Steam turbine and exhaust chamber therefor

Abstract

An exhaust chamber is equipped with: a diffuser that forms a diffuser space; an exhaust casing that forms an exhaust space communicating with the diffuser space; and an auxiliary exhaust frame that forms an auxiliary exhaust space having an annular shape centered around an axis, on the inside of the diffuser in the radial direction. The auxiliary exhaust frame has an opening that opens toward the outside in the radial direction from the interior of the auxiliary exhaust space, and that enables the exhaust space and the auxiliary exhaust space to communicate with each other.

Claims

1. An exhaust chamber of a steam turbine which guides steam flowing out from a last stage rotor blade row of a steam turbine rotor rotating around an axis to an outside, comprising: a diffuser into which the steam flowing out from the last stage rotor blade row flows, having an annular shape with respect to the axis, and forming a diffuser space that gradually spreads to a radial outer side with respect to the axis toward an axial downstream side; an exhaust casing having an exhaust port open toward the radial outer side, communicating with the diffuser space, spreading in a circumferential direction with respect to the axis, and forming an exhaust space that guides the steam flowing from the diffuser space to the exhaust port; and an auxiliary exhaust frame including a partial region on a radial inner side from the diffuser with respect to the axis, and forming an exhaust auxiliary space having an annular shape around the axis, wherein the diffuser has an outer diffuser having an annular cross section perpendicular to the axis, gradually spreading to the radial outer side toward the axial downstream side, and defining an edge on the radial outer side of the diffuser space, and an inner diffuser having an annular cross section perpendicular to the axis, gradually spreading to the radial outer side toward the axial downstream side, and defining an edge on the radial inner side of the diffuser space with respect to the axis, the exhaust casing has an exhaust port only on an exhaust side, out of a non-exhaust side and the exhaust side which are sides to opposite to each other with reference to the axis in an orthogonal direction orthogonal to the axis, the auxiliary exhaust frame has an opening open toward the radial outer side from an inside of the exhaust auxiliary space, in at least a portion on the non-exhaust side and the exhaust side with reference to the axis, and through which the exhaust space and the exhaust auxiliary space communicate with each other, and inside a circumferential region where the opening is present in the circumferential direction, an edge on the axial downstream side of the inner diffuser defines an edge on the axial upstream side opposite to the axial downstream side in the opening.

2. The exhaust chamber of a steam turbine according to claim 1, wherein the auxiliary exhaust frame has a frame downstream-side end plate that defines an edge on the axial downstream side in the exhaust auxiliary space, the exhaust casing has a casing downstream-side end plate that defines an edge on the axial downstream side in the exhaust space, the frame downstream-side end plate spreads in a direction including a radial component with respect to the axis and in the circumferential direction, and has an annular shape around the axis, the casing downstream-side end plate spreads in the direction including the radial component with respect to the axis and in the circumferential direction, and having an edge on the radial inner side having an annular shape around the axis, an edge on the radial outer side of the frame downstream-side end plate defines an edge on the axial downstream side of the opening, and the edge on the radial inner side of the casing downstream-side end plate and the edge on the radial outer side of the frame downstream-side end plate are connected to each other.

3. The exhaust chamber of a steam turbine according to claim 2, wherein an inner surface facing the exhaust auxiliary space in the frame downstream-side end plate and an inner surface facing the exhaust space in the casing downstream-side end plate are smoothly continuous with each other in a portion where the frame downstream-side end plate and the casing downstream-side end plate are connected to each other.

4. The exhaust chamber of a steam turbine according to claim 3, further comprising: a second exhaust auxiliary space communicating with at least a portion on the non-exhaust side in the exhaust space, and forming a second auxiliary exhaust frame different from a first exhaust auxiliary space which is the exhaust auxiliary space, in addition to a first auxiliary exhaust frame which is the auxiliary exhaust frame, wherein the exhaust casing has a casing outer peripheral plate that defines an edge on the radial outer side in the exhaust space, the second auxiliary exhaust frame has a second frame inner peripheral plate spreading in the circumferential direction and extending in a direction including an axial direction in which the axis extends from the casing downstream-side end plate, at a position on the non-exhaust side with reference to the axis and on the radial inner side from the casing outer peripheral plate, the second frame inner peripheral plate defines an edge on the radial inner side of the second exhaust auxiliary space, and an edge on an axial upstream side opposite to the axial downstream side in the second frame inner peripheral plate defines an edge on the radial inner side of a second opening through which the exhaust space and the second exhaust auxiliary space communicate with each other.

5. The exhaust chamber of a steam turbine according to claim 4, wherein the second frame inner peripheral plate gradually spreads to the radial outer side toward the axial upstream side.

6. The exhaust chamber of a steam turbine according to claim 4, wherein the second frame inner peripheral plate extends toward the axial downstream side from an end on the radial outer side of the casing downstream-side end plate, and the second exhaust auxiliary space is formed on the axial downstream side from the casing downstream-side end plate.

7. The exhaust chamber of a steam turbine according to claim 4, wherein the second frame inner peripheral plate extends toward the axial upstream side from a position on the radial inner side from an end on the radial outer side in the casing downstream-side end plate, and the second exhaust auxiliary space is formed on the axial upstream side from the casing downstream-side end plate.

8. The exhaust chamber of a steam turbine according to claim 1, wherein the auxiliary exhaust frame has a frame upstream-side end plate that defines an edge on the axial upstream side in the exhaust auxiliary space, the frame upstream-side end plate has an annular shape around the axis, and an edge on the radial outer side of the frame upstream-side end plate is connected to a portion that defines an edge on the axial upstream side of the opening, which is an edge on the axial downstream side of the inner diffuser.

9. The exhaust chamber of a steam turbine according to claim 8, wherein an inner surface facing the exhaust auxiliary space in the frame upstream-side end plate is a surface gradually facing the axial upstream side toward the radial inner side.

10. The exhaust chamber of a steam turbine according to claim 1, wherein the auxiliary exhaust frame has a frame upstream-side end plate that defines an edge on the axial upstream side in the exhaust auxiliary space, the frame upstream-side end plate has an annular shape around the axis, and an edge on the radial outer side of the frame upstream-side end plate is connected to the inner diffuser at a position on the axial upstream side from an edge on the axial upstream side of the opening.

11. A steam turbine comprising: the exhaust chamber of a steam turbine according to claim 1; the steam turbine rotor; a cylinder casing that covers an outer peripheral side of the steam turbine rotor; and a stator blade row disposed on an inner peripheral side of the cylinder casing, and in which an end on the radial outer side is attached to the cylinder casing, wherein the outer diffuser is connected to the cylinder casing.

12. An exhaust chamber of a steam turbine which guides steam flowing out from a last stage rotor blade row of a steam turbine rotor rotating around an axis to an outside, comprising: a diffuser into which the steam flowing out from the last stage rotor blade row flows, having an annular shape with respect to the axis, and forming a diffuser space that gradually spreads to a radial outer side with respect to the axis toward an axial downstream side; an exhaust casing having an exhaust port open toward the radial outer side, communicating with the diffuser space, spreading in a circumferential direction with respect to the axis, and forming an exhaust space that guides the steam flowing from the diffuser space to the exhaust port; and an auxiliary exhaust frame including a partial region on a radial inner side from the diffuser with respect to the axis, and forming an exhaust auxiliary space having an annular shape around the axis, wherein the diffuser has an outer diffuser having an annular cross section perpendicular to the axis, gradually spreading to the radial outer side toward the axial downstream side, and defining an edge on the radial outer side of the diffuser space, and an inner diffuser having an annular cross section perpendicular to the axis, gradually spreading to the radial outer side toward the axial downstream side, and defining an edge on the radial inner side of the diffuser space with respect to the axis, the exhaust casing has an exhaust port only on an exhaust side, out of a non-exhaust side and the exhaust side which are sides to opposite to each other with reference to the axis in an orthogonal direction orthogonal to the axis, the auxiliary exhaust frame has an opening open toward the radial outer side from an inside of the exhaust auxiliary space, in at least a portion on the non-exhaust side and the exhaust side with reference to the axis, and through which the exhaust space and the exhaust auxiliary space communicate with each other, and the opening has an annular shape with reference to the axis.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an overall sectional view of a steam turbine according to a first embodiment of the present invention.

(2) FIG. 2 is a sectional view of a main part of the steam turbine according to the first embodiment of the present invention.

(3) FIG. 3 is a perspective view of an inner diffuser and an auxiliary exhaust frame according to the first embodiment of the present invention.

(4) FIG. 4 is a view for describing a steam flow inside an exhaust chamber according to the first embodiment of the present invention.

(5) FIG. 5 is a view for describing a steam flow inside an exhaust chamber according to a comparative example.

(6) FIG. 6 is a sectional view of a main part of a steam turbine according to a second embodiment of the present invention.

(7) FIG. 7 is a perspective view of an inner diffuser and an auxiliary exhaust frame according to the second embodiment of the present invention.

