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研究生: 黃祥河
HSIANG-HO HUANG
論文名稱: 汽車引擎冷卻風扇之性能改善研究
Performance Improvement for an Automotive Engine Cooling Fan
指導教授: 林顯群
Sheam-Chyun Lin
口試委員: 陳呈芳
none
李基禎
none
莊斐志
none
學位類別: 碩士
Master
系所名稱: 工程學院 - 機械工程系
Department of Mechanical Engineering
論文出版年: 2008
畢業學年度: 96
語文別: 中文
論文頁數: 140
中文關鍵詞: 冷卻散熱風扇
外文關鍵詞: Cooling, thermal, fan
相關次數: 點閱:205下載:10
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摘要
汽車是靠引擎內燃燒而產生動力來 達到行駛之目的,然而燃燒所產生熱量有三分之一必需由冷卻系統帶走,因此如果冷卻不良會造成引擎過熱損害。目前車輛冷卻系統應用最廣泛的就是水冷式冷卻系統,利用循環之冷卻水來降低引擎溫度,再透過冷卻風扇來增加通過冷卻模組之空氣以提高散熱量,所以對於車輛冷卻系統來說引擎冷卻風扇之性能顯得格外重要。因此本文以汽車引擎冷卻風扇之改善作為目標,對於市售汽車引擎冷卻風扇進行改善及設計,並利用市售計算流體力學軟體進行數值模擬分析,改變風扇參數之設計來探討其效能變化,再透過製造實體模型進行實驗來驗證模擬的準確性。
相較於原型扇葉,本文將新型扇葉改為翼型設計,使其擁有較佳的氣動特性來提高風扇性能,並再考慮變化葉片數來探討對風扇性能之影響。在不增加馬達輸入功率限制下,結果發現NTUST-5設計相較於原型風扇之性能皆有所提升,在相同風扇轉速時,其最大靜壓與流量分別提高約13%與5%;另在不考慮輸入功率情形下設計之NTUST-7在最大靜壓較原形風扇提高了約13%、在最大流量提高約30%,由此結果証實了本設計相較於原型扇葉皆具有較佳之性能曲線,在相同轉速下可以提供引擎冷卻系統較佳之散熱能力。


Abstract
Automotives are powered by the internal combustion engine to offer a driving force for achieving the purpose of traveling; however, due to the unavoidable efficiency limitation, one-third of the combustion energy is transferred into dissipated heat, which may downgrade engine performance or even cause engine damage. Therefore, the heat dissipation must be removed via the cooling system. Nowadays, most automotive engines utilize the liquid-cooled system, which pumps and circulates the coolant to absorb the dissipated heat around the engine and to reject heat at the radiator by a cooling fan. The amount of removed heat depends on the amount of air flow driven by cooling fan. Thus, the fan performance is extremely important for the engine cooling system. Consequently, the purpose of this investigation is to establish an integrated design scheme for the automobile cooling fan.
This design procedure is comprised of fan design, numerical simulation, CNC mockup fabrication, and experimental verification. First of all, an automobile cooling fan is chosen from the commercial products to serve as the reference fan. Then, to validate the numerical model, the corresponding CFD simulations and experimental measurements are executed via a commercial code Fluent and an AMCA test chamber, respectively. Thereafter, several axial-flow fans with different blade numbers are constructed with the NACA airfoil and are numerically evaluated their characteristics, such as volume flow rate, static pressure, and power consumption. After analyzing all the numerical outcomes carefully under different emphases on power consideration and aerodynamic performance, NTUST-5 and NTUST-7 are selected to fabricate the mockups and measure their performances. The experimental results indicate that, with the same blade number and a similar power requirement, NTUST-5 yields a 13% static-pressure gain and a 5% enhancement on the volume flow rate compared to those for the reference fan. Also, NTUST-7 improves the maximum static pressure and flow rate by the impressive 13% and 30%, respectively. In conclusions, by using this established systematic design scheme, all the fan configurations with airfoil blade proposed here demonstrate a superior aerodynamic performance for resulting in an effective automobile cooling system.

中文摘要......................................................................I 英文摘要.....................................................................II 致謝........................................................................III 目錄..........................................................................V 圖索引.......................................................................IX 表索引......................................................................XII 符號索引....................................................................XIV 第一章 緒 論................................................................1 1.1 前言......................................................................1 1.2 文獻回顧 .................................................................2 1.2.1 風扇設計發展........................................................5 1.2.2 風扇性能改善........................................................8 1.2.3 數值方法...........................................................12 1.3 研究動機與方法...........................................................14 1.4 論文架構.................................................................20 第二章 汽車引擎冷卻系統簡介及風扇測試.......................................22 2.1汽車引擎冷卻系統概述......................................................22 2.2汽車引擎冷卻風扇簡介......................................................23 2.2.1 風扇離合器驅動風扇.................................................25 2.2.2 電動風扇...........................................................28 2.2.3 液壓冷卻風扇.......................................................28 2.3 汽車引擎冷卻風扇之測試...................................................30 2.3.1 性能量測設備.......................................................30 2.3.2 噪音量測設備與環境.................................................32 第三章 數值方法.............................................................36 3.1 FLUENT 簡介.............................................................37 3.2 紊流模式.................................................................40 3.2.1 k-ε紊流方程式.....................................................41 3.2.2 紊流模式其壁面處理方式.............................................43 3.3 數值計算方法.............................................................45 3.3.1求解流程 ...........................................................45 3.3.2離散方法 ...........................................................50 3.3.3速度與壓力耦合......................................................58 3.3.4網格品質............................................................61 3.3.5 邊界條件設定.......................................................62 第四章 原型風扇數值模擬分析與測試比較.......................................65 4.1風扇之實驗................................................................65 4.1.1 風扇之性能測試......................................................68 4.1.2 風扇之噪音測試......................................................68 4.2 原型風扇數值模擬.........................................................69 4.2.1 風扇之物理模型......................................................69 4.2.2 數值模型之建立......................................................72 4.2.3 數值邊界條件........................................................75 4.2.4 數值網格建置........................................................75 4.3 模擬結果.................................................................79 4.3.1 壓力等位圖分析.........................................................84 4.3.2 力矩分析...............................................................84 4.4 模擬與實驗之比較.........................................................86 第五章 新型風扇數值模擬分析與測試...........................................88 5.1 新型風扇扇葉設計.........................................................88 5.1.1 扇葉設計...............................................................90 5.1.2 高壓力、高流量扇葉設計.................................................90 5.1.3 與原形風扇相同輸入功率下的扇葉設計.....................................95 5.2 新型風扇數值模擬結果....................................................100 5.2.1 高壓力、高流量風扇的模擬結果..........................................100 5.2.2 與原形風扇相同輸入功率下的風扇數值模擬結果............................100 5.3 數值結果分析與選定模型製作..............................................106 5.3.1 新型風扇流場分析......................................................110 5.3.2 新型風扇壓力場分析....................................................119 5.4 實驗結果與綜合討論......................................................119 5.4.1 新型高壓、高流量之NTUST-7風扇.........................................124 5.4.2 與原型風扇相同輸入功率的新型NTUST-5風扇...............................125 六章 結論與建議............................................................130 6.1 結論...........................................................130 6.2 建議...........................................................132 參考文獻....................................................................134 作者簡介....................................................................139

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