Experimental investigation on stability of multi-decked protuberant foil gas journal bearing

A kind of new hydrodynamic gas foil bearing with multi-decked elastic supporting structure was proposed for the stable operation of the high speed rotor supported by gas foil bearing. In this kind of foil bearing, double or multi layers of protuberant foils with projection array are adopted as the supporting structure, and the bearing stiffness and damping characteristics adjustments can be realized through changing the pitch of spherical crown in the peripheral and axial directions as well as the arrangement of the supporting foils. The experimental investigation on the high speed rotor supported by the new foil bearing was conducted on a high speed turboexpander with the rotor diameter of 25 mm. The relations between rotor speed and supply pressure, and the feature of the rotor speed-up and speed-down processes using three typical arrangement modes were analyzed. The test results show that the stiffness and damping characteristics can be adjusted and improved effectively by adopting different foil arrangement modes for the rotor supported by elastic foil bearing, and the unstable wobble can be suppressed. In addition, stiffness and damping effect in conventional gas journal bearing may be improved by introducing multiple stiffness and damping characteristics generated in the multi-decked structure of elastic foil bearing, leading to a better stability and reliability of the present hydrodynamic gas foil bearing.