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Title: | 低動力微細氣泡裝置研發之研究 Research and Development of Low-Power Microbubble Generator |
Authors: | Kai-Chieh Lin 林楷傑 |
Advisor: | 侯文祥(Wen-Shang Hou) |
Keyword: | 微細氣泡,文氏管,泡沫浮除,影像處理法,粒度分佈, microbubble,venturi tube,flotation,image processing method,size distribution, |
Publication Year : | 2018 |
Degree: | 碩士 |
Abstract: | 微細氣泡具有良好的氣體溶解率與固體吸附率,目前水族缸市售沉水馬達大多附加氣泡管,使其在製造水流時提供增氧功能。本研究以低成本3D列印技術,自行設計適用於水族缸之文氏管型微細氣泡管,並與市售沉水馬達搭配之氣泡管比較。根據白努利定律(Bernoulli's Law),利用管路截面積差使液體流速增加,使外界氣體自動地被吸入管中,達到氣液混合目的。
本研究設定一微細氣泡管原型,並依據其加速區、束縮區、喉區、擴散區與擴散角度五個部位,更改管徑變化設計出共11組對照組,繪製草圖後以3D列印機製作成品。動力方面,挑選市售不同廠牌、流量一大一小之沉水馬達共2台,置於水缸內表底水層共2種水深,搭接自製氣泡管進行氣泡粒徑觀察及定量實驗。氣泡粒徑之定量使用影像處理法,將相機先以靜置法拍攝影像,再以軟體ImageJ將影像進行灰階化與二值化,計算在不同粒徑大小間之氣泡個數與粒度分佈,依據其結果選出有助於氣泡生成之幾何變化,組合出最佳之管徑配比後,再與市售沉水馬達搭配之氣泡管做比較。流體模擬則以軟體FLUENT進行模擬,分析原型管、最佳配比管與市售管在兩種水深共5種模組,探討不同幾何設計對管內流場的影響,將實驗與模擬結果相互對照。 依實驗結果,自製文氏管型微細氣泡管確實能增加微細氣泡生成之效果,本研究之自製最佳配比管幾何設計為:加速區長5mm、束縮區長10mm、喉區長7.5 mm、擴散區長15mm、擴散角度13度與束縮比值1/4。除了使用800L/H沉水馬達,放置水下5cm處,生成微細氣泡效果較差之外,自製最佳配比管均優於市售管,且隨著放置水深愈深效果愈明顯。使用1500L/H沉水馬達,放置水下15cm處時效果最好,在100~150μm數量差異最多,最佳配比管生成微細氣泡個數約為市售微細氣泡管之2.7倍,最佳配比管生成微細氣泡總個數約為市售微細氣泡管之2.5倍。幾何形狀影響粒度之差異性不大,除了最佳配比管於水下15cm處與市售管於水下12cm處之情況外,所有自製氣泡管與市售管之粒度分佈趨勢相似,且放置深度愈深,差異性愈小。而模擬結果可大致的呈現出與實驗相符之氣泡生成情形,但關於相似幾何設計之內流場探討,仍有許多模式與參數設定上之修正空間。 Microbubbles have effective dissolution rate of gas and adsorption rate of solid. Most of the commercially available submersible motors using in aquarium are provided with bubble tubes, in order to increase dissolved oxygen while bringing the water flow. This study designs a venturi type microbubble tube for aquarium with the 3D printer which cost lower, and make a comparison with the bubble tubes matched with the commercially available submersible motors. According to Bernoulli's Law, the liquid velocity is increased because of the difference in section area of the pipeline, it makes the air automatically inhaled into the tube to achieve the mixing purpose. In this study, setting up a prototype of the microbbuble tube which has 11 control groups by changing diameter of tubes, including acceleration portion, constriction portion, throat portion, divergence portion and the divergence angle. After sketching, products will be produced by 3D printer. For doing the experiment of observing and measuring bubble size, two sets of submersible motors are selected with different brands and flow rates, and placed them in two different water depths, and then installed the self-made bubble tube on the motor. Image processing method are used for quantification of bubble size. The images are captured with camera by static method, and they are grayscaled and binarized with software ImageJ to calculate the number and the size distribution of bubbles among different size. Selecting some geometric changes which helps bubble formed and make the best diameter ratio combination. Then, comparing the best-proportioning tube with bubble tubes matched with the commercially available submersible motors. The fluid simulation is simulated with software FLUENT. Analyzing the prototype tube, the best-proportioning tube and the commercially available tube in two water depths, a total count of 5 cases. Discussing the effects of different geometric designs on the flow field inside the tubes. Finally, the experiment and simulation results are compared with each other. According to the experimental results, the self-made venturi type microbubble tube can increase the number of microbubble. The best geometric design of the bubble tube in this study is: acceleration portion 5mm, constriction portion 10mm, throat portion 7.5mm, divergence portion 15mm, divergence angle 13 degrees, and ratio of constriction 1/4. The result of the bubble generation using the best-proportioning tube is better than commercially available tube, and the difference is lager as the depth of the water goes deeper, except for using 800L/H submersible motor and placing at 5cm underwater. The best result is obtained when using 1500L/H submersible motor and placing underwater at 15 cm. There is considerable difference in the range of 100 to 150μm, which the number of microbubbles generated by the best-proportioning tube is about 2.7 times the number generated by the commercially available tube. The total the number of microbubbles generated by the best-proportioning tube is about 2.5 times the number generated by the commercially available tube. Geometric designs hardly affect the size distribution. Except for the best-proportioning tube at 15cm underwater and the commercially available tube at 12cm underwater, all the self-made and commercially available tubes have similar tendency of size distribution, furthermore, the difference between two of them goes not obvious as water depth goes deeper. The results of simulation roughly showed the situation of the bubble generation, which is consistent with the experiment. However, there are still room for improvement about settings of model and parameter. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/72288 |
DOI: | 10.6342/NTU201803769 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 生物環境系統工程學系 |
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File | Size | Format | |
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ntu-107-1.pdf Restricted Access | 6.35 MB | Adobe PDF |
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