Nonlinear vibration mitigation of a rotor-casing system subjected to imbalance-looseness-rub coupled fault

Modern industrial requirements are continuously demanding better performances and higher rotational speeds from current aero-engines. Under this circumstance, mitigation of rotor vibration is of considerable importance for safe and efficient functioning of rotating machinery. The main objective of this paper is to investigate the application of nonlinear vibration absorber on vibration suppression of a rotor-casing system having imbalance-looseness-rub coupled fault. Due to large vibration amplitude and pedestal looseness, both the geometrical nonlinearity of the rotor shaft and the support nonlinearity are considered in the system. When dealing with blade-casing rub, the initial gap between them is treated to be in non-uniform distribution because of coating inhomogeneity. Then the equations of motion in the presence and absence of nonlinear vibration absorber are respectively obtained according to the Lagrange's equation. Through numerical simulation, the vibration mitigation of the rotor-casing system is realized in the different conditions of rotational speed and disc eccentricity. Moreover, from the perspective of vibration displacement and impact force, the effects of the nonlinear vibration absorber on the pedestal looseness and blade-casing rub are further discussed. The numerical results reveal that the nonlinear vibration absorber can effectively suppress the nonlinear vibration of the system and alleviate the detrimental influence of the coupled fault in a wide frequency range.