Axial flow turbine

Abstract

To provide an axial flow turbine which can be improved in the overall efficiency.SOLUTION: An axial flow turbine includes: a turbine shaft; a turbine rotor blade row; and a turbine housing having an exhaust chamber on a downstream side of the turbine rotor blade row. The turbine housing includes a flow guide portion having an inner peripheral-side wall surface forming a diffuser flow path for guiding the working fluid that has passed through the turbine rotor blade row to the gap from an inner wall of the exhaust chamber in a radially outward side. When a minimum distance between a rear edge end and a negative pressure surface of the other adjacent turbine rotor blade is denoted as throat s, a pitch of the plurality of turbine rotor blade is denoted as t, a blade height position at a blade root is 0%, and the blade height position at the blade tip end is 100%, a distribution of throat / pitch ratio in a blade height direction having a throat / pitch ratio at the 25% blade height position is smaller than a line segment between the blade root portion and a center portion in the blade height direction, and a throat / pitch ratio at the 75% blade height position is smaller than a line segment between the center portion and the blade distal end portion.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an axial flow turbine.

Background Art

[0002] Some axial flow turbines are formed with a diffuser flow path for guiding the exhaust gas that has passed through the turbine rotor blades to the outside in the radial direction in order to save space (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, the turbine rotor blades of an axial flow turbine are designed with the design concept of improving the efficiency of the turbine rotor blades. However, it is difficult to say that the efficiency of the entire axial flow turbine is necessarily improved with the above design concept.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide an axial flow turbine capable of improving the efficiency of the entire axial flow turbine.

Means for Solving the Problems

[0006] The axial flow turbine according to at least one embodiment of the present disclosure includes a turbine shaft, a turbine rotor blade row composed of a plurality of turbine rotor blades attached to the turbine shaft and arranged in a row in the circumferential direction of the turbine shaft, a turbine housing that rotatably accommodates the turbine rotor blade row and has an exhaust chamber on the downstream side of the turbine rotor blade row, the turbine housing, It includes a flow guide portion having an inner circumferential side wall surface that forms a diffuser flow path for guiding the working fluid that has passed through the turbine rotor blade row to the outside in the radial direction between the inner wall of the exhaust chamber. The shortest distance between the trailing edge of the turbine rotor blade and the suction surface of another turbine rotor blade adjacent to the turbine rotor blade is defined as the throat s, the pitch of the plurality of turbine rotor blades arranged in a row is defined as t, the blade height position of the blade root in the blade height direction from the blade root to the blade tip of the turbine rotor blade is defined as 0%, and the blade height position of the blade tip is defined as 100%. In this case, The distribution of the throat - pitch ratio s / t of the turbine rotor blade in the blade height direction is The throat - pitch ratio s / t at the 25% blade height position is smaller than the line segment connecting the throat - pitch ratio s / t of the blade root portion including the blade root and the throat - pitch ratio s / t of the central portion of the turbine rotor blade in the blade height direction, and The throat - pitch ratio s / t at the 75% blade height position is configured to be smaller than the line segment connecting the throat - pitch ratio s / t of the central portion and the throat - pitch ratio s / t of the blade tip portion including the blade tip.

Advantages of the Invention

[0007] According to at least one embodiment of the present disclosure, an axial - flow turbine capable of improving the efficiency of the entire axial - flow turbine is provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0009] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, but are merely illustrative examples.

[0010] (Axial Flow Turbine) FIG. 1 is a schematic half-sectional view along the axial direction of an axial flow turbine according to an embodiment of the present disclosure. As shown in FIG. 1, the axial flow turbine 1 according to some embodiments includes a turbine shaft 2 extending along a rotation center axis LA, a turbine rotor blade row 3, and a turbine housing 4.

[0011] Hereinafter, the direction in which the rotation center axis LA of the turbine shaft 2 extends (the left-right direction in FIG. 1) is defined as the axial direction of the turbine shaft 2 (axial flow turbine 1), the direction orthogonal to the rotation center axis LA is defined as the radial direction of the turbine shaft 2 (axial flow turbine 1), and the circumferential direction around the rotation center axis LA is defined as the circumferential direction of the turbine shaft 2 (axial flow turbine 1). In the present disclosure, each of the axial direction, the radial direction, and the circumferential direction of the turbine shaft 2 may be simply referred to as the axial direction, the radial direction, and the circumferential direction. Note that "along a certain direction" in the present disclosure includes not only a certain direction but also a direction inclined within a range of ±15° with respect to a certain direction.

