Three-dimensional Turbulence Numerical Calculation Of Flow Pattern In Forebay Of A Pumping Station

The intake forebay of the pump station is a building connecting the river channel and the intake pool of the pump station,which is an indispensable part in the discipline of pump station engineering.Its main function is to adjust and diffuse the flow in the forebay in the future,so as to make it more smooth and smooth when entering the inlet pool of the pump station,and provide stable inlet conditions for the pump.According to the inflow direction,the forebay of the pump station can be divided into two basic types:forward inflow and lateral inflow.The flow in the forebay shall meet the conditions of stable flow pattern,uniform velocity distribution and no backflow and vortex in the forebay.In some special cases,when the forebay is difficult to be arranged in the positive direction due to limited conditions,the lateral arrangement may lead to adverse flow patterns such as deflection,wall separation,reflux and vortex after the water enters the forebay.These bad flow patterns will seriously affect the flow pattern of the inlet pool and reduce the energy performance and cavitation performance of the pump.It needs to be adjusted through certain rectification measures to improve the overall inlet flow pattern of the pump.Taking a pumping station in Huguang,Chaohu,Anhui Province as research object,based on three-dimensional turbulence theory,N-S equation and standard K-?,the method of turbulence model equation is used to simulate the flow field of inlet channel under different inlet modes.The main research contents and conclusions are as follows:Using the numerical simulation software CFX,first establish a three-dimensional model for the original scheme,and then import the grid software to divide the unstructured grid.Given certain boundary conditions,use the CFX software to simulate and calculate the flow pattern in the forebay,and then import it into tecplot360 software for post-processing.According to the set characteristic section,obtain the corresponding flow pattern of the bottom layer and surface layer,The velocity distribution uniformity and velocity weighted average angle of the vertical section of the inlet channel are calculated.The original scheme is to retain the old station and build a new station.The new station is a lateral inlet pump station.Calculate and analyze the problems.Then consider four improvement schemes according to the original scheme,that is,consider the demolition of some villages in front of the station and gradually improve the inlet flow direction.From improvement scheme 1 to improvement scheme 4,the design inlet flow angle of the inlet pool gradually decreases,and to improvement scheme 4 becomes positive inlet,As the construction difficulty and cost of changing the terrain and then changing the water inlet direction through demolition in the improvement scheme are large,it is considered to rectify each improvement scheme and approach scheme 4 in data.According to the specific characteristics of the flow field in the forebay,in view of the lateral inflow of bad flow pattern in the original scheme and improved scheme 1 to improved scheme 3,a diversion wall is added for rectification transformation,and the corresponding numerical simulation is carried out to obtain each rectification scheme.By comparing the calculation results of the rectified scheme with the data results of the forward inflow of the improved scheme 4,according to the calculation results of the bottom and surface velocity distribution uniformity and weighted average angle of each scheme and the typical section in front of the inflow pool,combined with the actual situation of the project,scheme 3 is the closest to the forward inflow.Finally,scheme 3 is rectified by adding diversion wall and sill at the same time to explore whether it can be closer to the positive water inflow.The data show that the rectification measure of only adding diversion wall is better than adding diversion wall and sill at the same time.The research is of great significance to improve the operation efficiency of pump station units and ensure the safe and stable operation of pump station units.