HIGH EFFICIENCY ACTIVE DAMPING ON A FAN ROTOR BLADE IN CASE OF RESONANT VIBRATIONS BY MEANS OF PIEZOELECTRIC ACTUATORS

Severe resonant vibration is one of the main roots of turbomachinery blades failure. Forced response issues arise when the blades work in non-uniform flow fields. As a result unsteady aerodynamic pressures occur on the surfaces of the blade. If the frequency of the aerodynamic excitation matches an eigen-frequency of the blade, the vibration level may considerably increase and a drop in the life-cycle of the component could be entailed. The resonant vibration conditions could be identified at the design level by means of the Campbell diagram. Unfortunately, it is not possible to avoid all the resonant conditions, hence the mitigation of vibration has always been of the utmost importance for turbomachinery designers. Moreover an active damping system based on piezoelectric (PZT) actuators which is capable of tuning its behavior according to the resonant excitation, may be considered very attractive. In this work the forced response of a fan rotor blade, due to a stationary inlet flow distortion resulting from the presence of upstream struts, is taken into account. Some resonant conditions have been analyzed by means of Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) simulations. Thereafter a novel approach based on a proper distribution of the potential supplied to the electrodes of each PZT pair, in order to maximize the damping efficiency, is applied to the case of a plausible fan blade. The outcomes show that the proposed system is able to efficiently damp each resonant excitation and enhance the structural integrity of the blade.