Blade Forced Response Prediction for Industrial Gas Turbines: Part 2 — Verification and Application

Abstract

This is part two of a two-part paper. Part One describes the methodologies of a blade forced response prediction system. The emphasis of this part is to demonstrate the capability and computational efficiency of the system for predicting blade forced response. Part two firstly presents verification of the multistage time-linearized unsteady flow solver through comparison of predicted blade surface pressure distributions with data measured on a VKI transonic turbine stage. It concludes with presentation of the results of an analysis carried out on the last stage rotor blade of an ALSTOM three-stage transonic test compressor. In the analysis, strain gauge results together with Finite Element (FE) modal analysis identify the resonant crossings. The mode shape of the blade vibration is used in the CFD code to predict the blade aerodynamic damping. The aerodynamic damping is compared with the blade system damping obtained from the strain gauge tests. The variation is shown of aerodynamic and mechanical damping with blade mode shape. The blade unsteady modal forces induced by the upstream stators are derived from the calculated unsteady flows. The blade vibration at three resonant crossings is compared with those given by strain gauge measurements. Good comparisons and high computational efficiency demonstrate that the forced response methodologies described in Part One can be used in the blade design process to tackle blade aeromechanical issues.