[0012] (Turbine rotor blade row) The turbine rotor blade row 3 is attached to the turbine shaft 2 and is composed of a plurality of turbine rotor blades 30 arranged in a row in the circumferential direction of the turbine shaft 2. In the illustrated embodiment, the turbine shaft 2 has a disk portion 22 that protrudes radially outward from the outer peripheral surface 21 of the turbine shaft 2. Each of the plurality of turbine rotor blades 30 includes a blade root portion 31 including a blade root 311 connected to the outer peripheral surface 23 of the disk portion 22 of the turbine shaft 2, and a blade tip portion 32 including a blade tip (tip end) 321 spaced radially outward from the blade root 311 with respect to the rotation center axis LA. The turbine rotor blade row 3 may be integrally formed with the turbine shaft 2 or may be separate from the turbine shaft 2 and fixed to the turbine shaft 2 by welding or the like.

[0013] Figure 2 is a schematic cross-sectional view of a turbine rotor blade 30 according to an embodiment of the present disclosure. Each of the plurality of turbine rotor blades 30 has a leading edge end 301, a trailing edge end 302, a pressure surface 303, and a suction surface 304, as shown in Figure 2. The pressure surface 303 has a concave curved surface with one end connected to the leading edge end 301 and the other end connected to the trailing edge end 302 on one side in the circumferential direction of the turbine shaft 2. The suction surface 304 has a convex curved surface with one end connected to the leading edge end 301 and the other end connected to the trailing edge end 302 on the other side in the circumferential direction of the turbine shaft 2. Each of the plurality of turbine rotor blades 30 is configured such that the pressure surface 303 faces the suction surface 304 of the turbine rotor blade 30A(30) arranged adjacent to the one side in the circumferential direction of the turbine shaft 2 with a circumferential gap therebetween.

[0014] (Turbine housing) The turbine housing 4 is configured to rotatably accommodate the turbine shaft 2 and the turbine rotor blade row 3. The turbine housing 4 includes an annular inner annular portion 41 that covers the outer peripheral side (radial outside) of the outer peripheral surface 21 of the turbine shaft 2 with a radial gap therebetween, and an annular outer annular portion 42 that covers the outer peripheral side (radial outside) of the outer peripheral surface 411 of the inner annular portion 41 with a radial gap therebetween.

[0015] An annular flow path 43 extending along the axial direction of the turbine shaft 2 is formed between the outer peripheral surface 411 of the inner annular portion 41 and the inner peripheral surface 421 of the outer annular portion 42. The annular flow path 43 is a flow path for guiding the working fluid from one side (left side in Figure 1) in the axial direction of the turbine shaft 2 to the other side (right side in Figure 1). The turbine rotor blade row 3 is arranged in the annular flow path 43. Each of the plurality of turbine rotor blades 30 is configured such that the blade tip 321 faces the inner peripheral surface 421 of the outer annular portion 42 with a radial gap therebetween.

[0016] The axial flow turbine 1 may include a turbine stator blade row 5 disposed upstream of the turbine rotor blade row 3 in the flow direction of the working fluid in the annular flow path 43, that is, on the upstream side in the axial direction on the one side. The turbine stator blade row 5 is composed of a plurality of turbine stator blades 50 arranged in a row in the circumferential direction of the turbine shaft 2. In the illustrated embodiment, each of the plurality of turbine stator blades 50 has an outer peripheral end connected to the inner peripheral surface 421 of the outer annular portion 42 and an inner peripheral end connected to the outer peripheral surface 411 of the inner annular portion 41.

[0017] (Exhaust chamber) As shown in FIG. 1, the turbine housing 4 has an exhaust chamber 6 on the downstream side of the turbine rotor blade row 3 in the flow direction of the working fluid. The exhaust chamber 6 (turbine housing 4) includes an inner wall 61, one side wall surface 62, and the other side wall surface 63. The inner wall 61 has at least a part of a convex curved portion that bulges inward in the radial direction such that the distance (radial distance) from the rotation center axis LA increases as it goes toward the other side in the axial direction of the turbine shaft 2. Each of the one side wall surface 62 and the other side wall surface 63 extends along the radial direction of the turbine shaft 2. The other side wall surface 63 is located on the other side in the axial direction of the turbine shaft 2 relative to the one side wall surface 62 and is opposed to the one side wall surface 62 with an axial gap therebetween. An exhaust chamber flow path 64 for guiding the working fluid toward the outside in the radial direction is formed between the one side wall surface 62 and the other side wall surface 63. An outlet (outlet opening) 65 for discharging the working fluid from the exhaust chamber flow path 64 formed in the exhaust chamber 6 is formed in the exhaust chamber 6. The outer peripheral end 611 of the inner wall 61 is connected to the other side wall surface 63.

