An axial turbine includes a plurality of stages, each of the plurality of stages having stationary blades adjacent to each other along the turbine circumferential direction and corresponding moving blades adjacent to each other along the circumferential direction, each of the moving blade being located downstream of a corresponding one of the stationary blades along a flow direction of a working fluid, so as to be opposed to the corresponding stationary blade. In this axial turbine, each of the stationary blades is formed so that the intersection line between the outer periphery of the stationary blade constituting a stage having moving blades longer than moving blades in a preceding stage and a plane containing the central axis of the turbine, has a flow path constant diameter portion that includes at least an outlet outer periphery of the stationary blade and that is parallel to the central axis of the turbine.
1. An axial turbine comprising:
a plurality of stages, each of the plurality of stages including stationary blades adjacent to each other along the turbine circumferential direction and corresponding moving blades adjacent to each other along the circumferential direction, each of the moving blades being located downstream of a corresponding one of the stationary blades along a flow direction of a working fluid, so as to be opposed to the corresponding stationary blade,
wherein each of the stationary blades is formed so that the intersection line between the outer periphery of the stationary blade constituting a stage having moving blades longer than moving blades in a preceding stage and a plane containing the central axis of the turbine, has a flow path constant diameter portion that includes at least an outlet portion of the stationary blade and that is parallel to the central axis of the turbine,
wherein a height of the flow path constant diameter portion in the turbine radial direction substantially equals a height in the turbine radial direction, of a flow path effective range outer peripheral portion of the moving blade in the stage, and
wherein the stationary blade is formed so that the intersection line between the outer periphery thereof and a plane containing the central axis of the turbine has a flow path enlarged diameter portion that inclines to the outer peripheral side in the turbine radial direction, toward the downstream side along the flow direction of the working fluid, and that is located upstream of the flow path constant diameter portion.
2. The axial turbine according to claim 1 wherein, when the moving blade has a connection cover for connecting it with another moving blade adjacent thereto along the circumferential direction of the axial turbine, the flow path effective range outer peripheral portion of the moving blade is located between a height position of the inner peripheral surface of the connection cover, and a position located further toward the inner peripheral side in the turbine radial direction than the height position by the height of an rounded portion at the joint between the connection cover and the moving blade.
3. The axial turbine according to claim 1 , wherein, when the tip of the moving blade is a free end, the flow path effective range outer peripheral portion of the moving blade is the tip of the moving blade.
4. The axial turbine according to claim 1 , wherein the stationary blade is formed so that the value obtained by dividing a minimum gap between stationary blades adjacent to each other along the circumferential direction of the axial turbine by a distance in the circumferential direction between the stationary blades, becomes smaller on the outer peripheral side of the stationary blade than the intermediate portion of the stationary blade in the length direction thereof.
5. The axial turbine according to claim 1 , wherein the stationary blade is formed so as to incline to the rotational direction of the moving blade toward the peripheral side in the turbine radial direction, and so as to be bowed or bent in a manner such that the intermediate portion of the stationary blade in the length direction thereof protrudes in the rotational direction of the moving blade.
6. An axial turbine comprising:
a plurality of stages, each of the plurality of stages including stationary blades adjacent to each other along the turbine circumferential direction and corresponding moving blades adjacent to each other along the circumferential direction, each of the moving blade being located downstream of a corresponding one of the stationary blades along a flow direction of a working fluid, so as to be opposed to the corresponding stationary blade,
wherein each of the stationary blades is formed so that the intersection line between the outer periphery of the stationary blade constituting a stage having moving blades longer than moving blades in a preceding stage and a plane containing the central axis of the turbine, has a flow path constant diameter portion that includes at least an outlet portion of the stationary blade and that is parallel to the central axis of the turbine, and
wherein the stationary blade is formed so that the intersection line between the outer periphery thereof and a plane containing the central axis of the turbine has a flow path reduced diameter portion that passes to an outer side in the turbine radial direction further than the flow path constant diameter portion, and that contracts the flow path toward the flow path constant diameter portion.