Study On The Influence Of Submergence Depth Of Pumping Station Inlet On Vortex

There are often vortices in front of the water inlet of the pumping station.The vortices in the water inlet of the pumping station will worsen the flow pattern of the water inlet,and over time will cause many problems,such as pump vibration,unit efficiency reduction and so on,which threaten the safe operation of the pump.The results show that the strength of the vortex at the inlet of the pumping station is related to the submerged depth of the inlet.The submerged depth of the inlet determines the size of the dead water area,which provides the necessary conditions for the formation of the vortex.In essence,the problem of the vortex at the inlet is the problem of the submerged depth of the inlet.However,the previous research on the relationship between the vortex and the submergence depth of the pumping station inlet has obtained few academic achievements.It is urgent to continue to study the relationship between the vortex and the submergence depth of the pumping station inletBased on this background,this paper studies the flow characteristics of vortex at the inlet of multi-unit pumping station.The research method is divided into numerical simulation and model experiment.In the numerical simulation,considering that the change of starting flow may have certain influence on the occurrence and development of inlet vortex of pumping station channel under different submergence depth when the pump unit is actually running,this paper selects three common flow conditions during the operation of pumping station:Q0,1.25 Q0,1.5 Q0,Q0=0.8m3/s.Under each flow condition,eight different submergence depths of water inlet are selected as the research scheme,which are 1.1m(0.916hI)?0.9m(0.75hI)?0.7m(0.583hi)?0.5m(0.416hI)?0.3m(0.25hI)?0.1m(0.083hI)?0m?-0.1m(-0.083hI)(water inlet height hI=1.2m).The submergence depth of-0.1m(-0.083hI)indicates that the water level is 0.1m below the top plate of the flow channel.The results show that there are vortices in the water inlet of the pump passage at different submergence depth,including the water level 0.1m below the top plate of the passage,and the vortices appear near the side wall of the passage.When the water level is-0.1m(-0.083hI)below the top plate of the passage to the submergence depth 0.5m(0.416hI),the intensity of the vortices increases with the increase of the submergence depth.When the submergence depth is 0.5m(0.416hI)to 1.1m(0.916hI),the intensity of vortex decreases with the increase of submergence depth.In this paper,the physical index of vorticity is introduced.By analyzing the average vorticity of the vortex core section under different flow conditions,the variation law of the vorticity at the inlet of the pumping station is summarized.Under three different flow conditions,the vorticity increases with the increase of water depth when the water level is above the top of the channel,and reaches the maximum near the top of the channel.Then,with the increase of water depth,the vorticity began to decrease.At a certain depth below the roof,the vorticity value reached the minimum.When the water level is 0.1m(0.083hI)below the top of the channel,the variation of vorticity is similar to that of other submergence depths.Under three different flow conditions,the maximum value of vorticity is obtained at the top of the channel,and the vorticity decreases with the increase of water depth from the top of the channel.In this paper,the relationship between the vorticity peak value and the submergence depth is studied.Under the same flow condition,the vorticity peak value with the submergence depth of 0.5m(0.416hi)is the largest.When the submergence depth is greater than or less than 0.5m(0.416hI),the vorticity intensity is smaller than that under the submergence depth of 0.5m(0.416hI).Finally,the model experiment is carried out,and the eddy field at the inlet of the pumping station channel is measured with V3 V three-dimensional flow field measurement technology,which verifies the CFD numerical simulation results.Both numerical simulation and experimental measurement can better reflect the flow characteristics of vortex.