(8) FIG. 8 is a view for describing a steam flow inside an exhaust chamber according to the second embodiment of the present invention.

(9) FIG. 9 is a sectional view of a main part of a steam turbine according to a third embodiment of the present invention.

(10) FIG. 10 is a perspective view of an inner diffuser and an auxiliary exhaust frame according to the third embodiment of the present invention.

(11) FIG. 11 is a view for describing a steam flow inside an exhaust chamber according to the third embodiment of the present invention.

(12) FIG. 12 is a sectional view of a main part of a steam turbine according to a fourth embodiment of the present invention.

(13) FIG. 13 is a view for describing a steam flow inside an exhaust chamber according to the fourth embodiment of the present invention.

(14) FIG. 14 is a sectional view of a main part of a steam turbine according to a fifth embodiment of the present invention.

(15) FIG. 15 is a view for describing a steam flow inside an exhaust chamber according to the fifth embodiment of the present invention.

(16) FIG. 16 is a sectional view of a main part of a steam turbine according to a sixth embodiment of the present invention.

(17) FIG. 17 is a view for describing a steam flow inside an exhaust chamber according to the sixth embodiment of the present invention.

(18) FIG. 18 is a perspective view of an inner diffuser and an auxiliary exhaust frame in a modification example of the first embodiment according to the present invention.

DESCRIPTION OF EMBODIMENTS

(19) Hereinafter, various embodiments of a steam turbine including an exhaust chamber according to the present invention will be described in detail with reference to the drawings.

First Embodiment

(20) A first embodiment of the steam turbine according to the present invention will be described with reference to FIGS. 1 to 5.

(21) The steam turbine of the first embodiment is a two-way exhaust type steam turbine. Therefore, as illustrated in FIG. 1, the steam turbine includes a first steam turbine unit 10a and a second steam turbine unit 10b. Both the first steam turbine unit 10a and the second steam turbine unit 10b have a turbine rotor 11 rotating around an axis Ar, a casing 20 that covers the turbine rotor 11, a plurality of stator blade rows 17 fixed to the casing 20, and a steam inlet duct 19. Hereinafter, a circumferential direction around the axis Ar will be simply referred to as a circumferential direction Dc, and a radial direction with respect to the axis Ar will be referred to as a radial direction Dr. Furthermore, a side closer to the axis Ar in the radial direction Dr will be referred to as a radial inner side Dri, and a side opposite thereto will be referred to as a radial outer side Dro.

(22) The first steam turbine unit 10a and the second steam turbine unit 10b share a steam inlet duct 19. Components of the first steam turbine unit 10a excluding the steam inlet duct 19 are disposed on one side in an axial direction Da with reference to the steam inlet duct 19. In addition, components of second steam turbine unit 10b excluding the steam inlet duct 19 are disposed on the other side in the axial direction Da with reference to the steam inlet duct 19. In each of the steam turbine units 10a and 10b, a side of the steam inlet duct 19 is the axial direction Da will be referred to as an axial upstream side Dau, and a side opposite thereto will be referred to as an axial downstream side Dad.

(23) A configuration of the first steam turbine unit 10a and a configuration of the second steam turbine unit 10b are basically the same as each other. Therefore, hereinafter, the first steam turbine unit 10a will be mainly described.

(24) The turbine rotor 11 has a rotor shaft 12 extending in the axial direction Da around the axis Ar, and a plurality of rotor blade rows 13 attached to the rotor shaft 12. The turbine rotor 11 is supported to be rotatable around the axis Ar by a bearing 18. The plurality of rotor blade rows 13 are aligned in the axial direction Da. Each of the rotor blade rows 13 is configured to include a plurality of rotor blades aligned in the circumferential direction Dc. The turbine rotor 11 of the first steam turbine unit 10a and the turbine rotor 11 of the second steam turbine unit 10b are located on the same axis Ar, are connected to each other, and integrally rotate around the axis Ar.

(25) The casing 20 has a cylinder casing 21 and an exhaust chamber 25. The cylinder casing 21 forms a substantially conical space around the axis Ar, and covers an outer periphery of the turbine rotor 11. The plurality of rotor blade rows 13 of the turbine rotor 11 are disposed in the conical space. The plurality of stator blade rows 17 are aligned along the axial direction Da, and are disposed inside the conical space. Each of the plurality of stator blade rows 17 is disposed on the axial upstream side Dau of any one rotor blade row 13 of the plurality of rotor blade rows 13. The plurality of stator blade rows 17 are fixed to the cylinder casing 21.

(26) As illustrated in FIG. 2, the exhaust chamber 25 has a diffuser 26, an exhaust casing 30, and an auxiliary exhaust frame 40.

(27) The diffuser 26 has an annular shape with respect to the axis Ar, and forms a diffuser space 26s gradually facing the radial outer side Dro toward the axial downstream side Dad. The steam flowing out from the last stage rotor blade row 13a of the turbine rotor 11 flows into the diffuser space 26s. The last stage rotor blade row 13a is the rotor blade row 13 disposed on the most axial downstream side Dad, out of the plurality of rotor blade rows 13. The diffuser 26 has an outer diffuser (or steam guide, flow guide) 27 that defines an edge on the radial outer side Dro of the diffuser space 26s, and an inner diffuser (or bearing cone) 29 that defines an edge on the radial inner side Dri of the diffuser space 26s. The outer diffuser 27 has an annular cross section perpendicular to the axis Ar, and gradually spreads to the radial outer side Dro toward the axial downstream side Dad. The inner diffuser 29 also has an annular cross section perpendicular to the axis Ar, and gradually spreads toward the radial outer side Dro toward the axial downstream side Dad. The outer diffuser 27 is connected to the cylinder casing 21.

(28) The exhaust casing 30 has an exhaust port 31. The exhaust port 31 is open to the radial outer side Dro from the inside in a vertically downward direction. A condenser Co that returns steam to water is connected to the exhaust port 31. Therefore, the steam turbine of the present embodiment is a downward exhaust type condensing steam turbine. Here, a non-exhaust side Dpu and an exhaust side Dpe form mutually opposite sides with reference to the axis Ar in an orthogonal direction orthogonal to the axis Ar. The steam turbine of the present embodiment is the downward exhaust type condensing steam turbine as described above. Accordingly, the exhaust side Dpe is a vertically lower side, and the non-exhaust side Dpu is a vertical upper side.

(29) The exhaust casing 30 forms an exhaust space 30s communicating with the diffuser 26. The exhaust space 30s has an outer periphery of the diffuser 26 which spreads in the circumferential direction Dc with respect to the axis Ar, and guides the steam flowing from the diffuser space 26s to the exhaust port 31. The exhaust casing 30 has a casing downstream-side end plate 32, a casing upstream-side end plate 34, and a casing outer peripheral plate 36.

(30) The casing downstream-side end plate 32 defines an edge on the axial downstream side Dad of the exhaust space 30s. The casing downstream-side end plate 32 spreads in a direction including a component in the radial direction Dr and in the circumferential direction Dc, and is substantially perpendicular to the axis Ar. A portion above the axis Ar in the casing downstream-side end plate 32 has a substantially semicircular shape. On the other hand, a portion below the axis Ar in the casing downstream-side end plate 32 has a substantially rectangular shape. However, the casing downstream-side end plate 32 has a circular opening formed around the axis Ar. An edge on the circular opening forms an edge on the radial inner side Dri of the casing downstream-side end plate 32. A lower edge on the casing downstream-side end plate 32 forms a portion of an edge on the exhaust port 31.

(31) The casing outer peripheral plate 36 defines an edge on the radial outer side Dro of the exhaust space 30s. The casing outer peripheral plate 36 is connected to an edge on the radial outer side Dro of the casing downstream-side end plate 32, spreads in the axial direction Da, and spreads in the circumferential direction Dc around the axis Ar. The casing outer peripheral plate 36 has a semi-circular shape (semi-cylindrical shape) whose upper side forms a semi-cylinder. An edge on the axial downstream side Dad of the casing outer peripheral plate 36 is connected to the casing downstream-side end plate 32. In addition, a lower edge on the casing outer peripheral plate 36 forms a portion of an edge on the exhaust port 31.

(32) The casing upstream-side end plate 34 defines an edge on the axial upstream side Dau of the exhaust space 30s. The casing upstream-side end plate 34 is disposed on the axial upstream side Dau from the diffuser 26. The casing upstream-side end plate 34 spreads to the radial outer side Dro from an outer peripheral surface 21o of the cylinder casing 21. The casing upstream-side end plate 34 is substantially perpendicular to the axis Ar. Therefore, the casing upstream-side end plate 34 faces the casing downstream-side end plate 32 at an interval therebetween in the axial direction Da. A lower edge on the casing upstream-side end plate 34 forms a portion of the edge on the exhaust port 31. In an edge on the radial outer side Dro of the casing upstream-side end plate 34, a portion excluding a portion forming the edge on the exhaust port 31 is connected to the casing outer peripheral plate 36.

