having vertical bearing supports 12 and 13 with bearing assemblies 14 and 15 mounted at the ends thereof an integral rotor subassembly 16 is provided with a tubular shaft 17 at one end and a solid cylindrical power transmitting shaft 18 at the other end journaled in the bearing assemblies 14 and 15 respectively the rotor subassembly 16 generally comprises a compressor 24 at one end and a turbine 25 at the other maintained in fixed spaced apart relationship by direct connection to the end of a tubular housing or hub 26 the compressor is formed of outer radial walls 27 and 28 connected together by means of a peripheral axial wall 29 to form a partially closed chamber the outer radial wall 28 is provided with an axial aperture and is affixed to one end of the tubular hub 26 the outer radial wall 27 is provided with a central aperture and is affixed at the inward edge to the tubular shaft 17 the compressor 24 is additionally provided with an inner radial wall 30 and a spiral partition web 31 disposed between and affixed at its edges by welding or other suitable means to the outer radial wall 27 and the inner radial wall 30 the structure cooperating to define a spiral chamber 32 the inner radial wall 30 has a central aperture to which is connected a tubular combustion housing 33 having a tapered end 34 the inner radial wall 30 cooperates with the outer radial.