Aeroelastic Investigation of a Transonic Research Compressor

Abstract

The trend in modern compressor design is towards higher stage loading and less structural damping, resulting in increased flutter risk. The understanding of the underlying aeroelastic effects, especially at highly loaded BLISK rotors, is small. This paper reports on the analysis of flutter phenomena in a modern transonic compressor. The geometry examined here is the one-and-a-half stage transonic research compressor operated by Technische Universität Darmstadt. High blade deflections recorded during throttling measurements point to an aerodynamic excitation. Therefore, numerical investigations are carried out using the CFD-Code TRACE developed at the German Aerospace Center (DLR). Simulations are compared to measured compressor speed lines to validate the steady state results. The open source Finite Element code CalculiX is used to simulate the rotor blade eigenmodes and -frequencies. The results are then used in time-linearized calculations to determine the onset of flutter. These calculations confirm that there is an aerodynamic excitation of the first torsional eigenmode and blade flutter is at risk. A sensitivity study is carried out to further investigate the aerodynamic conditions under which structural vibrations become unstable and to identify influencing factors.