| The pumped storage power plant studied in this paper is a major project of the State Grid Corporation of China to promote energy restructuring,implement the strategy of western development and serve the revitalization and development of old revolutionary areas,and is also the first pumped storage power plant project under construction in northwest China.The spillway of the lower reservoir of the pumped storage power station is the main drainage structure of the power station,which is of great significance to the safe operation of the whole reservoir system.In this paper,the hydraulic model test method is used to test and study the hydraulic characteristics of the spillway in the lower reservoir of the pumped storage power station,and the test measurements obtained the drainage capacity at different water levels;water flow patterns at different gate openings;and water flow patterns,water surface lines and pressure distribution and flow velocity distribution along the drainage channel;the possibility of water cavitation and the downstream scouring situation was analyzed.The improvement scheme of floodway gas mixing and erosion reduction facilities and flow diversion nose-can was proposed.A detailed analysis and study of the schemes under different working conditions is carried out to verify their rationality.The main research results are summarized as follows.(1)The original design spillway discharge capacity complies with the design requirements;the bottom pressure of the spillway in each working condition is positive,with the minimum pressure appearing on the weir surface and in the Vochi section,and the pressure in the anti-arc section and the nose-can section are both higher;the flow rate in each working condition in the spillway trough gradually increases along the course,with the maximum flow rate in the spillway trough approaching 35m/s and the minimum water flow cavitation number 0.218,which makes it easy for cavitation and cavitation damage to occur,so air mixing and corrosion reduction facilities need to be set up.The original scheme design conditions when the left side of the tongue of the water is close to the left bank,resulting in a greater depth of the left bank,the tongue of the water in the small flow is not picked up or just picking up,the impact of the right bank slope,the need to optimize the picking up of the nose of the body type.(2)With reference to the research results and engineering practices of similar projects in China,we have analyzed the flow patterns and gas mixing effects of the gas mixing and reduction facilities of the picking,convex type and combined type gas mixing and reduction facilities,and determined the gas mixing scheme of the picking type;by adjusting the turn of the overflow channel outlet sidewall and opening the opening in the middle of the picking,we control the flow direction of the water tongue of the picking and realize the longitudinal diffusion and pulling of the water tongue,and obtain the optimized scheme with better downstream position and lighter local scour.(3)Systematic testing and verification of the recommended scheme is carried out,and the results show that:the cavity is stable under all operating conditions and the downstream splash disappears;the recommended scheme of the nose-and-kan is better for the longitudinal stretching of the flow,and the tongue does not scour the bank slopes under all operating conditions,and no scouring occurs at the base of the dam and the nose-and-kan under all operating conditions,and the scouring at the downstream energy dissipation zone is significantly reduced under small and medium flows..Through the study of the nose-can picking characteristics,the recommended spillway operating reservoir level should be greater than 936.5m,and should avoid the gate in the low opening conditions of long-term operation. |
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