粗糙度對生質柴油撞擊熱表面之油滴影響研究

Effects of Roughness on the Droplet Behaviors of Biodiesel Impinging the Hot Surface

熊本源(Ben-Yuan Shiung)

指導教授 ： 吳澤松

崑山科技大學/工程學院/機械工程研究所/碩士(2012年)

摘要

本研究探討油滴撞擊熱板表面之動態行為，實驗在固定油滴高度下改變參數有兩個溫度、六個不同粗糙表面、四種油進而觀察油滴撞擊於不同粗糙表面參數下將會發生之動態情形，並以高速攝影機擷取油滴撞擊熱板影像實驗之數據，將與油滴撞擊進行實驗結果比對。由實驗結果顯示，油滴撞擊在沸點溫度以下，油滴動態過程為擴散、回縮、分裂、震盪、沸騰、穩定等現象；當油滴撞擊在沸點溫度以上，此時油滴動態較劇烈，則會產生擴散、沸騰、汽化、飛濺、彈跳直到離開表面等現象。而研究中，撞擊動量、熱板溫度、液滴性質皆有密切的關係，而液滴撞擊的動量包含液滴密度、表面張力、直徑大小及撞擊速度等相關因子。在比較不同粗糙表面時，油滴撞擊於高溫平滑表面熱板之動態較易分裂彈跳；反之，撞擊於高溫鐵砂表面之動態較易劇烈沸騰。
同時油品在高溫時會因黏度與表面張力下降，而使得油滴之擴散直徑增加。比較生質柴油在不同粗糙度表面情況，於光滑熱板表面上熱傳遞效率較快且摩擦力也小，使油滴在回縮現象也較為迅速且明顯；於粗糙熱板表面上，因表面粗糙關係，使油附著在熱板上而形成分裂現象。

關鍵字

粗糙度 ； 油滴撞擊熱板 ； 高速攝影 ； 生質柴油

並列摘要

ABSTRACT
This research discusses the dynamic condition when the oil drop impact to the heat plate. It includes several variable parameters like 2 temperatures, six different rough surfaces and 4 kinds of oils to observe the change of dynamic condition when the oil drop hit different rough surfaces. At the same time, it takes the data from the experiment with high speed camera which will be contrast with the experiment results. The experiment results show that when the oil drop hitting under the boiling point, the dynamic processes have phenomenon like expansion, shrink, split up, vibration, boiling and stabilization. When the oil drop hitting over the boiling point, the dynamic processes are more severe and include phenomenon like expansion, boiling, vaporization, splash, bouncing and leaving the surface.
In this research, the impact momentum, the temperature of heating plate, and the drop quality have close relationship. The momentum of drop impact include several related factors like drop density, surface extension, diameter and impact speed. In the comparison of different rough surfaces, when the oil drop in the high temps and smooth surface heating plate, the dynamic condition shows that the oil drop is easily to split up and bouncing. On the contrary, when the oil drop in high temps pellet surface, the dynamic condition shows that the oil drop is easily to severe boiling.
Simultaneously, the viscosity and surface extension of oil will decrease under the high temperature, this will increase the extension diameter of oil drop. In the comparison of the condition that the bio-diesel on the different rough surface, the heat transfer efficiency in the smooth is faster and less friction. It also make the oil drop have rapid and obviously phenomenon as shrink. On the rough heating plate, the oil drop will form the phenomenon as split up cause the rough surface.

並列關鍵字

rough level ； oil drop hitting plate ； high speed photography ； bio-diesel

參考文獻

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