| Because the thin-walled water inlet structure has the advantages of less materials and simple structure,it has been continuously adopted in my country’s hydropower projects.At the location of the thin-walled water inlet structure,vortices often occur.The vortices not only deteriorate the inlet flow pattern and reduce the flow capacity,but also cause the vibration of the unit and reduce the power generation efficiency in severe cases.In order to comprehensively study the characteristics of the flow pattern and stress-strain characteristics of the thin-walled inlet,this paper takes the thin-walled inlet project of Wudongde Hydropower Station as the research object,and uses a combination of theoretical analysis and numerical simulation to analyze the flow under four conditions.State characteristics and their stress and strain are analyzed.In the analysis of flow characteristics,the characteristics of thin-walled inlets and the laws of movement of water flow are studied,and the standard turbulence model is used to analyze the flow characteristics of thin-walled inlets.In fluid-solid coupling,the mathematical equations of fluid-solid coupling are determined,and the static structure is adopted.The mechanical method analyzes the stress and strain characteristics of the structure.(1)Analyze the flow pattern characteristics of the thin-walled inlet through the vortex core distribution and the flow velocity in the vortex core,pressure distribution and pressure size,flow pattern distribution,etc.The results are as follows:Velocity distribution of the trash rack section: under four working conditions,there is a vortex core around the middle pier in the front section,and the flow velocity in the vortex core increases with the decrease in elevation;from the horn to the bottom plate,the vortex at the end of the middle pier The core distribution shapes are different;the water flows from the bell mouth to the exit of the transition section,and the closer to the central axis,the more stable the water flow pattern,and the flow lines are symmetrically distributed about the diversion pier;except for the dead water level conditions,the remaining three conditions From the top beam of the water inlet to the position of the lower bell mouth,the velocity of the vortex core at the tail of the middle pier is the smallest,and the velocity of the vortex core on both sides of the tail of the middle pier is the largest.The closer to the inner wall of the inlet,the greater the velocity of the vortex core and the strongest strength.Pressure distribution of trash rack section: Under four working conditions,there is a high pressure area inside the vortex core at the front end of the middle pier;from the top beam of the water inlet to the position of the lower bell mouth,the tail and tail of the middle pier to the inner wall of the water inlet two areas They are all low-pressure areas;except for the design flood level conditions,the pressure at the exit of the central axis of the transition section is the highest in the other three conditions.Flow velocity distribution of the inlet lock chamber section: Under four working conditions,the internal flow velocity of the vortex core formed at the top of the inlet lock chamber section under the three working conditions of design flood level,normal storage level and dead water level is the maximum flow velocity of the section;check the flood level Under working conditions,due to the difference in water inlet flow and water level elevation,there is a small vortex core with the highest velocity in the middle of the right side of the diversion pier within 3.5m of the upstream direction of the accident door slot.Pressure distribution of the inlet gate chamber section: in the four working conditions,along the flow direction of the water,the pressure distribution at the top of the gate chamber section is small;at the positions of the inspection door groove and the accident door groove,the pressure distribution on both sides of the door groove is different under different working conditions the same.Velocity distribution in the transition section: under four working conditions,the rectangular inlet section of the transition section only has two vortex cores at the top and bottom in the two working conditions of check flood level and design flood level.The other two working conditions have rectangular inlet sections at the top and bottom.There are 3 vortex nuclei in the middle and bottom,along the direction of water flow,the number of vortex nuclei gradually decreases.At the exit position of the transition section,there is only one vortex core at the top;The axis is symmetrically distributed;along the direction of the water flow,the flow velocity increases successively,and the strength of the vortex core gradually increases.Pressure distribution in the transition section: in the four working conditions,following the flow direction of the water,the average pressure of the water flows from the rectangular inlet section of the transition section to the circular outlet section,and the average pressure gradually decreases;except for the design flood level working condition,the other three working conditions are circular There are a large number of disorder areas at the exit positions.(2)Analyze the stress and strain of the thin-walled inlet structure of the hydropower station,and the results are as follows:The strain value(20.44mm)under normal storage conditions is greater than the check flood level(20.00mm),greater than the design flood level(5.00mm),and greater than the dead water level(4.00mm).Check that the structural stress concentration position under three conditions of flood level,normal storage level and dead water level is different from the design flood level.It is mainly distributed at the junction of the top beam of the inlet and the side pier.The stress concentration of the design flood level is mainly distributed in The location at the junction of the side pier and the bottom plate trash trough.The structural displacement and deformation areas under the check flood level and the normal storage level are roughly the same.The undeformed area of the displacement under the design flood level is the smallest,and the undeformed area of the dead water level is the largest. |
