Effect of Sector Mode Shape Variation on the Aerodynamic Stability of a Low-Pressure Turbine Sectored Vane

Abstract

The paper presents a method to investigate the flutter appearance in a cascade, where blades are connected together in a number of identical sectors. The key parameters of the method are vibration amplitudes and mode shapes of the blades belonging to the same sector. The aerodynamic response from a sectored vane cascade is calculated based on the aerodynamic work influence coefficients of freestanding blades performed with two-dimensional inviscid linearized flow solver. A case study based upon the presented methodology shows that, despite stabilizing effect of tying blades together into sectors, a sectored vane consisting of six low-pressure turbine blades vibrating with real single modes, and identical amplitudes can be unstable at realistic design conditions.