An Aerodynamic Parameter for Low Pressure Turbine Flutter

Abstract

This paper presents a study on lowpressure (LP) turbine bending flutter. The study is performed using a semianalytical model, which is validated against experimental and computational fluid dynamics (CFD) data. The validation highlights the ability of even the simplest models to represent accurately the flutter behavior of the LP turbine assemblies. A parametric study is then performed into the effect of modifications of the blade camber line on the stability of bending modes. Variations in maximum camber position, leading edge and trailing edge metal angles, and stagger are considered. The modifications are applied to a family of aerodynamically well designed aerofoils and to a family of aerodynamically poorly designed aerofoils. Trends relating damping to the parameters describing the camber line modifications are identified. These trends are found to apply to both families of aerofoils. Furthermore, it is found that the behavior of all aerofoils studied can be characterized by their behavior at a specific flow angle and by a simple algebraic relation based on true incidence. This behavior also seems to be universal.