摘要
大部分的軸流扇為了避免引發額外的噪音，通常設計成奇數葉片轉子，而額外的噪音可能來自轉子與扇框或馬達的交互作用亦或是轉子本身。本研究測試了偶數葉片轉子搭配改良式扇框、三相馬達和長靜葉。結果顯示，在改善扇框入風口的情況下，可以減少葉片表面的流場壓力震盪，進而減低扇葉頻率的第一倍頻噪音值，但是扇葉頻率的諧波噪音則可能因為流場結構比較穩定的關係而提高。使用三相馬達可以降低部份高頻的寬頻噪音，但是其對整體噪音值的影響有限。改善入風口狀況與使用三相馬達或許有助於降低噪音，但對於風扇的Fan curve 並沒有提升效果。最後一個實驗是在出風口加長靜葉設計，其功效在噪音與Fan curve 都有明顯改善，其中噪音降低主要是由於大部分的寬頻噪音都降低了，而Fan curve 在操作區上則因為有靜葉關係而提升。適當的改良扇框的幾何外型結構，即可獲的相當不錯的效果，並不需要變更扇葉或是轉子的設計。希望本文的實驗結果可以拋磚引玉，鼓勵更多人探索偶數葉片的轉子可能性，發掘其特點，使散熱風扇的葉片數設計可以更多元化。
並列摘要
Most of axial flow fans are designed to be odd-blade rotor to avoid extra noise which may result from the interaction between rotor and frame shape or motor else rotor itself. In this study, even-blade rotor with improved inlet frame, 3-phase motor, and long stator are tested. The results show that improving fan inlet condition can reduce the first peak noise of the discrete frequency caused by rotor due to decrease the velocity fluctuation around the blade surface but may rise other harmonic passing frequency noise because of stable flow structure. Using 3-phase motor can make broad band noise lower at high frequency area but the contribution to overall noise is not obvious. Improving flow inlet condition or using 3-phase motor may reduce noise but that are not effective in fan curve. The last experiment uses long stator to guide flow in the fan outlet that makes difference in noise and fan curve performance. Noise improvement is mainly from the reduction of broad band noise. Besides, fan curve performance also has large progress in the operation area which is due to long stator effect. Properly modifying frame geometric structure can obtain good result without changing blade or rotor design. The purpose of this study was to encourage more people to investigate the feature of even-blade rotor, discover it’s advantage, and enrich the design of number of blade.