基於維護烹調者健康權益的考量，本文將針對抽油煙機之內部構造進行改良，以達有效且快速地排除烹調油煙之目標。故先對市面上多台傳統式抽油煙機進行品質測試，測試結果雖均符合中國國家標準CNS-3805之規範，但觀察內部結構發現外殼曲度與出口導角處等處，均有待加強與改善之空間。因此接著進行原型之數值模擬，藉由流場可視化來探討其產生的物理現象，並分析評估其結果後根據其缺失作風機外殼的改善。首先將風機外殼變更為漸擴蝸型流道，經模擬後證實漸擴型外殼其外緣壓力較不會壓迫葉輪出口風量的排放，有助於流量的提升，但舌部仍有嚴重流量逆流回風機內之情形。為改善此狀況隨後變更了舌部起始角度，以減少舌部流體因葉輪旋轉而帶回風機內，並於出口設計一漸縮之圓錐體，幫助出口流體導向以增加出口正向流出面積之比率；模擬結果顯示，舌部逆流之況狀較原始風機少了許多，整體流量因此提升了20.6%，靜壓則提升了8.4%；在出風口方面，因有了漸縮圓錐體的導向幫助，有效流出面積之比率高達96.3%，對計算出口流量剖面來說有很佳之狀態。本研究建立一套抽油煙機之完整設計模式，可提供廠商一系統化分析與研發工具，對提升整體性能與效率等方面將有所助益。

Range hood is used extensively in kitchen ventilation for maintaining the air quality and preventing pollution. A substantial demand for the high-performance, low-noise range hood exists especially due to recent report regarding the increasing lump cancer female patients. Thus, the purpose of this research is to enhance the aerodynamic performance of range hood by taking advantage of the CFD calculations to visualize the flow patters inside this device. At first, a typical range hood is chosen as the reference model based on the test report from consumer magazine. A detailed visualization on flow field for this original design is executed and carefully examined via CFD calculation. The shortcomings for this model are summarized to serve as the solid foundation for further improvements. Afterwards, several amendments are imposed on the new design to fix the reversed flow through cut-off, the circulation patterns along the outside region of scroll and at zone near the guiding vane in fan discharge. These modifications include reducing the cut-off clearance, increasing the cut-off angle, the spiral housing, a gradual guiding vane, and a nozzle-shape conical outlet. Later, a comprehensive flow field simulation is performed to validate the above improving alternatives. Apparently, a significant reduction on cut-off reversed flow and a 96.3% effective outlet area are observed from the CFD outcomes. It follows that a 20.6% increase on airflow and an 8.4% pressure gain are achieved. In conclusion, this work offers a reliable tool and an important guideline for the improving design of range hood in a rigorous and systematic manner.

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