- 學位論文
應用壓力螢光感測塗料技術於90度微彎管內流場量測與分析
The Study of 90 Degree Elbow Microchannel Flow Using Pressure-Sensitive Paint
摘要
本研究主要為應用螢光壓力量測技術於各式微彎管流場，量測其二維壓力分佈並進行流場分析，了解流道不同幾何參數對於90度微彎管流場的影響。所量測的微彎管流場包括四組不同流道深度及寬度的銳角90度微彎管、兩次45度微彎管以及圓弧微彎管，而量測的雷諾數範圍介於88至442之間。在銳角90度彎管的實驗中，實驗所使用4X顯微物鏡可量測流道內全域壓力分佈(空間解析度達3.7 μm/pixel)、10X顯微物鏡則可量測局部彎管處詳細的壓力分佈(空間解析度達1.5 μm/pixel)。 對於不同流道寬度的銳角90度彎管，在相似雷諾數下，由全域的壓力量測結果可發現流道寬度400 μm的流道(400w100d)其彎管前上游端與彎管後下游處之直管壓力趨勢變化之間有明顯的壓力差，流道寬度200 μm的流道(200w100d)中則沒有，而此壓力差將隨著雷諾數降低而減小。在局部彎管處壓力分佈則發現在彎管處外壁有明顯的高壓區，低壓區則位於出彎處之內壁。對於不同流道深度的銳角90度彎管，由於量測的雷諾數較低，彎管處壓力變化較不清楚，但仍可由無因次化之壓力分佈途中觀察到流道100 μm(400w100d)以及200 μm(400w200d)的全域壓力分佈與400w100d的流道所觀測到的趨勢相似，流道深度60 μm(400w60d)的全域壓力分佈則與200w100d相似。 對於不同彎管方式的討論則藉由局部彎管處壓力分佈中發現兩次45度角彎管在兩個轉彎的地方皆有高壓區域出現，但其範圍皆小於相似雷諾數於銳角彎管的範圍。圓弧彎管則於流道彎管處外壁發現沿著外壁分布的高壓區。比較三種轉彎方式之無因次化壓力分佈則發現銳角及兩次45度角彎管之高壓區皆會隨著雷諾數降低而減少，圓弧彎管則不變。 本研究同時利用等效直管長度計算公式比較90度微彎管流道之次要損失。對於銳角90度彎管，雷諾數越大則次要損失亦隨之增加，且較寬的流道其次要損失上升的斜率亦較大，400 μm寬的流道其次要損失將於雷諾數大於200時超過200 μm寬的流道之次要損失，而流道深度越深其次要損失亦越強。兩次45度彎管之次要損失亦會隨著雷諾數增加而變高，但變化幅度小於銳角90度彎管。圓弧彎管之次要損失則不隨著雷諾數改變。
並列摘要
This study aims to apply Pressure-Sensitive Paint technique to various 90 degree elbow microchannels in order to measure two dimensional pressure distributions and perform analysis in Reynolds number range from 88 to 442. Different designs of 90 degree elbow microchannels are investigated in this study including sharp turn 90 degree microchannels with different channel widths and depths, a double turn elbow microchannel and a round turn microchannel. A 4X and a 10X objective lenses are used to capture the luminescent signals inside the microchannels, and these lenses can deliver magnification of images of 3.7 μm and 1.5 μm per pixel spatial resolution. During the investigation of sharp turn microchannel, two microchannels with different widths are studied. From the global pressure distributions acquired from microchannel inlet to exit, significant pressure differences are observed at the locations between before the turn and after the turn in the microchannel with 400 μm width, which cannot be identified in the microchannel with 200 μm width. In local pressure measurement around the corner, threre is a high pressure zone near the outside wall of corner and also a low pressure region at the inner wall downstream after the corner. As for study with different depths of microchannels, the sharp microchannels with 200 μm depth and 100 μm depth have the same trend which are like the results acquired in the microchannel with 400 μm width,. For different elbow designs of double turn and round turn, there are two high pressure zones obersved in double turn microchannel near each 45 degree turn. There is a high pressure region continuously developing around the outside wall of round turn microchannel at different Reynolds conditions. In order to compare the pressure loss in different cases which is considered as minor loss of energy, the equation calculating equivilent length for the 90 degree turns in the microchannel flow is used. For the microchannel flow with 90 degree sharp turn, the minor loss increases as the Renolds number comes larger. If the Reynolds number is greater then 200, the minor loss estimated in the microchannel with 400 μm width becomes larger than the one with 200 μm width, and the minor loss is always greater if the depth of microchannel is bigger. From the experimental results acqruied in this study with different designs of 90 degree elbow microchannel flows, the physical phenomena of flow patterns in such devices become clearer.