Gas turbine

Abstract

This turbine comprises a turbine rotor, a turbine casing, a plurality of turbine rotor cascades, a plurality of turbine stator cascades, and a diffuser which forms an exhaust gas flow path through which exhaust gas flows from one side in the axial direction toward another side, and which is provided on the other side in the axial direction from a last stage rotor cascade. The diffuser has an inner cylinder, an outer cylinder that forms the exhaust gas flow path between the outer cylinder and the inner cylinder, and a strut which connects the inner cylinder and the outer cylinder in the radial direction. The outer cylinder has a first inclined surface which extends outward from the inside in the radial direction going from an inlet of the exhaust gas flow path toward the other side in the axial direction. The first inclined surface forms an angle of 16° to 24°, inclusive, with the axis. In the turbine rotor blades in the final stage turbine rotor cascade, the throat width of an end that is outward in the radial direction relative to the axis is set to be greater than the throat width of a middle part in the radial direction.

Description

Technical Field

[0001] The present disclosure relates to Ga a turbine. This application claims priority to Japanese Patent Application No. 2021-050511, filed on Mar. 24, 2021, the content of which is incorporated herein by reference.

Background Art

[0002] A gas turbine mainly includes a compressor that generates compressed air, a combustor that generates high-temperature and high-pressure combustion gas by mixing fuel with the compressed air and burning it, a turbine driven by the combustion gas, and a cylindrical diffuser that guides the exhaust from the turbine. As exemplified in Patent Document 1 below, the diffuser has an inner cylinder extending along the axis of the gas turbine, an outer cylinder provided on the outer peripheral side of the inner cylinder to form an exhaust flow path between the inner cylinder and the outer cylinder, and struts connecting the inner cylinder and the outer cylinder. In the diffuser described in Patent Document 1, the outer cylinder gradually increases in diameter toward the downstream side. That is, the inner peripheral surface of the outer cylinder is inclined with respect to the axis in a cross-sectional view including the axis. Thereby, the flow of the exhaust from the turbine is decelerated and the static pressure is recovered midway through passing through the diffuser.

[0003] Here, it is known that a pressure loss occurs in the flow of the exhaust when flowing through the diffuser. Most of the pressure loss is caused by the struts being exposed to the flow of the exhaust. In order to suppress the pressure loss in the struts and improve the performance of the diffuser, it is essential to reduce the flow velocity of the exhaust upstream of the struts. Therefore, it is necessary to make the inclination angle of the inner peripheral surface of the outer cylinder as large as possible.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, if the inclination angle of the inner peripheral surface of the outer cylinder is made excessively large, there is a risk that the flow will separate from the inner peripheral surface and vortices will be generated. When vortices are generated, the aerodynamic performance of the diffuser will be impaired. As a result, the performance of the turbine may be affected.

[0006] The present disclosure has been made to solve the above problems, and an object thereof is to provide a turbine with further improved performance by reducing pressure loss. Ga

Means for Solving the Problems

[0007] ​In order to solve the above problems, a gas turbine according to the present disclosure includes a turbine rotor that extends along an axis and is rotatable about the axis, and a plurality of turbine stator blade rows and a plurality of turbine rotor blade rows that are alternately arranged in a single row in the axial direction of the turbine rotor. The turbine includes a diffuser that is provided downstream of the final stage rotor blade row that is located on the most downstream side in the flow direction of combustion gas along the axis among the plurality of turbine rotor blade rows, and forms an exhaust flow path through which exhaust gas flows from an inlet to an outlet. The diffuser has an inner cylinder, an outer cylinder that covers the inner cylinder from the outer peripheral side and forms the exhaust flow path between the inner cylinder and the outer cylinder, and a plurality of struts that are provided at an intermediate position of the exhaust flow path, are arranged in the circumferential direction of the axis, and connect the inner cylinder and the outer cylinder in the radial direction. The outer cylinder has a first inclined surface that extends from the radially inner side to the radially outer side around the axis as it goes from the axial direction inlet side to the axial direction outlet side of the exhaust flow path. The first inclined surface forms an angle of 16° or more and 24° or less with respect to the axis in a cross-sectional view including the axis. In the plurality of turbine rotor blades that constitute the final stage rotor blade row, the throat width of the radially outer end portion with respect to the axis is set to be larger than the throat width of the intermediate portion in the radial direction. In each of the turbine rotor blades that constitute the final stage rotor blade row, the tip side end surface on the radially outer side extends radially outward as it goes from the upstream side to the downstream side in the flow direction of combustion gas along the axis, and the angle formed by the tip side end surface with respect to the axis is set to be larger than the angle formed by the first inclined surface with respect to the axis. 。

Advantages of the Invention

[0008] According to the present disclosure, a gas turbine with further improved performance due to reduced pressure loss can be provided. Ga

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0010] (Configuration of Gas Turbine) Hereinafter, the gas turbine 10 according to the embodiment of the present disclosure will be described with reference to FIGS. 1 to 7. As shown in FIG. 1, the gas turbine 10 includes a compressor 20, a combustor 30, a turbine 40, and a diffuser 60. The compressor 20 compresses the air A taken in from the outside to generate high-pressure compressed air. The combustor 30 mixes the fuel F with the compressed air and burns it to generate high-temperature and high-pressure combustion gas G. The turbine 40 is rotationally driven by the combustion gas G.

