Performance analysis of high-speed aerostatic thrust bearing lubricated by high-pressure natural gas adopting the Elrod-Ng turbulent model

An aerostatic thrust bearing lubricated by natural gas (ATB-NG) is an ideal supporting component for a natural gas turbo-expander. However, complex turbulent flow exists in the gas film if the ATB-NG operates at high-pressure and high-speed conditions, leading to prediction errors in bearing performance by using a laminar model. This article establishes a modified Reynolds equation adopting the Elrod-Ng turbulent model to calculate the performance of an aerostatic thrust bearing (ATB). The result demonstrates that the gas flow state experiences laminar flow, transitional flow, and turbulent flow sequentially with the increase in rotation speed, causing ATB performance calculated by the turbulent model to deviate from that of the laminar model. Moreover, the critical rotation speed, at which gas flow state transitions from transitional flow to turbulent flow, is related to the ratio of gas density to viscosity. Compared with the result calculated by laminar model, the load capacity, mass flow rate, and stiffness calculated by turbulent model increases by 5.4%–88.1%, decreases by 1.6%–24.3%, and grows by 4.5%–69.9%, respectively, while the operating condition changes (operating pressure: 2–4.2 MPa, operating temperature: 280–335 K, and bearing clearance: 8–30 μm). Furthermore, the performance of the ATB-NG is poorer than that of an aerostatic thrust bearing lubricated by air (ATB-AIR) at different working conditions.