Structure Vibration of Hydropower House Induced by Francis Turbine Based on Flow CFD

Abstract

ABSTRACT The method of CFD is adopted to carry out 3-D unsteady higher solving rate and accuracy. The collocated grid were used in this calculation, the central difference method was used to discretize the diffusion term of the momentum equations, the second-order upwind scheme was used to discretize the convection term, and momentum interpolation was used for the pressure term of the revised velocity equation to prevent the wave-shaped pressure field. In the unsteady flow calculation, the first-order implicit scheme was used to discretize the time term. For the boundary condition, the total pressure and the velocity direction at the spiral case inlet and the average pressure at the draft tube outlet were given. Copyright © 2008 by ASME 3 Analysis of the calculation result Comparison between numerically simulated and observed hydraulic pressure fluctuations at the man hole of the draft tube is presented in ∫∫ ∫∫ The consistency of the fluctuations effect was achieved through the adjustment of the interpolation. Finally, the loads transfer between structure and fluid was achieved via the procedure above. The load transfer of the shaft system According to the characteristics of hydroturbine units, the hydraulic pressure can be transferred not only through the walls of draft tube and spiral case, but through the guide bearings and pushing bearings, which was caused by hydraulic unbalanced force and hydraulic thrust. Based on the two equations above, considering the actual contact between the mechanical structure and the concrete structure, the loads on the guide bearings were allocated to the corresponding locations on the house model. In contrast to the hydraulic unbalanced force, the location of the hydraulic thrust was more definite. According to the transfer mechanism of vertical forces, for the umbrella hydrogenerator unit in Wanjiazhai plant, the axial hydraulic thrust was transferred from the thrusting guide bearing to the lower frame, and then to the lower frame base. Thus, the hydraulic thrust was taken by the lower frame. Vibrational response of the house The vibrational response of the house structure under the hydraulic loads was simulated using the method described above. The FEA software used was ANSYS. According to the hydropower plant criterion, the vibration displacements of the stator base and the rotor base, the lower frame base, were investigated