3-D Numerical Simulation Of The Hydraulic Exciting Vibration In Hydraulic Turbine

The strong vibrations of Francis hydro turbine unit occur frequently both at home and abroad due to excitation by flowing fluid, and the problems of blade cracks of a runner with middle and high specific speed are commonly observed. The vibrations are possibly endangering the safely operation of the unit. Therefore, the study on the hydraulic exciting vibration characteristics in turbine and finding the reason of vibrations are of great significance to ensure safety and stability of the unit.In this thesis, the flow-induced vibration mechanism and the fundamental principle were introduced, Numerical simulation of flow field was introduced, especially RNG k-εturbulence model. Some theories of flow acoustics were described, and a few basic acoustic sources and acoustic radiations of flow field on hydrodynamic noise were referred to. Moreover, approaches utilizing ADINA to calculate acoustic power were generalized.The main works of this thesis are as follows:(1) 3-D model of Francis turbine was constructed by Unigraphics, the components contained volute, stay vanes, guide vanes, runner and draft tube.(2) Vibration mode of the Francis turbine was analyzed with ADINA. The natural fre??cies and mode shapes of the runner both in air and in water were calculated, and the comparative analysis were done. Moreover, the effects of the changes of fluid density and bulk modulus on the dynamic characteristics of runner were discussed in detail.(3) The hydraulic exciting vibration in turbine was simulated with 3-D modeling for finding the reasons of turbine vibration. Because of computer capacities and the time restriction, a few components had been simplified appropriatly. Fluid-structural coupling method was utilized via ADINA to investigate flow field, acoustic field and stress distribution of runner, and the reasons of vibration and noise level produced from turbulence in turbine were analyzed. Hence, the results of simulation were analyzed and regarded as the referrence to better design of turbine.