A 3D Time-Linearized Method for Turbomachinery Blade Flutter Analysis

Nowadays engine weight reduction is a major concern for aero-engine designers: they need to reduce the impact of increasing fuel price on operation costs on one side and the environmental impact on the other, by lowering fuel consumption and emissions. The goal of engine weight reduction is often achieved by decreasing the number of mechanical parts and by adopting thin and highly loaded blades. This approach, while helping to reduce engine life cost, significantly increases the relevance of aerodynamically induced vibration phenomena (flutter and forced response), which can result in blade high-cycle fatigue failures. Predicting and avoiding fluid-blade interaction-induced vibrations has thus become a primary objective in aero-engine design. During the ongoing research effort on Computational Aeroelasticity (CA) at the “Sergio Stecco” Department of Energy Engineering (University of Florence), an aeroelastic solver has been developed, in collaboration with Avio Group. This solver, named Lars (time-Linearized Aeroelastic Response Solver), was designed to work together with the Traf steady/unsteady aerodynamic solver ([1], [2]). A first Lars variant solves quasi-three-dimensional aeroelastic equations and is also the basis for a flutter screening procedure for real and complex modes (see [3]); a fully three-dimensional variant has also been developed. The aim of this paper is to present this three-dimensional method for turbomachinery blade flutter analysis. The approach adopted is uncoupled and time-linearized (see [4] for an overview of computational aeroelasticity methods).