A bump type gas foil bearing was designed to meet the requirements of reliability and stability of high speed turbomachinery employed in engineering and an experimental investigation into the bump type gas foil bearing was carried out on a gas bearing high speed turbo-expander rotor test rig. The bump type gas foil bearing mainly consists of compliant top plate foil and bottom bump foil layers. In the experiment

the turbo-expander rotor was driven by compressed air with the pressure of 0.1-1.15 MPa and a volume flow rate of up to 600 m

3

/h(under standard conditions)from a 75 kW Atlas scroll compressor

. Two bump type gas foil bearings having the foil 0.05 mm and 0.07 mm in thickness were applied in an industrial 150 m

3

/h(under standard conditions)oxygen high speed turbo-expander in which the diameter of the rotor is 25 mm. The vibration characteristics and the stability were examined. The results show that stiffness was one of the most important factors in bearing performance. The good stiffness characteristic of the 0.05 mm foil promoted effectively the vibration performance of the bearing

and the maximum rotational speed reached 93 366 r/min. In comparison

the larger stiffness of 0.07 mm foil caused the instable rotation of the rotor at 93 161 r/min. When the maximum rotating speed of the turboexpander rotor was 93 000 r/min

the present bump type gas foil bearing had good stiffness and damping performance. In addition

the maximum vibration amplitudes were smaller than 20 μm

thus effectively inhibiting the rotor whir in the high speed turbo-expander.