[0011] The compressor 20 has a compressor rotor 21, a compressor casing 25, and a plurality of compressor stator blade rows 26. The compressor rotor 21 has a compressor rotating shaft 22 and a plurality of compressor moving blade rows 23. The compressor rotating shaft 22 extends along the axis Ac and is rotatable about the axis Ac. The compressor moving blade rows 23 are arranged in a plurality along the axis Ac direction at intervals on the outer peripheral surface of the compressor rotating shaft 22. Although not shown in detail, each compressor moving blade row 23 has a plurality of compressor moving blades arranged in the circumferential direction along the outer peripheral surface of the compressor rotating shaft 22.

[0012] The compressor casing 25 has a cylindrical shape that covers the compressor rotor 21 from the outer peripheral side. A plurality of compressor stator blade rows 26 arranged in the axis Ac direction are provided on the inner peripheral surface of the compressor rotor 21. The above-mentioned compressor moving blade rows 23 and compressor stator blade rows 26 are arranged alternately in the axis Ac direction. More specifically, one compressor stator blade row 26 is provided on one side in the axis Ac direction of one compressor moving blade row 23.

[0013] An intermediate chamber 16 is connected to the other side in the axis Ac direction of the compressor casing 25. The combustor 30 is arranged in this intermediate chamber 16.

[0014] The turbine 40 has a turbine rotor 41, a turbine casing 45, and a plurality of turbine stator blade rows 46. The turbine rotor 41 has a turbine rotating shaft 42 and a plurality of turbine moving blade rows 43. The turbine rotating shaft 42 extends along the axis Ac and is rotatable about the axis Ac. The turbine moving blade rows 43 are arranged in a plurality along the axis Ac direction at intervals on the outer peripheral surface of the turbine rotating shaft 42. Although not shown in detail, each turbine moving blade row 43 has a plurality of turbine moving blades arranged in the circumferential direction along the outer peripheral surface of the turbine rotating shaft 42. Among the plurality of turbine moving blade rows 43 arranged in the axis Ac direction, the turbine moving blade row 43 on the most other side in the axis Ac direction is defined as the final stage moving blade row 43A. Also, in the following description, the turbine moving blades included in this final stage moving blade row 43A are referred to as the final stage moving blade row 50.

[0015] The above-described compressor rotor 21 and turbine rotor 41 are coaxially connected along the axis Ac to form a gas turbine rotor 11. The compressor casing 25, the intermediate chamber 16, and the turbine casing 45 are coaxially connected along the axis Ac to form a gas turbine casing 15. The gas turbine rotor 11 is integrally rotatable about the axis Ac inside the gas turbine casing 15. In the following description, the side where the compressor 20 is located as viewed from the turbine 40 (i.e., one side in the direction of the axis Ac) may be simply referred to as the "upstream side", and the opposite side (i.e., the other side in the direction of the axis Ac) may be simply referred to as the "downstream side".

[0016] The diffuser 60 is provided to reduce the flow velocity of the exhaust gas (exhaust gas) discharged from the turbine 40 and recover the static pressure. The diffuser 60 is connected to the downstream side of the turbine casing 45. The diffuser 60 includes an inner cylinder 62, an outer cylinder 61, a plurality of struts 63, and a plurality of manholes 64. The inner cylinder 62 extends along the axis Ac. Inside the inner cylinder 62, a bearing device 80 (described later) for rotatably supporting the above-described gas turbine rotor 11 is accommodated. In this embodiment, as an example, the outer diameter of the inner cylinder 62 is constant from the upstream side to the downstream side. It should be noted that a configuration in which the outer diameter of the inner cylinder 62 gradually decreases from the upstream side to the downstream side may also be adopted.

[0017] The outer cylinder 61 has a cylindrical shape that covers the inner cylinder 62 from the outer peripheral side. The space between the outer cylinder 61 and the inner cylinder 62 is an exhaust gas flow path E through which the exhaust gas discharged from the turbine 40 flows. The inner diameter of the outer cylinder 61 gradually increases from the upstream side to the downstream side. Therefore, the flow path cross-sectional area of the exhaust gas flow path E gradually increases toward the downstream side.