[0018] (Flow guide portion) As shown in FIG. 1, the turbine housing 4 includes a flow guide portion 7. The flow guide portion 7 has an inner peripheral side wall surface 71 that forms a diffuser flow path 70 for guiding the working fluid that has passed through the turbine rotor blade row 3 between the inner wall 61 of the exhaust chamber 6 to the outside in the radial direction. The flow guide portion 7 is disposed inside the exhaust chamber 6. The flow guide portion 7 is an annular body that covers the outer peripheral side (radial outer side) of the inner wall 61 via the diffuser flow path 70, and the inner peripheral side wall surface 71 faces the inner wall 61 via the diffuser flow path 70. The inner peripheral side wall surface 71 has at least a part of a convex curved portion that bulges toward the radially inner side such that the distance (radial distance) from the rotation center axis LA increases as it goes toward the other side in the axial direction of the turbine shaft 2.

[0019] The exit (exit opening) 73 of the diffuser flow path 70 is formed by the trailing edge end 72 of the flow guide portion 7 and the portion where the distance from the trailing edge end 72 of the inner wall 61 is the shortest. The diffuser flow path 70 communicates with the exhaust chamber flow path 64 on the downstream side of the diffuser flow path 70 via the exit 73.

[0020] (Throat - pitch ratio) As shown in FIG. 2, the shortest distance between the trailing edge end 302 of the turbine rotor blade 30 and the suction surface 304 of another turbine rotor blade 30A adjacent to the turbine rotor blade 30 is defined as the throat s, and the pitch of the plurality of turbine rotor blades 30, 30A arranged in a row is defined as t. The throat - pitch ratio s / t is obtained by dividing the throat s by the pitch t.

[0021] Each of FIGS. 3 to 5 is an explanatory diagram for explaining the distribution of the throat pitch ratio s / t of the turbine rotor blade 30 with respect to the blade height position in one embodiment of the present disclosure. FIG. 6 is a schematic half-sectional view along the axial direction of the axial flow turbine 01 according to a comparative example. The axial flow turbine 01 according to the comparative example has the same configuration as the axial flow turbine 1 of the present disclosure except for the turbine rotor blade 30 as shown in FIG. 6. In FIGS. 3 to 5, a graph is shown with the blade height position on the horizontal axis and the throat pitch ratio s / t on the vertical axis. In FIGS. 3 to 5, broken lines L1, L2, and L3 showing the distribution of the throat pitch ratio s / t of two specific examples of the axial flow turbine 1 of the present disclosure with respect to the blade height position, and a straight line L4 showing the distribution of the throat pitch ratio s / t of the axial flow turbine 01 according to the comparative example with respect to the blade height position are shown.

[0022] The direction from the blade root portion 31 (blade root 311) to the blade tip portion 32 (blade tip 321) of the turbine rotor blade 30 is defined as the blade height direction. The blade height position in the blade height direction of the blade root 311 is defined as 0%, and the blade height position in the blade height direction of the blade tip 321 is defined as 100%. In one embodiment, the blade root portion 31 has a blade height position in the range of 0% or more and 10% or less, and the blade tip portion 32 has a blade height position in the range of 90% or more and 100% or less. And the central portion 33 in the blade height direction of the turbine rotor blade 30 has a blade height position in the range of 40% or more and 60% or less.

[0023] In FIGS. 3 to 5, a line segment LS1 connecting the throat pitch ratio s / t at the blade root portion 31 (in the illustrated example, 0% blade height position, blade root 311) and the throat pitch ratio s / t at the central portion 33 (in the illustrated example, 50% blade height position), and a line segment LS2 connecting the throat pitch ratio s / t at the central portion 33 (in the illustrated example, 50% blade height position) and the throat pitch ratio s / t at the blade tip portion 32 (in the illustrated example, 100% blade height position, blade tip 321) are shown.

[0024] In the axial flow turbine 01 according to the comparative example, as shown by the straight line L4 in FIGS. 3 to 5, the throat pitch ratio s / t monotonically decreases toward the tip 321 side in the blade height direction. In this case, as shown in FIG. 6, separation of the flow of the working fluid from the inner wall 61 forming the diffuser flow path 70 may occur, leading to a pressure loss in the diffuser flow path 70.

[0025] In the axial flow turbine 1 according to some embodiments, as shown in FIGS. 3 to 5, the distribution of the throat pitch ratio s / t in the blade height direction of the above-described turbine moving blade 30 is such that the throat pitch ratio s / t at the 25% blade height position is smaller than the line segment LS1 connecting the throat pitch ratio s / t of the blade root 31 and the throat pitch ratio s / t of the central portion 33, and the throat pitch ratio s / t at the 75% blade height position is smaller than the line segment LS2 connecting the throat pitch ratio s / t of the central portion 33 and the throat pitch ratio s / t of the blade tip portion 32.

