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Yin J.-L.,Zhejiang University | Liu J.-T.,Zhejiang University | Wang L.-Q.,Zhejiang University | Wei X.-Z.,State Key Laboratory of Hydropower Equipment
Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics | Year: 2011

In order to investigate the pressure fluctuation characteristics in the guide vanes and stay vanes of pump turbine under off-design conditions, unsteady renolds averaged Navier-Stokes simulation(URANS) detached eddy simulation(DES) were carried out. The results showed that the DES method can be used to capture the pressure fluctuation characteristics. And then, the pressure signals under the operating condition Q/QD=0.15 were analyzed in the time domain and frequency domain respectively. The results suggested that low frequency pressure fluctuations(f/9fn=11.27%) are remarkable and the pressure signal in the stay vanes is not affected by the runner while that in guide vanes is influenced obviously.

Jia Y.,Harbin Institute of Technology | Jia Y.,Harbin Electrical Power Equipment Co | Wei X.,State Key Laboratory of Hydropower Equipment
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2015

In order to design and validate the auxiliary impeller required by the cycle power of the oil-lubricated external circulation cooling system on the reactor coolant pump's bi-directional thrust bea-ring, the CFD method is applied to present a numerical analysis for the pressure feature and flow rate within the oil impeller. The objective is to demonstrate the vector distribution of the relative velocity on the center surface of the flow path, and to verify the possibility of creating any flush angle from the inlet flow of the vane, the pros and cons of the vane shape design and how well it functionally matches the vane. The numerical analysis intuitively reflects the flow parameters and patterns generated by the designed shape of the vane, indicates the fact that the velocity at the vane's inlet mainly affects the tangent angle; thus, effectively lowers the damaging impact on any system devices located adjacent to the rear outlet of the vane. Through simulation of the oil-lubricating circulation, numerical analysis are comparatively analyzed with the testing results, for all 5 complete working processes, deviations are uniformly less than 5% and precisely satisfied lubricating oil's flow, head, zero-impact on flows and other operating requirements. This paper concludes the practical application of a simplified numerical analysis and reasoning could replace the repetitive testing employed in the traditional design process for axial auxiliary impellers. It has been successfully applied in the design of reactor coolant pump. ©, 2015, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved.

Yin J.,Shanghai JiaoTong University | Wang D.,Shanghai JiaoTong University | Walters D.K.,Mississippi State University | Wei X.,State Key Laboratory of Hydropower Equipment
Science China: Physics, Mechanics and Astronomy | Year: 2014

Instability of pump turbine with S-shaped curve is characterized by large fluctuations of rotational speed during the transient processes. For investigating this phenomenon, a numerical model based on the dynamic sliding mesh method (DSSM) is presented and used to numerically solve the 3D transient flow which is characterized by the variable rotation speed of runner. The method is validated by comparison with measured data for a load rejection process in a prototype pump turbine. The results show that the calculated rotation speed agrees well with the experimental data. Based on the validated model, simulations were performed for the runaway process using an artificially assumed operating condition under which the unstable rotation speed is expected to appear. The results confirm that the instability of runner rotational speed can be effectively captured with the proposed method. Presented results include the time history profiles of unit flow rate and unit rotating speed. The internal flow characteristics in a typical unstable period are discussed in detail and the mechanism of the unstable hydraulic phenomenon is explained. Overall, the results suggest that the method presented here can be a viable alternative to predict the dynamic characteristics of pump turbines during transient processes. © 2014 Science China Press and Springer-Verlag Berlin Heidelberg.

Zhou W.-J.,Zhejiang University | Wei X.-S.,Zhejiang University | Wei X.-Z.,State Key Laboratory of Hydropower Equipment | Wang L.-Q.,Zhejiang University
Journal of Zhejiang University: Science A | Year: 2014

Based on the finite element method (FEM) and the Lagrange equation, a novel nonlinear model of a double disc rotor-seal system, including the coupled effects of the gravity force of the discs, Muszynska's nonlinear seal fluid dynamic force, and the mass eccentricity of the discs, is proposed. The fourth order Runge-Kutta method is applied to solve the motion equations of the system and numerically determine the vibration response of the center of the discs. The dynamic behavior of the system is analyzed using bifurcation diagrams, time-history diagrams, axis orbit diagrams, Poincaré maps, and amplitude spectrums. With the rotor speed increasing, the system presents rich forms including periodic, multi-periodic, quasi-periodic, and chaotic motion. We also discuss the effects of the distance between the two discs, the mass of the discs, seal clearance, seal length, and seal drop pressure on the dynamic behavior of the system. The numerical results demonstrate that a symmetrical disc structure, small disc mass, proper seal clearance, long seal length and high seal drop pressure can enhance the stability of a double disc rotor-seal system. The results provide a theoretical foundation for the design of multi-stage sealing systems. © 2014 Zhejiang University and Springer-Verlag Berlin Heidelberg.

Li R.,State Key Laboratory of Hydropower Equipment
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2015

This paper describes the end-surface cavitation of a Francis runner, analyzes the cause for this type of cavitation, and suggests some precautions. A brief discussion on the similarity between prototype and model turbines is given. © Copyright.

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