大型泵被廣泛應用於污水處理廠、防洪抽水站與電廠冷卻系統。在抽水井的設計上，目前較廣為參考之工程規範如美國標準（ANSI/HI）、英國標準(BHRA）及日本標準(JSME)等，均僅提供抽水井結構單純的情況，對於額外增加的各種結構物，仍須進行水工模型試驗以確保安全；換言之，在額外增加結構物後造成的影響，目前瞭解以及資料仍舊不足。
　　在抽水井之諸多附屬必要結構中，攔污網為最重要設施之一，其主要為保障抽水井幫浦之安全及效率，避免上游的垃圾雜物進入抽水管線，惟假使同一濾網或漸進渠道被隔成兩半之兩邊濾網清除雜物之狀態不一致時，可能由此產生不均勻流場，使得進入吸入口前流況產生較大的不對稱速度分布。
　　本文以模型實驗的方法，模擬現場設置攔污網且發生不均勻阻塞之狀況，利用質點影像測速儀（PIV）觀測抽水井吸入口附近流場之流速，藉以得到渦度及部分紊流強度，並由轉速計觀測得旋轉角度，藉由以上資料討論濾網不均勻阻塞對於流場之影響。
　　試驗結果顯示濾網不均勻阻塞時，會影響流場中的流速分布，使渦旋生成位置偏移，並增強渦流強度及紊流強度，而流場中之旋轉角度會隨著濾網配置之不對稱程度增加而增加，足以超過一般合格標準（5度）。

　The large-scale pump is widely used in the sewage treatment plant, flood pumping station and cooling system of power plant. While designing the sump, the project technical specification such as Unite States Standard (ANSI/HI), Britain's standard (BHRA) and Japan's standard (JSME), etc. are widely consulted at present. Those project technical specifications can only offer the situation of the sump with simple structures. However, while the extra structures increasing, it still has to do the physical modeling test to ensure the security. In other words, the authentic data and report are still insufficient about the influence caused of increasing extra structures.
　In a great deal of the necessary structure to the sump, screen is one of the most important facilities. It’s function is to prevent the rubbish of the upper flow entering the pipe in order to conserve the safety and efficiency of sump. However, if the screen or approaching channel are divided into two parts and in different state of clearness, there probably will induce non-uniform flow that makes the flow condition before entering the suction bell generate more asymmetrical velocity distribution.
　This study uses the method of physical modeling test to simulate the situation that the screens are not uniformly removing the rubbish .Then, use PIV to measure the flow velocity in the ambient of the intake bell .Finally we can get the vorticity and turbulent intensity. The swirl angle is also measured by swirl meter . The influence of the non-uniform clearness screen of the flow field is discussed by the data mentioned above.
　The result of the experiment shows that the non-uniform clearness of the water screen will influence the velocity distribution of flow field that makes the vortex producing position skew and strengthens vortex intensity and turbulence intensity. Also, the swirl angle in the flow field will be increased as the increasing of the unsymmetry of the filter screen disposes that will exceed the general qualified standard (5 degrees).

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