Nonlinear dynamic characteristics of a power-turbine rotor system with branching structure

Abstract

The branching structure is commonly utilized in the rotor system due to several merits, such as enabling a more compact structure and achieving a higher power-weight ratio, and also usually omitted or concentrated on a disk in the form of lumped mass during modeling, resulting in an inability to achieve the desired modeling accuracy. The aim of this paper is to investigate the nonlinear dynamic characteristics of a power-turbine rotor system with branching structure in turbo-shaft engine. Considering the branching structure and the effect of nonlinear oil-film force due to the squeeze film damper (SFD), the dynamic model of the power-turbine rotor system with branching structure is developed by means of finite element method. Meanwhile the critical speeds and mode shapes of the power-turbine rotor system are achieved by numerical calculation, simulation and experiment. The results reveal that the calculation results of the critical speeds and mode shapes are in good agreement with the simulation and experimental results. Moreover, the detailed comparison of vibration responses of the power-turbine rotor system with and without SFD is conducted, and the effects of oil-film clearance, length and viscosity on vibration responses are further investigated, respectively. The numerical results reveal that when the oil-film clearance goes up, the vibration amplitude at resonance goes down and the opposite is also true, moreover, increasing the oil-film length or decreasing the oil-film viscosity will improve the vibration-reduction performance of SFD.