(33) As illustrated in FIG. 1, the exhaust casing 30 of the first steam turbine unit 10a and the exhaust casing 30 of the second steam turbine unit 10b are connected to and integrated with each other.

(34) As illustrated in FIGS. 2 and 3, the auxiliary exhaust frame 40 includes a partial region on the radial inner side Dri from the diffuser 26, and forms an exhaust auxiliary space 40s having an annular shape around the axis Ar.

(35) The auxiliary exhaust frame 40 has an opening 41 open toward the radial outer side Dro from the inside of the exhaust auxiliary space 40s, and through which the exhaust space 30s and the exhaust auxiliary space 40s communicate with each other. The opening 41 is has an annular shape around the axis Ar. An edge on the axial upstream side Dau of the opening 41 is defined by an edge on the axial downstream side Dad of the inner diffuser 29. Hereinafter, in the opening 41, a portion facing vertically upward from the inside of the exhaust auxiliary space 40s will be referred to as a non-exhaust side opening portion 41u, and a portion facing vertically downward from the inside of the exhaust auxiliary space 40s will be referred to as an exhaust side opening portion 41e.

(36) The auxiliary exhaust frame 40 has a frame downstream-side end plate 42, a frame upstream-side end plate 43, and a frame inner peripheral plate 44.

(37) The frame downstream-side end plate 42 defines an edge on the axial downstream side Dad in the exhaust auxiliary space 40s. The frame downstream-side end plate 42 is an annular plate spreading in the direction including the component in the radial direction Dr and in the circumferential direction Dc. The edge on the radial outer side Dro of the frame downstream-side end plate 42 is connected to the edge on the radial inner side Dri of the casing downstream-side end plate 32. An inner surface facing the exhaust auxiliary space 40s in the frame downstream-side end plate 42 and an inner surface facing the exhaust space 30s in the casing downstream-side end plate 32 are smoothly continuous with a portion where the frame downstream-side end plate 42 and the casing downstream-side end plate 32 are connected to each other. In the present embodiment, both the inner surface facing the exhaust auxiliary space 40s in the frame downstream-side end plate 42 and the inner surface facing the exhaust space 30s in the casing downstream-side end plate 32 are surfaces spreading in the radial direction Dr and the circumferential direction Dc, and are connected to be flush with each other. Therefore, the inner surface facing the exhaust auxiliary space 40s in the frame downstream-side end plate 42 and the inner surface facing the exhaust space 30s in the casing downstream-side end plate 32 are located one virtual plane spreading in the radial direction Dr and the circumferential direction Dc.

(38) The edge on the axial downstream side Dad of the opening 41 is defined by the edge on the radial outer side Dro of the frame downstream-side end plate 42.

(39) The frame upstream-side end plate 43 defines the edge on the axial upstream side Dau in the exhaust auxiliary space 40s. The frame upstream-side end plate 43 is an annular plate spreading in the radial direction Dr and the circumferential direction Dc. The edge on the radial outer side Dro of the frame upstream-side end plate 43 is connected to the edge on the axial downstream side Dad of the inner diffuser 29, that is, a portion of the inner diffuser 29 which defines the edge on the axial upstream side Dau of the opening 41.

(40) The frame inner peripheral plate 44 defines the edge on the radial inner side Dri in the exhaust auxiliary space 40s. The frame inner peripheral plate 44 connects the edge on the radial inner side Dri of the frame upstream-side end plate 43 and the edge on the radial inner side Dri of the frame downstream-side end plate 42. The frame inner peripheral plate 44 has an upstream-side inner peripheral plate 45 and a downstream-side inner peripheral plate 46. The upstream-side inner peripheral plate 45 has an annular shape around the axis Ar, and extends in the axial direction Da. The edge on the axial upstream side Dau of the upstream-side inner peripheral plate 45 is connected to the edge on the radial inner side Dri of the frame upstream-side end plate 43. The downstream-side inner peripheral plate 46 has an annular shape around the axis Ar, and gradually extends to the radial outer side Dro toward the axial downstream side Dad. The edge on the axial upstream side Dau of the downstream-side inner peripheral plate 46 is connected to the edge on the axial downstream side Dad of the upstream-side inner peripheral plate 45. The edge on the axial downstream side Dad of the downstream-side inner peripheral plate 46 is connected to the edge on the radial inner side Dri of the frame downstream-side end plate 42.

(41) Next, before an advantageous effect of the exhaust chamber 25 is described, an exhaust chamber of a comparative example will be described with reference to FIG. 5.

(42) The exhaust chamber 25x of the comparative example has a diffuser 26x and an exhaust casing 30x, as in the exhaust chamber 25 of the present embodiment. However, the exhaust chamber 25x of the comparative example does not have the auxiliary exhaust frame 40 of the exhaust chamber 25 in the present embodiment. The diffuser 26x of the comparative example has the outer diffuser 27 and an inner diffuser 29x, as in the diffuser 26 of the present embodiment. However, since the exhaust chamber 25x of the comparative example does not have the auxiliary exhaust frame 40, the openings 41u and 41e of the present embodiment are not formed in the inner diffuser 29x of the comparative example. As in the exhaust casing 30 of the present embodiment, the exhaust casing 30x of the comparative example has a casing downstream-side end plate 32x, the casing upstream-side end plate 34, and the casing outer peripheral plate 36. An edge on the axial downstream side Dad of the inner diffuser 29x of the comparative example is connected to the casing downstream-side end plate 32x.

(43) As a result of analyzing a steam flow inside the exhaust chamber 25x of the comparative example, it was found that the steam flows inside the exhaust chamber 25x as follows.

(44) The steam flowing out from the last stage rotor blade row 13a of the turbine rotor to the axial downstream side Dad flows into the diffuser space 26s. While the steam flows toward the axial downstream side Dad inside the diffuser space 26s, the steam flows toward the radial outer side Dro, and flows into the exhaust space 30s.

(45) Inside the exhaust space 30s and in a region on the non-exhaust side Dpu (hereinafter, referred to as a non-exhaust side exhaust space 30su) with reference to the axis Ar, the steam flowing into the exhaust space 30s along the inner peripheral surface of the outer diffuser 27 flows in an extending direction of a tangent line in an end on the radial outer side Dro of the inner peripheral surface of the outer diffuser 27, that is, in a tangential direction. When the steam collides with the casing outer peripheral plate 36, a portion of the steam flows to the axial upstream side Dau along the casing outer peripheral plate 36, and a portion of the steam flows to the axial downstream side Dad along the casing outer peripheral plate 36.

(46) The steam flowing to the axial upstream side Dau along the casing outer peripheral plate 36 gradually changes a flow direction to the circumferential direction Dc, and flows to the exhaust side Dpe along the casing outer peripheral plate 36. Then, the steam is exhausted from the exhaust port 31. On the other hand, the steam flowing to the axial downstream side Dad along the casing outer peripheral plate 36 flows to a base portion side of the last stage rotor blade row 13a along the casing downstream-side end plate 32x and the inner diffuser 29x. That is, the steam flowing to the axial downstream side Dad along the casing outer peripheral plate 36 flows to the radial inner side Dri along the casing downstream-side end plate 32x. Furthermore, while the steam flows toward the radial inner side Dri along the inner peripheral surface of the inner diffuser 29, the steam flows to the axial upstream side Dau. Therefore, steam flows back in a region along the casing downstream-side end plate 32x inside the exhaust space 30s and in a region along the inner diffuser 29x inside the diffuser space 26s. The steam flowing back inside the diffuser space 26s flows close to the outer diffuser 27 side, and flows again to the radial outer side Dro. Therefore, a circulation region Zx in which the steam circulates is formed inside the exhaust main flow path S and inside a region on the non-exhaust side Dpu (hereinafter, referred to as a non-exhaust side main flow path Su) with reference to the axis Ar. The exhaust main flow path S is a space in which the diffuser space 26s and the exhaust space 30s are combined with each other.

(47) On the other hand, inside the exhaust space 30s and inside a region on the exhaust side Dpe with reference to the axis Ar (hereinafter, referred to as an exhaust side exhaust space 30se), a flow direction of the steam flowing into the exhaust space 30s along the inner peripheral surface of the outer diffuser 27 is a direction including a component in the tangential direction in which the tangential line extends in the end on the radial outer side Dro of the inner peripheral surface and a directional component on a side closer to the exhaust port 31 in the circumferential direction Dc with respect to the axis Ar. The reason is as follows. The steam containing a large amount of the component in the circumferential direction Dc flows into a region on the exhaust side Dpe from a region on the non-exhaust side Dpu inside the exhaust chamber 25x. In addition, the above-described tangential direction includes a directional component facing the radial outer side Dro. Inside the exhaust side exhaust space 30se, the exhaust port 31 is formed on the radial outer side Dro. Therefore, inside the exhaust main flow path S and in a region on the exhaust side Dpe with reference to the axis Ar (hereinafter, referred to as an exhaust side main flow path Se), the backflow of the steam is not substantially generated as in the region on the non-exhaust side Dpu.

