Structural Response Due to Blade Vane Interaction

Abstract

The structural response of a bladed turbine disk due to excitation from an upstream stator row was measured using strain gages. Rig testing performed in a realistic aerodynamic environment was preceded by a static vibratory search in which individual blade frequencies and system modes were identified by strain response and holography. In the rig testing special emphasis was placed on identifying the dynamic response resulting from the interaction between the vanes and blades. An analytical description of the forcing function which results from the difference between the number of blades and the number of vanes is presented and correlated with detailed blade responses both in terms of amplitude and interblade phasing. In particular, the combination of 26 inlet vanes and the 30 rotor blades yielded strong dynamic responses in two modes of the four diametral family. The experimental results augmented by the analytical formulation of excitation created by the difference in vane and blade numbers have conclusively identified a mechanism for large blade dynamic response which should be considered in the design phase of bladed disk systems.