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研究生:李岳松
研究生(外文):Yueh-sung Li
論文名稱:雙吸入後傾式離心風機性能之數值模擬分析
論文名稱(外文):Numerical Analysis of The Performance of Double-Suction Backward-Curved Centrifugal Fan
指導教授:黃仁智黃仁智引用關係
指導教授(外文):Jen-Jyh Hwang
學位類別:碩士
校院名稱:國立中山大學
系所名稱:機械與機電工程學系研究所
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2007
畢業學年度:95
語文別:中文
論文頁數:116
中文關鍵詞:舌部入口錐入口間隙渦殼離心風機
外文關鍵詞:CutoffInlet ConeInlet ClearanceCentrifugal FanVolute
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風機內部的流場分析在過去被認為是工程上最困難的問題之ㄧ,在計算流體力學(CFD)發展之後,許多風機流場相關的問題現在都能夠得到很好的解答。
本文以數值方法模擬入口錐對渦殼舌部離心風機之性能影響,主要目的是要藉由流場可視化模擬,觀測流經風機內部流場分佈特性,探討不同入口錐造型、入口間隙大小、入口錐位置與渦殼舌部半徑、舌部角度對離心風機性能曲線的影響。文中以Reynolds-Averaged Navier-Stokes equations 結合Standard κ-ε turbulence model來模擬雙吸人後傾式離心風機內部三維穩定不可壓縮性紊流流場,並以有限體積法解之。此外並以實驗來驗證數值模式的準確性。經由研究結果顯示(i)入口錐可讓空氣平滑進入內部,減少空氣在葉輪葉片的流動分離,但空氣流經入口錐所造成之摩擦損失,亦會降低風機之性能;(ii)入口間隙的存在會使空氣在渦殼內部產生循環流,導致部分空氣由葉輪的出口經入口間隙在回流至葉輪的入口,造成風機性能降低,此項氣流回流之洩露量,會隨著入口間隙的增加而增加,並受入口錐外型影響;(iii)入口錐深入葉輪的長度,會影響並干擾葉輪上各葉片入口氣流流場分布的均勻性。深入長度越長,兩葉片間之流場空間會被較大的渦流區佔有,因而降低風機的性能;(iv)改變渦殼舌部之半徑與角度對風機性能提升幫助不大。
在離心風機性能改善方面,當間隙由11mm縮小至5mm,出口平均全壓增加約3.26%;將入口錐往葉輪內部擺放20mm,出口平均全壓減少6.32%;修改入口錐外型,出口平均全壓大幅提升約5.4%;將舌尖半徑由25mm減少至15mm,會使出口全壓增加約1%。
The interior flowfield analysis of fan has been considered to be one of the most difficult problems in the past. With the advent of computational fluid dynamics (CFD) methods, many flow problems inside the fan can now be solved with a good degree of accuracy.
  A numerical study of the influence of inlet cone and volute cutoff on a centrifugal fan performance is presented in this work. Using the flow-visualization simulating analysis of the flow-flied characteristic of air across the inner of centrifugal fan, the performance curve with different inlet cone shape, inlet clearance gap, cone position, extending angle and curvature radius of cutoff arc were obtained and explored. The Reynolds-Averaged Navier- Stokes equations with the Standard k-ε turbulence model is used to simulate the three-dimensional, steady, incompressible, turbulent flow field inside a double-suction backward-curved centrifugal fan and is solved by control volume method. The numerical model is validated by experimental data. The results showed that (i) the inlet cone can induce the air to enter into the impeller smoothly and uniformly, which reduces the flow-separation occurrence along the blade surface. However, the inlet cone with larger friction loss will also slightly lessen the fan performance; (ii) recirculation zones appear inside the volute channel due to the existence of inlet clearance gap between inlet cone and volute, which results in part of fluid leaving from the impeller outlet re-entering into the impeller inlet and reducing the fan performance. This recirculation leakage ratio of fluid through inlet clearance gap increases with increasing inlet clearance gap, which is also depends on the shape of inlet cone; (ii) the distance of inlet cone extending into the impeller will interfere the uniformity of inlet airflow distribution along each blade height. The longer the extending distance, the larger the vortex zone occupying the inter-blade space which makes less fan performance; (iv) it makes only little improvement in the fan performance to change the shape of volute cutoff.
  It is found that (1) decreasing the inlet clearance from 11mm to 5mm, the outlet average total pressure increases about 3.26%; (2) increasing the distance of inlet cone extending into the impeller from 0mm from 20mm, the outlet average total pressure decreases about 6.32%; (3)changing the shape of inlet cone, the outlet average total pressure increases up to 5.4%, and (4) reducing the tongue radius of volute cutoff from 25mm to 15mm, the performance efficiency of fan promotes slightly about 1%.
目 錄............................................................................ I
表目錄.........................................................................IV
圖目錄.........................................................................V
符號表.........................................................................X
摘 要............................................................................XIII
ABSTRACT ...............................................................XIV
第一章 緒論 .................................................................1
1.1 前言........................................................................1
1.2 文獻回顧................................................................2
1.2.1 實驗性能改善相關文獻.....................................2
1.2.2 數值模擬分析相關文獻.....................................3
1.3 研究重點及架構....................................................6
第二章 離心風機基本理論..........................................8
2.1 離心式風機之構造及分類....................................8
2.2 角動量方程式........................................................11
2.3 葉輪基本方程式....................................................12
2.4 渦殼線型................................................................17
2.5 離心風機之各種損失............................................18
第三章 離心風機流場模擬理論與數值方法..............19
3.1 基本統御方程式....................................................19
3.1.1紊流流場模式......................................................20
3.2 數值邊界條件........................................................21
3.2.1對流–擴散方程式的差分形式..........................21
3.2.2壓力–速度耦合關係的處理..............................23
第四章 實驗方法與結果..............................................27
4.1 實驗方法................................................................27
4.2實驗設備.................................................................29
4.2.1 實驗本體.............................................................29
4.2.2 量測設備.............................................................32
4.3實驗過程與步驟.....................................................34
4.3.1 壓力.....................................................................34
4.3.2 流量.....................................................................34
4.4 實驗結果................................................................35
第五章 數值結果分析..................................................37
5.1 風機模型電腦圖檔之建立....................................37
5.2 數值分析主要步驟................................................40
5.2.1 格點獨立.............................................................48
5.3模擬與實驗比對......................................................49
5.4流場對稱性探討.....................................................50
5.4.1 風機內部壓力場分析.........................................52
5.4.2 風機Z剖面流場分析...........................................54
5.4.3 風機渦殼Y剖面流場分析...................................63
5.5入口錐與風機性能的影響......................................65
5.5.1 不同入口間隙的性能曲線比較圖......................65
5.5.2 入口錐不同位置之性能曲線比較圖..................75
5.5.3 不同入口錐外型對風機性能的比較圖..............79
5.6渦殼舌部對後傾式離心風機的影響......................89
5.6.1 不同舌尖半徑(r)之後傾式離心風機的性能比較圖
........................................................................................91
5.6.2 不同舌片角度(α)之後傾式離心風機的性能比較圖.....93
第六章 結論與建議...........................................................95
6.1 結論.............................................................................95
6.2 建議.............................................................................95
參考文獻............................................................................97
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