(48) As described above, in the comparative example, a portion of a cross-sectional area of the flow path inside the exhaust main flow path S cannot be effectively used to exhaust the steam. Consequently, the pressure loss of the steam increases.

(49) In a case of a low load operation having a low flow rate of the steam flowing into the steam turbine, or in a case of low vacuum inside the condenser Co, with regard to a directional component in the flow direction of the steam flowing out from the last stage rotor blade row 13a of the turbine rotor, a component in the circumferential direction Dc around the axis Ar, that is, a turning component is relatively larger than a directional component toward the axial downstream side Dad. Therefore, in this case, the steam flowing out from the last stage rotor blade row 13a of the turbine rotor has a strong tendency to be deflected to the radial outer side Dro inside the diffuser space 26s. Therefore, in the steam flowing into the diffuser space 26s, the flow rate of the steam on the outer diffuser 27 side is higher than the flow rate of the steam on the inner diffuser 29x side. That is, in the case of the low load operation or in the case of low vacuum inside the condenser Co, the flow of the steam flowing along the inner peripheral surface of the outer diffuser 27 increases. Therefore, in the comparative example, in the case of the low load operation or in the case of low vacuum inside the condenser Co, the amount of steam flowing back inside the exhaust chamber 25x further increases, and the pressure loss of the steam increases.

(50) Next, an advantageous effect of the exhaust chamber 25 in the present embodiment described above will be described with reference to FIG. 4.

(51) As a result of analyzing the flow of the steam inside the exhaust chamber 25 in the present embodiment, it was found that the steam flows inside the exhaust chamber 25 as follows.

(52) In the present embodiment, the steam flowing out from the last stage rotor blade row 13a of the turbine rotor to the axial downstream side Dad also flows into the diffuser space 26s, as in the comparative example. While the steam flows toward the axial downstream side Dad inside the diffuser space 26s, the steam flows toward the radial outer side Dro, and flows into the exhaust space 30s.

(53) As in the comparative example, inside the non-exhaust side exhaust space 30su, the steam flowing into the non-exhaust side exhaust space 30su along the inner peripheral surface of the outer diffuser 27 flows in the extending direction of the tangent line in the end of the radial outer side Dr on the inner peripheral surface of the outer diffuser 27, that is, in the tangential direction. When the steam collides with the casing outer peripheral plate 36, a portion of the steam flows to the axial upstream side Dau along the casing outer peripheral plate 36, and a portion of the steam flows to the axial downstream side Dad along the casing outer peripheral plate 36.

(54) The steam flowing to the axial upstream side Dau along the casing outer peripheral plate 36 gradually changes a flow direction to the circumferential direction Dc, and flows to the exhaust side Dpe along the casing outer peripheral plate 36. Then, the steam is exhausted from the exhaust port 31. On the other hand, the steam flowing to the axial downstream side Dad along the casing outer peripheral plate 36 flows to the radial inner side Dri along the casing downstream-side end plate 32.

(55) Incidentally, the pressure inside the exhaust auxiliary space 40s is higher than the pressure inside the exhaust side main flow path Se. Therefore, the fluid inside the exhaust auxiliary space 40s flows into the exhaust side main flow path Se via the exhaust side opening portion 41e of the auxiliary exhaust frame 40. In addition, the pressure inside the non-exhaust side main flow path Su is higher than the pressure inside the exhaust auxiliary space 40s. Therefore, a portion of the steam inside the non-exhaust side main flow path Su enters the inside of the exhaust auxiliary space 40s via the non-exhaust side opening portion 41u of the auxiliary exhaust frame 40.

(56) Therefore, in the present embodiment, as described above, even when the steam flowing to the radial inner side Dri is generated along the casing downstream-side end plate 32 inside the non-exhaust side main flow path Su, that is, even when the backflow of the steam is generated, the steam enters the inside of the exhaust auxiliary space 40s via the non-exhaust side opening portion 41u of the auxiliary exhaust frame 40. Then, as described above, the steam flows into the exhaust side main flow path Se via the exhaust side opening portion 41e of the auxiliary exhaust frame 40, and is exhausted from the exhaust port 31.

(57) In the present embodiment, the non-exhaust side opening portion 41u of the auxiliary exhaust frame 40 is open toward the radial outer side Dro from the inside of the exhaust auxiliary space 40s. Therefore, in the present embodiment, the steam flowing to the radial inner side Dri along the casing downstream-side end plate 32 inside the non-exhaust side exhaust space 30su is likely to flow into the exhaust auxiliary space 40s via the non-exhaust side opening portion 41u of the auxiliary exhaust frame 40. In addition, in the present embodiment, an edge on the radial outer side Dro of the frame downstream-side end plate 42 in the auxiliary exhaust frame 40 is connected to an edge on the radial inner side Dri of the casing downstream-side end plate 32 in the exhaust casing 30. Moreover, in the present embodiment, an inner surface facing the exhaust auxiliary space 40s in the frame downstream-side end plate 42 and an inner surface facing the exhaust space 30s in the casing downstream-side end plate 32 are smoothly continuous with a portion where the frame downstream-side end plate 42 and the casing downstream-side end plate 32 are connected to each other. Therefore, in the present embodiment, resistance in a process in which the steam flowing to the radial inner side Dri along the casing downstream-side end plate 32 inside the non-exhaust side exhaust space 30su enters the inside of the exhaust auxiliary space 40s can be minimized. In the present embodiment, from a viewpoint described above, the steam flowing to the radial inner side Dri along the casing downstream-side end plate 32 inside the non-exhaust side main flow path Su can easily flow into the exhaust auxiliary space 40s via the non-exhaust side opening portion 41u of the auxiliary exhaust frame 40.

(58) In the present embodiment, the backflow of the steam is not substantially generated inside the exhaust side main flow path Se, as in the comparative example.

(59) As described above, in the present embodiment, a portion of the steam flowing back inside the exhaust main flow path S can flow into the exhaust auxiliary space 40s. Therefore, in the present embodiment, the circulation region Z in which the steam flows back inside the exhaust main flow path S decreases than that in the comparative example, and the circulation region Z is limited within a region on to the radial outer side Dro inside the exhaust main flow path S. Therefore, in the present embodiment, the pressure loss of the steam decreases than that of the comparative example, and the pressure recovery amount of the steam inside the exhaust main flow path S can be improved.

Second Embodiment

(60) A second embodiment of the steam turbine according to the present invention will be described with reference to FIGS. 6 to 8.

(61) The steam turbine of the present embodiment is different from the steam turbine of the first embodiment only in a configuration of an exhaust chamber. Therefore, hereinafter, the exhaust chamber according to the present embodiment will be mainly described.

(62) As illustrated in FIGS. 6 and 7, an exhaust chamber 25a in the present embodiment has the diffuser 26, the exhaust casing 30, and an auxiliary exhaust frame 40a, as in the exhaust chamber 25 in the first embodiment. The diffuser 26 in the present embodiment is basically the same as the diffuser 26 in the first embodiment. In addition, the exhaust casing 30 in the present embodiment is basically the same as the exhaust casing 30 in the first embodiment. However, the auxiliary exhaust frame 40a in the present embodiment is different from the auxiliary exhaust frame 40 in the first embodiment.

(63) As in the auxiliary exhaust frame 40 in the first embodiment, the auxiliary exhaust frame 40a in the present embodiment includes a partial region on the radial inner side Dri from the diffuser 26, and forms the exhaust auxiliary space 40s having an annular shape around the axis Ar.

(64) As in the auxiliary exhaust frame 40 in the first embodiment, the auxiliary exhaust frame 40a has the opening 41 open toward the radial outer side Dro from the inside of the exhaust auxiliary space 40s, and through which the exhaust space 30s and the exhaust auxiliary space 40s communicate with each other. The opening 41 in the present embodiment has the annular shape around the axis Ar. An edge on the axial upstream side Dau of the opening 41 is defined by an edge on the axial downstream side Dad of the inner diffuser 29. In the opening 41, the portion facing vertically upward from the inside of the exhaust auxiliary space 40s is the non-exhaust side opening portion 41u, and the portion facing vertically downward from the inside of the exhaust auxiliary space 40s is the exhaust side opening portion 41e.

(65) As in the auxiliary exhaust frame 40 in the first embodiment, the auxiliary exhaust frame 40a in the present embodiment has the frame downstream-side end plate 42, the frame upstream-side end plate 43a, and the frame inner peripheral plate 44.

