Reduced Thermomechanical Model of Transient Rotordynamics Resulting From Radial Rotor-Stator Contact

The present study focuses on the turbine transient dynamics when operating in a standalone mode. In a gas turbine engine, this state corresponds to the turbine stages being disconnected from the compressors. As a result, the rotordynamics of the turbine is governed by two opposing torques: one from aerodynamic forces, assumed constant, and the other from radial rubbing within a labyrinth seal on the turbine disc. The primary objective is to quantify the transient rotational speed and ensure it remains within the safety limits for motor integrity. Given the anticipated high levels of heat generation, it is also crucial to evaluate contact temperatures to identify regions vulnerable to melting wear. This paper presents an example in which the rotor is modeled using Timoshenko beam elements, while the stator is represented by 3D finite elements to capture the assembly details of the seal and housing components. To optimize computation time, reduction methods are applied to the stator's thermomechanical model, simplifying the contact treatment to a 2D problem. The rotor-stator system is then solved in the time domain using Carpenter algorithm, which predicts a response in backward precessional motion with intermittent contact before transitioning to a dry whip regime. Frequency analysis reveals that this shift is triggered by resonance in coupled rotor-stator modes. The frictional torque ultimately reaches levels sufficient to decelerate the turbine, while also causing temperature rises above the melting point.