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《Journal of Hydroelectric Engineering》 2018-09
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Analysis on the relationship between swirling flow at outlet of a Francis turbine runner and vortex rope inside draft tube

ZHONG Lintao;LAI Xide;LIAO Gonglei;ZHANG Xiang;School of Energy and Power Engineering,Xihua University;Key Laboratory of Fluid and Power Machinery,Ministry of Education,Xihua University;Sichuan Provincial Machinery Research & Design Institute;  
In order to predict the vortex rope during the design process for hydro turbine, the relationship between the runner outlet's swirling flow of Francis turbine and the vortex rope inside the draft tube was analyzed. A 180-meter head Francis turbine is numerically simulated under three typical operating conditions by using the Reynolds-averaged Navier-Stokes(RANS) equations. The shape of vortex rope visualizations was compared with the results of the model test for verifying the correctness of simulation. Then, the swirl number, the velocity profile of runner outlet and the swirl number along the centerline of draft tube cone was analyzed to explain vortex rope formation under typical conditions. The results show that the swirl number at outlet of runner increase with the decrease of operating flow rate. When the swirl number at the outlet of the runner is greater than the critical value, the helical vortex rope, the low velocity zone and the backflow are formed in the draft tube. Meanwhile, when the swirl number is less than the critical value, there is no obvious vortex rope forming in the draft tube.
【Fund】: 四川省科技计划重点项目(2017GZ0053; 2017NZ0031);; 国家自然科学基金(51379179);; 流体及动力机械教育部重点实验室(西华大学)项目
【CateGory Index】: TK733.1
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