[0018] The outer cylinder 61 and the inner cylinder 62 are connected in the radial direction by struts 63. That is, the struts 63 support the outer cylinder 61 with respect to the inner cylinder 62 from the radially inner side. The struts 63 are provided at an intermediate position of the exhaust passage E in the direction of the axis Ac. The detailed arrangement of the struts 63 will be described later. A plurality of struts 63 are arranged at intervals in the circumferential direction. Each strut 63 extends radially between the inner circumferential surface of the outer cylinder 61 and the outer circumferential surface of the inner cylinder 62. Although not shown in detail, it is desirable that the strut 63 has a streamline cross-sectional shape that extends from the upstream side to the downstream side when viewed in the radial direction.

[0019] Manholes 64 are provided at intervals in the direction of the axis Ac on the downstream side of the struts 63. The manholes 64 extend radially between the outer cylinder 61 and the inner cylinder 62. A plurality of manholes 64 are arranged at intervals in the circumferential direction. Various pipes and wirings are accommodated inside the manholes 64.

[0020] (Detailed Configuration of the Final Stage Rotor Blade Row and Diffuser) Subsequently, with reference to FIG. 2, the detailed configuration of the above-described final stage rotor blade row 50 and diffuser 60 will be described. As shown in the figure, the final stage rotor blade row 50 has a disk 70 and a rotor blade body 50H. The disk 70 is attached to the turbine rotating shaft 42. The disk 70 has a disk shape centered on the axis Ac. The rotor blade body 50H is provided on the outer circumferential surface 70A of the disk 70. The rotor blade body 50H extends radially outward from the outer circumferential surface 70A.

[0021] As will be described in detail later, the rotor blade body 50H has an airfoil cross-sectional shape when viewed in the radial direction. The edge facing the upstream side in the rotor blade body 50H is defined as the leading edge 50A. The edge facing the downstream side in the rotor blade body 50H is defined as the trailing edge 50B. The end face facing the outer side in the radial direction of the rotor blade body 50H is defined as the tip-side end face 50C. The tip-side end face 50C extends from the inner side in the radial direction toward the outer side as it goes from the upstream side to the downstream side. That is, the tip-side end face 50C is inclined at an angle θ1 with respect to the axis Ac in a cross-sectional view including the axis Ac. This angle θ1 is appropriately set within the range of 20° or more and 25° or less. The tip-side end face 50C faces the inner peripheral surface 45A of the turbine casing 45 with a radial gap therebetween. The inner peripheral surface 45A gradually increases in inner diameter as it goes from the upstream side to the downstream side.

[0022] Furthermore, the end portion on the inner side in the radial direction of the rotor blade body 50H is defined as the hub-side end face 50D. The hub-side end face 50D is in contact with the outer peripheral surface 70A of the disk 70. Although not shown in detail, a serrated uneven portion is formed on the inner side in the radial direction of the hub-side end face 50D. A groove corresponding to this uneven shape is formed in the disk 70. The rotor blade body 50H is supported in a non-detachable manner by the engagement of the uneven shape formed on the blade root and the inner surface of the groove.

[0023] The inner cylinder 62 of the diffuser 60 covers the shaft end of the turbine rotating shaft 42 from the outer peripheral side. A bearing device 80 is provided inside the inner cylinder 62. The bearing device 80 rotatably supports the turbine rotating shaft 42. Specifically, a journal bearing is exemplified as the bearing device 80 provided at this position. The journal bearing supports the radial load by the turbine rotating shaft 42. The surface facing the outer peripheral side of the inner cylinder 62 is defined as the outer peripheral surface 62A. This outer peripheral surface 62A is at the same position in the radial direction as the outer peripheral surface 70A of the disk 70 described above. Here, the "same" mentioned here refers to substantial sameness, and design tolerances and manufacturing errors are allowed.

[0024] The inner peripheral surface of the outer cylinder 61 is formed by a first inclined surface 61A and a second inclined surface 61B. The first inclined surface 61A is connected to the downstream side of the inner peripheral surface 45A of the turbine casing 45. The first inclined surface 61A extends from the inner side in the radial direction to the outer side as it goes from the upstream side to the downstream side. That is, the first inclined surface 61A is inclined at an angle θ2 with respect to the axis Ac in a cross-sectional view including the axis Ac. This angle θ2 is appropriately determined within the range of 16° or more and 24° or less. Therefore, the difference between the angle θ1 formed by the tip-side end surface 50C of the moving blade body 50H described above with respect to the axis Ac and the angle θ2 formed by the first inclined surface 61A with respect to the axis Ac is in the range of 0° or more and 5° or less.

[0025] The second inclined surface 61B extends downstream from the first inclined surface 61A. The second inclined surface 61B extends from the inner side in the radial direction to the outer side as it goes from the upstream side to the downstream side, similar to the first inclined surface 61A. That is, the second inclined surface 61B is inclined with respect to the axis Ac. The angle formed by the second inclined surface 61B with respect to the axis Ac is smaller than the angle θ2 formed by the first inclined surface 61A with respect to the axis Ac. More specifically, this angle is desirably about 8°.

