Monolithic approaches to transient thermo-mechanical interaction in nonlinear rotor systems

Aero-engine rotor systems may experience severe thermally-induced failures during start-up acceleration, maneuvering actions, or other harsh operational conditions, creating a significant demand for accurately analyzing transient thermo-mechanical coupling characteristics. In traditional partitioned approaches, mechanical and thermal fields are solved separately, considering the transient process being weakly coupled in rotor systems. This paper proposes accurate and general monolithic approaches for transient thermo-mechanical interaction analysis in nonlinear rotor systems, overcoming the limitation of communication between partitions for inevitable result distortion. Coupled governing equations are constructed as general second-order ordinary differential equations based on motion and heat balance equations. Monolithic approaches are formulated using the generalized-α and linear two-step numerical integration methods. The resulting nonlinear problems are solved using the Newton–Raphson scheme with a fully coupled Jacobian matrix. The accuracy, computational time, and sensitivity to algorithm coefficients of the monolithic approaches are evaluated by numerical experiments. The results indicate that thermo-mechanical problems during transients are strongly coupled necessitating simultaneous solution. Moreover, the monolithic approaches demonstrate excellent generality when applied to a high-dimensional dual-rotor system, capturing rapid and intense transient thermo-mechanical interactions. This capability can help optimize the design of aero-engine rotor systems under complex operational conditions.