Low speed rotor shaft for a small twin spool gas turbine engine

Abstract

An inner rotor shaft for use in a small twin spool gas turbine engine, the inner rotor shaft having a hollow middle section formed of a smaller diameter hollow section on a compressor end and a larger diameter hollow section on the turbine end of the shaft. Solid shaft end extend from the hollow section to form a forward solid shaft end to secure the fan rotor disk and an aft solid shaft end to secure the turbine rotor disk. A parabolic shaped transition section joins the forward shaft end to the smaller diameter hollow section, and a conical shaped transition section joins the aft shaft end to the larger diameter hollow section. A conical shaped transition piece joins the two hollow sections together to form an inner rotor shaft that can fit within a minimal space between the compressor rotor disk and the annular combustor assembly of the engine. The conical shaped transition section on the turbine end is so shaped in order to fit within a space formed inside the high pressure turbine rotor disk of the engine in order to minimize the axial spacing between the bearings that support the inner rotor shaft and raise the critical speed of the shaft to a safe level above the operating speed of the engine in order to make such a small twin spool gas turbine engine possible.