| Large pumping station with especial low head is applied widely to projects of water diversion, water environment improvement, urban flood control, agriculture irrigation and drainage, etc. The large pumping station with especial low head has characters of low head and large discharge, and the pumping station which is applied to the projects of water diversion and water environment improvement also has character of long run time. The pumping station has high standard in pump system efficiency, and requires that the pump system has advantages of simple structure, good electromotor radiating and cooling condition, convenient installation and service, convenient operating maintenance and low equipment investment. Especial low head pump system which is suitable to the pumping station has advantages of little hydraulic loss and high pump system efficiency, and the pump system includes four types:horizontal extension shaft pump system, bulb tubular pump system, shaft tubular pump system, submerged tubular pump system. Each type of pump system has each character, what is the difference among different type of pump systems and which type of pump system should be chosen to be applied to the pumping station with especial low head are the questions that need to be researched.With the background of construction of large pumping station with especial low head in our country, sufficient optimum hydraulic design for different type of pump systems have been completed respectively, so as to improve their hydraulic performance as far as possible. Based on the optimum hydraulic design research, their hydraulic performance was compared, and their comprehensive index including pump assembly structure, installation and service, operating management and equipment investment were compared. According to the comparative results, the especial low head pump system which has excellent hydraulic performance and has advantages of simple structure, convenient installation and service, convenient operating management and low investment was find out. The main research contents and achievements are as follows:(1) According to the functions and hydraulic design requirements of inlet&outlet conduit of especial low head pump system, objectives of optimum hydraulic design for pump system and inlet&outlet conduit were put forward, and objective functions of optimum hydraulic design for inlet&outlet conduit were set up. Based on the relationship among pump system efficiency, pump efficiency and conduit efficiency, the opinion that the conduit efficiency is as important as the pump efficiency was pointed out. Level and development trend of the pump efficiency was analyzed, different between pump model test section and pump segment of low pump system was researched, and efficiency of the pump model test section was modified. Relationship among the conduit efficiency, pump system head and conduit hydraulic loss was researched, to reduce the conduit hydraulic loss as far as possible which is the key problem of optimum hydraulic design for especial low head pump system was put forward, and detail solution approaches to reduce the conduit hydraulic loss were put forward from angles of lowering the flow velocity and improving the flow pattern in the conduit. Method of optimum hydraulic design for especial low head pump system was studied, advantages and disadvantages of pump system model test research method and pump system numerical simulation research method were analyzed, conduit model test research method and conduit numerical simulation research method were put forward, relationships among these research methods were studied, and study approach of "relying mainly on conduit analysis research method and supplemented by pump system research method, relying mainly on numerical simulation research method and supplemented by model test research method" was put forward for optimum hydraulic design of especial low head pump system.(2) By applying the conduit numerical simulation method,3-D turbulent flow numerical simulation and optimum hydraulic design for inlet and outlet conduit of horizontal front extension shaft pump system have been completed respectively, the conduit hydraulic performance was improved, laws of water flow motion and turbulence kinetic energy distribution in the conduit were revealed. By applying the pump system numerical simulation method,3-D turbulent flow numerical simulation for optimization scheme of the pump system has been completed, water flow motion law in the pump system was analyzed, and the conduit numerical simulation results were verified. By applying the conduit model test method, model tests for optimization scheme of the inlet and outlet conduit have been completed respectively, flow patterns in the conduits were observed and conduit hydraulic losses were tested, and the conduit numerical simulation results were verified and validated. By applying the conduit numerical simulation method,3-D turbulent flow numerical simulation and optimum hydraulic design for inlet and outlet conduit of horizontal rear extension shaft pump system has been completed respectively, the conduit hydraulic performance was improved, laws of water flow motion and turbulence kinetic energy distribution in the conduit were revealed. By applying the pump system numerical simulation method,3-D turbulent flow numerical simulation for optimization scheme of the pump system has been completed, water flow motion law in the pump system was analyzed, and conduit numerical simulation results were verified. Based on the optimum hydraulic design for the horizontal front extension shaft pump system and horizontal rear extension shaft pump system respectively, their hydraulic losses were compared, hydraulic loss of the horizontal front extension shaft pump system is less than that of the horizontal rear extension shaft pump system.