Thermomechanical transient dynamics of radial rotor–stator contact

Abstract

The present paper discusses the numerical investigation of structural interactions initiated radially between a turbine shaft and an annular stator. The rotorshaft is modeled under the rigid bodies assumption while the stator is discretized in space with curved Bernoulli beam elements. The turbomachine is assumed to be driven by two torques: the first one is prescribed from aerodynamics while the second one is induced by sliding friction from Coulomb’s model and must be assessed. The study is motivated by the need to predict the dynamic behavior of the rotorshaft in the presence of radial contact between the labyrinth and the annular stator. If rotordynamics accounting for unilateral and frictional contact is widely developed in literature, the combination with an unknown rotational velocity and thermomechanical coupling must still be investigated. Indeed, heat generation and subsequent thermal expansion is expected to modify the contact interface and the dynamic response. The system is solved in the time domain and contact treatment is achieved though a modified version of the Carpenter algorithm. The identification of the conditions affecting the rotational speed is achieved through a sensitivity analysis on the stator properties, friction coefficient and coefficient of thermal expansion. Results confirm that the higher the friction coefficient and stator stiffness are, the lower the maximum rotational velocity value is. It is also shown that high temperatures are located in specific regions on the stator and that the temperature peaks are amplified with thermal expansion.