| 摘要: | 本研究目的在探討與驗證透過本研究規劃的扇葉設計流程，經過流場數值分析與單向流固耦合扇葉結構分析，能完成符合冷凝器系統散熱能力之軸流風機扇葉設計。同時確保風機扇葉結構強度安全無虞，且扇葉整體自然頻率不會與風機設計轉速基頻產生共振，避免扇葉因共振發生斷裂破壞。
本研究設計之軸流風機必須滿足擬開發冷凝器系統解熱能力需求，即風量為8580 m3/h、風壓為50 Pa。依照本研究扇葉設計流程，先針對扇葉安裝角及翼型進行設計，透過五個模型經過流場數值分析後，模型五扇葉轉速950 rpm之模擬性能曲線能滿足冷凝器系統解熱能力需求。為了降低扇葉生產成本，針對模型五進行鈑金化扇葉設計後，經過流場數值分析再次確認鈑金化扇葉模擬性能曲線能滿足冷凝器系統解熱能力需求。後續以較高的轉速1050 rpm進行單向流固耦合結構分析，利用最大von Mises等效應力值判斷各零件是否超過材料降伏強度為標準，確認扇葉結構強度足夠，然後進行樣品打樣，透過風洞實驗、輪穀平台應變值量測及自然頻率實驗確認流場數值分析模型與結構分析模型為有效之分析模型。
本研究設計之鈑金扇葉風機經過符合MACA 210-07規範之風洞儀器測試，驗證其性能曲線滿足冷凝器系統解熱能力需求，即風量為8580 m3/h、風壓為50 Pa。扇葉各零件以材料降伏強度為標準來計算安全係數，其結果為輪穀平台安全係數為2.57，葉片安全係數為2.14，墊片安全係數為4.81，螺栓安全係數為1.78。顯示各零件結構具有足夠強度承受所設定之負載條件。鈑金扇葉之第一模態自然頻率為24.6 Hz，而轉速1050 rpm的基頻為17.5 Hz，顯示鈑金扇葉本體不會與轉速基頻產生共振現象。
;The purpose of this study is to propose and verify a design process for the impellers of an axial-flow fan to meet the heat dissipation requirements of a condenser system. A finite element analysis (FEM) technique is applied to determining the flow field and performing the structural analysis with a fluid-solid coupling method. The natural frequency is determined to make sure that resonance is not going to take place in operation of such a fan.
The key specifications for such an axial-flow fan include an air flow of 8580 m3/h and a wind pressure of 50 Pa. Through fluid dynamics analysis with FEA, a proper set of setting angle and airfoil is selected for the impeller geometry to meet the requirements at a fan speed of 950 rpm among five initial designs considered. A fabrication process using sheet metal, for reducing cost, is further considered in making the final design of the impellers. The final design of the sheet metal impellers is verified to meet the requirements in fluid mechanics by FEA simulation. Subsequently, a fluid-solid coupling FEA simulation is conducted to assess the structural integrity of the impeller design at a higher fan speed of 1050 rpm. As no structural failure is predicted by the simulation according to the von Mises criterion, a mockup of the impeller design is fabricated for testing. Experiments such as wind tunnel test, strain measurement for hub platform, and natural frequency measurement are then conducted on the mockup sample to evaluate its performance and stability and to verify the simulations.
Experiments and simulations, based on the specification of MACA 210-07, both verify that the sheet metal impellers designed in this study can meet the heat dissipation requirements of a condenser system. A good structural integrity is expected, as the safety factor for the components hub of platform, blade, washer, and bolt is 2.57, 2.14, 4.81, and 1.78, respectively. The natural frequency of the first modal vibration is 24.6 Hz which is higher than the maximum working fan speed of 1050 rpm (17.5 Hz). Accordingly, no resonance is expected to take place. |
