Study of the Effect of the Scatter of Acoustic Modes on Turbine Flutter

Abstract

Abstract The prediction of aerodynamic damping is a relevant issue for turbomachinery design trends. Most of the conventional analysis methodologies for the study of aeroelastic forcing in use until recently neglect any hypothetical effects of adjacent rows. However, in recent years, it has become unquestionable that acoustic waves and nearly convected perturbations reflected in neighboring rows play a significant role in the evaluation of the overall unsteady loading of the blades. In this paper, a study of the impact of these effects in flutter stability margin is performed. For this analysis, ITP Aero’s in-house unsteady 3D frequency domain linearized RANS solver is used. The subject of this research is a setup which is a close representation of a proper LPT geometry. The influence of neighboring rows is examined, taking into consideration how the interactions between rows are scattered into several circumferential modes, as well as into radial modes. A quantitative assessment of all these effects is performed to understand the relative relevance of each one of them, and the results of unsteady aerodynamic blade loading are compared with those of a single-row simulation.