Study On Numerical Computation And Model Test Of Horizontal Shaft Pre-extension Pump System

The main features of The East-Route Project of South-to-North Water Transfer are low head, large discharge and long operational time (5000 hours/per year). For a low-head pumping station, how to select pump system type scientifically is the key problem for the design of pumping station in the Project of South-to-North Water Transfer. It is not only influence on both of the investment of the pumping station construction and the daily-water-transfer cost, but also related to the reliability of the pumping station operation. Consequently, it is a vital work to make intensive studies on the pump system types which are intended to be adopted by the East-Route Project of South-to-North Water Transfer.The conduits of a bulb tubular pump system are level and free, in theory this type of pump system should has advantages of smooth flow and low head lost and is expected to operate with higher pump system efficiency under the condition of low pumping station head. The type of bulb tubular pump system has been selected by 7 pumping stations with especial low-head in the East-Route Project of South-to-North Water Transfer. On the other hand, the structure of a large bulb tubular pump system is more complicated and its investment is higher, and was seldom applied at home and abroad. As a result, the experiences on the design, construction, operation and maintenance for this type of pump system are rather lack.The shortcomings of bulb tubular pump system on its structure could be overcome by horizontal shaft pre-extension pump system, however, due to so-called lower efficiency it has not been recognized so far. In fact, researches on the hydraulic performance of horizontal shaft pre-extension pump system were very little before, especially, on the optimum hydraulic design of its inlet and outlet conduit and evaluation for their hydraulic performance.In order to comprehensively understand and compare more types of pump system, it's very necessary to study other types of pump system suitable for low head pumping station without limitation of bulb turbine pump system. Therefore, the horizontal shaft pre-extension pump system is chosen to be studied in detail in this paper. The horizontal shaft pre-extension pump system is studied based on the following aspects:(1)By the help of Fluent, a CFD software, the numerical computations of 3D turbulent flow for the horizontal inlet and outlet conduit are completed respectively, and their interior flow fields and head lost are computed.(2)By the help of Fluent, a CFD software, the numerical computation of 3D turbulent flow for the horizontal shaft pre-extension pump system is completed, then the pump system efficiency and head lost of conduit are computed.(3)According to the actual condition of horizontal shaft pre-extension pump system, various important teleology problems, such as construction of grid model, treatment of boundary conditions, selection of turbulence model and so on, are discussed.(4)Transparence horizontal conduit model tests are executed for the optimized inlet and outlet conduit. The flow patterns in conduits are observed and the head lost are measured. The test results make it clear that the numerical computation results are consistent with the model test results.The study on hydraulic performance of prefixing & postposition bulb tubular pump system of H pumping station with low-head had been completed. Their hydraulic performance is compared with that of the optimized horizontal shaft pre-extension pump system, in the light of which the following conclusions are obtained: The energy performance of horizontal shaft pre-extension pump system is little inferior to that of prefixing bulb tubular pump system, while is little superior to that of postposition bulb tubular pump system.