TECHNICAL FIELD
[0001] The present disclosure relates to a steam turbine exhaust chamber and a steam
turbine.
The present application claims priority based on Japanese Patent Application No. 2020-
137367 filed on August 17, 2020, with the Japanese Patent Office, the contents of which are
10 incorporated herein by reference.
BACKGROUND ART
[0002] In an exhaust flow passage of a steam turbine exhaust chamber, when a steam flow
flows backward along a bearing cone in a diffuser flow passage formed between the bearing
15 cone and a flow guide, the effective flow-passage area of the diffuser flow passage (the flowpassage area of steam that flows toward the outlet without flowing back toward the rotor in
the diffuser flow passage) decreases and the pressure loss increases, which may lead to
performance deterioration of the steam turbine exhaust chamber.
[0003] Patent Document 1 discloses providing a structure (guide plate) that protrudes
20 inward in the radial direction from the wall surface of the steam turbine exhaust chamber to
suppress a reverse flow of the steam flow along the bearing cone.
Citation List
Patent Literature
25 [0004]
Patent Document 1: US6419448B
SUMMARY
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Problems to be Solved
[0005] As a result of extensive research conducted by the present inventors, it was found
that a vertical vortex falling from the upper section of the steam turbine exhaust chamber may
cause generation of a reverse flow in the steam flow along the bearing cone inside the diffuser
5 flow passage between the bearing cone and the flow guide. Thus, it is considered critical to
suppress intrusion of the vertex vortex into the diffuser flow passage in order to improve the
performance of the exhaust chamber.
[0006] In the structure for suppressing a reverse flow described in Patent Document 1, it
is difficult to suppress intrusion of the vertical vortex into the diffuser flow passage effectively,
10 and thus the effect to suppress an increase in the pressure loss in the diffuser flow passage is
limited.
[0007] In view of the above, an object of the present disclosure is to provide a steam
turbine exhaust chamber and a steam turbine capable of suppressing an increase in the
pressure loss in the diffuser flow passage between the bearing cone and the flow guide.
15
Solution to the Problems
[0008] To achieve the above object, according to at least one embodiment of the present
disclosure, a steam turbine exhaust chamber for guiding steam after passing through a rotor
blade of a final stage of a steam turbine to outside of the steam turbine, includes: a casing; a
20 bearing cone disposed along a circumferential direction of a rotor of the steam turbine inside
the casing; and a flow guide disposed along the circumferential direction at a radially outer
side of the bearing cone inside the casing, the flow guide forming a diffuser flow passage
between the flow guide and the bearing cone. An inner surface of the casing includes an
inner circumferential surface extending along an axial direction of the rotor at a radially outer
25 side of the flow guide and a side wall surface connecting the inner circumferential surface and
the bearing cone, a first protruding portion is formed on the side wall surface along the
circumferential direction above a horizontal plane including a rotational axis of the rotor, the
first protruding portion protruding outward in a radial direction of the rotor, and the first
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protruding portion is positioned at an outer side, in the radial direction, of a downstream end
of an inner circumferential surface of the flow guide in at least a partial range in the
circumferential direction.
5 Advantageous Effects
[0009] According to the present disclosure, provided is a steam turbine exhaust chamber
and a steam turbine capable of suppressing an increase in the pressure loss in the diffuser flow
passage between the bearing cone and the flow guide.
10 BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a schematic diagram schematically showing a cross section of a steam
turbine 2 according to an embodiment, taken along the axial direction.
FIG. 2 is a diagram for describing the advantageous effect or the like of a protruding
portion 26.
15 FIG. 3 is a diagram showing an example of the relationship between the position θ in the
circumferential direction and the length L of the protruding portion 26 (an example of the
circumferential-direction distribution of the length L of the protruding portion 26).
FIG. 4 is a diagram for describing the definition of the position θ in the circumferential
direction.
20 FIG. 5 is a diagram for describing the distance R, the distance ‘r’ and the flow passage
width W.
FIG. 6 is a diagram showing an example of the relationship between the position θ in the
circumferential direction and the distance ‘r’ between the root end 26a of the protruding
portion 26 and the rotational axis C (an example of the circumferential-direction distribution
25 of the distance ‘r’).
FIG. 7 is a diagram schematically showing an example of the arrangement of the
plurality of protruding portions 26 (26A to 26D).
FIG. 8 is a diagram schematically showing an example of the arrangement of the
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plurality of protruding portions 26 (26E and 26F).
FIG. 9 is a schematic diagram showing a cross section of an exhaust chamber 8 of a
steam turbine 2 according to another embodiment, taken along the axial direction.
