本文利用拉凡格式法(Levenberg-Marquardt Method)結合商用套裝軟體CFD-ACE+，進行離心式風扇蝸殼流道幾何之反算設計。將設計半徑設為設計參數，並以最大風量為目標函數，經反覆疊代計算後求得最佳化離心式風扇蝸殼流道幾何外型。並由拉凡格式法搭配商用套裝軟體CFD-ACE+確實可以得到最大風量時之風扇蝸殼流道外型。由結果顯示不同之設計半徑會有不一樣之流場情況，在蝸殼流道外型上亦會有不一樣的結果。經CFD-VIEW將流場可視化後，可從速度場及壓力場觀察到最佳化風扇較初始風扇於蝸殼流道內壓力集中之現象有大幅改善，進而使速度分布均勻，致空氣於蝸殼流道內部流動更加順暢。其中也改善出口流道之回流現象與舌部出口處的渦旋現象，並使扇葉間之壓差減小。最後並進行實驗驗證，以證明吾人設計之風扇在實際上亦有其效果，由實驗結果顯示在風量上提升了6.46%，且因流場流動穩定與壓力集中效應減小，故在噪音上減小了5.32%，因此達到本文之離心式風扇蝸殼流道最佳化設計的目標。

This thesis utilize the technique of the Levenberg-Marquardt Method (LMM) together with the commercial package CFD-ACE+ for an optimal design of volute housing of a centrifugal fan. Design radius is set to the design parameters and the maximum airflow rate is set to the objective function. Then, we calculated by iteratively to obtain the optimum design of volute housing for a centrifugal fan. According to the above method, we can get the optimum geometry of a centrifugal fan with maximum airflow rate.
The results show that the different design radius will result in different flow field situations with the changes in the appearance of the volute housing. By the flow patterns, we can see the phenomenon of pressure concentration improve significantly in volute housing, and the velocity distribution is more uniform in optimized fan. Optimized fan not only improves the phenomenon of reflow in outlet channel but also improves the phenomenon of vortex at tongue, and thus make the pressure difference smaller between blades.
Experimental results show that the airflow rate increased to 6.46%. Also, because of the flow is more stable and reduced pressure concentration we have 5.32% noise reduction in optimized fan. Therefore, the optimum design of volute housing for a centrifugal fan achieve the goal of this thesis.

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