Experimental And Simulation Study On Vortex Structure And Scale Effect In Pump Station Intake

The intake is an important part of the pump station,whose flow state and hydraulic characteristics have an important influence on the performance of the pump,and the bad flow state is often accompanied with the emergence of hydraulic phenomena such as vortex.The vortex that may appear in the intake is generally divided into two kinds,the free surface vortex and the subsurface vortex,which are the important factors that affect the operation efficiency and stability of the pumping station.Therefore,it is of great significance to study the flow law and the cause of vortex generation in the intake.In order to study the vortex in the intake of pump station,the flow and correlation vortex in the intake are numerically simulated by the fluid volume(VOF)method and the Embedded Large Eddy Simulation(ELES)method.The grid of ELES turbulence model is systematically analyzed,and the numerical simulation results are compared with the experimental results of PIV picture on average velocity and vortex field,which shows that this simulation method can be used to further explore the second-order turbulence parameters,such as turbulent kinetic energy and Reynolds stress.Then the process of vortex evolution is characterized according to the spatiotemporal characteristics of free surface,and the basic mechanism of vortex formation and evolution in the intake is deeply discussed by using turbulent kinetic energy and Reynolds stress to reveal the anisotropic turbulent structure and momentum transfer around the vortex by ELES simulation results.In others papers,a great deal of research has been done on the vortex problem in the intake of pumping station,but there is no unified conclusion on the possible scale effect phenomenon in vortex experiment.When the Reynolds number of the model is less than the critical value,it is possible to have a scale effect,which leads to the "distortion" of the model experiment.In the previous search for the critical Reynolds number of scale effect,it is basically the prototype to carry on the hydraulic experiment proportional scaling according to the general Vortex model similarity criterion,and this method often has to design the different scaling proportion model to carry on the experiment research.Based on the comparison results between the above ELES and PIV methods,by changing the Reynolds number of the motion viscosity,the vortex of the pumping station intake under the same simulation condition of the same model is simulated,the size of different Reynolds number ring and tangential velocity are compared,and the scale effect is found in the simulated working condition of Re=220,00,which indicates that viscous force begin to work.Aiming at the shortcoming that the traditional pump station generally follows the ANSI/HI standard design,the vortex device has the disadvantages of complex structure,long construction period and high cost.In this paper,a cross vortex device installed directly on the suction pipe is proposed,in order to verify the inhibitory effect of the vortex device on the vortex around the inlet pipe proposed in this paper,Taking the physical model of Recharge pumping station in a thermal power plant as the experimental platform,the model experiment is carried out by using particle image velocity measurement(PIV)technology.Under the condition of satisfying the critical inundation depth required by the model,two kinds of flow(large and small)conditions were selected to test the effect of the vortex device.The influence of the vortex device on the inlet vortex of various pumps is compared by intercepting the vorticity flow chart measured by PIV at different distances from the free surface and the wall surface.The experimental results show that the vortex device can prevent the vortex suction pump produced by the wall surface and the free surface,and it has little effect on the bottom vortex.