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| Experimental study on floating objects being intercepted by and passing trash racks in pumping station |
| QIU Baoyun1*, LIU Di1,2, YUAN Lianchong3, ZHAO Tong1 |
| 1. College of Electrical and Power Engineering, Yangzhou University, Yangzhou, Jiangsu 225127, China; 2. College of Computer Engineering, Suzhou Vocational University, Suzhou, Jiangsu 215000, China; 3. The East Route of South-to-North Water Diversion Project Jiangsu Water Source Co., Ltd., Nanjing, Jiangsu 210000, China |
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Abstract Trash racks shall be set in the pump station before water inflow to intercept large volume floating objects, so as to avoid flow, efficiency reduction and motor overload caused by water pump entanglement. However, in order to reduce the head loss of sewage interception and the amount of sewage removal, small floating objects are allowed to pass through the pump through the grid. If a single floa-ting object in front of the trash rack is intercepted by the trash rack, the interception probability of subsequent small-size floating objects being intercepted will increase. In order to master the characteristics of floats being intercepted by and passing the trash rack, the movement of typical floats in water flow was observed by experimental methods, and the conditions and general laws of floats passing and being intercepted by trash racks were explored. The investigation results show that the probability of floats passing through the trash racks is related to the grid spacing, the size and character of the floats and flow velocity. The probability of floating objects passing through the racks of floats decreases with the increase of object-spacing ratio δ(the ratio of the float length to the space between the rack bars). When the distance ratio δ increases to the critical value δc, the probability curve of floating objects passing through the racks tends to be horizontal. For the floats objects with certain type and size, the probability of passing through the racks can be reduced by reducing the spacing between trash rack bars under the condition that the floats which pass through the racks could pass through the pump impeller. However, when δ reaches the critical value δ =δc, increasing the object-spacing ratio δ by increasing the rack bar density has little effect on improving the probability of float interception, on the contrary, it will increase the cost and hydraulic loss of the trash racks. The research results of this paper are of great significance for improving the design and operation management of trash racks and trash cleaning machine.
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Received: 07 October 2020
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