[0026] By making the distribution of the throat pitch ratio s / t in the blade height direction of the turbine moving blade 30 smaller than the line segments LS1 and LS2 at the 25% blade height position and the 75% blade height position respectively, and making the throat pitch ratio s / t of each of the blade root 31 and the blade tip portion 32 of the turbine moving blade 30 relatively large, the flow velocity on each of the inner wall 61 side and the inner peripheral side wall surface 71 side in the diffuser flow path 70 can be increased. Thereby, separation of the flow of the working fluid from each of the inner wall 61 and the inner peripheral side wall surface 71 forming the diffuser flow path 70 can be suppressed, and thus a decrease in the efficiency of the entire axial flow turbine 1 can be suppressed. And by making the throat pitch ratio s / t of the central portion 33 in the blade height direction of the turbine moving blade 30 relatively large, the flow velocity distribution from the inner wall 61 side to the inner peripheral side wall surface 71 side at the outlet 73 of the diffuser flow path 70 can be made relatively uniform (see FIG. 1), so that the pressure recovery performance of the exhaust chamber 6 and the efficiency improvement of the entire axial flow turbine 1 can be achieved.

[0027] In the axial flow turbine 1 according to some embodiments, as shown by the broken lines L1 and L2 in FIGS. 3 and 4, for the above-described turbine moving blades 30, the distribution of the throat pitch ratio s / t in the blade height direction of the turbine moving blades 30 has a maximum value E1 formed between the blade root 31 and the blade tip 32, a root side minimum value E2 formed between the blade root 31 and the maximum value E1, and a blade tip side minimum value E3 formed between the maximum value E1 and the blade tip 32, and is configured to have these values.

[0028] In the embodiment shown in FIGS. 3 and 4, the blade root 31 has a larger throat pitch ratio s / t than the root side minimum value E2, and the throat pitch ratio s / t gradually decreases as it goes from the blade root 311 to the root side minimum value E2 in the blade height direction. The throat pitch ratio s / t gradually increases as it goes from the root side minimum value E2 to the maximum value E1 in the blade height direction.

[0029] In the embodiment shown in FIGS. 3 and 4, the throat pitch ratio s / t gradually decreases as it goes from the maximum value E1 to the blade tip side minimum value E3 in the blade height direction. The blade tip 32 has a larger throat pitch ratio s / t than the blade tip side minimum value E3, and the throat pitch ratio s / t gradually increases as it goes from the blade tip side minimum value E3 to the blade tip 321 in the blade height direction. Note that the root side minimum value E2 may be a value larger than the blade tip side minimum value E3, may be a value smaller than the blade tip side minimum value E3, or may be the same value as the blade tip side minimum value E3. The maximum value E1 may have a larger or smaller throat pitch ratio s / t compared to the blade root 31 and the blade tip 32.

[0030] The distribution of the throat pitch ratio s / t in the blade height direction of the turbine rotor blade 30 is formed into a shape having a maximum value E1, a root side minimum value E2, and a tip side minimum value E3. By making the throat pitch ratios s / t of the root portion 31, the tip portion 32, and the central portion 33 of the turbine rotor blade 30 relatively large, the flow velocity distribution from the inner wall 61 side to the inner peripheral side wall surface 71 side at the outlet 73 of the diffuser flow path 70 can be made relatively uniform. Therefore, the pressure recovery performance of the exhaust chamber 6 and the efficiency improvement of the entire axial flow turbine 1 can be achieved.

[0031] In some embodiments, as shown in FIGS. 3 and 4, for the turbine rotor blade 30 described above, the maximum value E1 of the throat pitch ratio s / t is formed within the range where the blade height position is 40% or more and 60% or less. By making the throat pitch ratio s / t maximum at the central portion (range of 40% or more and 60% or less) in the blade height direction of the turbine rotor blade 30, the flow velocity distribution from the inner wall 61 side to the inner peripheral side wall surface 71 side at the outlet 73 of the diffuser flow path 70 can be made more uniform. Therefore, the pressure recovery performance of the exhaust chamber 6 and the efficiency of the entire axial flow turbine 1 can be improved more effectively.

[0032] As shown in FIGS. 3 and 4, it is preferable that the root side minimum value E2 of the throat pitch ratio s / t is formed within the range where the blade height position is 20% or more and 30% or less. It is preferable that the tip side minimum value E3 of the throat pitch ratio s / t is formed within the range where the blade height position is 70% or more and 80% or less.

[0033] In addition, in some embodiments, the distribution of the throat pitch ratio s / t in the blade height direction of the turbine rotor blade 30 may be configured not to have the maximum value E1, the root side minimum value E2, and the tip side minimum value E3. For example, in the embodiment shown in FIG. 5, the throat pitch ratio s / t at the 25% blade height position is larger than the throat pitch ratio s / t at the central portion 33 (specifically, the 50% blade height position).

