Discharge coefficient influence on the performance of aerostatic journal bearings

Aerostatic journal bearings need externally pressurized air. The discharge coefficient is usually assumed constant for sonic and subsonic flow conditions. However, some authors found that it is variable as a function of the pressure ratio, orifice throat discharge and supply pressures. The present study is a theoretical investigation of the discharge coefficient influence on the performance of aerostatic journal bearings. The Reynolds equation for compressible fluids is solved by the finite element method with triangular linear elements. For 0.5 eccentricity ratio, the bearing load carrying capacity difference is 0.5%, although the bearing total mass flow rate difference is 7.4%.