Effects of bearing clearance and supporting stiffness on performances of rotor-bearing system with multi-decked protuberant gas foil journal bearing

Abstract

The supporting stiffness and coulomb damping in a bearing play significant roles in the smooth operation of rotor-bearing system. The performance of multi-decked protuberant gas foil journal bearing is evaluated experimentally in a high-speed turboexpander. The effect of radial clearance on the bearing performance is analyzed based on the relationship between rotor speed and supply pressure in the speed-up and speed-down processes. The maximal speed of the 25 mm diameter rotor reached as high as 100 kr/min, and subsynchronous vibrations are suppressed in the tests. For the bearings with 0.05 mm protuberant foils, there will be thermal runaway problem with −20 µm clearance, while unstable operation appears with 80 µm clearance. For the bearing with 0.07 mm protuberant foil, the vibration amplitude is constrained within smaller amplitude due to stiffer supporting structure. The test results indicate that the bearing can operate stably under different gas film thickness and supporting stiffness, and that this kind of foil bearing can be applied in high-speed turbomachinery due to its stability and adaptability.