[0034] In some embodiments, as shown in FIGS. 3 to 5, the above-described turbine rotor blade 30 is configured such that the throat pitch ratio s / t has a maximum value at the blade root portion 31 (in the illustrated example, the blade root 311). Note that the throat pitch ratio s / t may have a maximum value at a blade height position other than the blade root 311 at the blade root portion 31. Since the axial flow turbine 1 has a structure that guides the working fluid to the outside in the radial direction, the flow of the working fluid is likely to separate from the inner wall 61 forming the blade root portion 31 side of the diffuser flow path 70. By maximizing the throat pitch ratio s / t at the blade root portion 31, the separation of the flow of the working fluid from the inner wall 61 forming the blade root portion 31 side of the diffuser flow path 70 can be more reliably suppressed.

[0035] FIG. 7 is a schematic cross-sectional view along the axial direction of the axial flow turbine 1 according to an embodiment of the present disclosure. FIG. 8 is a schematic cross-sectional view orthogonal to the axial direction of the axial flow turbine 1 according to an embodiment of the present disclosure. FIG. 8 schematically shows a cross-section along line A-B shown in FIG. 7. As shown in FIG. 8, in a part of the circumferential direction, an outlet 65 of the exhaust chamber 6 for discharging the working fluid from the exhaust chamber 6 is formed in the turbine housing 4. As shown in FIG. 8, in the circumferential direction, with respect to a reference line LB passing through the rotation center C of the turbine shaft 2 and parallel to the outlet 65 of the exhaust chamber 6, the side where the outlet 65 of the exhaust chamber 6 is located (the upper side in the figure) is defined as the exhaust side, and the side separated from the outlet 65 of the exhaust chamber 6 with respect to the reference line LB (the lower side in the figure) is defined as the anti-exhaust side.

[0036] In the illustrated embodiment, the outlet 65 of the exhaust chamber 6 is formed above the turbine shaft 2 in the vertical direction with respect to the rotation center C, the upper side of the rotation center C is the exhaust side, and the lower side of the rotation center C is the anti-exhaust side. In the cross-sectional view shown in FIG. 8, the reference line LB is orthogonal to the axis LC of the outlet 65 of the exhaust chamber 6. The exhaust chamber 6 includes an anti-exhaust side wall surface 66 formed in an arc shape on the anti-exhaust side and an exhaust side wall surface 67 formed along the axis LC on the exhaust side in the cross-sectional view shown in FIG. 8.

[0037] Hereinafter, the circumferential angular positions of the two intersections of the reference line LB with the wall surface of the exhaust chamber 6 are defined as 90° and 270°, respectively, and a circumferential angle α (see FIG. 8) is defined such that the range of 90° or more and 270° or less is the exhaust side.

[0038] In some embodiments, as shown in FIG. 7, in the above-described flow guide portion 7, the outlet area AU of the diffuser flow path 70 in at least a part of the exhaust side is configured to be larger than the outlet area AL of the diffuser flow path 70 in the anti-exhaust side. As shown in FIG. 7, the opening area at the trailing edge 312 of the blade root 311 of the turbine rotor blade 30 is defined as the inlet area A1 of the diffuser flow path 70. The diffuser flow path 70 has an increasing opening area toward the downstream side of the diffuser flow path 70.

[0039] Since the diffuser flow path 70 is a deceleration flow path for decelerating the working fluid, within a range where the separation of the flow of the working fluid from the wall surface forming the diffuser flow path 70 does not occur, by increasing the area ratio, which is the ratio of the outlet area of the diffuser flow path 70 to the inlet area, the discharge velocity of the working fluid from the diffuser flow path 70 can be reduced, and the exhaust loss of the axial flow turbine 1 can be reduced. By increasing the flow velocity on each of the inner wall 61 side and the inner circumferential wall surface 71 side at the outlet 73 of the diffuser flow path 70, the separation of the flow of the working fluid from the wall surface forming the diffuser flow path 70 occurs on the higher area ratio side, so that the exhaust loss of the axial flow turbine 1 can be effectively reduced. Further, the exhaust side with a high separation margin can have a larger area ratio than the anti-exhaust side, thereby more effectively reducing the exhaust loss of the axial flow turbine 1.

[0040] In some embodiments, as shown in FIG. 7, in the above-described flow guide portion 7, the axial length LFU of the flow guide portion 7 in at least a part of the exhaust side is smaller than the axial length LFL of the flow guide portion 7 in the anti-exhaust side.