[0026] The upstream edge of the strut 63 described above is the strut leading edge 63A, and the downstream edge is the strut trailing edge 63B. The strut leading edge 63A is located on the first inclined surface 61A. On the other hand, the strut trailing edge 63B is located on the second inclined surface 61B. That is, the strut 63 is arranged across the first inclined surface 61A and the second inclined surface 61B in the direction of the axis Ac.

[0027] Here, let the cross-sectional area of the exhaust passage E at the inlet (the upstream end) of the diffuser 60 (the cross-sectional area as viewed from the direction of the axis Ac) be S1. Further, let the cross-sectional area of the exhaust passage E at the leading edge 63A of the strut (the cross-sectional area as viewed from the direction of the axis Ac) be S2. That is, the cross-sectional areas S1 and S2 refer to the area of the annular region surrounded by the outer peripheral surface 62A of the inner cylinder 62 and the inner peripheral surface (the first inclined surface 61A) of the outer cylinder 61. At this time, the ratio (area ratio) of the cross-sectional area S1 to the cross-sectional area S2 is desirably in the range of 1.25 or more and 1.40 or less. More desirably, this area ratio is in the range of 1.28 or more and 1.37 or less. Most desirably, this area ratio is 1.30. Note that when realizing the above cross-sectional area ratio, the area reduction due to the fillet portion formed in the attachment portion of the strut 63 does not need to be considered.

[0028] (Further detailed configuration of the final-stage moving blade row) Next, with reference to FIGS. 3 to 6, a further detailed configuration of the final-stage moving blade row 50 (the moving blade body 50H) will be described. As shown in FIG. 3, the moving blade body 50H has an airfoil cross-sectional shape when viewed in the radial direction. That is, the moving blade body 50H is curved toward one side in the circumferential direction from the leading edge 50A to the trailing edge 50B. The surface of the moving blade body 50H facing one side in the circumferential direction (that is, the surface facing the rear side in the rotation direction of the turbine rotation axis 42) is defined as the positive pressure surface 50P. The positive pressure surface 50P is curved and recessed toward the other side in the circumferential direction. The surface of the moving blade body 50H facing the other side in the circumferential direction (that is, the surface facing the front side in the rotation direction of the turbine rotation axis 42) is defined as the negative pressure surface 50N. The negative pressure surface 50N is curved and convex toward the other side in the circumferential direction.

[0029] Furthermore, in this moving blade body 50H, the cross-sectional shapes are different at the tip-side end face 50C, the hub-side end face 50D, and the intermediate position (the intermediate portion 50M) in the radial direction. Here, as shown in FIG. 4, let the throat width at the tip-side end face 50C and the hub-side end face 50D be A1. Also, let the outflow angle at the tip-side end face 50C and the hub-side end face 50D be θ3. Further, as shown in FIG. 5, let the throat width at the intermediate portion 50M be A2. Also, let the outflow angle at the intermediate portion 50M be θ4.

[0030] At this time, as shown in these figures, the throat width A1 at the chip side end face 50C and the hub side end face 50D is set to be larger than the throat width A2 at the intermediate portion 50M. Here, the throat width refers to the flow path width at the position (throat position) where the minimum separation distance is the smallest between a pair of moving blade bodies 50H adjacent to each other in the circumferential direction. The throat width gradually decreases from the chip side end face 50C toward the intermediate portion 50M, and gradually increases from the intermediate portion 50M toward the hub side end face 50D.

[0031] Furthermore, the outlet angle θ3 at the chip side end face 50C and the hub side end face 50D is set to be smaller than the outlet angle θ4 at the intermediate portion 50M. Here, the outlet angle refers to the angle formed by the flow passing between a pair of adjacent moving blade bodies 50H with respect to the axis Ac. The outlet angle gradually increases from the chip side end face 50C toward the intermediate portion 50M, and gradually decreases from the intermediate portion 50M toward the hub side end face 50D.

[0032] As shown by the two-dot chain line in FIG. 6, in the conventional moving blade, the outlet angle was set to gradually decrease from the chip side toward the hub side. On the other hand, in the moving blade body 50H according to the present embodiment, as shown by the solid line, the outlet angle is set to gradually increase from the chip side toward the hub side and then gradually decrease toward the hub side. Thus, in the moving blade body 50H, the outlet angle is smaller than that of the intermediate portion 50M on the chip side and the hub side. That is, the throat width is larger than that of the intermediate portion 50M on the chip side and the hub side.