(66) The frame downstream-side end plate 42 defines an edge on the axial downstream side Dad in the exhaust auxiliary space 40s. The frame downstream-side end plate 42 is the same as the frame downstream-side end plate 42 in the first embodiment, and is an annular plate spreading in the direction including the component in the radial direction Dr and in the circumferential direction Dc. The edge on the radial outer side Dro of the frame downstream-side end plate 42 is connected to the edge on the radial inner side Dri of the casing downstream-side end plate 32.

(67) The frame upstream-side end plate 43a defines an edge on the axial upstream side Dau in the exhaust auxiliary space 40s. As in the frame upstream-side end plate 43 in the first embodiment, the frame upstream-side end plate 43a is an annular plate spreading in the radial direction Dr and the circumferential direction Dc. However, unlike the frame upstream-side end plate 43 in the first embodiment, the frame upstream-side end plate 43a gradually spreads to the axial upstream side Dau toward the radial inner side Dri. Therefore, the inner surface facing the exhaust auxiliary space 40s in the frame upstream-side end plate 43a is a surface gradually facing the axial upstream side Dau toward the radial inner side Dri. The edge on the radial outer side Dro of the frame upstream-side end plate 43a is connected to the edge on the axial downstream side Dad of the inner diffuser 29, that is, the portion in the inner diffuser 29 which defines the edge on the axial upstream side Dau of the opening 41.

(68) The frame inner peripheral plate 44 defines the edge on the radial inner side Dri in the exhaust auxiliary space 40s. The frame inner peripheral plate 44 connects the edge on the radial inner side Dri of the frame upstream-side end plate 43a and the edge on the radial inner side Dri of the frame downstream-side end plate 42 to each other. As described above, the frame upstream-side end plate 43a gradually spreads to the axial upstream side Dau toward the radial inner side Dri. Therefore, the edge on the radial inner side Dri of the frame upstream-side end plate 43a is located on the axial upstream side Dau from the edge on the radial outer side Dro of the frame upstream-side end plate 43a.

(69) As described above, the edge on the radial inner side Dri of the frame upstream-side end plate 43a in the present embodiment is located on the axial upstream side Dau from the edge on the radial outer side Dro of the frame upstream-side end plate 43a. Therefore, even when in the axial direction Da, the position of the edge on the axial upstream side Dau of the opening 41 in the present embodiment is the same as the position of the edge on the axial upstream side Dau of the opening 41 in the first embodiment, and even when in the axial direction Da, the position of the edge on the axial downstream side Dad of the opening 41 in the present embodiment is the same as the position of the edge on the axial downstream side Dad of the opening 41 in the first embodiment, a volume of the exhaust auxiliary space 40s in the present embodiment can be increased than a volume of the exhaust auxiliary space 40s in the first embodiment.

(70) Next, an advantageous effect of the exhaust chamber 25a in the present embodiment described above will be described with reference to FIG. 8.

(71) In the present embodiment, as in the comparative example and the first embodiment, the steam flowing out from the last stage rotor blade row 13a of the turbine rotor to the axial downstream side Dad flows into the diffuser space 26s. While the steam flows toward the axial downstream side Dad inside the diffuser space 26s, the steam flows toward the radial outer side Dro, and flows into the exhaust space 30s.

(72) As in the comparative example and the first embodiment, in the non-exhaust side exhaust space 30su, the steam flowing to the radial inner side Dri, that is, the backflow of the steam is generated along the casing downstream-side end plate 32. In the present embodiment as well, as in the first embodiment, the steam enters the exhaust auxiliary space 40s through the non-exhaust side opening portion 41u of the auxiliary exhaust frame 40a. Therefore, in the present embodiment, the circulation region Z in which the steam flows back inside the exhaust main flow path S also decreases than that in the comparative example, and the circulation region Z can be limited within a region on the radial outer side Dro inside the exhaust main flow path S. Therefore, in the present embodiment, the pressure loss of the steam decreases than that of the comparative example, and the pressure recovery amount of the steam inside the exhaust main flow path S can be improved.

(73) In addition, in the present embodiment, as described above, the volume of the exhaust auxiliary space 40s can be increased than the volume of the exhaust auxiliary space 40s in the first embodiment. Therefore, even when the flow rate of the steam flowing to the radial inner side Dri increases along the casing downstream-side end plate 32 inside the non-exhaust side exhaust space 30su, it is possible to cope with the increased flow rate. That is, in the present embodiment, even when the flow rate of the backflow of the steam increases, the steam can be introduced into the exhaust auxiliary space 40s.

(74) Incidentally, in the first embodiment, as illustrated in FIG. 4, with regard to the directional component in the flow direction of the steam flowing into the exhaust side main flow path Se from the inside of the exhaust auxiliary space 40s via the exhaust side opening portion 41e, the directional component on the radial outer side Dro is larger than the directional component in the axial direction Da. In addition, the component in the axial direction Da in the flow direction of the steam flowing inside the exhaust side exhaust main flow path Se is larger than the component in the axial direction Da in the flow direction of the steam flowing into the exhaust side main flow path Se from the inside of the exhaust auxiliary space 40s via the exhaust side opening portion 41e. Therefore, in the first embodiment, the flow of the steam flowing into the exhaust side main flow path Se from the inside of the exhaust auxiliary space 40s via the exhaust side opening portion 41e and the steam flowing inside the exhaust side main flow path Se are mixed with each other at a large angle. Therefore, in the first embodiment, a flow turbulence of the steam flowing inside the exhaust side main flow path Se increases, and the pressure loss of the steam is slightly increased.

(75) As described above, the frame upstream-side end plate 43a of the present embodiment gradually spreads to the axial upstream side Dau toward the radial inner side Dri. In other words, the frame upstream-side end plate 43a of the present embodiment gradually spreads to the axial downstream side Dad toward the radial outer side Dro. Therefore, in the present embodiment, the directional component on the radial outer side Dro in the flow direction of the steam flowing into the exhaust side main flow path Se from the inside of the exhaust auxiliary space 40s via the exhaust side opening portion 41e is smaller than the directional component on the radial outer side Dro in the flow direction of the steam in the first embodiment. Therefore, in the present embodiment, compared to the first embodiment, the flow turbulence of the steam flowing inside the exhaust side main flow path Se can be suppressed, and an increase in the pressure loss of the steam can be suppressed.

Third Embodiment

(76) A third embodiment of the steam turbine according to the present invention will be described with reference to FIGS. 9 to 11.

(77) The steam turbine in the present embodiment is different from the steam turbine in the first embodiment and the second embodiment only in a configuration of an exhaust chamber. Therefore, hereinafter, the exhaust chamber according to the present embodiment will be mainly described.

(78) As illustrated in FIGS. 9 and 10, an exhaust chamber 25b in the present embodiment also has the diffuser 26, the exhaust casing 30, and the auxiliary exhaust frame 40b, as in the exhaust chambers 25 and 25a in the first embodiment and the second embodiment. The diffuser 26 in the present embodiment is basically the same as the diffuser 26 in the first embodiment and the second embodiment. In addition, the exhaust casing 30 in the present embodiment is basically the same as the exhaust casing 30 in the first embodiment and the second embodiment. However, the auxiliary exhaust frame 40b in the present embodiment is different from the auxiliary exhaust frames 40 and 40a in the first embodiment and the second embodiment.

(79) As in the auxiliary exhaust frames 40 and 40a in the first embodiment and the second embodiment, the auxiliary exhaust frame 40b in the present embodiment also includes a partial region on the radial inner side Dri from the diffuser 26, and forms the exhaust auxiliary space 40s having an annular shape around the axis Ar.

(80) As in the auxiliary exhaust frame 40 in the first embodiment, the auxiliary exhaust frame 40b also has the opening 41 open toward the radial outer side Dro from the inside of the exhaust auxiliary space 40s, and through which the exhaust space 30s and the exhaust auxiliary space 40s communicate with each other. The opening 41 in the present embodiment has the annular shape around the axis Ar. An edge on the axial upstream side Dau of the opening 41 is defined by an edge on the axial downstream side Dad of the inner diffuser 29. In the opening 41, the portion facing vertically upward from the inside of the exhaust auxiliary space 40s is the non-exhaust side opening portion 41u, and the portion facing vertically downward from the inside of the exhaust auxiliary space 40s is the exhaust side opening portion 41e.

(81) As in the auxiliary exhaust frame 40 in the first embodiment and the second embodiment, the auxiliary exhaust frame 40b in the present embodiment has the frame downstream-side end plate 42, the frame upstream-side end plate 43b, and the frame inner peripheral plate 44.

(82) The frame downstream-side end plate 42 defines an edge on the axial downstream side Dad in the exhaust auxiliary space 40s. The frame downstream-side end plate 42 is the same as the frame downstream-side end plate 42 in the first embodiment and the second embodiment, and is an annular plate spreading in the direction including the component in the radial direction Dr and in the circumferential direction Dc. The edge on the radial outer side Dro of the frame downstream-side end plate 42 is connected to the edge on the radial inner side Dri of the casing downstream-side end plate 32.

