KEYWORDS Gas Film Bearings, Air Bearings, Turbomachinery
EXPERIMENTAL ASSESSMENT OF DRAG AND ROTORDYNAMIC RESPONSE FOR A POROUS TYPE AIR BEARING
Gas film bearings are attractive means to support lightweight rotating equipment. In particular, tilting pad journal bearings permit operation with minute clearances and offer high stiffness for accurate positioning. The paper presents measurements to evaluate the performance of novel porous carbon-graphite tilting pad gas bearings for high speed applications. The bearing pads are flexibly supported and installed with an interference on their rotor. Upon supply of an external pressurized gas media enables friction free operation. Measurements of the rotational speed coast down response of rigid rotor (MR=0.86 kg) serve to identify the drag friction coefficient for operation with air supply pressures ranging from 5.2 bar to 7.9 bar and from a top speed of 40 krpm. As the supply pressure increases, the flow rate and film thickness increase while the drag friction coefficient decreases. The dynamic response of the rotor reveals mostly synchronous components due to rotor imbalance.