本研究主要目標為在不影響高功率馬達風扇之散熱能力下，改良其散熱風扇與馬達外罩以降低整體運轉噪音，本文採用175-HP高功率馬達當作改善標的和基準，建立一套系統化的數值模擬工具針對其完整之流、熱及聲場進行分析，同時確認重要之設計改善參數。首先運用數值方法估算馬達各項損失及電磁場，分析結果得知其總發熱瓦數為5.7KW，此瓦數即為熱場模擬的重要依據；因為馬達過熱將導致效率降低與使用壽命縮短，因此馬達降噪之改善需在不影響馬達散熱情況下進行。本研究利用計算流體力學分析軟體(Fluent)，針對原始馬達風扇進行完整熱、流與聲場模擬分析，並與實驗量測之結果相互驗證，以證明建構之數值模型的可信度。原始風扇模擬結果流量為809.1 CFM，選取其中一片散熱鰭片進行監測，高、低溫分別為75.7℃及51℃，接者由模擬觀察發現風扇出口氣流無特定流向地擴散出去，且風扇與風罩間距離過大導致產生渦旋，因此確立主要改良應包括葉輪及風罩，最後將兩者結合做出較適化參數設計。同時依氣流出口方向，此將葉輪改變成斜流扇型式，如此使風扇出口流體較為集中且具有方向性，而斜流扇出口會影響流量及出口氣體流動，因此執行參數化分析以得到較適化方案；並且藉葉輪直徑縮小以降低流量及噪音，將較適化斜流扇葉輪直徑縮小2公分，以達到進一步降噪的目的。至於風罩改善則是依據設計後的葉輪流場，且參考漸擴管路之幾何外形，除讓風扇出口更加平順外，也消除葉輪與風罩間距過大所產生之渦漩，這規劃明顯會使流量增加；最後結合風罩改善與斜流扇縮小葉輪完成整套設計，數值結果顯示其流量比原始設計略為下降5%，但散熱鰭片之溫度約下降2℃。較適化方案模擬結果與原始相比流量略微下降，但散熱效果較佳且噪音值降低(3.3~5 dBA)，故將其進行實體化開模製作，並組裝於馬達進行實驗量測，實測之降噪效果可降低4~7 dBA，與模擬結果有些許誤差；探討後發現由於模擬只計算氣動噪音，並未計入振動噪音導致差異產生，唯此誤差值仍在可接受範圍。至於馬達散熱部分藉由量測鰭片間不同位置之風速，間接來推算其散熱能力，測試數據顯示與模擬結果之趨勢相同，這更加驗證數值分析之準確性。綜合歸納上述結果，本文所設計之較適化的高功率馬達風扇，成功地在不影響其散熱性能下達到降噪目的，而本研究建立分析改善模式可供馬達散熱設計之重要參考。

This research focuses on the noise reduction on a permanent-magnet motor under the same cooling performance. A systematic design scheme of the thermal module is established by considering the concerns on aerodynamic, acoustic, and thermal aspects. It is well known that the dissipating energy of motor, including mechanical, copper, and core losses, is critical for the thermal-module design and is difficult to estimate accurately. At first, the electromagnetic field is calculated numerically for providing information to estimate the core and copper losses in a rational manner. As a result, the summation of core, copper, and friction losses for this 175-Hp motor is 5.7 KW, which is the heat needed to dissipate by the thermal module. Then, an integrated CFD and experimental effort is implemented to the motor system for validating the numerical model used in this study. Moreover, several alternatives of fan design and housing arrangement are proposed and assessed for decreasing the acoustic noise generation while the temperature distribution on motor is kept similarly with a 2℃temperature reduction over the cooling fins. Subsequently, based on the numerical predication, the appropriate design, which consists of a smaller inline fan impeller with a 2-cm diameter reduction and a streamlined housing geometry, successfully reduce the noise generations by 3-5 dBA over various locations under the 3,000 rpm operating speed. Furthermore, the set of motor mockup is manufactured and assembled for testing its cooling and acoustic performances for confirming the actual noise-reduction effect. The measurement indicates that a similar noise reduction (4-7 dBA) is attained while an acceptable deviation range (5-7 dBA) between CFD and test results is observed. In summary, the temperatures for permanent magnet and winding core of motor should be maintained well below their safe operating limits. Consequently, the design and analysis tool established here offers a rigorous and systematic scheme for the thermal management on the high-power motor.

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