Effect of radial offset bucket blades of nozzle jet on stability of Pelton turbines
QING Qiwei1, DENG Fangxiong1, LI Wenbin1, DENG Huiming2,YU Zhishun2, LU Jiaxing2, LIU Xiaobing2*
1. CHN Energy Dadu River Geshizha Hydropower Development Co., Ltd., Danba, Sichuan 626300, China; 2. Key Laboratory of Fluid and Power Machinery, Ministry of Education, Xihua University, Chengdu, Sichuan 610039, China
Abstract：Aiming at the problem that the nozzle jet centerline is often offset from the runner bucket blade pitch circle during the actual installation and maintenance of the Pelton hydraulic turbine, VOF multiphase flow model and SST k-ω turbulence model were used to numerically simulate and analyze the pressure pulsation and runner force inside the bucket blade of the Pelton hydraulic turbine of Guodian Dadu River Jiniu Hydropower Station, after which the hydraulic turbine oscillation, stress on the runners and efficiency were measured before and after the jet offset, and the effect of the radial offset of the nozzle jet centerline from the bucket pitch circle on the stability of the Pelton turbine was analyzed. During data simulation, the turbine was set to operate under three conditions as follows: nozzle jet centerline offset toward the outer edge of the runner bucket blade, offset toward the runner center, and no offset condition. The results show that the radial offset of the jet causes a significant increase in the axial force and pressure pulsation of the turbine, while the radial force and efficiency are reduced, and the pressure pulsation of the offset to the outer edge of the bucket blade is greater than that of the offset to the center of the runner, and even greater than that of the non-offset condition. According to the numerical simulation results, the maximum axial force reaches 2.27 times of the non-offset condition, the measured axial vibration is 3.40 times higher and the radial oscillation is 1.30 times higher than that of the non-offset condition after shifting to the outer edge of the bucket blade.