(83) The frame upstream-side end plate 43b defines an edge on the axial upstream side Dau in the exhaust auxiliary space 40s. The frame upstream-side end plate 43b is the same as the frame upstream-side end plate 43 in the first embodiment, and is an annular plate spreading in the radial direction Dr and the circumferential direction Dc. However, unlike the frame upstream-side end plates 43 and 43a in the first embodiment and the second embodiment, the edge on the radial outer side Dro of the frame upstream-side end plate 43b is connected to the inner diffuser 29 at a position on the axial upstream side Dau from the edge on the axial upstream side Dau of the opening 41.

(84) As described above, the edge on the radial outer side Dro of the frame upstream-side end plate 43b in the present embodiment is connected to the inner diffuser 29 at the position on the axial upstream side Dau from the edge on the axial upstream side Dau of the opening 41. Therefore, even when in the axial direction Da, the position of the edge on the axial upstream side Dau of the opening 41 in the present embodiment is the same as the position of the edge on the axial upstream side Dau of the opening 41 in the first embodiment, and even when in the axial direction Da, the position of the edge on the axial downstream side Dad of the opening 41 in the present embodiment is the same as the position of the edge on the axial downstream side Dad of the opening 41 in the first embodiment, the volume of the exhaust auxiliary space 40s in the present embodiment can be increased than the volume of the exhaust auxiliary space 40s in the first embodiment and the second embodiment.

(85) Next, an advantageous effect of the exhaust chamber 25b in the present embodiment described above will be described with reference to FIG. 11.

(86) As in the comparative example, the first embodiment, and the second embodiment, in the present embodiment, the steam flowing out from the last stage rotor blade row 13a of the turbine rotor to the axial downstream side Dad also flows into the diffuser space 26s. While the steam flows toward the axial downstream side Dad inside the diffuser space 26s, the steam flows toward the radial outer side Dro, and flows into the exhaust space 30s.

(87) As in the comparative example and the first embodiment, in the non-exhaust side exhaust space 30su, the steam flowing to the radial inner side Dri, that is, the backflow of the steam is generated along the casing downstream-side end plate 32. As in the first embodiment and the second embodiment, in the present embodiment, the steam also enters the inside of the exhaust auxiliary space 40s via the non-exhaust side opening portion 41u of the auxiliary exhaust frame 40b. Therefore, in the present embodiment, the circulation region Z in which the steam flows back inside the exhaust main flow path S also decreases than that in the comparative example, and the circulation region Z can be limited within a region on the radial outer side Dro inside the exhaust main flow path S. Therefore, in the present embodiment, the pressure loss of the steam also decreases than that of the comparative example, and the pressure recovery amount of the steam inside the exhaust main flow path S can be improved.

(88) In addition, in the present embodiment, as described above, the volume of the exhaust auxiliary space 40s can be increased than the volume of the exhaust auxiliary space 40s in the first embodiment and the second embodiment. Therefore, even when the flow rate of the steam flowing to the radial inner side Dri increases along the casing downstream-side end plate 32 inside the non-exhaust side exhaust space 30su, it is possible to cope with the increased flow rate. That is, in the present embodiment, even when the flow rate of the backflow of the steam increases, the steam can be introduced into the exhaust auxiliary space 40s.

(89) As described above, the edge on the radial outer side Dro of the frame upstream-side end plate 43b of the present embodiment is connected to the inner diffuser 29 at the position on the axial upstream side Dau from the edge on the axial upstream side Dau of the opening portions 41u and 41e. Therefore, in the present embodiment, a portion of the steam inside the exhaust auxiliary space 40s on the exhaust side Dpe with reference to the axis Ar flows along the inner peripheral surface of the inner diffuser 29. The inner peripheral surface of the inner diffuser 29 gradually spreads to the axial downstream side Dad toward the radial outer side Dro. Accordingly, a portion of the steam inside the exhaust auxiliary space 40s gradually flows to the axial downstream side Dad toward the radial outer side Dro. Therefore, in the present embodiment, the directional component on the radial outer side Dro in the flow direction of the steam flowing into the exhaust side main flow path Se from the inside of the exhaust auxiliary space 40s via the exhaust side opening portion 41e is smaller than the directional component on the radial outer side Dro in the flow direction of the steam in the first embodiment. Therefore, in the present embodiment, as in the second embodiment, compared to the first embodiment, the flow turbulence of the steam flowing inside the exhaust side main flow path Se can be suppressed, and the pressure loss of the steam can decrease.

Fourth Embodiment

(90) A fourth embodiment of the steam turbine according to the present invention will be described with reference to FIGS. 12 and 13.

(91) The steam turbine in the present embodiment is a modification example of the steam turbine in the third embodiment.

(92) As illustrated in FIG. 12, as in the exhaust chamber 25b in the third embodiment, the exhaust chamber 25c in the present embodiment also has the diffuser 26, the exhaust casing 30, and the auxiliary exhaust frame 40b. The exhaust chamber 25c in the present embodiment further includes a second auxiliary exhaust frame 50c in addition to a first auxiliary exhaust frame 40b which is the auxiliary exhaust frame 40b in the third embodiment.

(93) The second auxiliary exhaust frame 50c communicates with at least a portion on the non-exhaust side Dpu in the exhaust space 30s, and forms a second exhaust auxiliary space 50s different from the first exhaust auxiliary space 40s which is the exhaust auxiliary space 40s described above. The second exhaust auxiliary space 50s is a space spreading in the circumferential direction Dc along the casing outer peripheral plate 36 on the axial downstream side Dad from the casing downstream-side end plate 32, at least in a region on the non-exhaust side Dpu with reference to the axis Ar.

(94) The second auxiliary exhaust frame 50c has a second frame outer peripheral plate 52, a second frame inner peripheral plate 53, and a second frame downstream-side end plate 54. The second frame outer peripheral plate 52 extends from the edge on the axial downstream side Dad of the casing outer peripheral plate 36 to the axial downstream side Dad and, spreads in the circumferential direction Dc, at least in a region on the non-exhaust side Dpu with reference to the axis Ar. The second frame inner peripheral plate 53 extends from the edge on the radial outer side Dro of the casing downstream-side end plate 32 to the axial downstream side Dad, and spreads in the circumferential direction Dc, at the position on the radial inner side Dri from the casing outer peripheral plate 36 and the second frame outer peripheral plate 52, at least in the region on the non-exhaust side Dpu with reference to the axis Ar. The second frame downstream-side end plate 54 is a plate spreading in the radial direction Dr and the circumferential direction Dc, at least in the region on the non-exhaust side Dpu with reference to the axis Ar. The edge on the radial outer side Dro on a second frame downstream-side end plate 54 is connected to the edge on the axial downstream side Dad of the second frame outer peripheral plate 52. In addition, the edge on the radial inner side Dri of the second frame downstream-side end plate 54 is connected to the edge on the axial downstream side Dad of the second frame inner peripheral plate 53.

(95) The edge on the axial upstream side Dau of the second frame outer peripheral plate 52 defines the edge on the radial outer side Dro of the second opening 51 serving as the opening through which the exhaust space 30s and the second exhaust auxiliary space 50s communicate with each other. In addition, the edge on the axial upstream side Dau of the second frame inner peripheral plate 53 defines the edge on the radial inner side Dri of the second opening 51.

(96) Next, an advantageous effect of the exhaust chamber 25c in the present embodiment described above will be described with reference to FIG. 13.

(97) The exhaust chamber 25c in the present embodiment has the first auxiliary exhaust frame 40b the same as the exhaust chamber 25b in the third embodiment. Accordingly, as in the third embodiment, a circulation region Zc inside a non-exhaust side exhaust main flow path Su can be reduced, compared to the comparative example, and the circulation region Zc can be limited within a region on the radial outer side Dro inside the exhaust main flow path S.

(98) In the present embodiment, the region on the radial outer side Dro inside the exhaust main flow path S communicates with the second exhaust auxiliary space 50s. Therefore, a portion of the steam inside the region on the radial outer side Dro inside the exhaust main flow path S flows into the second exhaust auxiliary space 50s. As a result, the circulation region Zc inside the exhaust main flow path S further decreases due to the presence of the second exhaust auxiliary space 50s. A portion of the steam flowing into the second exhaust auxiliary space 50s circulates inside the second exhaust auxiliary space 50s, and thereafter, immediately returns to the exhaust main flow path S. In addition, the remaining portion of the steam flowing into the second exhaust auxiliary space 50s returns to the inside of the exhaust main flow path S from an end in the circumferential direction Dc of the second exhaust auxiliary space 50s spreading in the circumferential direction Dc.

(99) As described above, in the present embodiment, the circulation region Zc in the exhaust main flow path S can be reduced, compared to the third embodiment.

Fifth Embodiment

(100) A fifth embodiment of the steam turbine according to the present invention will be described with reference to FIGS. 14 and 15.

(101) The steam turbine in the present embodiment is a modification example of the steam turbine in the third embodiment.

