Thermal Growth Simulations of the Rotor and Auxiliary Bearing Contact Events

As an essential component in the system of the HTR-10 helium turbine generator electromagnetic bearings, auxiliary bearings provide mechanical backup protection in case of the events of magnetic bearing failure happen. When contact events happen, highly localized and transient temperatures will arise from frictional heating over the dynamically varying contact area in the very short term and dissipate through the bearing in the longer term. When excessive temperature level occurs, rapid failure may be anticipated, thus it will become a serious threat to the safety of the HTR. This paper presents a detailed analysis of thermal growths due to the mechanical rub for a rotor drop on auxiliary bearings. With the aim to numerically analyze the heat generation and temperature rise, a 1D thermal model of the ball bearing composed of heat transfer network and heat sources based on heat transfer equations is established. The Matlab codes are developed to complete the numerical analysis, and an infrared method is utilized to investigate the temperature rise at the rotor/inner race contact surface. By the comparison between simulation results and the experimental data, this paper illustrates the thermal growth during a rotor drop process, which is highly non-linear. The results reveal that the axial contact force is critical to the bearing heat generation, and the ceramic balls with superior thermal properties are recommended.Copyright © 2014 by ASME