Influence of Shock Wave on Turbomachinery Blade Row Flutter

Abstract

The influence and effect of a shock wave on the flutter characteristics of a turbomachinery blade row is described. High-fidelity numerical analysis is used to understand the behavior of turbomachinery blade row flutter in the presence of an oscillating shock wave. The unsteady Navier-Stokes equations are solved on a dynamically deforming, body-fitted grid to obtain the unsteady aerodynamic load on a vibrating blade. An energy exchange method is used for calculating the aerodynamic damping to determine the blade row flutter characteristics. A transonic forward swept fan configuration, which showed flutter at part speed conditions in wind-tunnel tests, is analyzed. The shock wave was found to influence strongly the aerodynamic damping, with outboard stations providing the main contribution. The interblade phase angle of blade motion and the location of shock wave determined the influence of shock wave on blade stability. The influence of shock motion was found to be linear for a small amplitude of blade oscillation. The observations from the numerical analysis are used to develop an algebraic model for calculating the work done on the blade because of an oscillating shock wave.