Patent ID: 7089728

Claim:
A microturbine engine comprising: a recuperator having a hot gas flow path and a cool gas flow path; a compressor providing a flow of compressed gas to the cool gas flow path of the recuperator, the compressed gas being heated within the recuperator; a source of fuel providing a flow of fuel; a combustor receiving the heated flow of compressed gas from the recuperator and the flow of fuel from the source of fuel, and combusting a mixture of compressed gas and fuel to produce a flow of hot gas; a radial flow turbine receiving the flow of hot gas from the combustor and discharging a flow of exhaust gas; a power transfer assembly including a turbine wheel constructed of a nickel alloy, a gear shaft constructed of a low-carbon carburized gear material and having a pinion gear integrally formed therein, and a transition portion between and welded to each of the turbine wheel and gear shaft, the turbine wheel being within the radial flow turbine and rotating in response to the flow of hot gas through the turbine; a bull gear in meshing engagement with the pinion gear and rotating in response to rotation of the pinion gear at a speed lower than the rotational speed of the power transfer assembly; and an electric generator and generating electricity in response to rotation of the bull gear.