Effects of humid air on aerodynamic journal bearings

The development of aerodynamic bearings applications where ambient conditions cannot be controlled (e.g., for automotive fuel cell compressor) raises the question of the effects of condensation in the humid air on performance. A modified Reynolds equation is obtained in relation to humid air thermodynamic equations, accounting for the variation of compressibility and viscosity in the gas mixture. The load capacity and stability of plain and herringbone-grooved journal bearings is computed on a wide range of operating and ambient conditions. In general, performance metrics show an independence on humid-air effects at moderated temperature, although the stability of the grooved journal bearing exhibits strong variations in particular conditions. In consequence, a safety margin of 25% is suggested for the critical mass.