(102) As illustrated in FIG. 14, as in the exhaust chambers 25b and 25c in the third embodiment and the fourth embodiment, an exhaust chamber 25d in the present embodiment also has the diffuser 26, the exhaust casing 30, and the first auxiliary exhaust frame 40b. The exhaust chamber 25d in the present embodiment further includes a second auxiliary exhaust frame 50d, as in the exhaust chamber 25c in the fourth embodiment.

(103) As in the second auxiliary exhaust frame 50c in the fourth embodiment, the second auxiliary exhaust frame 50d communicates with at least a portion on the non-exhaust side Dpu in the exhaust space 30s, and forms a second exhaust auxiliary space 50s different from the first exhaust auxiliary space 40s. The second exhaust auxiliary space 50s is a space spreading in the circumferential direction Dc along the casing outer peripheral plate 36 on the axial downstream side Dad from the casing downstream-side end plate 32, at least in a region on the non-exhaust side Dpu with reference to the axis Ar.

(104) As in the second auxiliary exhaust frame 50c in the fourth embodiment, the second auxiliary exhaust frame 50d has the second frame outer peripheral plate 52, the second frame inner peripheral plate 53d, and the second frame downstream-side end plate 54.

(105) As in the second frame outer peripheral plate 52 in the fourth embodiment, the second frame outer peripheral plate 52 extends to the axial downstream side Dad from the edge on the axial downstream side Dad of the casing outer peripheral plate 36, and spreads in the circumferential direction Dc, at least in the region on the non-exhaust side Dpu with reference to the axis Ar.

(106) As in the second frame inner peripheral plate 53 in the fourth embodiment, the second frame inner peripheral plate 53d extends to the axial downstream side Dad from the edge on the radial outer side Dro of the casing downstream-side end plate 32, and spreads in the circumferential direction Dc, at the position on the radial inner side Dri from the casing outer peripheral plate 36 and the second frame outer peripheral plate 52, at least in the region on the non-exhaust side Dpu with reference to the axis Ar. However, unlike the second frame inner peripheral plate 53 of the fourth embodiment, the second frame inner peripheral plate 53d gradually extends to the radial inner side Dri toward the axial downstream side Dad from the edge on the radial outer side Dro of the casing downstream-side end plate 32. In other words, the second frame inner peripheral plate 53d gradually extends to the radial outer side Dro toward the axial upstream side Dau.

(107) As in the second frame downstream-side end plate 54 in the fourth embodiment, the second frame downstream-side end plate 54 is a plate spreading in the radial direction Dr and the circumferential direction Dc, at least in the region on the non-exhaust side Dpu with reference to the axis Ar. The edge on the radial outer side Dro on the second frame downstream-side end plate 54 is connected to the edge on the axial downstream side Dad of the second frame outer peripheral plate 52. In addition, the edge on the radial inner side Dri of the second frame downstream-side end plate 54 is connected to the edge on the axial downstream side Dad of the second frame inner peripheral plate 53d.

(108) The edge on the axial upstream side Dau of the second frame outer peripheral plate 52 defines the edge on the radial outer side Dro of the second opening 51 serving as the opening through which the exhaust space 30s and the second exhaust auxiliary space 50s communicate with each other. In addition, the edge on the axial upstream side Dau of the second frame inner peripheral plate 53 defines the edge on the radial inner side Dri of the second opening 51.

(109) Next, an advantageous effect of the exhaust chamber 25d in the present embodiment described above will be described with reference to FIG. 15.

(110) The exhaust chamber 25d in the present embodiment has the first auxiliary exhaust frame 40b the same as the exhaust chambers 25b and 25c in the third embodiment and the fourth embodiment. Accordingly, as in the third embodiment and the fourth embodiment, compared to the comparative example, the circulation region Zc inside the non-exhaust side exhaust main flow path Su can be reduced, and the circulation region Zc can be limited within the region on the radial outer side Dro inside the exhaust main flow path S.

(111) In the present embodiment, as in the fourth embodiment, the region on the radial outer side Dro in the exhaust main flow path S communicates with the second exhaust auxiliary space 50s. Therefore, a portion of the steam in the region on the radial outer side Dro inside the exhaust main flow path S flows into the second exhaust auxiliary space 50s. As a result, the circulation region Zc inside the exhaust main flow path S further decreases due to the presence of the second exhaust auxiliary space 50s. A portion of the steam flowing into the second exhaust auxiliary space 50s circulates inside the second exhaust auxiliary space 50s, and thereafter, immediately returns to the inside of the exhaust main flow path S. In addition, the remaining portion of the steam flowing into the second exhaust auxiliary space 50s returns to the inside of the exhaust main flow path S from an end in the circumferential direction Dc of the second exhaust auxiliary space 50s spreading in the circumferential direction Dc.

(112) The second frame inner peripheral plate 53d of the second auxiliary exhaust frame 50d in the fifth embodiment gradually extends to the radial outer side Dro toward the axial upstream side Dau. Therefore, the steam flowing into the second exhaust auxiliary space 50s is more likely to circulate inside the second exhaust auxiliary space 50s, compared to the fourth embodiment. In the steam flowing into the second exhaust auxiliary space 50s, the amount of the steam returning into the exhaust main flow path S immediately decreases. Conversely, the amount of the steam returning into the exhaust main flow path S from the end in the circumferential direction Dc of the second exhaust auxiliary space 50s spreading in the circumferential direction Dc increases. That is, the second auxiliary exhaust frame 50d in the present embodiment has a structure in which the steam flowing into the second exhaust auxiliary space 50s positively returns into the exhaust main flow path S from the end in the circumferential direction Dc of the second exhaust auxiliary space 50s spreading in the circumferential direction Dc. Therefore, in the present embodiment, the circulation region Zc inside the exhaust main flow path S can be further reduced than that in the fourth embodiment.

Sixth Embodiment

(113) A sixth embodiment of the steam turbine according to the present invention will be described with reference to FIGS. 16 and 17.

(114) The steam turbine in the present embodiment is a modification example of the steam turbine in the third embodiment.

(115) As illustrated in FIG. 16, an exhaust chamber 25e in the present embodiment also has the diffuser 26, the exhaust casing 30, and the first auxiliary exhaust frame 40b, as in the exhaust chambers 25b, 25c, and 25d in the third to fifth embodiments. The exhaust chamber 25e in the present embodiment further includes a second auxiliary exhaust frame 50e, as in the exhaust chambers 25c and 25d in the fourth embodiment and the fifth embodiment.

(116) The second auxiliary exhaust frame 50e communicates with at least a portion on the non-exhaust side Dpu in the exhaust space 30s, and forms a second exhaust auxiliary space 50se different from the first exhaust auxiliary space 40s. The second exhaust auxiliary space 50se is a space spreading in the circumferential direction Dc along the casing outer peripheral plate 36 on the non-exhaust side Dpu from the casing downstream-side end plate 32, at least in the region on the axial upstream side Dau with reference to the axis Ar. Therefore, unlike the second exhaust auxiliary space 50s in the fourth embodiment and the fifth embodiment, the second exhaust auxiliary space 50se in the present embodiment is formed inside the exhaust casing 30.

(117) The second auxiliary exhaust frame 50e has a second frame outer peripheral plate 52e, a second frame inner peripheral plate 53e, and a second frame downstream-side end plate 54e. The second frame outer peripheral plate 52e is formed in a portion on the axial downstream side Dad of the casing outer peripheral plate 36, at least in a region on the non-exhaust side Dpu with reference to the axis Ar. The second frame downstream-side end plate 54e is formed in a portion on the radial outer side Dro of the casing downstream-side end plate 32, at least in the region on the non-exhaust side Dpu with reference to the axis Ar. The second frame inner peripheral plate 53e is a plate gradually extending to the radial outer side Dro toward the axial upstream side Dau from the casing downstream-side end plate 32, and spreading in the circumferential direction Dc toward the direction of Dc, at the position on the radial inner side Dri from the casing outer peripheral plate 36, at least in the region on the non-exhaust side Dpu with reference to the axis Ar.

(118) The edge on the axial upstream side Dau of the second frame outer peripheral plate 52e defines the edge on the radial outer side Dro of the second opening 51e serving as the opening through which the exhaust space 30s and the second exhaust auxiliary space 50s communicate with each other. In addition, the edge on the axial upstream side Dau of the second frame inner peripheral plate 53e defines the edge on the radial inner side Dri of the second opening 51e.

(119) Next, an advantageous effect of the exhaust chamber 25e in the present embodiment described above will be described with reference to FIG. 17.

(120) The exhaust chamber 25e in the present embodiment has the first auxiliary exhaust frame 40b the same as the exhaust chambers 25b, 25c, and 25d in the third to fifth embodiments. Accordingly, as in the third to fifth embodiments, a circulation region Ze inside the non-exhaust side exhaust main flow path Su can be reduced, compared to that in the comparative example, and the circulation region Ze can be limited within the region on the radial outer side Dro inside the exhaust main flow path S.