FIG. 10 is a diagram for describing the advantageous effect of the configuration
5 depicted in FIG. 9.
FIG. 11 is a schematic diagram schematically showing a cross section of a steam turbine
2 according to another embodiment, taken along the axial direction.

1. A steam turbine exhaust chamber for guiding steam after passing through a rotor blade
of a final stage of a steam turbine to outside of the steam turbine, the steam turbine exhaust
5 chamber comprising:
a casing;
a bearing cone disposed along a circumferential direction of a rotor of the steam turbine
inside the casing; and
a flow guide disposed along the circumferential direction at a radially outer side of the
10 bearing cone inside the casing, the flow guide forming a diffuser flow passage between the
flow guide and the bearing cone,
wherein an inner surface of the casing includes an inner circumferential surface
extending along an axial direction of the rotor at a radially outer side of the flow guide and a
side wall surface connecting the inner circumferential surface and the bearing cone,
15 wherein a first protruding portion is formed on the side wall surface along the
circumferential direction above a horizontal plane including a rotational axis of the rotor, the
first protruding portion protruding outward in a radial direction of the rotor, and
wherein the first protruding portion is positioned at an outer side, in the radial direction,
of a downstream end of an inner circumferential surface of the flow guide in at least a partial
20 range in the circumferential direction.
2. The steam turbine exhaust chamber according to claim 1,
wherein a tip end portion of the first protruding portion is bended toward the side wall
surface in the axial direction.
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3. The steam turbine exhaust chamber according to claim 1,
wherein a tip end portion of the first protruding portion is bended toward the flow guide
in the axial direction.
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4. The steam turbine exhaust chamber according to any one of claims 1 to 3,
wherein a length from a root end to a tip end of the first protruding portion varies
depending on a position in the circumferential direction.
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5. The steam turbine exhaust chamber according to claim 4,
wherein the length of the first protruding portion decreases with distance toward an
upper side along the circumferential direction in at least a partial range in the circumferential
direction.
10
6. The steam turbine exhaust chamber according to any one of claims 1 to 5,
wherein a distance between a root end of the first protruding portion and the rotational
axis varies depending on a position in the circumferential direction.
15 7. The steam turbine exhaust chamber according to claim 6,
wherein the distance between the root end of the first protruding portion and the
rotational axis decreases with distance toward an upper side along the circumferential
direction, in at least a partial range in the circumferential direction.
20 8. The steam turbine exhaust chamber according to any one of claims 1 to 7,
wherein, when, regarding a position in the circumferential direction, one of directions
indicated by a horizontal line orthogonal to the rotational axis is defined as zero degrees and a
position vertically above the rotational axis is defined as 90 degrees,
the first protruding portion is disposed only in a partial range between zero and 180
25 degrees in the circumferential direction.
9. The steam turbine exhaust chamber according to claim 8,
wherein at least a part of the first protruding portion is disposed inside a range between
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30 and 150 degrees in the circumferential direction.
10. The steam turbine exhaust chamber according to any one of claims 1 to 9,
wherein the side wall surface has a plurality of protruding portions protruding outward
5 in the radial direction at a position at an outer side of a downstream end of an inner
circumferential surface of the flow guide in a radial direction of the rotor, above a horizontal
plane including the rotational axis of the rotor,
wherein the plurality of protruding portions are arranged at intervals in the
circumferential direction, and
10 wherein the plurality of protruding portions include the first protruding portion.
11. The steam turbine exhaust chamber according to claim 10,
wherein the plurality of protruding portions include a second protruding portion
disposed at a position higher than the first protruding portion, and
15 wherein a length from a root end to a tip end of the second protruding portion is longer
than a length from a root end to a tip end of the first protruding portion.
12. The steam turbine exhaust chamber according to claim 10,
wherein a recess portion is formed on an upper end of the first protruding portion.
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13. The steam turbine exhaust chamber according to claim 12,
wherein the plurality of protruding portions include a second protruding portion
disposed opposite to the first protruding portion across a vertical plane including the
rotational axis, and
25 wherein a recess portion is formed on an upper end of the second protruding portion.
14. The steam turbine exhaust chamber according to any one of claims 1 to 13,
wherein a cavity is formed on an outer circumferential surface of the bearing cone.
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15. The steam turbine exhaust chamber according to claim 14,
wherein a width of an opening end of the cavity in the axial direction is smaller than a
width of a bottom surface of the cavity in the axial direction.
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16. The steam turbine exhaust chamber according to claim 14 or 15,
wherein a position closest to the rotor blade at a bottom surface of the cavity is
positioned at an inner side, in the radial direction, of a position farthest from the rotor blade at
the bottom surface.