Response Prediction of a Turbine Blade through Modal, Harmonic and Contact analysis Using Finite Element Method

Authors : H. S. Desai Gowda, P. G. Mukunda, Mervin A. Herbert, and R. K. Giridhar

Abstract

Generally jet engines operate at around 10,000 rpm, Thrust bearings and journal bearings are the critical part of a design using fan and turbine blades .They are subjected to fatigue load and high cycle fatigue failure is due to large resonance stresses or due to flutter. The resonance stresses can be lowered by decreasing force of excitation or changing the resonance frequency or by increasing the damping. The force of excitation is mainly due to the guide vanes. These vanes allow variation of the aerodynamic force on the blades. The failure can be reduced by reducing the force of excitation by changing the configuration of the vanes but in many cases it may not be feasible. Altering the configuration of vanes to minimize the force of excitation may be a very difficult task. Changing the resonance frequency may reduce the vibration problem. Avoiding resonance frequencies may not be possible for turbine having variable service speed. The aim is to understand and analyze the various parameters influencing the vibratory response of blade (considered as a beam element) in the assembly of turbine. Response prediction is carried out for turbines subjected to excitation force with and without damping through modal, harmonic and contact analysis using ANSYS.Keywords—Turbine blades, Fatigue failure, Resonance frequency, Aerodynamic force, Variable speed, Damping

Keywords : Turbine blades, Fatigue failure, Resonance frequency, Aerodynamic force, Variable speed, Damping