液態油品撞擊高溫表面之高速影像分析研究

High Speed Photographic Analysis and Studies for the Liquid Oil Impacting on a High Temperature Surface

何德川(Te-Chuan Ho)

指導教授 ： 張育斌 ； 周煥銘

崑山科技大學/工程學院/機械工程研究所/碩士(2006年)

https://doi.org/10.6828/KSU.2006.00042

摘要

本研究採用實驗方式探討液態油品撞擊高溫表面的問題，藉由高速攝影所擷取的瞬間影像來了解液滴撞擊之運動行為，以助液滴撞擊過程的動力特性研究。實驗對象為潤滑油、燃料、純水等三種不同特性之工作流體(六種油品)，實驗過程的控制參數為液滴性質、表面溫度。
本研究先建立液滴撞擊之先前評估設備，經由改變液滴撞擊高溫表面之溫度與不同油品之黏度等參數，特別著重於動態尺度變化與撞擊後液滴變化型態之分析研究。實驗結果顯示：一、表面溫度在室溫下之情況，液滴撞擊後會產生擴散、回縮、震盪與穩定等純機械撞擊的效應。二、表面溫度在該液滴之沸點（含）以下的情況，液滴撞擊後會產生擴散、回縮、向上拉升、整體震盪或沸騰等機械撞擊效應與溫度效應。三、表面溫度在明顯高於該液滴之沸點的情況，由於溫度越高表面張力越小，以致高溫作用使壓差大於表面張力，因此，液滴撞擊後會產生擴散、沸騰、飛濺、瞬間炸開、噴射成數以萬計的微小液滴與彈跳等機械撞擊效應與高溫效應。四、黏度與表面張力越大，則擴散到最大直徑之值就越小，表面張力越大，回縮至最小直徑之值也越小。五、表面溫度越高，炸開之小液滴之直徑就越小；直徑越大其所需之加熱能量越大，因此彈跳週期就越長。當表面溫度增加，其彈跳高度越高，彈跳週期就越長。六、在相同溫度而不同油品黏度的情況，黏度越低擴散至最大直徑越大，而且回縮至最小直徑也越小，黏度差異越大，擴散至最大直徑或回縮至最小直徑之差異性也越大。以回縮趨勢而言，黏度低的比黏度高的回縮趨勢明顯。然而相同油品黏度在不同溫度下的直徑變化，則以溫度較高者變化較大。

關鍵字

黏度 ； 高速攝影 ； 高溫表面 ； 液滴 ； 撞擊

並列摘要

The phenomena of the liquid oil droplet impacting on a high temperature surface were studied experimentally in this paper. By using the high-speed camera with the photoflood system, the kinematic modes and the dynamic properties of the above impacting process can be investigated in detail. Moreover, six kinds of fluids (such as oils, fuels and the pure water) were selected as the testing materials in this study. The major parameters were the droplet properties and the surface temperature.
First of all, the previous testers were established to appraise the effects of the surface temperatures and the oil viscosities on the impacting process. Secondly, the dynamic variations for the micro size of the liquid droplet during the impacting process were especially analyzed systematical. Finally, the experimental results of this paper can be concluded as followings: (1) the variations of the impacting process under the average room temperature can be classified into four states: spreading, recoiling, oscillating and steady states. They showed the pure mechanical impacting effects. (2) the variations of the impacting process for the surface temperature which was smaller than the boiling point of the fluid can be classified as: spreading, recoiling, draging up, oscillating or boiling states. The above results were influenced by both of the mechanical impacting and the heating effects. (3) the variations of the impacting process for the surface temperature exceeded the boiling point of the fluid can be classified as: spreading, boiling, spattering, flashy explosion, spraying droplets and spring. The mechanical impacting and the high temperature effects both caused the above results. Moreover, the above results can be reasonally explained by that the surface tension was smaller than the pressure difference under the high temperature. (4) the maximum diameter of the droplet decreased with increasing the viscosity and the surface tension. Moreover, the minimum diameter also decreased with increasing the surface tension. (5) the diameter of the spraying droplet decreased with increasing the surface temperature. Moreover, the spring period increased with increasing the diameter of the spraying droplet or the surface temperature. (6) the maximum diameter of the droplet increased and the minimum diameter decreased with decreasing the viscosity of the fluids. The trend of recoiling was significantly for the low viscosity. However, the variations of the droplet diameter were severe for the high temperature cases.

並列關鍵字

high temperature surface ； impact ； high speed photography ； viscosity ； droplet

參考文獻

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