Abstract: An evaporatively cooled internal combustion engine includes a compressor, a combustion chamber and a turbine for transmitting work performed by the rapid expansion of combusted working fluid. The turbine includes an arrangement of stators and rotors. Each of the rotors defines an internal cavity which includes a vaporization section which corresponds roughly to the rotor blade and a condensing section which corresponds roughly to the rotor disc. A radial array of circumferentially disposed capture shelves is provided in the vaporization section for capturing cooling fluid contained within the internal cavity and flowing radially outwardly in a centrifugal field generated during rotation of the rotor. The capture shelves restrict the flow of the cooling fluid to distribute the fluid over the inner surface of the rotor in the vaporization section.