[0033] (Function and Effect) Subsequently, the operation of the gas turbine 10 according to the present embodiment will be described. When driving the gas turbine 10, first, a rotational force is applied to the compressor rotor 21 by an external drive source. Thereby, the compressor rotor 21 rotates around the axis Ac, and external air is supplied to the compressor 20. QiAir A is taken in. The air A taken in by the compressor 20 flows from the upstream side to the downstream side within the compressor casing 25 and contacts the compressor stator blade row 26 and the compressor rotor blade row 23 midway. The compressor stator blade row 26 changes the flow direction of the air A and optimizes the inflow angle to the downstream compressor rotor blade row 23. Further, as the air A is pumped by the compressor rotor blade row 23, its pressure gradually rises and it becomes compressed air. The compressed air is led to the combustor 30 located on the downstream side of the compressor 20. In the combustor 30, fuel F is mixed with this compressed air and burned to generate combustion gas G. The combustion gas G is led to the turbine 40 located on the downstream side of the combustor 30.

[0034] In the turbine 40, the combustion gas G contacts the turbine stator blade row 46 and the turbine rotor blade row 43. The turbine stator blade row 46 changes the flow direction of the combustion gas G and optimizes the inflow angle to the downstream turbine rotor blade row 43. Further, as the combustion gas G flows around the turbine rotor blade row 43, it gives rotational energy to the turbine rotor 41 via the turbine rotor blade row 43. Thereby, the gas turbine rotor 11 rotates around the axis Ac. The exhaust gas discharged from the turbine 40 flows through the diffuser 60 and after the static pressure is recovered midway, it is led to other external equipment (not shown).

[0035] Here, it is known that a pressure loss occurs in the flow of the exhaust gas when flowing through the diffuser 60. Most of the pressure loss is caused by the strut 63 being exposed to the flow of the exhaust gas. In order to suppress the pressure loss in the strut 63 and improve the performance of the diffuser 60, it is essential to lower the flow velocity of the exhaust gas upstream of the strut 63. Therefore, it is necessary to make the inclination angle of the inner peripheral surface of the outer cylinder 61 as large as possible.

[0036] However, if the inclination angle of the inner peripheral surface of the outer cylinder 61 is made excessively large, the flow may not fully follow the inner peripheral surface, resulting in flow separation and the generation of vortices. When vortices are generated, the aerodynamic performance (static pressure recovery amount) of the diffuser 60 is impaired. As a result, it may affect the performance of the gas turbine 10.

[0037] Therefore, in the present embodiment, the above-described configuration is adopted. According to the above configuration, the angle formed by the first inclined surface 61A of the outer cylinder 61 with respect to the axis Ac is set to be 16° or more and 24° or less, which is larger than that of the conventional diffuser. As a result, it is possible to further reduce the flow velocity of the exhaust gas flowing through the exhaust passage E in the region upstream of the strut 63. As a result, the flow of the exhaust gas flowing around the strut 63 is less likely to be affected by the strut 63. That is, the pressure loss caused by the strut 63 can be further reduced.

[0038] Furthermore, in the final-stage rotor blade row 50, the throat width A1 at the radially outer end (tip side) is larger than the throat width A2 at the intermediate portion 50M. As a result, the total pressure at the radially outer end increases. Therefore, it is also possible to reduce the possibility of flow separation occurring at the first inclined surface 61A.

[0039] More specifically, on the tip side, since the throat width is larger than that at the intermediate portion 50M, the amount of power obtained from the combustion gas of the final-stage rotor blade row 50 decreases on the tip side. On the other hand, since the outflow angle on the intermediate portion 50M side is large (that is, the throat width is small), the amount of power obtained from the combustion gas increases at the intermediate portion 50M. Here, as shown by the two-dot chain line in FIG. 7, conventionally, from the tip side to the hub side of the final-stage rotor blade row, the total pressure of the exhaust gas at the inlet of the diffuser 60 is almost constant, and flow separation is likely to occur in the vicinity of the wall surfaces of the outer cylinder 61 and the inner cylinder 62. As a result, there is a possibility that the static pressure recovery amount in the diffuser 60 becomes small. In contrast, in the present embodiment, as shown by the solid line in FIG. 7, the total pressure of the exhaust gas at the inlet of the diffuser 60 is higher on the tip side than at the intermediate portion 50M of the rotor blade body 50H. Therefore, it is possible to make the angle θ2 formed by the first inclined surface 61A with respect to the axis Ac larger than in the conventional case. As a result, flow separation is even less likely to occur in the vicinity of the wall surfaces of the outer cylinder 61 and the inner cylinder 62. As a result, it is possible to further increase the static pressure recovery amount in the diffuser 60.

[0040] Furthermore, according to the above configuration, in the final-stage rotor blade row 50, the throat width A1 at the end on the radially inner side (hub side) is larger than the throat width A2 at the intermediate portion 50M. As a result, the total pressure not only on the tip side but also on the hub side increases. Therefore, it is possible to reduce the possibility of flow separation occurring on the outer peripheral surface 62A of the inner cylinder 62. As a result, the static pressure recovery amount in the diffuser 60 further increases, and the performance of the gas turbine 10 can be further improved.

