Mechanism of hybrid velocity distribution law in high pressure aerostatic thrust bearings
摘要
Investigating the mechanism of velocity distribution is crucial for understanding the flow behavior of high Reynolds number airflow in high pressure aerostatic thrust bearings (HPATBs). A novel one-dimensional (1D) adiabatic non-isentropic steady flow model for the flow channel and a two-dimensional (2D) axisymmetric numerical model for the entire flow field are established respectively. Both types of solutions indicate that supersonic and subsonic airflow exist simultaneously within the parallel gas film segment when its height hp is 0.3 mm. This velocity distribution pattern, termed the hybrid velocity distribution law, has seldom been documented in existing literature. Through analyzing the mathematical equation of the 1D flow model and exploring the relationship between the changes in cross-sectional area, the wall friction and the total flow driving potential, the inherent mechanism of variation in airflow velocity inside the flow channel is revealed. The high-speed airflow in the HPATB has a distinctive law of motion. It differs from the high-speed airflow in an axisymmetric Laval nozzle. Under the operating conditions discussed herein, the parallel gas film in the HPATB features a localized supersonic flow region enveloped by subsonic portions of the turbulent boundary layers from both upper and lower walls, which constitutes a viscous, rotational supersonic flow zone. The study has the potential to be useful in an industrial point of view since it contains information and analysis tools that can help the development of such devices.