[0041] FIG. 9 is an explanatory diagram for explaining the distribution of the axial length LF of the flow guide portion 7 with respect to the circumferential position in one embodiment of the present disclosure. The curve L6 shown in FIG. 9 shows the distribution of the axial length LF of the flow guide portion 7 with respect to the circumferential position in the embodiment shown in FIG. 7. The straight line L7 shown in FIG. 9 shows a case where the axial length LF of the flow guide portion 7 is made constant. As shown in FIG. 9, the axial length LF (LFU) is minimized at the central portion on the exhaust side (in the range where the circumferential angle α is 160° or more and 200° or less), and the axial length LF (LFL) is maximized at the central portion on the anti-exhaust side (in the range where the circumferential angle α is 0° or more and 20° or less or 340° or more and 360° or less). The axial length LF gradually increases from the central portion on the exhaust side toward the central portion on the anti-exhaust side. In the embodiment shown in FIG. 9, the axial length LF (LFU) is minimized when the circumferential angle α is 180°, and the axial length LF (LFL) is maximized when the circumferential angle α is 0°. In a certain embodiment, the minimum length of the axial length LF is at most 5% shorter than the maximum length. Further, in a certain embodiment, when the axial length from the trailing edge 312 of the blade root 311 of the turbine rotor blade 30 to one side wall surface 62 is defined as L5, the axial length LF of the flow guide portion 7 is 50% or more and 70% or less with respect to L5 over the entire circumference.

[0042] By making the axial length LFU on the exhaust side of the flow guide portion 7 smaller than the axial length LFL on the anti-exhaust side, the area ratio on the exhaust side can be made larger than that on the anti-exhaust side. Thereby, the exhaust loss of the axial flow turbine 1 can be more effectively reduced.

[0043] FIG. 10 is a schematic cross-sectional view along the axial direction of the axial flow turbine 1 according to one embodiment of the present disclosure. In some embodiments, as shown in FIG. 10, for the flow guide portion 7 described above, the inclination angle θU of the trailing edge 72 of the flow guide portion 7 with respect to the axial direction at at least a part on the exhaust side is larger than the inclination angle θL of the trailing edge 72 of the flow guide portion 7 with respect to the axial direction on the anti-exhaust side.

[0044] FIG. 11 is an explanatory diagram for explaining the distribution of the inclination angle θ with respect to the axial direction of the trailing edge 72 of the flow guide portion 7 in one embodiment of the present disclosure. The curve L8 shown in FIG. 11 shows the distribution of the inclination angle θ with respect to the axial direction of the trailing edge 72 of the flow guide portion 7 in the embodiment shown in FIG. 10 with respect to the circumferential position. The straight line L9 shown in FIG. 11 shows the case where the inclination angle θ is constant. As shown in FIG. 11, the inclination angle θ (θU) is maximum at the central portion on the exhaust side (in the range where the circumferential angle α is 160° or more and 200° or less), and the inclination angle θ (θL) is minimum at the central portion on the anti-exhaust side (in the range where the circumferential angle α is 0° or more and 20° or less or 340° or more and 360° or less). The inclination angle θ gradually decreases from the central portion on the exhaust side toward the central portion on the anti-exhaust side. In the embodiment shown in FIG. 11, the inclination angle θ (θU) is maximum when the circumferential angle α is 180°, and the axial length inclination angle θ (θL) is minimum when the circumferential angle α is 0°. In some embodiments, the maximum angle of the inclination angle θ is 5° or more larger than the minimum angle.

[0045] By making the inclination angle θU on the exhaust side of the flow guide portion 7 larger than the inclination angle θL on the anti-exhaust side, the area ratio on the exhaust side can be made larger than that on the anti-exhaust side. Thereby, the exhaust loss of the axial flow turbine 1 can be more effectively reduced. In some embodiments, the axial length LFU on the exhaust side of the flow guide portion 7 may be made smaller than the axial length LFL on the anti-exhaust side, and the inclination angle θU on the exhaust side of the flow guide portion 7 may be made larger than the inclination angle θL on the anti-exhaust side.

[0046] In the axial flow turbine 1 according to some embodiments, as shown in FIGS. 1, 7, and 10, the turbine rotor blade row 3 included in the axial flow turbine 1 is single-stage. In the embodiments shown in FIGS. 1, 7, and 10, the turbine stator blade row 5 included in the axial flow turbine 1 is also single-stage. When the turbine rotor blade row 3 included in the axial flow turbine 1 is single-stage, the improvement in efficiency in the diffuser flow path 70 and the exhaust chamber 6 has a greater impact on the improvement in the overall efficiency of the axial flow turbine 1 than the improvement in efficiency in the turbine rotor blade row 3. By making the distribution of the throat pitch ratio s / t in the blade height direction of the turbine rotor blade 30 smaller than the line segments LS1 and LS2 at the 25% blade height position and the 75% blade height position, or having a shape with a maximum value E1, a minimum value E2 on the hub side, and a minimum value E3 on the tip side, the efficiency in the diffuser flow path 70 and the exhaust chamber 6 can be improved, and thus the overall efficiency of the axial flow turbine 1 can be effectively improved.

