Study On Flow Induced Vibrations And Rotor System Vibvation In Hydro-turbine

Stability of hydraulic turbine is a very important problem during the design of the turbine. Cavitation, efficiency and power etc. were usually considered in the past during the design, however, the rotordynamic character of the shaft system was not taken into consideration. With the increasing turbine size, unit capacity, the relative stifness of the shaft system becomes weak. At the same time, because of the existance of the crown clearance and the band clearance, the unstability of large hydraulic turbine become significant. The study of the turbine shaft system stability become a popular topic. The contents of the paper is as following:3D model of the reduced hydraulic turbine was built, and the mesh was generated in ICEM. The steady and unsteady flow in the turbine under normal conditions were simulated and analyzed. The pressure fluctuation of points assembled in the model were obtained during the transient simulation. The unsteady force on one blade and the whole runner were also calculated. The characters of pressure fluctuation and radial forces on runner blade were analyzed with FFT transformation. Meanwhile, aproximate analytical solution was obtained by fixing the forces from the simulation of real turbine which is important for the rotor dynamic analysis of turbine rotor system.Transient process is a very important period in the starting, stopping and adjusting of hydraulic turbines in whick unsteady phenomenens such as unexpected vibration, noise often occur. The study of pressure and veclocity distribution in hydaulic turbine is of great importance to the analysis of hydraulic turbine stability characters. Flow field in the reduced turbine including velocity distribution, pressure fluctuation of several points, radial force on the runner and hydraulic torque of guide vanes in turbine condition, braking condition and reverse pump were simulated with the guide vand opening of7%. The results was analyzed and compared with that of normal operating conditions. And the flow field of turbine under small guide vane opening was evaluated with the entropy analysis method proposed in the paper.Reynolds equation was solved in the paper by simplifying the renolds equation. Perturbation method and asymmetrical boundary conditions are adopted in the solving process. The rotor dynamic model of rotor-seal system in the turbine was built up. And the analytical solution of runner force obained for the turbine in nornal codition and small guide vane opening codition were employed into the turbine rotor system. The vibration character of the turbine shaft system was simulated. Furthermore, principles how the seal structure influence the turbine rotor dynamic character was summerizedPressure fluctation of points in the chosen turbine was acquired in the turbine experimental system and the data was processed. The rotor dynamic characters of real turbine including displacements and shaft orbit of upper guide bearing and turbine guid bearing were tested in a certain turbine unit. The results were compared with the simulation data. The feasibility of the method propsed in the paper was validated.Flow condition, radial force on the runner and hydraulic torque on the guide vane were studied in the paper. The difference of flow condition in hydraulic turbine between the small opening condition and normal conditions were analyzed. Flow induced force model was obtained by solving the reynolds equation. And the rotor dynamic character of the turbine shaft system was studied. In the final section, entropy production theory was introduced to analyze the flow in the turbine.