A linear equivalent method for determining rotor stability under large disturbances

The stability of rotor systems under large disturbances is often a concern in the design process of rotating machinery. Under this condition, rotor systems show significantly different dynamic behaviors from linear systems. This paper proposes a method for determining rotor system stability under large disturbances. Equivalent stiffness and damping coefficients are defined and a linear system is constructed equivalent to the original system from an energy perspective, so as to indirectly determine the stability of the original system. The influence of large disturbances is described by the oil film boundary migration effect. The proposed method is verified by directly solving the nonlinear dynamic equations. The results show that the method proposed gives results consistent with the direct solving method, while avoids solving the divergent process, resulting in lower computational costs. Furthermore, this paper investigates the effects of several factors under large disturbances in rotor systems with the proposed method. This work may be helpful in qualitative analysis of rotor stability under large disturbances.