[0041] In addition, in the above configuration, the flow path cross-sectional area (cross-sectional area S2 ) of the diffuser at the upstream edge (strut leading edge 63A) of the strut 63 and the flow path cross-sectional area (cross-sectional area S1 ) at the inlet of the diffuser 60, the area ratio S2 / S1 is set to be 1.28 or more and 1.37 or less, which is larger than that of a conventional gas turbine. As a result, it is possible to further reduce the exhaust flow velocity in the region upstream of the strut 63.

[0042] Furthermore, in the final-stage rotor blade row 50, the tip-side end face 50C extends radially outward as it goes from the upstream side to the downstream side when viewed in the circumferential direction. Also, the angle θ1 formed by the tip-side end face 50C with respect to the axis Ac is set to be larger than the angle θ2 formed by the first inclined face 61A with respect to the axis Ac. The exhaust flow component that goes radially outward along the tip-side end face 50C is guided by the first inclined face 61A located on the downstream side. Since the angle θ1 formed by the tip-side end face 50C with respect to the axis Ac is larger than the angle θ2 formed by the first inclined face 61A with respect to the axis Ac, the above-mentioned flow component adheres to the first inclined face 61A while being pressed radially inward. As a result, it is possible to further suppress the occurrence of flow separation on the first inclined face 61A. Thereby, it is possible to avoid the generation of vortices on the first inclined face 61A.

[0043] Further, in the above configuration, the difference between the angle θ1 formed by the chip-side end face 50C with respect to the axis Ac and the angle θ2 formed by the first inclined face 61A with respect to the axis Ac is 0° or more and 5° or less. Here, as described above, since the throat width at the chip-side end face 50C is made larger than the throat width at the intermediate portion 50M, the total pressure of the exhaust gas on the chip side can be maintained high. As a result, it becomes possible to make the difference between the angle θ1 and the angle θ2 smaller than before. In other words, as long as the angle θ1 is larger than the angle θ2, it becomes possible to expand the angle θ2 formed by the first inclined face 61A with respect to the axis Ac to the maximum allowable limit. Thereby, the separation of the flow on the first inclined face 61A can be further suppressed.

[0044] In addition, in the above configuration, the strut 63 is arranged so as to straddle the first inclined face 61A and the second inclined face 61B in the direction of the axis Ac. Thereby, before contacting the strut 63, the exhaust gas flow becomes a state where it is sufficiently decelerated in the region on the first inclined face 61A side. As a result, it becomes possible to further reduce the pressure loss due to the strut 63.

[0045] (Other Embodiments) The embodiments of the present disclosure have been described above. Note that various changes and modifications can be made to the above-described respective configurations without departing from the gist of the present disclosure. For example, in the above embodiment, an example in which the strut 63 is arranged so as to straddle the first inclined face 61A and the second inclined face 61B of the outer cylinder 61 has been described. However, the arrangement of the strut 63 is not limited to the above. For example, a configuration in which the strut 63 is arranged only on the second inclined face 61B can also be adopted. According to such a configuration, by flowing along the first inclined face 61A, the flow velocity of the exhaust gas can be further decreased in the region upstream of the strut 63. As a result, it becomes possible to further reduce the pressure loss due to the strut 63.

[0046] Furthermore, in the above embodiment, only the throat width and the outflow angle of the final-stage moving blade row 50 have been described. However, the finalStage The stationary blade row can also be configured with the same throat width and outlet angle as the last-stage moving blade row 50.

[0047] <Appendix> The turbines 40 and gas turbines 10 described in each embodiment are understood as follows, for example.

[0048] (1) The turbine 40 according to the first aspect includes a turbine rotor 41 that extends along the axis Ac and is rotatable about the axis Ac, a turbine casing 45 that covers the turbine rotor 41 from the outer peripheral side, a plurality of turbine moving blades arranged in the circumferential direction of the axis Ac on the outer peripheral surface of the turbine rotor 41, a plurality of turbine moving blade rows 43 arranged in the direction of the axis Ac, a plurality of turbine stationary blades provided on the inner peripheral surface of the turbine casing 45 so as to be adjacent to the turbine moving blades on one side in the direction of the axis Ac and arranged in the circumferential direction, a plurality of turbine stationary blade rows 46 arranged in the direction of the axis Ac, and a diffuser 60 provided on the other side in the direction of the axis Ac of the last-stage moving blade row 43A, which is the most other side in the direction of the axis Ac among the plurality of turbine moving blade rows 43, and forms an exhaust gas flow path E through which the exhaust gas flows from one side to the other side in the direction of the axis Ac. The diffuser 60 includes an inner cylinder 62 that extends along the axis Ac, an outer cylinder 61 that covers the inner cylinder 62 from the outer peripheral side and forms the exhaust gas flow path E between the inner cylinder 62 and the outer cylinder 61, and a plurality of struts 63 provided at an intermediate position of the exhaust gas flow path E, connecting the inner cylinder 62 and the outer cylinder in the radial direction and arranged in the circumferential direction. The outer cylinder 61 has a first inclined surface 61A that extends from the inner side to the outer side in the radial direction centered on the axis Ac from the inlet of the exhaust gas flow path E on one side in the direction of the axis Ac toward the other side. The first inclined surface 61A forms an angle of 16° or more and 24° or less with respect to the axis Ac in a cross-sectional view including the axis Ac. In the turbine moving blades of the last-stage moving blade row 43A, the throat width A1 of the radially outer end portion with respect to the axis Ac is set to be larger than the throat width A2 of the intermediate portion 50M in the radial direction.

