大型泵被廣泛地應用於污水處理廠、防洪抽水站及電廠循環冷卻水系統，而攸關大型泵能否有效率地運轉或其機件壽命能否合乎預期，其關鍵因素之一即是流體在進入吸水口前之流場能否保持一定之均勻與穩定，因此介於抽水站前池及吸入口間之抽水井設計就顯得格外重要。儘管抽水井之幾何設計可參考一些廣為應用之設計準則，如美國之HI標準和英國之BHRA準則，然而其設計參考值只能適用於較簡單之邊界情況，面對現場常有之複雜地形和抽水井內部結構，仍需要水工模型試驗加以較驗。
　　本文旨在以水工模型試驗探討大型泵抽水井在不同閘門沒水深和不同福祿數下之漸進段流場特性。試驗模型採用成大水工試驗所針對協和電廠循環冷卻水抽水井所設計之模型，長度比尺為1：10。文中利用超音波都卜勒流速儀(ADV)量測抽水井之三維流場，討論在各種試驗條件下之其平均流速、流速標準偏差和渦流強度分佈特性，並藉由轉速計觀測吸入口喉部旋轉角度來探討其影響程度。
　　試驗結果顯示在無閘門配置下，抽水井流場之流速分佈頗為均勻；在有閘門配置下，水體通過閘門後，會在閘門後方發生分離現象並明顯形成一Y軸向之主要渦流，此時上層水體之流速標準偏差和渦流強度均明顯增加，形成主要擾動源。當閘門沒水深增加時，水體受到影響範圍增大，渦流強度、流速標準偏差和旋轉角度也都有增加的趨勢。當福祿數增加時，渦流強度、流速標準差和旋轉角度也愈大，此與前人研究中福祿數對於抽水井流場影響之趨勢相同。

　　Large-scale pumps have been extensively used in sewage treatment plants, flood control pumping stations, and circulating cooling water system of electric power plants. To keep these pumps work efficiently, the flow field in front of the suction pipe must keep uniform and stable. So the design of a sump that is normally defined to be between a forbay and a suction pipe has been a very important issue. Although the geometric design of sump can refer to guidelines which were widely used, ex., the HI Standards and BHRA guidelines, these guidelines are only valid for a simple geometry. In case for complex situations, an evaluation of the preliminary design is still needed through physical modeling tests.
　　The objectives of present paper are to investigate the pump sump flow fields under different sluice gate submergences and Froude Numbers through physical modeling tests. A 1:10 scale intake model, similar to the circulating water pump in the Shen-Ho Power Plant, was used. Detailed three-dimensional measurements of the approach flow in the pump sump were obtained by using an Acoustic Doppler Velocimeter(ADV). The distributions of mean velocity, velocity standard deviation, and vorticity in the pump sump under difference experimental conditions were discussed. The swirl angles at the throat of the suction pipe were also measured by swirl meter to investigate the influence of different sluice gate submergences and Froude Numbers.
　　The experimental results show that without sluice gate, the pump-approach flow distributions are uniform. With sluice gate, flow separation occurred behind the sluice gate and transverse vortices formed. The velocity standard deviation and vorticity increase at higher depths. The flow at higher positions becomes the main source of disturbance. As the sluice gate submergence increases, the influenced range of flow enlarged. And vorticity, velocity standard deviation, and swirl angle also increase. As the Froude Number increases, vorticity, velocity standard deviation, and swirl angle also increase. This trend is the same as references mentioned.

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