Patent ID: 7048509

Claim:
An axial turbine comprising: a plurality of turbine stages disposed in an axial direction of a turbine shaft, each of the plurality of turbine stages comprising a turbine nozzle unit having nozzle blades, which are disposed in a row in a circumferential direction of an annular passage formed between an outer diaphragm ring and an inner diaphragm ring; and a turbine movable blade unit, which is disposed on a downstream side of the turbine nozzle unit and has movable blades implanted in a row on the turbine shaft in a circumferential direction thereof, wherein said nozzle blades have a profile in which a throat-pitch ratio “s/t” is maximized at a blade-central portion in height, wherein “s” being a shortest distance between a rear edge of a nozzle blade and a back side of another nozzle blade that is adjacent to said nozzle blade, and “t” being a pitch of the nozzle blades disposed in the row, minimized in a position between the blade-central portion in height and a blade-root portion and increased from a minimized value to said blade-root portion.