Performance analysis of an aerostatic thrust bearing lubricated by supercritical CO2 utilizing Elrod-Ng turbulence model

Abstract

An aerostatic thrust bearing lubricated by supercritical carbon dioxide (ATB-SCO₂) is ideal axial support component for the rotating shaft of an SCO₂ cycle power generator. However, little literature is related to the performance analysis of an ATB-SCO₂ and laminar model is commonly used, leading to significant errors in bearing performance predictions. In this article, the modified Reynolds equation based on Elrod-Ng turbulence model and orifice discharge equation are combined and solved by finite difference method for calculating the static performance of an ATB-SCO₂. Moreover, the turbulence effect on ATB-SCO₂ static performance is investigated by analyzing the flow field characteristics in lubricating film. The results indicate that SCO₂ on thrust plate is in a turbulent state. Load capacity and stiffness calculated by turbulence model are larger while mass flow rate is lower compared to those of obtained by laminar model. The fluid velocity varies steeply near-wall and smoothly in middle of lubricating film due to the increased effective viscosity in middle of lubricating film. Load capacity and stiffness increase with the increase of supply pressure and rotational speed, and decrease with the growth of film thickness. Furthermore, the static performance of an ATB-SCO₂ is significantly influenced by pressure-equalizing groove depth (when the depth is <50 µm) and restrictor number, and the effects of pressure-equalizing groove width can be neglected.