[0047] FIG. 12 is a schematic cross-sectional view along the axial direction of a supercharger 100 including the axial flow turbine 1 according to an embodiment of the present disclosure. In some embodiments, as shown in FIG. 12, the above-described axial flow turbine 1 is mounted on the supercharger 100. The supercharger 100 includes the axial flow turbine 1 and a centrifugal compressor 101 attached to the turbine shaft 2 of the axial flow turbine 1. The centrifugal compressor 101 is driven in conjunction with the rotation of the turbine shaft 2 of the axial flow turbine 1, which is driven by exhaust gas (working fluid) discharged from an internal combustion engine (not shown), and is configured to compress the intake air led to the internal combustion engine.

[0048] Since there is a demand to make the size of the axial flow turbine 1 mounted on the supercharger 100 compact, the axial flow turbine 1 has a diffuser flow path 70 for guiding the exhaust gas, which is the working fluid, to the outside in the radial direction. By using the axial flow turbine 1 having such a diffuser flow path 70 as the axial flow turbine 1 according to some of the above-described embodiments, the overall efficiency of the axial flow turbine 1 can be improved.

[0049] In this specification, expressions indicating relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent states where there are tolerances or relative displacements with angles or distances that can achieve the same function. For example, expressions indicating that things such as "identical", "equal", and "homogeneous" are in an equal state not only strictly represent an equal state, but also represent states where there are tolerances or differences that can achieve the same function. Also, in this specification, expressions indicating shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in a geometrically strict sense, but also represent shapes including uneven portions, chamfered portions, etc. within a range where the same effect can be obtained. Also, in this specification, the expressions "comprising", "including", or "having" a component do not exclude the existence of other components.

[0050] The present disclosure is not limited to the above-described embodiments, and includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.

[0051] The content described in some of the above-described embodiments can be understood as follows, for example.

[0052] 1) The axial flow turbine (1) according to at least one embodiment of the present disclosure includes a turbine shaft (2), a turbine rotor blade row (3) composed of a plurality of turbine rotor blades (30) attached to the turbine shaft (2) and arranged in a row in the circumferential direction of the turbine shaft (2), a turbine housing (4) that rotatably houses the turbine rotor blade row (3) and has an exhaust chamber (6) on the downstream side of the turbine rotor blade row (3). The turbine housing (4) A flow guide portion (7) having an inner peripheral side wall surface (71) that forms a diffuser flow path (70) for guiding the working fluid that has passed through the turbine rotor blade row (3) radially outward between the inner wall (61) of the exhaust chamber (6). Define the shortest distance between the trailing edge (302) of the turbine rotor blade (30) and the suction surface (304) of another turbine rotor blade (30A) adjacent to the turbine rotor blade (30) as the throat s, define the pitch of the plurality of turbine rotor blades (30, 30A) arranged in a row as t, define the blade height position of the blade root (311) in the blade height direction from the blade root (311) to the blade tip (321) of the turbine rotor blade (30) as 0%, and define the blade height position of the blade tip (321) as 100%. In this case, The distribution of the throat - pitch ratio s / t of the turbine rotor blade (30) in the blade height direction is The throat - pitch ratio s / t at the 25% blade height position is smaller than the line segment (LS1) connecting the throat - pitch ratio s / t of the blade root portion (31) including the blade root (311) and the throat - pitch ratio s / t of the central portion (33) of the turbine rotor blade (30) in the blade height direction, and The throat - pitch ratio s / t at the 75% blade height position is configured to be smaller than the line segment (LS2) connecting the throat - pitch ratio s / t of the central portion (33) and the throat - pitch ratio s / t of the blade tip portion (32) including the blade tip (321).

[0053] According to the configuration of 1) above, the distribution of the throat pitch ratio s / t in the blade height direction of the turbine rotor blade (30) is made smaller than the line segments (LS1, LS2) at the 25% blade height position and the 75% blade height position respectively, and the throat pitch ratio s / t of each of the blade root (31) and the blade tip (32) of the turbine rotor blade (30) is made relatively large, whereby the flow velocities on the inner wall (61) side and the inner peripheral side wall surface (71) side in the diffuser flow path (70) can be increased. Thereby, the separation of the flow of the working fluid from each of the inner wall (61) and the inner peripheral side wall surface (71) forming the diffuser flow path (70) can be suppressed, and thus the efficiency reduction of the entire axial flow turbine (1) can be suppressed. And by making the throat pitch ratio s / t of the central portion (33) in the blade height direction of the turbine rotor blade (30) relatively large, the flow velocity distribution from the inner wall (61) side to the inner peripheral side wall surface (71) side at the outlet (73) of the diffuser flow path (70) can be made relatively uniform, so that the pressure recovery performance of the exhaust chamber (6) and the efficiency improvement of the entire axial flow turbine (1) can be achieved.

