Self-acting Air-lubricated Bearing without Oil Lubrication

One of the advanced technologies incorporated into a micro gas turbine (MGT) is the dynamic air-lubricated (no oil lubrication) bearing. We investigated the performance characteristics of a self-acting air-lubricated bearing in a 50-kWe MGT. From the results of our experiments, we were able to clarify the following. (1) The thrust load of 300 N incurred by a 50kWe MGT cannot be supported by the dynamic air pressure generated by a pocket-type bearing with a micro-meter size groove. (2) The target performance (a film thickness of at least 20 μm at a load of 300 N) can be achieved by introducing compressed air (air pressure of equal to or more than 120 kPa) into the rotor disc surface through a pocket-groove. (3) The performance characteristics of the selfacting air-lubricated bearing were improved when a new structure featuring a rear-mounted thrust bearing with a sheet-spring was adopted.