Rotor–Stator Interactions in a 2.5-Stage Axial Compressor—Part II: Impact of Aerodynamic Modeling on Forced Response

Abstract

The main objective of this study is the validation of numerical forced response predictions through experimental blade vibration measurements for higher order modes of a blade-integrated disk (blisk). To this end, a linearized and a nonlinear frequency domain CFD methods are used, as well as a tip timing measurement system. The focus is on the blade excitation by downstream vanes, in particular, because this study shows that the correct prediction of acoustic modes is of key importance in this case. The analysis of these modes is presented, both experimentally and numerically, in Part I of this publication. The grid independence study for the aerodynamic work on the blade surface conducted in this part shows a possible prediction uncertainty of more than 100% when a coarse grid is chosen. For the validation of the numerical setup, a study was performed using different turbulence and transition models. The results are compared to the measured performance map, to a 2D field traverse conducted with a pneumatic probe, and to data gained by unsteady pressure sensors mounted in the casing of the compressor. Flow features relevant for the prediction of blade stresses are best represented using the SST turbulence model in combination with the γ–ReΘ transition model. Nonlinear simulations with this setup are able to predict the blade stresses due to downstream excitation with an average difference of 23% compared to tip timing measurements. Single row linearized CFD methods have shown to be incapable of making a correct stress prediction when acoustic modes form a major part of the exciting mechanisms. In summary, this two-part publication proves the importance of acoustic rotor–stator interactions for blade vibrational stresses excited by downstream vanes in a state-of-the-art high-pressure compressor.

Reconstructing Compressor Non-Uniform Circumferential Flow Field From Spatially Undersampled Data—Part 1: Methodology and Sensitivity Analysis

“…In addition to the primary excitations including the wakes from upstream stator rows and the potential fields from the downstream vanes, acoustic modes (also known as Tyler-Sofrin modes) generated by rotor-stator interactions occur at blade passing frequency and can contribute to rotor resonance. In a recent two-part study conducted by Terstegen et al [5] and Sanders et al [6], the existence of the acoustic Tyler-Sofrin modes was confirmed experimentally in a three-stage axial compressor, and the corresponding analysis demonstrated the importance of acoustic rotor-stator interactions for blade resonant response.…”

Forced Response Analysis of an Embedded Compressor Rotor Induced by Stator Disturbances and Rotor–Stator Interactions

“…Many efforts have been made to accurately predict the blade response, including using a fluid-structure-coupled method [6][7][8], investigating the influence of the turbulence model [9], damping [6,7], boundary condition [8,9], and mesh densities [8,10], etc. These studies are helpful but mainly focus on the influence of numerical methods.…”

“…Schoenenborn [18] showed that the R1-S1-R2 interaction modes can lead to different blade excitations in the circumferential direction. Terstegen et al [9,19] investigated the effect of rotor-stator interactions on the rotor blade response of a 2.5-stage axial compressor. They performed detailed and comprehensive azimuthal mode analyses and stress predictions.…”

Influence of Position of Intake Struts on Unsteady Load and Vibration of First-Stage Rotor

“…With the development of heavy-duty gas turbines, the mass flow rate and single-stage load of compressors and the alternating aerodynamic force borne by blades continue to rise, resulting in increasingly prominent fluid-induced blade vibration [1]. The vibration problems faced by compressor blades mainly include the flutter and forced vibration caused by intake distortion [2,3], rotor-stator interference [4,5], stall and surge [6,7], and drop vortex [8,9]. The accidents caused by the forced vibration of gas turbines account for 25% of the total blade accidents, which cannot be ignored [10].…”