(3) By applying the conduit numerical simulation method,3-D turbulent flow numerical simulation and optimum hydraulic design for inlet and outlet conduit of front-positioned bulb tubular pump system have been completed respectively, the conduit hydraulic performance was improved, laws of water flow motion and turbulence kinetic energy distribution in the conduit were revealed. By applying the pump system numerical simulation method,3-D turbulent flow numerical simulation for optimization scheme of the pump system has been completed, water flow motion law in the pump system was analyzed, and the conduit numerical simulation results were verified. By applying the conduit model test method, model tests for optimization scheme of the inlet and outlet conduit have been completed respectively, flow patterns in the conduits were observed and conduit hydraulic losses were tested, and the conduit numerical simulation results were verified and validated. By applying the conduit numerical simulation method,3-D turbulent flow numerical simulation and optimum hydraulic design for inlet and outlet conduit of rear-positioned bulb tubular pump system have been completed respectively, the conduit hydraulic performance was improved, laws of water flow motion and turbulence kinetic energy distribution in the conduit were revealed. By applying the pump system numerical simulation method,3-D turbulent flow numerical simulation for optimization scheme of the pump system has been completed, water flow motion law in the pump system was analyzed, and conduit numerical simulation results were verified. By applying the conduit model test method, model tests for optimization scheme of the inlet and outlet conduit have been completed respectively, flow patterns in the conduits were observed and conduit hydraulic losses were tested, and the conduit numerical simulation results were verified and validated. Based on the optimum hydraulic design for the front-positioned bulb tubular pump system and rear-positioned bulb tubular pump system respectively, their hydraulic losses were compared, hydraulic loss of the front-positioned bulb tubular pump system is less than that of the rear-positioned bulb tubular pump system.(4) In order to realize parameter design of conduit, on the basis of analyzing the characters of inlet and outlet conduit of front-positioned shaft tubular pump system, geometry mathematic models of inlet and outlet conduit were set up respectively. By applying the conduit numerical simulation method,3-D turbulent flow numerical simulation and optimum hydraulic design for inlet and outlet conduit of front-positioned shaft tubular pump system have been completed respectively, the conduit hydraulic performance was improved, laws of water flow motion and turbulence kinetic energy distribution in the conduit were revealed. Influence of conduit control dimensions that are length, width and height on hydraulic performance of inlet and outlet conduit were studied, and relationship curves between conduit hydraulic performance and control dimensions were gained. By applying the pump system numerical simulation method,3-D turbulent flow numerical simulation for optimization scheme of the pump system has been completed, water flow motion law in the pump system was analyzed, and the conduit numerical simulation results were verified. By applying the conduit model test method, model tests for optimization scheme of the inlet and outlet conduit have been completed respectively, flow patterns in the conduits were observed and conduit hydraulic losses were tested, and conduit numerical simulation results were verified and validated. By applying the conduit numerical simulation method,3-D turbulent flow numerical simulation and optimum hydraulic design for inlet and outlet conduit of rear-positioned shaft tubular pump system have been completed respectively, the conduit hydraulic performance was improved, laws of water flow motion and turbulence kinetic energy distribution in the conduit were revealed. By applying the pump system numerical simulation method,3-D turbulent flow numerical simulation for optimization scheme of the pump system has been completed, water flow motion law in the pump system was analyzed, and the conduit numerical simulation results were verified. By applying the conduit model test method, model tests for optimization scheme of the inlet and outlet conduit have been completed respectively, flow patterns in the conduits were observed and conduit hydraulic losses were tested, and conduit numerical simulation results were verified and validated. Based on the optimum hydraulic design for the front-positioned shaft tubular pump system and rear-positioned shaft tubular pump system respectively, their hydraulic losses were compared, hydraulic loss of the front-positioned shaft tubular pump system is less than that of the rear-positioned shaft tubular pump system. Flow patterns of the inlet and outlet conduit of front-positioned shaft tubular pump system were analyzed in detail from all angles of view, the research indicates that main reason of the excellent hydraulic performance of the pump system is due to its excellent internal characteristics. By applying the pump system model test method, hydraulic performance of the front-positioned shaft tubular pump system was tested, test results indicate that hydraulic performance of the pump system is very excellent:pump system efficiency at design head operation point(the design head is3.1m, the design discharge is33.4m3/s) and average head operation point(the average head is2.7m, the design discharge is33.4m3/s) are83.11%and83.02%respectively, and the critical net positive suction heads at the two operation points are4.63m and4.28m respectively.(5) Based on sufficiently optimum hydraulic design for different types of especial low head pump system, their hydraulic performance was compared quantitative, according to the conduit hydraulic loss the pump systems are in turn as follows:front-positioned bulb tubular pump system, front-positioned shaft tubular pump system, rear-positioned bulb tubular pump system, horizontal front extension shaft pump system, horizontal rear extension shaft pump system and rear-positioned shaft tubular pump system. Pump system efficiency and comprehensive index of three types of pump systems which are horizontal front extension shaft pump system, rear-positioned bulb tubular pump system and front-positioned shaft tubular pump system were compared, and the comprehensive index includes civil works dimension, pump assembly structure, bearing load condition, electromotor radiating and cooling, equipment investment, installation and service, operating maintenance, etc. The comparative result indicates that the front-positioned shaft tubular pump system gains very excellent hydraulic performance under the condition of especial low head, and has advantages of simpler structure, better electromotor radiating and cooling condition, more convenient installation and service, lower investment and more convenient operating maintenance. So it can be extensively applied to especial low head pumping stations. |
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