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Zhuang X.,China Agricultural University | Zhou L.,China Agricultural University | Zhou Y.,Hangzhou Resource Power Equipment Co. | Wu L.,Hangzhou Resource Power Equipment Co. | Wang Z.,Tsinghua University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2014

The ventilation cooling system of large vertical hydro-generator is of great significance to its safe and stable operation, and it is very necessary to study on the flow field characteristics of the generator closed-circuit ventilation system. At present, due to the structural complexity of the stator ventilating ducts in generator, full port modeling simulation needs large amount of calculation, which brings certain difficulties to the numerical study on the full port flow field. This paper proposes a method to study the circulating flow field by modeling the minimal periodic unit, and adopts the multiple reference frame coordinates, as well as porous media model of cooler in CFX software during the numerical calculation. The calculation results show that air flow rate of ventilating ducts is small at the generator neutral position, so a method of increasing the cross-sectional area is recommended to improve the uniformity of the stator ventilation. The flow field of the section at yoke ventilating duct entrance presents certain inhomogeneity, which proves that it is not accurate to set boundary condition in the local modeling calculation. There is disadvantageous vortex in the flow field of the generator end. This paper further sets the transition arc plates at the generator end to achieve the results of disadvantageous vortex eliminated and the air flow rate increased by 15.3% compared with the original design. The research results can provide reference for the optimization design of the generator ventilation system. © 2014 Chin. Soc. for Elec. Eng.

He M.,China Agricultural University | Fu L.P.,Hangzhou Resource Power Equipment Co. | Zhou L.J.,China Agricultural University | Guo Q.,China Agricultural University | Wang Z.W.,Tsinghua University
IOP Conference Series: Earth and Environmental Science | Year: 2012

Cavitation is a well-known problem in centrifugal pumps, causing serious damage and substantial head losses. However, the reason for the sudden head drop in cavitation curves is not fully understood. In this paper, the transient three-dimensional cavitating flow field in a centrifugal pump was calculated using RNG k-ε turbulence model and Rayleigh Plesset cavitation model. The NPSH-H curve and the cavitation development in the whole passage were predicted. The blade loading and energy transfer are analyzed for various cavitation conditions. The results show that the existing of the cavities changes the load distribution on blades. With the decrease of NPSH the loads on blades tend to increases in the rear part but decreases in the front part. If NPSH is not so low, sometimes the overall torque may increase slightly, thus the head may also increase slightly. But if the NPSH become low and reach a threshold value, the overall torque will also decrease. At the same time, the energy dissipation in the vortices increases greatly because of the growth of the cavities. These two reasons make the head drop rapidly. © Published under licence by IOP Publishing Ltd.

Xiao Y.X.,Tsinghua University | Sun D.G.,Hangzhou Resource Power Equipment Co. | Wang Z.W.,Tsinghua University | Zhang J.,Tsinghua University | Peng G.Y.,Nihon University
IOP Conference Series: Earth and Environmental Science | Year: 2012

The unsteady flow within the entire flow passage of a pump-turbine with misaligned guide vanes (MGV) device under the rated speed was simulated using the Reynolds-averaged Navier-Stokes equations together with the k-ω based SST turbulence model. Three kinds of MGV arrangement of different opening angles were chosen to analyse the influence of MGV on the pressure pulsation in the flow passages of spiral case, stay vanes, guide vanes, rotating runner blades and draft tube. The characteristics of the dominant frequency of the unsteady flows in different flow parts under different misaligned guide vane arrangement/openings and the hydraulic performance of the pump-turbine were investigated at the turbine operating condition. The computation result shows that the MGV can decrease the peak-to-peak amplitude of the pressure fluctuation in the whole flow passage except the rotating runner blades. The low frequencies and the influence of Rotor Stator Interaction (RSI) in the entire flow passage vary with the arrangement/ openings of MGV. © 2013 Published under licence by IOP Publishing Ltd.

Zhi F.,Tsinghua University | Hu W.,Hangzhou Resource Power Equipment Co. | Yan Z.,China Agricultural University | Wang Z.,Tsinghua University
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2015

Small spring-supported thrust bearing, advantageous in great bearing capacity and good heat dissipation, is widely used in the hydro turbine. To study this type of bearing, we calculated three-dimensional thermo-elastic hydrodynamic lubrication and developed a new method of equivalent spring stiffness. And we examined the influences of the thrust pad's elastic deformation and thermal deformation and the spring's compression deformation, including the factors of thrust bearing performance, i. e. rotation speed, initial temperature, thickness of thrust pad, etc. This paper presents the results and a discussion on the relationship of bearing performance versus different arrangement of the spring and comes to a conclusion that the performance depends on the number of springs in the oil region and central thrust pad's radial region and the number should be optimized at the design stage. ©, 2015, Tsinghua University Press. All right reserved.

Fu L.,Hangzhou Resource Power Equipment Co. | Yan Z.,China Agricultural University | Wu L.,Hangzhou Resource Power Equipment Co. | Zhi F.,China Agricultural University | Wang Z.,Tsinghua University
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2013

The stability test research for turbine generator set of Himmetli power station showed that the vibration amplitude of upper bracket was out of limits in specific load zone. Based on the measured experimental data, the relationship between vibration signals of upper bracket and pressure pulsation signals of spiral case inlet, head cover and draft tube is analyzed. The dynamic characteristics of upper bracket and stator bracket are analyzed and the natural frequency is obtained. The results show that the frequency of turbine pressure pulsation in the load zone is close to the natural frequency of upper bracket, which leads to the resonance of structure of the upper bracket. The test of air admission for vibration reduction, adding high pressure air from head cover into runner, has also been done. The results show that, through the spectrum analysis of the pressure pulsation signals of spiral case inlet, head cover and draft tube after air admission, the frequency which causes resonance has disappeared and the vibration amplitude has been reduced greatly. Based on the actual situation of power plant, some practicable measures of air admission, that is, inserting the pressure air compensating pipe under the original natural air compensating valve side, are proposed. After putting these measures into practice, no resonance phenomenon occurs when the unit operates in that specific load zone.

He Y.,Tsinghua University | Sun D.,Hangzhou Resource Power Equipment Co. | Zhai L.,Tsinghua University | Wang Z.,Tsinghua University
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2015

In this paper, a 3D nonlinear FEM is used to analyze an embedded spiral casing structure with different thicknesses of spiral steel lining. The results show that even if the thickness of steel spiral case is reduced, its von mises stress or the tensile stress and cracked area of its surrounding concrete does not increase significantly. Even in load rejection condition, after thinning the spiral steel lining, its maximum stress is still less than the yield strength, reaching only one-fifth of the latter, far from its ultimate bearing capacity. This paper also analyzes the spiral structure under overloading and obtains a process of crack initiation and propagation in the surrounding concrete. © Copyright.

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