Influence of elastic deformation of the blade on the flow field in the blade cascade

Abstract

Flutter of turbine and compressor blades represents a serious problem for designers of large turbomachines. In real machines, measurements of flutter conditions are hardly possible. Therefore, tests on linear blade cascades with movable blades play important role in investigations of flutter. In the current research, a simple blade cascade for controlled flutter testing was developed. The blades in this test rig undergo high-frequency oscillations which induce inertial forces. The influence of the elastic deformation of the blade on the flow field is studied in this work by means of experiments and numerical simulations. First, the computational and experimental modal analysis was done to obtain eigenfrequencies and modal damping. The deformed shape of the blade due to high-frequency oscillation was acquired by structural transient analysis. The influence of the elastic deformation on the flow field was then studied by CFD analysis for two incidence angles both for the deformed (elastic) and undeformed (idealized rigid) blade. Flow field was only very weakly distorted due to the blade elastic deformation. The total torque induced by aerodynamic and inertial forces was evaluated. The inertial loading is an order of magnitude larger than loading due to fluid flow.