Fractional-order modeling and nonlinear dynamic analyses of the rotor-bearing-seal system

Unexpected vibrations induced by sealing and bearing faults in the rotor-bearing-seal system seriously affect the health and reliability of the rotating machinery. Here, to study the vibration performances more accurately, the sealing force model is extended from a very narrow integer-order scope to a flexible fractional-order scope, and a novel fractional-order mathematical model of the rotor-bearing-seal system is established from the view of engineering applications by using the finite element method. As a pioneering work, the effect of the fractional order of sealing on the journal and rotor are analyzed under different rotational speeds. Besides, the dynamic characteristics of the rotor-bearing-seal system with the changing rotational speed, mass eccentricity of rotor, sealing clearance and sealing pressure drop at a specific fractional order of sealing are also studied in detail. Then some stability discussions of the system are presented, which is synchronous with some special frequency characteristics. Finally, the methods and results can efficiently provide a theoretical reference for the design and operation of the rotor-bearing-seal system and be applied to forecasting and diagnosing vibration faults of them. (C) 2020 Elsevier Ltd. All rights reserved.