Gas turbine and outer shroud
A gas turbine includes a turbine blade, a turbine vane, a ring segment circumferentially surrounding the turbine blade, an outer shroud circumferentially surrounding the turbine vane, and a combustion gas flow-path provided in the ring segment and the outer shroud. The outer shroud is positioned on an upstream side of the ring segment in a gas flow direction of the combustion gas. Seal gas, of which temperature is lower than that of the combustion gas, is fed between the ring segment- and the outer shroud into the combustion gas flow-path. The outer shroud has a guide surface that is provided on an inner circumference thereof on a downstream side of the gas flow direction. The guide surface is formed such that a flow passage area of the combustion gas flow-path is gradually increased.
1. A gas turbine comprising:
a plurality of turbine blades mounted to a rotatable turbine shaft;
a plurality of turbine vanes secured so as to be axially opposite with respect to the turbine blades;
a plurality of ring segments circumferentially surrounding the turbine blades, respectively;
a plurality of outer shrouds circumferentially surrounding the turbine vanes, respectively, the outer shrouds being provided so as to be axially opposite with respect to the ring segments; and
a combustion gas flow-path provided in the ring segments and the outer shrouds, for passing combustion gas, wherein
a first outer shroud of the plurality of outer shrouds is positioned on an upstream side of a first ring segment of the plurality of ring segments in a gas flow direction of the combustion gas,
seal gas having a temperature lower than a temperature of the combustion gas is fed between the first ring segment and the first outer shroud into the combustion gas flow-path,
an inner diameter of the first ring segment is larger than that of the first outer shroud,
an outer diameter of a turbine blade surrounded by the first ring segment is larger than that of a turbine vane surrounded by the first outer shroud,
the first outer shroud has a guide surface that is provided on an inner circumference thereof on a downstream side of the gas flow direction, and the guide surface guides the combustion gas passing therein toward an inner circumferential surface of the first ring segment,
the guide surface changes a part of the combustion gas flowing toward the first ring segment, and
the guide surface is formed such that a flow passage area of the combustion gas flow-path is gradually increased,
the gas turbine has a plurality of areas including:
a first area being an area on an inner circumferential surface of the first outer shroud on a downstream side of the first turbine vane;
a second area being an area on an inner circumferential surface of the first ring segment on an upstream side of the first turbine blade;
a third area being an area on an inner circumferential surface of the first ring segment where the first turbine blade is located; and
a fourth area being an area on an inner circumferential surface of the first ring segment on a downstream side of the first turbine blade,
the guide surface is provided in the first area,
an intersection point between a tangent of the guide surface and the inner circumferential surface of the first ring segment is positioned on the second area.
2. The gas turbine according to claim 1 , wherein
a downstream end portion of the guide surface is positioned radially outwardly with respect to an inner circumferential surface of the first outer shroud on an upstream side of the guide surface.
3. The gas turbine according to claim 1 , wherein an upstream end portion of the inner circumferential surface of the first ring segment is positioned radially outwardly with respect to a tangent on the downstream end portion of the guide surface.
4. The gas turbine according to claim 1 , wherein the guide surface is formed by notching the inner circumference of the first outer shroud on the downstream side.
5. The gas turbine according to claim 1 , wherein the guide surface is formed at a projecting portion provided by projecting with respect to the inner circumference of the first outer shroud on the downstream side.
6. The gas turbine according to claim 1 , wherein the guide surface is formed at a curved surface.
7. The gas turbine according to claim 1 , wherein an angle of a tangent on a downstream end portion of the guide surface with respect to an axial direction of the turbine shaft is ranged from 10° or larger to 30° or smaller.
8. The gas turbine according to claim 1 , wherein the guide surface does not include a convex surface.
9. A plurality of outer shrouds for circumferentially surrounding a plurality of turbine vanes, the outer shrouds being provided so as to be axially opposite with respect to a plurality of ring segments and the turbine vanes being secured so as to be opposite with respect to a plurality of turbine blades in an axial direction of a rotatable turbine shaft, the outer shrouds comprising:
a combustion gas flow-path provided in the ring segments and the outer shrouds, for passing combustion gas, wherein
a first outer shroud of the plurality of outer shrouds is positioned on an upstream side of a first ring segment of the plurality of ring segments in a gas flow direction of the combustion gas,
an inner diameter of the first ring segment is larger than that of the first outer shroud,
an outer diameter of a turbine blade surrounded by the first ring segment is larger than that of a turbine vane surrounded by the first outer shroud,
seal gas having a temperature lower than a temperature of the combustion gas is fed between the first ring segment and the first outer shroud into the combustion gas flow-path,
the first outer shroud of the plurality of outer shrouds has a guide surface that is provided on an inner circumference thereof on a downstream side of the gas flow direction, and the guide surface guides the combustion gas passing therein toward an inner circumferential surface of the first ring segment,
the guide surface changes a part of the combustion gas flowing toward the first ring segment, and
the guide surface is formed such that a flow passage area of the combustion gas flow-path is gradually increased,
among a first area being an area on an inner circumferential surface of the first outer shroud on a downstream side of the first turbine vane, a second area being an area on an inner circumferential surface of the first ring segment on an upstream side of the first turbine blade, a third area being an area on an inner circumferential surface of the first ring segment where the first turbine blade is located and a fourth area being an area on an inner circumferential surface of the first ring segment on a downstream side of the first turbine blade the guide surface is provided in the first area,
an intersection point between a tangent of the guide surface and the inner circumferential surface of the first ring segment is positioned on the second area.
10. The plurality of outer shrouds according to claim 9 , further comprising:
an inner circumferential surface provided upstream of the guide surface, wherein a downstream end portion of the guide surface is positioned radially outwardly with respect to the inner circumferential surface.
11. The plurality of outer shrouds according to claim 9 , wherein a tangent on a downstream end portion of the guide surface is positioned radially inwardly an upstream end portion of an inner circumferential surface of the first ring segment.
12. The plurality of outer shrouds according to claim 9 , wherein the guide surface is formed by notching the inner circumference of the first outer shroud on the downstream side.
13. The plurality of outer shrouds according to claim 9 , wherein the guide surface is formed at a projecting portion provided by projecting with respect to the inner circumference of the first outer shroud on the downstream side.
14. The plurality of outer shrouds according to claim 9 , wherein the guide surface is formed at a curved surface.
15. The plurality of outer shrouds according to claim 9 , wherein an angle of a tangent on a downstream end portion of the guide surface with respect to an axial direction of the turbine shaft is ranged from 10° or larger to 30° or smaller.