An Overview of Time-Domain Computational Methods for Aeroelastic Instabilities of Multi-Stage Compressor

Abstract

Modern gas turbine design continues to move towards improved performance, reduced weight and reduced cost. As turbomachinery blade aerofoils are thinned to improve performance and reduce weight, aeroelastic issues such as flutter, forced response and stall driven vibrations become more predominant. Moreover, as the use of blisks (blade-integrated-disks) with very low mechanical damping becomes more common in modern compressor designs, accurate prediction of compressor aeroelastic stability in a multi-row environment becomes vital. This paper presents a review of aeroelasticity research carried out at Rolls-Royce Vibration University Technology Centre (VUTC) at Imperial College over the past 20 years. The aim is to summarise the unusual aeroelastic issues observed in multi-stage compressors into one document so that it can be used by other researchers in the field. Blade passing forced response is not addressed here as their existence can be detected by a Campbell diagram. The results presented here are based on numerical methods but where possible data from experiments are used to verify the numerical findings.

Spectral proper orthogonal decomposition of compressor tip leakage flow

“…From previous measurements, nonsynchronous vibration usually occurs on the first or second torsional mode whose frequency is between 5 and 20 EO. 3,47 The numerical results in this work (i.e., single-passage DDES simulations) suggest that strong unsteady blade forces between 5 and 20 EO can occur at the NS condition, which are mainly induced by the vortex shedding downstream the main TLV breakdown. When considering a full-annulus flow domain in the simulation, the vortex shedding in one blade passage can interact with that in another, which potentially forms circumferentially traveling cells that intensify the low-frequency unsteady blade forces further.…”