SUPPRESSION OF VIBRATORY STRESSES IN TURBINE STRUCTURAL COMPONENTS SUBJECTED TO AERODYNAMIC LOADING

Abstract

Vibratory stresses are the main cause of failure in gas turbine engines and other rotating machinery components. These stresses must be attenuated to an acceptable level through an efficient process in order to prevent failures in turbine blades. Previous studies have shown that a thin magneto mechanical coating layer can make a significant contribution to the damping and reduction of these vibratory stresses. Previous studies on analyzing the damping characteristics of these coatings for various applications, such as beams and turbine blades, employed general solid mechanics loads. In this study, we numerically compute aerodynamic loads on one and a half stage axial turbine and applied these loads on the blade via a mapping procedure in order to bring more reality to the problem. We employ a three-dimensional finite-volume based solver to simulate the flow in the turbine using SST model to account for turbulence effects. Sliding mesh technique is used to allow the transfer of flow parameters across the sliding rotor/stator interfaces. In order to model a single passage configuration, profile transformation method is used. A free vibration analysis has been performed to obtain natural frequencies and corresponding mode shapes to analyze resonance conditions. The computed CFD loads are then applied to an uncoated and coated turbine blade through a finite-element analysis (FEA) package. A forced response analysis is performed at the critical frequencies to obtain vibratory stresses. Numerical results show suppression of vibratory stresses at various low and high frequency vibration modes. The results are benchmarked against published data and closely match the expected outcome. The research presents an effective procedure for suppression of vibratory stresses in gas turbine engine component subjected to real world aerodynamic loading. The new procedure is a significant improvement towards more realistic simulation based solutions for vibration suppression problems.