High efficiency split flow turbine for compressible fluids

A multistage axial flow turbine for compressible fluids in which the fluid leaving the antepenultimate stage is separated into coaxial radially inner and radially outer flows which are subject to substantially the same decrease in enthalpy between the outlet from the antepenultimate stage and the outlet of the turbine, the inner flow passing through the penultimate and final stages with respective decreases in enthalpy of h.sub.1 and h.sub.2 and the outer flow passing through only the final stage, the rotor blades of the last stage including a wall serving as a barrier between the inner flow and the outer flow, the rotor blades of the last stage having a discontinuity in variation in profile from root to tip with the profile of the blade radially outward of the wall between the two flows being more highly curved than that radially inward of said wall, and the degree of reaction of said rotor blades at this barrier when operating under optimum conditions having a value x.sub.2 on the outer flow side which is substantially equal to x.sub.1 .multidot.h.sub.2 /(h.sub.2 +h.sub.1) where x.sub.1 is the value of the degree of reaction on the inner flow side such that the pressure on the radially outward side of the wall is maintained substantially equal to the pressure on the radially inward side of the wall across said last stage rotor blades.