Vibration analysis of dual rotor system equipped with active friction dampers based on harmonic balance method and sensitivity analysis

Abstract

Numerical investigations are essential in appropriately determining normal forces for active dry friction dampers (ADFDs) within rotor systems, although existing methods suffer from the deficits of low-efficiency and over-simplifications. Within this paper, a harmonic-balance-based approach is proposed to efficiently obtain the responses of ADFDs-dual rotor system and a local sensitivity analysis is developed together with it to directly visualize the influences of ADFDs. The fixed-interface mode synthesis method and the trajectory tracing method are first utilized to reduce the system dimension. Then, a novel sampling strategy is proposed for the harmonic balance procedure to guarantee the orthogonality of Fourier basis. The resultant nonlinear equation is solved by the arclength continuation technique. To visually present the variation of rotor responses as the normal force of ADFD changes, a local sensitivity analysis method is developed together with the harmonic-balance-based solver. The frequency-domain sensitivity coefficients are derived analytically to facilitate computation of sensitivities. Numerical validations are carried to show the efficiency and accuracy of the developed method. The influences of ADFDs on rotor responses are discussed both numerically and experimentally. It is found that, due to the multiple excitations in dual rotor system, rotor whirl motions could exhibit the characteristics of multi-valued frequencies. The influences of ADFD on rotor responses are related to the rotational speeds, the ADFD normal forces and the ADFD installation positions. The developed method could intuitively show the influences of these factors on rotor vibration suppression, which provides an efficient tool for parameter optimization.