Transient Thermal Modeling of Ball Bearing Using Finite Element Method

Abstract

Gas turbines are fitted with rolling element bearings, which transfer loads and supports the shafts. The interaction between the rotating and stationary parts in the bearing causes a conversion of some of the power into heat, influencing the thermal behavior of the entire bearing chamber. To improve thermal modeling of bearing chambers, this work focused on modeling of the heat generated and dissipated around the bearings, in terms of magnitude and location, and the interaction with the components/systems in the bearing chamber. A thermal network (TN) model and a finite element (FE) model of an experimental high-pressure shaft ball bearing and housing were generated and a comparison to test rig results have been conducted. Nevertheless, the purpose of the thermal matching process that focused on the FE model and experimental data is to provide a template for predicting temperatures and heat transfers for other bearing models. The result of the analysis shows that the predictions of the TN are considerate, despite the simplifications. However, lower relative errors were obtained in the FE model compared to the TN model. For both methods, the highest relative error is seen to occur during transient (acceleration and deceleration). This observation highlights the importance of boundary conditions and definitions: surrounding temperatures, heat split and the oil flow, influencing both the heat transfer and heat generation. These aspects, incorporated in the modeling and benchmarked with experimental data, can help facilitate other related cases where there is limited or no experimental data for validation.