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- 저자 : Pavesi Giorgio (검색결과 2 건)
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Numerical Study on Rotating Characteristics of Unsteady Flow Inner Pump-turbine in Pump Mode
Jun Yang,Tian Xie,Pavesi Giorgio,Xiaohua Liu,Jun Liu 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.3
In order to investigate the formation of the rotating stall in diffuser of pump-turbine in pump mode, the unsteady flow with radial rotating characteristics before the occurrence of rotating stall are investigated by detached eddy simulation. The results indicate that the unsteady flow patterns which occur in the return channel both at full and part load conditions contain two periodical disturbances with frequencies St≈0.042 and St≈0.085, and the Strouhal number St is frequency normalized by blade passing frequency of impeller. These periodical disturbances not only influence the pressure field but also cause rotating characteristics in diffuser channels. One is composed of 4 cells propagating at 0.073 times of impeller rotating speed. The other one is made up of 3 rotating cells with 0.2 times of backward impeller rotating speed. Meanwhile, there are two radial rotating characteristics which contribute the spectra peak at blade pass frequency in diffuser. One is at the inlet of diffuser propagating at impeller rotating speed with 7 cells, and the other one contains 4 cells with about 1.75 backward impeller rotating speed.
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Wang Wenjie,Han Zhenhua,Pei Jin,Pavesi Giorgio,Gong Xiaobo,Yuan Shouqi 한국CDE학회 2023 Journal of computational design and engineering Vol.10 No.1
To reduce the energy consumption of large centrifugal pumps, modified heuristic intelligent algorithms are used to directly optimize the diffuser of centrifugal pumps. Considering the hydraulic efficiency under the design condition as the optimization target, in this study, 14 geometric parameters such as the inlet diameter, outlet diameter, and leading and trailing vane angles of the diffuser are selected as design variables, and the modified particle swam optimization and gravitational search algorithm are used to directly search for optimization in the design space. The performance and loss of internal entropy production of the different models before and after optimization are compared and analyzed in detail. The results show that the global optimization ability of the modified algorithm is improved. The diffuser model changes from cylindrical to twisted, the vane wrap angle increases, and the thickness of the leading edge decreases. Under the design condition, the efficiency of modified particle swarm optimization algorithm solution is increased by 2.75% and modified gravitational search algorithm solution by 2.21%, while the power remains unchanged. Furthermore, the optimization solution has the largest lift efficiency improvement under part-load conditions. After optimization, the unstable flow in the model is improved and internal entropy production loss is reduced significantly. The interior of the diffuser is dominated by turbulent entropy production and direct entropy production under different operating conditions, and the wall entropy production accounts for the smallest proportion.
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