(121) In the present embodiment, the region on the radial outer side Dro inside the exhaust main flow path S communicates with the second exhaust auxiliary space 50se. Therefore, a portion of the steam in the region on the radial outer side Dro inside the exhaust main flow path S flows into the second exhaust auxiliary space 50se. A portion of the steam flowing into the second exhaust auxiliary space 50se circulates inside the second exhaust auxiliary space 50se, and thereafter, immediately returns into the exhaust main flow path S. In addition, the remaining portion of the steam flowing into the second exhaust auxiliary space 50se returns into the exhaust main flow path S from the end in the circumferential direction Dc of the second exhaust auxiliary space 50se spreading in the circumferential direction Dc.

(122) As in the second frame inner peripheral plate 53d in the fifth embodiment, the second frame inner peripheral plate 53e in the sixth embodiment gradually extends to the radial outer side Dro toward the axial upstream side Dau. Therefore, the steam flowing into the second exhaust auxiliary space 50se is more likely to circulate inside the second exhaust auxiliary space 50se, compared to the fourth embodiment. Therefore, in the steam flowing into the second exhaust auxiliary space 50se, the amount of the steam returning into the exhaust main flow path S immediately decreases. Conversely, the amount of the steam returning into the exhaust main flow path S from the end in the circumferential direction Dc of the second exhaust auxiliary space 50se spreading in the circumferential direction Dc increases. That is, as in the fifth embodiment, the second auxiliary exhaust frame 50e in the present embodiment also has a structure in which the steam flowing into the second exhaust auxiliary space 50se positively returns into the exhaust main flow path S from the end in the circumferential direction Dc of the second exhaust auxiliary space 50se spreading in the circumferential direction Dc. Therefore, as described above, although the second exhaust auxiliary space 50se in the present embodiment is formed inside the exhaust casing 30, the circulation region Ze inside the exhaust casing 30 can be further reduced than that in the third embodiment.

Various Modification Example

(123) The second frame downstream-side end plates 54 and 54e in the fourth to sixth embodiments extend in the radial direction Dr. However, the second frame downstream-side end plates 54 and 54e may be portions on the radial outer side Dro, and may gradually extend to the axial upstream side Dau toward the radial outer side Dro. In addition, the second frame downstream-side end plates 54 and 54e may be portions on the radial inner side Dri, and may gradually extend to the axial downstream side Dad as the second frame downstream-side end plates 54 and 54e extend to the radial outer side Dro.

(124) The casing downstream-side end plate 32 in each of the above-described embodiments extends in the radial direction Dr. However, the casing downstream-side end plate 32 may be a portion on the radial outer side Dro, and may gradually extend to the axial upstream side Dau as the casing downstream-side end plate 32 extends to the radial outer side Dro. In addition, the casing downstream-side end plate 32 may be a portion on the radial inner side Dri, and may gradually extend to the axial downstream side Dad as the casing downstream-side end plate 32 extends to the radial outer side Dro.

(125) The steam turbines in the fourth to sixth embodiments are modification examples of the steam turbine in the third embodiment. However, the configurations of the second auxiliary exhaust frames 50c, 50d, and 50e in the fourth to sixth embodiments may be applied to the steam turbine in the first embodiment or the second embodiment.

(126) The second exhaust auxiliary spaces 50s and 50se in the fourth to sixth embodiments are spaces spreading in the circumferential direction Dc, in the region on the non-exhaust side Dpu with reference to the axis Ar. However, the second exhaust auxiliary spaces 50s and 50se may be annular spaces formed around the axis Ar.

(127) All of the openings 41 of the auxiliary exhaust frames (first auxiliary exhaust frame) in the above-described respective embodiments have an annular shape formed around the axis Ar. The edge on the axial upstream side Dau of the opening 41 is an entire peripheral edge on the axial downstream side Dad of the inner diffuser 29. Therefore, the entire peripheral edge on the axial downstream side Dad of the inner diffuser 29 is separated from the casing downstream-side end plate 32 in the axial direction Da. As illustrated in FIG. 18, an auxiliary exhaust frame (first auxiliary exhaust frame) 40f may have a non-exhaust side opening portion 41uf and an exhaust side opening portion 41ef which are vertically open upward from the inside of the exhaust auxiliary space 40s. In this case, a portion of the edge on the axial downstream side Dad of the inner diffuser 29f defines the edge on the axial upstream side Dau of the non-exhaust side opening portion 41uf, the other portion defines the edge on the axial upstream side Dau of the exhaust side opening portion 41ef, and the remaining portion is connected to the casing downstream-side end plate 32 or the frame downstream-side end plate 42. That is, the respective openings 41uf and 41ef in this case are formed by cutting out a portion of the inner diffuser 29f. Although FIG. 18 illustrates a modification example of the first embodiment, the openings 41 in the second to sixth embodiments may be formed in the same manner as described above.

(128) As described above, independent openings are formed on the non-exhaust side Dpu and the exhaust side Dpe. Even in this case, it is possible to reduce a decrease in efficiency in the portion on the non-exhaust side Dpu inside the exhaust chamber. However, as in each of the above-described embodiments, in a case of an annular opening, the steam flows from the non-exhaust side Dpu to the exhaust side Dpe in a space where the exhaust auxiliary space 40s and the exhaust space 30s are integrated with each other. Accordingly, it is not necessary to consider a loss in a branching portion or a merging portion of the opening. On the other hand, when the independent openings are formed on the non-exhaust side Dpu and the exhaust side Dpe, the flow may be disturbed near an inlet or an outlet of each opening, thereby causing a possibility of a pressure loss. Therefore, when the independent openings are formed on the non-exhaust side Dpu and the exhaust side Dpe, it is necessary to carefully examine the length of the opening in the circumferential direction of each opening.

(129) The steam turbine in the above-described respective embodiments is a downward exhaust type. However, the steam turbine may be a laterally exhaust type. In this case, in the non-exhaust side Dpu and the exhaust side Dpe which form mutually opposite sides with respect to the axis Ar in an orthogonal direction orthogonal to the axis Ar, for example, the non-exhaust side Dpu is the left side with reference to the axis Ar, and the exhaust side Dpe is the right side with reference to the axis Ar.

(130) All of the exhaust casings 30 in the above-described respective embodiments have the casing upstream-side end plate 34. However, in a case of a two-way exhaust type, the exhaust space 30s of the first steam turbine unit 10a and the exhaust space 30s of the second steam turbine unit 10b are caused to communicate with each other in the region on the non-exhaust side Dpu with reference to the axis Ar. In this manner, the upstream-side end plate can be omitted.

(131) All of the steam turbines of the above-described respective embodiments are the two-way exhaust types. However, the present invention may be applied to a steam turbine in which the exhaust is not branched.

INDUSTRIAL APPLICABILITY

(132) In the exhaust chamber according to an aspect of the present invention, the pressure recovery amount can be increased by reducing the pressure loss of the steam.

REFERENCE SIGNS LIST

(133) 10a: first steam turbine unit 10b: second steam turbine unit 11 turbine rotor 12: rotor shaft 13: rotor blade row 13a: last stage rotor blade row 17: stator blade row 18: bearing 19: steam inlet duct 20: casing 21: cylinder casing 25, 25a, 25b, 25c, 25d, 25e, 25x: exhaust chamber 26: diffuser 26s: diffuser space 27: outer diffuser 29, 29f: inner diffuser 30,30x: exhaust casing 30s: exhaust space 30se: exhaust side exhaust space 30su: non-exhaust side exhaust space 31: exhaust port 32: casing downstream-side end plate 34: casing upstream-side end plate 36: casing outer peripheral plate 40, 40a, 40b, 40c: auxiliary exhaust frame (first auxiliary exhaust frame) 40s: exhaust auxiliary space (first exhaust auxiliary space) 41: opening 41u: non-exhaust side opening portion 41uf: non-exhaust side opening 41e: exhaust side opening portion 41ef: exhaust side opening 42: frame downstream-side end plate 43, 43a, 43b: frame upstream-side end plate 44: frame inner peripheral plate 45: upstream-side inner peripheral plate 46: downstream-side inner peripheral plate 50c, 50d, 50e: second auxiliary exhaust frame 50s, 50se: second exhaust auxiliary space 51, 51e: second opening 52, 52e: second frame outer peripheral plate 53, 53d, 53e: second frame inner peripheral plate 54, 54e: second frame downstream-side end plate Co: condenser S: exhaust main flow path Se: exhaust side main flow path Su: non-exhaust side main flow path Z, Zc, Ze: circulation region Ar: axis Da: axial direction Dau: axial upstream side Dad: axial downstream side Dc: circumferential direction Dr: radial direction Dri: radial inner side Dro: radial outer side Dpu: non-exhaust side Dpe: exhaust side