[0049] According to the above configuration, the angle formed by the first inclined surface 61A with respect to the axis Ac is set to be 16° or more and 24° or less, which is larger than that of the conventional diffuser. Thereby, it becomes possible to further reduce the flow velocity of the exhaust gas flowing through the exhaust passage E in the region on one side in the direction of the axis Ac rather than the strut 63. As a result, the pressure loss due to the strut 63 can be further reduced. Further, in the turbine blade of the final stage moving blade row 43A, the throat width A1 at the radially outer end is larger than the throat width A2 at the intermediate portion 50M. Thereby, the total pressure at the radially outer end becomes high. Therefore, it is also possible to reduce the possibility of flow separation occurring at the first inclined surface 61A.

[0050] (2) In the turbine 40 according to the second aspect, in the turbine blade of the final stage moving blade row 43A, the throat width A1 at the radially inner end is set to be larger than the throat width A2 at the intermediate portion 50M in the radial direction.

[0051] According to the above configuration, in the turbine blade of the final stage moving blade row 43A, the throat width A1 at the radially inner end is larger than the throat width A2 at the intermediate portion 50M. Thereby, the total pressure at the radially inner end becomes high. Therefore, it is possible to reduce the possibility of flow separation occurring on the outer peripheral surface 62A of the inner cylinder 62.

[0052] (3) In the turbine 40 according to the third aspect, the area ratio between the flow passage cross-sectional area of the diffuser 60 at the edge on one side in the direction of the axis Ac of the strut 63 and the flow passage cross-sectional area of the diffuser 60 at the inlet on one side in the direction of the axis Ac is 1.28 or more and 1.37 or less.

[0053] According to the above configuration, it becomes possible to further reduce the flow velocity of the exhaust gas in the region on one side in the direction of the axis Ac of the strut 63.

[0054] (4) In the turbine 40 according to the fourth aspect, in the turbine blade of the final stage moving blade row 43A, on the tip side end face 50C on the radially outer side, as it goes from one side to the other side in the direction of the axis Ac when viewed in the circumferential direction, it extends radially outward, and the angle θ1 formed by the tip side end face 50C with respect to the axis Ac is set larger than the angle θ2 formed by the first inclined surface 61A with respect to the axis Ac.

[0055] According to the above configuration, the flow component directed radially outward along the tip side end face 50C is guided by the first inclined surface 61A on the other side in the direction of the axis Ac. Since the angle θ1 formed by the tip side end face 50C with respect to the axis Ac is larger than the angle θ2 formed by the first inclined surface 61A with respect to the axis Ac, the above flow component adheres to the first inclined surface 61A as if it is pressed against it. As a result, the separation of the flow on the first inclined surface 61A can be further suppressed.

[0056] (5) In the turbine 40 according to the fifth aspect, the difference between the angle θ1 formed by the tip side end face 50C with respect to the axis Ac and the angle θ2 formed by the first inclined surface 61A with respect to the axis Ac is 0° or more and 5° or less.

[0057] According to the above configuration, the separation of the flow on the first inclined surface 61A can be further suppressed.

[0058] (6) In the turbine 40 according to the sixth aspect, the outer cylinder 61 further has a second inclined surface 61B that extends from the radially inner side to the radially outer side as it extends on the other side in the direction of the axis Ac of the first inclined surface 61A and from one side to the other side in the direction of the axis Ac, and the angle formed by the second inclined surface 61B with respect to the axis Ac in a cross-sectional view including the axis Ac is smaller than the angle θ2 formed by the first inclined surface 61A with respect to the axis Ac, and the strut 63 is arranged across the first inclined surface 61A and the second inclined surface 61B in the direction of the axis Ac.

[0059] According to the above configuration, the strut 63 is disposed across the first inclined surface 61A and the second inclined surface 61B. Thereby, before contacting the strut 63, the exhaust flow becomes a state of being sufficiently decelerated in the region on the first inclined surface 61A side. As a result, it is possible to further reduce the pressure loss caused by the strut 63.

[0060] (7) The gas turbine 10 according to the seventh aspect includes a compressor 20 that generates high-pressure air by compressing air A, a combustor 30 that mixes fuel with the high-pressure air to generate combustion gas G, and a turbine 40 that is driven by the combustion gas G.

