Forced Response Reduction of a Turbine Impeller

Low engine order excitation may cause a seriously strong vibration response of radial turbine wheels manufactured in one piece. Consequently, high cycle fatigue failure might be an issue. On the other hand, recent developments have shown that using intentional mistuning of blades enables to attenuate the forced response depending on favorable aeroelastic conditions. In the present paper an intentional mistuning pattern is designed to attenuate the forced response of a 12 bladed turbine impeller focusing on the first bending mode due to an engine order 10 excitation. Resulting a more than 40% reduction of the maximum forced response is predicted by employing a reduced order model, which could be validated within test runs. Independently, the focus is on analyzing the robustness of the intentional mistuning pattern with respect to additional random mistuning caused by geometrical deviations of rotor blades and guide vanes due to manufacturing. In detail the impact of three sources of random mistuning is evaluated: Structural mistuning, aerodynamic mistuning, and forcing mistuning.