Auxiliary power unit for use in an aircraft

Abstract

Inefficiencies in the operation of auxiliary power units producing electric and hydraulic power along with bleed air resulting from independence in the demand for power may be minimized in a system including at least one bleed air consuming system (84, 86), an electrical generator (92), a hydraulic pump (90), and a turbine wheel (10, 20) for driving the generator (92) and the pump (90). Also included is a combustor (32) for receiving fuel and compressed air and producing gases of combustion to drive the turbine wheel (10, 20). A rotary compressor (10, 14) is coupled to the turbine wheel to be driven thereby. The compressor (10, 14) is a radial discharge compressor with an impeller having blades (14) extending from an inlet end (40) to a discharge end (42) and a shroud (18) to the blades (14). Two axially spaced annular ports (44, 46; 44, 50) are adjacent the discharge end (42). The one of the ports (44, 46) nearer the shroud ( 18) is connected to the bleed air consuming system (84, 86) with the other of the ports (44, 50) being connected to the combustor (32) to provide compressed air thereto. Variable inlet guide vanes (76) are adjacent the inlet ends (40) and extend only partially across the inlet (74) thereto so that varying the position of the vanes (76) will vary the volume of air discharged into only one of the ports (44, 46; 44, 50).