Fluid Structure Interaction Analysis for Prediction of Centrifugal Compressor Dynamic Stresses

Abstract

Centrifugal compressor impellers experience dynamic loading from flow structures generated by upstream and downstream compressor components. This loading can cause high cycle fatigue and ultimately impeller failure if not accounted for during the design of the impeller. This paper reviews the use of Fluid Structure Interaction as a method for the prediction of these unsteady pressures and resultant dynamic stresses. This paper describes a recent analysis effort to predict dynamic pressures and aerodynamic damping in an industrial centrifugal compressor application. Specific fluid meshing and solution strategies are discussed including a direct time dependent full 360 degree sliding mesh solution and a single passage pitch change solution, using either a Time Transformation or a Fourier Transformation method. Also discussed is the methodology for imposing dynamic pressures from a computational fluid dynamic (CFD) analysis on a forced harmonic structural response analysis to predict unsteady impeller stresses. Particular attention is paid to the post processing of the predicted stress field to inform a prediction of the acceptability of the fatigue performance of the impeller.