Study on double-layer protuberant gas foil journal bearings with different foil layers arrangement

Abstract

With the excellent damping performance, gas foil bearing (GFB) is becoming the promising hydrodynamic lubrication structure for high speed turbomachinery. To improve the performance of the conventional GFBs, a new double-layer gas foil bearing (PGFB) with double-layer protuberant strip as elastic support is developed. A 2D numerical model based on Reynolds equation and Kirchhoff equation is established to determine the gas film thickness, gas film pressure and foil deflection. Static performance and dynamic performance of three PGFBs with different elastic foil layers arrangement are presented and compared qualitative dues to the difficulties in measuring the practice eccentricity and load capacity with high speed rotor-bearing system. By applying in a turboexpander with θ25mm rotor diameter, the three PGFBs are tested. Because the three PGFBs share the same rotor structure and the same air supply pressure, the rotor drag torque and the bearing static load are almost the same in the tests. The experimental results show that all the PGFBs run well in turboexpander. Rotating speed, temperature and enthalpy differences and rotor synchronous vibration under the same turboexpander air supply pressure are compared. The numerical model predicted well the qualitative difference of the loading performance of the three PGFBs.