臺灣大學: 化學工程學研究所呂理平鄭楷?Cheng, Kai-LiKai-LiCheng2013-03-272018-06-282013-03-272018-06-282010http://ntur.lib.ntu.edu.tw//handle/246246/252278氣液二相流噴嘴被大量使用於現代光電產業之霧化、塗料與清洗程序中。其中霧化噴嘴之清洗效能對於液晶螢幕顯示器 (Thin Film Transistor-Liquid Crystal Display, TFT-LCD) 之製程良率有顯著之影響。在TFT-LCD之清洗程序中，欲提升霧化噴嘴之效能，必須先了解氣液二相流在噴嘴中之流態，故本研究以一維穩態氣液二相流模型計算流體於噴嘴中之流態以模擬霧化噴嘴清洗器，並探討進口參數之操作範圍與最適化操作條件。 吾人由氣體動力學中一維穩態氣體流態模型為基礎，藉由拖曳力模型描述液珠在氣體載體中之行為，推導噴嘴之一維穩態氣液二相流模型，並在已知進口條件下以四階Runge-Kutta法計算二相流於漸縮-漸擴噴嘴 (拉瓦爾噴嘴)中之流態。吾人以氣液二相流模型計算稀相水氣混合物於拉瓦爾噴嘴之流態結果顯示，在亞聲速操作下，流體之流速於噴嘴喉部達到最大值，並隨流域截面積擴大而減小，與文獻之結果吻合。由於本研究著重於噴嘴之臨界操作，故吾人以上述流體模型探討二相流於漸縮噴嘴之流態，並改變操作參數以比較計算之結果。根據結果顯示，以進口壓力做為操作變因，在臨界流操作下，液體之出口速度達最大值，其最大動量在清洗程序中可達到物理衝擊之效應。而根據吾人計算之噴嘴流經銳孔中之能量變化趨勢，氣體之能量在出口處達最大值，其能量轉換亦可增進清洗效能。 吾人以流體之束縮截面定義清洗器出口處與清洗物之距離。由於束縮截面之計算牽涉二維動量方程式。故吾人利用相同條件，以FLUENT軟體計算流體於一般工業用規格銳孔流量計之束縮截面位置，並與實驗結果相比較。依結果所示，氣體於小型銳孔之束縮截面與文獻結果較吻合，故吾人以上述方式計算1”、1/2”與1/4” Sch 40管之銳孔束縮截面位置，並決定清洗器與清洗物表面之距離。The gas-liquid droplet two-phase fluid flowing through a de Laval nozzle (converging-diverging nozzle) is essential to spray forming, coating technology, and cleansing process of modern electro-optical industry. In TFT LCD''s (thin film transistor liquid crystal display) industry, a damage-free and easily-assembled cleansing device with high cleansing effectiveness is needed. This study focused on the flow condition in a spray type cleanser and the optimization of cleansing effectiveness. The flow problem in the nozzle can be treated in a quasi-one-dimensional manner to simulate the entire converging-diverging nozzle flow field of gas entrained with dilute liquid droplets. Given the input condition of gas and liquid droplets, the simulation was started by using the gas-liquid two phase flow model. The governing equations were derived from a generalized one-dimensional gas flow model in a variable area duct, where the behavior of liquid droplets entrained in the gas flow was described by the drag law. The equations were solved by fourth-order Runge-Kutta method. According to the results, the maximum flow speed occurs near the throat of the nozzle under subsonic operation. Since the optimization of a spray type cleanser depends on the exit flow speed in the literature, a spray jet utilizing converging nozzle operating at choking condition was proposed by numerical calculation in this study. The maximum total energy in the nozzle and the orifice was proposed as another factor of optimization of cleansing effectiveness, and the results showed that the maximum total energy occurs at the same location with the maximum flow speed. The stand-off distance between the nozzle exit and target surface was determined by the position of minimum flow area where the flow speed reaches minimum. The minimum flow area of orifice flow is defined as vena contracta, which is at the downstream of the exit plane. The exact position of vena contracta was determined by CFD software FLUENT, and the results were in good agreement with experimental data in the literature.2421639 bytesapplication/pdfen-US氣液二相流拉瓦爾噴嘴束縮截面工業清洗Gas-liquid two phase flowDe Laval nozzlevena contractaindustrial cleansingthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/252278/1/ntu-99-R97524048-1.pdf