Patent ID: 6368055
Filing Date: 2002-04-09
Classification: F01D,Y10S

Abstract:
An axial-flow turbine comprising:an outer diaphragm ring and an inner diaphragm ring forming together an annular fluid passage; and a plurality of nozzle blades disposed in the annular passage, each of the nozzle blades being formed into a warped shape such that a central portion in a lengthwise direction of the nozzle blade maximally projects in a downstream direction, wherein said annular fluid passage has a stepped portion at an inner surface of the outer diaphragm ring and an outer surface of the inner diaphragm ring, the stepped portion having a curvature surface so that the height of the fluid passage is reduced in a downstream direction thereof, wherein said stepped portion has a height in a radial direction of the fluid passage, the height being described by the relationships: 0&lE;h1/L1<0.05 0.12/L1<0.2 where L1 is the height of a leading edge of the nozzle blades, h1 is the height of the stepped portion of the inner diaphragm ring and h2 is the height of the stepped portion of the outer diaphragm ring, wherein each of the nozzle blades has an axial distance from the leading edge of the diaphragm to the trailing edge of the nozzle blades, the axial distance being described by the relationships: Ztwhere Zt is the axial distance at the outermost end of the nozzle blades, Zr is the axial distance at the innermost end of the same and Zp is the axial distance at the central portion of the same, and wherein said fluid passage is structured such that the inner surface of the outer diaphragm ring and the outer surface of the inner diaphragm ring are outwards inclined in the downstream direction.