| With the rapid development of national economy,a large number of large-scale low lift pumping station are being built or planned to built in our country.It is used for urban flood control and waterlogging control,modern agricultural irrigation,water environment improvement and cross regional water allocation.In order to meet the needs of the construction of large-scale low head pumping station,especially the needs of the construction of large-scale pumping station in the east line of South to North Water Transfer Project,a large number of researches on various types of low head pumping system have been carried out since 1980s in China.The recognition,development and application of the most suitable low head pump system in China experienced the process from the near-positioned bulb tubular pump system,the inclined axial pump system to the front-positioned shaft tubular pump system.Since 2007,the efficiency of the front-positioned shaft tubular pump system in Pizhou station of the first phase of the east line of South to North Water Transfer Project has caught up with that of the bulb tubular pump.The application demand of front-positioned shaft tubular pump system is increasing.It is expected that more and more low head pumping stations will adopt this type of pump device.By referring to the existing research data on the front-positioned shaft tubular pump system,the following two problems are summarized:1.The design level of each design unit is unbalanced,and the efficiency of the front-positioned shaft tubular pump system designed is quite different,which does not reach the level that this type of pump system should reach;2.repeated design research leads to waste of human and material resources.Based on the above background,this paper puts forward and carries out the research on the hydraulic design standardization of the front-positioned shaft tubular pump system.The main research contents and achievements are as follows:1.The main control dimensions and parameters of the outlet conduit of the front-positioned shaft tubular pump system are analyzed for the built and under construction pumping stations.It is found that the width,length,plane diffusion angle and facade diffusion angle of the outlet conduit have little change and the coefficient of variation is small.It is considered that the basic conditions for the hydraulic design standardization of the outlet conduit of the front-positioned shaft tubular pump are available,and further research work is carried out.2.By means of 3-D turbulent flow numerical,the influence of three parameters:the plane diffusion angle,the facade diffusion angle and the length of the section from circular to rectangular,on the hydraulic performance of the outlet conduit of the front-positioned shaft tubular pump system is studied.The results show that:?with the increase of the plane diffusion angle,the head loss of the outlet conduit first increases and then decreases,In the plane diffusion angle range of 17°?19°,the loss value is the smallest.The numerical simulation results show that the flow pattern in the outlet conduit is good and there is no bad flow pattern.The smaller the plane diffusion angle is,the smoother the diffusion flow is.With the increase of plane diffusion angle,the low velocity region moves to the entrance.?When the facade diffusion angle is in the range of 0°?7°,the head loss of the outlet conduit does not change with the increase of the facade diffusion angle.When the diffusion angle is greater than 7°,the loss value increases obviously.It can be seen that when the facade diffusion angle is small,it has little effect on the hydraulic performance of the outlet conduit,which is not the main factor affecting the hydraulic performance of the outlet conduit.The numerical simulation results show that with the increase of the facade diffusion angle,the flow field of each scheme still maintains a good flow pattern,and the range of low-speed region is small,and the flow pattern has no obvious change.? With the increase of the length of section from circular to rectangular,the water head loss of the conduit decreases first and then increases,and the water head loss is the smallest when the length of section length is 0.6 With the increase of the length of the transition section,the overall flow pattern of the flow field in each scheme is better,and there is no bad flow pattern such as vortex shedding.3.The nominal average flow rate of the pump and the width of the outlet conduit are taken as the first and second key parameters of the hydraulic design standardization of the outlet conduit.According to the statistical results of the main control parameters of the outlet conduit and the optimized hydraulic design results of the outlet conduit,the standardized value range of the nominal average flow rate and the width of the outlet section of the outlet conduit are determined,and the two are combined to form the 32 schemes to standardize the hydraulic design of water conduit The schemes that do not meet the requirements of plane diffusion angle and facade diffusion angle are eliminated,and 17 schemes of hydraulic design standardization of outlet conduit are obtained.4.The results of 3-D turbulent flow numerical show that the conduit hydraulic loss of 17 schemes is less than 0.13m,the flow diffuses smoothly from the inlet to the outlet,the flow velocity changes evenly,there is no any bad flow pattern such as flow separation and eddy current in the conduit,and the hydraulic performance is excellent.The 17 schemes of hydraulic design standardization of outlet conduit meet the requirements of reasonable series division,strong universality and convenient application.5.The standardized pump model is the same as the tested pump system of South to North Water Transfer Project and the overall dimensions are exactly the same.The research on the hydraulic design standardization of the inlet conduit of the front-positioned shaft tubular pump system has been completed,and the hydraulic performance of the inlet conduit hydraulic design standardization schemes is excellent;The research on the hydraulic design standardization of the inlet and outlet conduit of the front-positioned shaft tubular pump system has been completed,and the basic conditions for the hydraulic design standardization of the front-positioned shaft tubular pump system have been met.6.Visual Basic language is used to compile the hydraulic design standardization program of the front-positioned shaft tubular pump system,This paper analyzes the problems that need to be paid attention to when programming the pump system,and focuses on the problems that need to be paid attention to when programming the inlet and outlet conduit.7.Combined with the specific parameters of a front-positioned shaft tubular pump station,the hydraulic design of the pump station is carried out by using the hydraulic design standardization program,forming the standardized pump system scheme;the three-dimensional turbulent flow numerical calculation of the flow field under different working conditions of the standardized pump system scheme of the pump station is carried out.The calculation results show that the hydraulic performance of the standardized pump system is excellent,the inlet and outlet conduit of the pump device keep a good flow pattern,the flow lines of the conduit are clear and there is no bad flow pattern under the working conditions of 0.8Q0,1.0Q0 and 1.2Q0.Based on the prediction of the energy performance of the pump device,the flow head curve and flow efficiency curve of the pump device are obtained.The prediction results show that the efficiency of the pump device reaches 82.5%.Comparing the numerical simulation results of the pump with the model test of the pump,it is found that the distribution trend of the energy performance curves of the flow head and the flow efficiency of the pump is the same.Although there are some errors in the results,the error range of the main operating points is not much different.In this paper,the standardization research work of the front-positioned shaft tubular pump system is completed,and corresponding programs are compiled to facilitate the application of the standardization results.The research results of the hydraulic design standardization of the front-positioned shaft tubular pump system have been applied in the actual project,and achieved good results.The research results are of great significance to improve the hydraulic design level and promote the application of the front-positioned shaft tubular pump system... |
PDF Full Text Request