Patent ID: 8714951

Claim:
A method of manufacturing a high expansion ratio energy transfer device, the method comprising the steps of: (a) providing a housing comprising: (1) a central portion having a bore formed therein; and (2) an end plate forming an arcuate inlet passage, the inlet passage comprising a radial height and a circumferential extent; (b) providing an outer rotor rotatable in the central portion bore, the outer rotor comprising a female gear profile formed in a radial portion defining a plurality of roots; (c) providing an inner rotor with a male gear profile defining a plurality of lobes in operative engagement with the outer rotor; and (d) forming a duct by maintaining a minimum radial distance between an outer rotor root and a corresponding inner rotor lobe, the duct comprising a radial height, a circumferential extent, and a depth to define a duct volume, wherein the duct radial height at a duct end face is substantially equivalent to the inlet passage radial height at a leading edge of the inlet passage.