Abstract: Fuel cell or other combustor apparatus which utilizes a compressor as a source of compressed air. The exhaust is routed to a expander turbine which partially powers the compressor and is on a common shaft therewith. The shaft is borne by hydrodynamic foil bearings. In order to maintain a high compressor speed, compressed air in excess of combustor requirements is bled from the air inlet to the combustor and is preferably passed to the expander turbine.