume of the droplet, and numbers of satellite drop. Increasing the diameter of the orifice will increase the volume and reduce the velocity of the droplet. The adjustment of increasing amplitude or frequency of the nozzle plate raise the input energy, so it will increase the velocity, reduce the volume, and shorten the breakup time of the droplet. But increasing the amplitude or the frequency causes more satellite drops. On the hydrophobic boundary, the velocity will increase, the volume will decrease, and the breakup time will shorten.