Simulation and Investigation of an Intentionally Mistuned Blisk Rotor in a High Pressure Compressor

Abstract

In modern aircraft engines, the blade integrated disk (blisk) technology is widely implemented. While the blisk design brings numerous advantages including weight reduction, aerodynamic efficiency improvement, and manufacturing simplification, its low mechanical damping due to the absence of friction between disk and blades makes the rotor more susceptible to vibration. Given that damages to blisk rotors sometimes require the whole assembly to be replaced, effort has been made to alleviate the unexpected vibration amplitude within operating range, among which intentional mistuning is regarded as one of the commonly used techniques. Mistuning refers to blade-to-blade deviation of mechanical properties, which is inevitable in practice due to manufacturing tolerances or wear. Through the application of intentional mistuning, it is expected that the amplitude of synchronous or non-synchronous vibration (NSV) will be reduced without severely losing aerodynamic performance. In this paper, the effect of intentional mistuning has been investigated for the blisk rotor of a 1.5-stage transonic research compressor at Technical University of Darmstadt. According to the previous test campaign, the baseline rotor has shown its susceptibility to NSV due to the first torsion mode in the near stall region. Attempts have been made to alleviate this problem by using intentional mistuning. In order to have a comprehensive understanding of the effect of the applied mistuning pattern, simulations were performed using a finite-volume-method (FVM) based CFD solver to produce comparable results as shown in the test campaign. In the simulation, mistuned systems were modeled in comparison with the nominal tuned reference. Geometrical disturbance and frequency disturbance were introduced to the tuned model first separately and then simultaneously. In this way, the contribution of aerodynamic and structural mistuning to suppress NSV is identified based on the aeroelastic output.