Multiphysics based Modal and Harmonic Analysis of Axial Turbines

Abstract

The presented work discusses the vibration behavior of an axial turbine, analyzed using the finite element method (FEM) using commercial software ANSYS®. The turbine was modeled as a 2-D plate type of structure discretized with 4-noded shell 63 elements to save computational time. Constraints were applied keeping in view the actual operating conditions. The turbine was modeled with more than one FE meshes. Mesh sensitivity analysis was carried out to ensure the quality and independence of the results. Modal analysis was conducted to calculate a few initial natural frequencies. Results were studied against the operating frequency of the turbine. After carrying out the modal analysis, harmonic analysis was performed to see the response of the turbine under dynamic loading. The nature and cause of the dynamic loading are also discussed in relation to dynamic behavior. It was observed that the turbine is safe in its entire range of operation as far as the phenomenon of resonance is concerned. Also, it was observed that the maximum harmonic response of the turbine on the application of dynamic loading is far lesser than its failure limit within the specified operating range.