Rub impact response analysis of Jeffcott rotor for simply supported end conditions and fluid film bearings: a comparative study

In this paper, a comparative study on rub-impact responses of rotor for simply supported end conditions and fluid film bearings is presented. A 2 degree of freedom (dof) Jeffcott rotor model is used. Fluid film bearing is modelled using short bearing approach given by Ocvirk theory. Stiffness damping coefficients of the bearings are incorporated in the rotor equation of motion. The equation of motion is solved by using Runge-Kutta numerical integration method. Rub-impact responses are analysed by using Fast Fourier Transform (FFT) and orbit plots. It is found that with compare to simply supported end conditions 6X, 7X, 8X and 9X frequency components are absent in the Y direction response at operating speed ω = 1.3ω_n for the rotor supported on fluid film bearings. In addition, 2X and 3X frequency components are present in the Z direction response at operating speed ω = 1.3ω_n.