Research On The Forebay Flow Pattern And Rectification Of Zhekou Pump Station

Constrained by terrain,investment,and other factors,the relative compact layout is often adopted in small and medium-sized drainage pump stations,which cannot meet the requirements of the national design specifications in some cases.After the construction,the layout often causes undesirable flow patterns such as swirl and return flow in the intake structure,resulting in problems such as unit vibration and performance degradation,which seriously interfere with the safety of the pump station.Therefore,it is of great significance for such a kind of pump stations to eliminate or mitigate the influence of undesirable flow patterns.Taking Zhekou Pump Station as engineering background,which is under the administration of Xiajiang Hydro-junction Project in Jiangxi Province,the inducement of main problems in current operation is explored and analysed in this paper by numerical simulation method,and several rectification measures for subsequent modification are proposed.The main content and conclusions are listed as follows:(1)The model of Zhekou Pump Station is established to carry out numerical simulations of the flow field of original scheme under design water level,minimum water level,and maximum water level.The reliability of the numerical results is verified by comparing them with the practical feedback from the relevant management unit.According to the analysis of the calculation results,it is found that both side walls of the forebay levels have large backflow zones under the three characteristic water level,which results in severe inflow deflection of Unit 1 and Unit 3 sumps.There are swirls on one side of the sumps,which are related to the vibration of the unit or even the failure of the unit startup under partial water levels.(2)More than three types of rectification measures are adopted in the forebay to improve the unfavorable flow pattern of the pump station,including sill,column,and diversion pier.It is concluded that the comprehensive rectification effect of the straight diversion pier is fairly better as analyzed by the streamlines,velocity distribution diagram for the characteristic section,and evaluation indexes.The swirl area of the forebay and sumps has been reduced,and the inflow condition has been improved.(3)For further evaluation of the vortex in the sumps,the Omega criterion is utilized to identify the structure of the vortex.It is shown that there are surface vortices and bottom vortices of different degrees in the sumps,which are the significant factors of unit vibration.Therefore,the cross vortex baffle is adopted in the sumps,and the reasonable design parameters are also tested.The influence of the harmful vortex is suppressed effectively in the sump to ensure the stability of the unit operation.