隨著各式電腦主機與處理器設計的微型化發展之下，所形成日益嚴苛的空間限制與環境阻抗大幅影響了散熱效果。因此，在不同操作環境中評估風扇性能，以及開發高效能散熱風扇的需求也隨之而起。本研究為完整評估風扇性能，以市面上常見款式之十二公分軸流風扇與八公分後傾式離心扇作為研究目標，將風扇各操作點的流場分析、風扇效率計算、扭力估算與噪音分析，藉由數值模擬方式詳細地作一整合式之探討；並規劃製作相關的風扇原型以進行性能實驗比較，結果顯示數值計算之風扇性能與聲壓頻譜均與量測結果有良好之一致性，充分證實此完整深入之風扇性能評估方式可提供相關性能改善設計之參考。
此外，本研究亦結合葉柵理論分析與反向設計方法來發展一套風扇設計流程，先以適當的數值模式計算低雷諾數下NACA-44系列翼形的升阻力係數，建立一可靠且可供設計程式讀取之翼形資料庫。接著以一目標操作點為依據，設計出風扇幾何相關參數；並且，在相同的幾何外型參數下、藉由改變不同阻抗下之流量、修正全壓設定，找出其它操作點的速度與壓力分佈；再建立風扇實體模型以進行實驗量測與數值計算之分析，並將程式設計之不同操作點的軸向速度、全壓分佈與攻角值和數值模擬作比較，結果顯示其趨勢相當一致。這表示本研究之設計程序與理念能夠符合，可呈現風扇實際運轉下的流場機制，並具有一定的可靠性。
綜合來說，本研究提供了一套整合氣動、機電、噪音之完整風扇性能評估方式，風扇設計者可從相關評估資訊中擬定性能改善方案。而使用反向設計程式，則可讓設計者直接找出符合操作點之風扇外型，並在設計過程之中能夠立即得到各操作點的流場資訊；此完整之評估方法與設計流程皆能大幅擴增風扇工程師的設計視野，提升高效能風扇之設計效率。

Due to the increasing system resistance and space limitation on computer devices, the requirement for developing high-performance cooling fans is recently existed. The performance evaluation of fan design under different operating conditions is evidently in great demand for practical engineering applications. Therefore, this comprehensive study is aimed to offer the overall technical information for thoroughly evaluating the fan performance. At first, a 120mm-diameter axial-flow fan and an 80 mm-diameter backward-inclined centrifugal fan are chosen to serve as the research subjects for demonstration purpose. Numerical simulations are then utilized to perform the detailed flow visualization, torque calculation, efficiency estimation, and noise analysis for comparing to the experimental results. As a result, the predicted fan performance and sound pressure level (SPL) spectrum agree well with experimental tests. The complete evaluation outcome for fans provides detailed flow information for performance enhancement.
In addition, this research also developed an integrated design scheme through combining the cascade theory and inverse design procedure for small axial-flow fans. First of all, a reliable set of low-Reynolds-number aerodynamic characteristics for NACA airfoils is constructed to serve as the design database via the CFD calculation incorporated with a dependable turbulent model. Then, with the inputs of design conditions and few geometric settings, this design program can generate a fan configuration to meet with the desired performance requirement. Furthermore, by changing the operating flow rate for this fan geometry, this design approach can yield the axial velocity and the pressure distributions for various operating points over the entire performance curve. Thereafter, a CNC-fabricated prototype and a 3D numerical model are chosen to validate the design prediction of fan performance via both experimental and CFD approaches. As a result, a slight deviation among the designed, experimental, and numerical outcomes is observed throughout the P-Q performance curve. The detailed distributions on the axial velocity, the total pressure, and variation of angle-of-attack are all in good agreements between numerical results and design settings under various operating points. It implies that this design program can yield reasonable design outcomes. In conclusion, this study establishes an integrated aerodynamic, acoustic, and electro-mechanical evaluation approach and develops a systematic and user-friendly inverse design program to provide the fan engineer’s design ability.

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