[0061] According to the above configuration, it is possible to provide the gas turbine 10 with further improved performance by further reducing the pressure loss in the diffuser 60.

Industrial Applicability

[0062] According to the present disclosure, it is possible to provide a turbine and a gas turbine with further improved performance by reducing the pressure loss.

Explanation of Signs

[0063] 10 Gas turbine 11 Gas turbine rotor 15 Gas turbine casing 16 Intermediate chamber 20 Compressor 21 Compressor rotor 22 Compressor rotating shaft 23 Compressor blade row 25 Compressor casing 26 Compressor stator blade row 30 Combustor 40 Turbine 41 Turbine rotor 42 Turbine rotating shaft 43 Turbine blade row 43A Final stage blade row 45 Turbine casing 45A Inner peripheral surface 46 Turbine stator blade row 50 Final stage rotor blade row 50A Leading edge 50B Trailing edge 50C Tip side end face 50D Hub side end face 50H Rotor blade body 50M Intermediate part 50N Suction surface 50P Pressure surface 60 Diffuser 61 Outer cylinder 61A First inclined surface 61B Second inclined surface 62 Inner cylinder 62A Outer peripheral surface 63 Strut 63A Strut leading edge 63B Strut trailing edge 64 Manhole 70 Disk 70A Outer peripheral surface 80 Bearing device Ac Axis A Air E Exhaust flow path F Fuel G Combustion gas θ1,θ2 Angles θ3,θ4 Outlet angles

Claims

1. A turbine including a turbine rotor that extends along an axis and is rotatable about the axis, and a plurality of turbine stator blade rows and a plurality of turbine rotor blade rows that are alternately arranged in a single row in the axial direction of the turbine rotor. Among the plurality of turbine rotor blade rows, a diffuser that is provided downstream of the final stage rotor blade row located on the most downstream side in the flow direction of combustion gas along the axis, and forms an exhaust flow path through which exhaust gas flows from an inlet to an outlet. Comprising: The diffuser: An inner cylinder; An outer cylinder that covers the inner cylinder from the outer peripheral side and forms the exhaust flow path between the inner cylinder and the outer cylinder; A plurality of struts that are provided at an intermediate position of the exhaust flow path, are arranged in the circumferential direction of the axis, and connect the inner cylinder and the outer cylinder in the radial direction; Having: The outer cylinder has a first inclined surface that extends from the radially inner side to the radially outer side around the axis from the axial direction inlet side to the axial direction outlet side of the exhaust flow path; The first inclined surface forms an angle of 16° or more and 24° or less with respect to the axis in a cross-sectional view including the axis; In the plurality of turbine rotor blades constituting the final stage rotor blade row, the throat width of the radially outer end portion with respect to the axis is set to be larger than the throat width of the intermediate portion in the radial direction. In each of the turbine rotor blades constituting the final stage rotor blade row, the tip side end face on the radially outer side extends radially outward from the upstream side to the downstream side in the flow direction of combustion gas along the axis, and the angle formed by the tip side end face with respect to the axis is set to be larger than the angle formed by the first inclined surface with respect to the axis. A gas turbine.

2. The gas turbine according to claim 1, wherein in the plurality of turbine rotor blades constituting the final stage rotor blade row, the throat width of the radially inner end portion is set to be larger than the throat width of the intermediate portion in the radial direction.

3. The area ratio S2 / S1 of the flow path cross-sectional area S2 of the diffuser at the front edge located on the axial direction inlet side of the strut and the flow path cross-sectional area S1 at the inlet of the diffuser is 1.28 or more and 1.37 or less. The gas turbine according to claim 1 or 2.

4. The difference between the angle formed by the tip-side end face with respect to the axis and the angle formed by the first inclined face with respect to the axis is 0° or more and 5° or less. The gas turbine according to any one of claims 1 to 3.

5. The outer cylinder further has a second inclined face that extends from the axial direction inlet side to the axial direction outlet side along the axial direction outlet side of the first inclined face and extends from the radially inner side to the outer side as it goes from the axial direction inlet side to the axial direction outlet side. In a cross-sectional view including the axis, the angle formed by the second inclined face with respect to the axis is smaller than the angle formed by the first inclined face with respect to the axis, and the strut is arranged across the first inclined face and the second inclined face in the axial direction. The gas turbine according to any one of claims 1 to 4.

6. In each of the turbine blades constituting the final stage moving blade row, the angle formed by the tip-side end face with respect to the axis is 20° or more and 25° or less with respect to the axis. The gas turbine according to any one of claims 1 to 5.

7. A compressor that generates high-pressure air by compressing air, A combustor that mixes fuel with the high-pressure air to generate combustion gas, The gas turbine according to any one of claims 1 to 6, comprising

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