[0054] 2) In some embodiments, it is the axial flow turbine (1) described in 1) above, The distribution of the throat pitch ratio s / t in the blade height direction of the turbine rotor blade (30) is configured to have a maximum value (E1) formed between the blade root (31) and the blade tip (32), a blade root side minimum value (E2) formed between the blade root (31) and the maximum value (E1), and a blade tip side minimum value (E3) formed between the maximum value (E1) and the blade tip (32).

[0055] According to the configuration of 2) above, the distribution of the throat pitch ratio s / t in the blade height direction of the turbine rotor blade (30) is shaped to have a maximum value (E1), a minimum value on the blade root side (E2), and a minimum value on the blade tip side (E3). By making the throat pitch ratio s / t of each of the blade root portion (31), the blade tip portion (32), and the central portion (33) of the turbine rotor blade (30) relatively large, the flow velocity distribution from the inner wall (61) side to the inner peripheral side wall surface (71) side at the outlet (73) of the diffuser flow path (70) can be made relatively uniform. Therefore, the pressure recovery performance of the exhaust chamber (6) and the efficiency improvement of the entire axial flow turbine (1) can be achieved.

[0056] 3) In some embodiments, the axial flow turbine (1) described in 1) or 2) above, wherein the turbine rotor blade (30) is configured such that the throat pitch ratio s / t has a maximum value at the blade root portion (31).

[0057] According to the configuration of 3) above, in the axial flow turbine (1), due to the structure that guides the working fluid radially outward, the separation of the flow of the working fluid from the wall surface (inner wall 61) forming the blade root portion (31) side of the diffuser flow path (70) is likely to occur. By making the throat pitch ratio s / t at the blade root portion (31) maximum, the separation of the flow of the working fluid from the wall surface (inner wall 61) forming the blade root portion (31) side of the diffuser flow path (70) can be more reliably suppressed.

[0058] 4) In some embodiments, the axial flow turbine (1) described in 2) above, wherein the turbine rotor blade (30) is configured such that the maximum value (E1) of the throat pitch ratio s / t is formed within the range where the blade height position is 40% or more and 60% or less.

[0059] According to the configuration of 4) above, by maximizing the throat pitch ratio s / t in the central portion (in the range of 40% or more and 60% or less) in the blade height direction of the turbine rotor blade (30), the flow velocity distribution from the inner wall (61) side to the inner peripheral side wall surface (71) side at the outlet (73) of the diffuser flow path (70) can be made more uniform. Therefore, the pressure recovery performance of the exhaust chamber (6) and the efficiency of the entire axial flow turbine (1) can be improved more effectively.

[0060] 5) In some embodiments, it is the axial flow turbine (1) described in any one of 1) to 4) above, the turbine housing (4) has an outlet (65) of the exhaust chamber (6) formed in a part in the circumferential direction for discharging the working fluid from the exhaust chamber (6), in the circumferential direction, when the side where the outlet (65) of the exhaust chamber (6) is located is defined as the exhaust side with respect to a reference line (LB) passing through the rotation center (C) of the turbine shaft (2) and parallel to the outlet (65) of the exhaust chamber (6), and the side separated from the outlet (65) of the exhaust chamber (6) with respect to the reference line (LB) is defined as the anti-exhaust side, the flow guide portion (7) is, configured such that the outlet area (AU) of the diffuser flow path (70) in at least a part of the exhaust side is larger than the outlet area (AL) of the diffuser flow path (70) in the anti-exhaust side.

[0061] According to the configuration of 5) above, since the diffuser flow path (70) is a deceleration flow path for decelerating the working fluid, within the range where separation of the flow of the working fluid from the wall surface forming the diffuser flow path (70) does not occur, by increasing the area ratio, which is the ratio of the outlet area of the diffuser flow path (70) to the inlet area, the discharge velocity of the working fluid from the diffuser flow path (70) can be reduced, and the exhaust loss of the axial flow turbine (1) can be reduced. By increasing the flow velocity on each of the inner wall (61) side and the inner peripheral side wall surface (71) side at the outlet of the diffuser flow path (70), the separation of the flow of the working fluid from the wall surface forming the diffuser flow path (70) occurs on the higher area ratio side, so that the exhaust loss of the axial flow turbine (1) can be effectively reduced. Furthermore, the exhaust side with a high separation margin can have a larger area ratio compared to the anti-exhaust side, thereby more effectively reducing the exhaust loss of the axial flow turbine (1).

[0062] 6) In some embodiments, it is the axial flow turbine (1) described in 5) above, wherein the flow guide portion (7) is, the axial length (LFU) of the inner peripheral side wall surface (71) in at least a part of the exhaust side is smaller than the axial length (LFL) of the inner peripheral side wall surface (71) in the anti-exhaust side.

[0063] According to the configuration of 6) above, by making the axial length (LFU) of the exhaust side of the flow guide portion (7) smaller than the axial length (LFL) of the anti-exhaust side, the area ratio of the exhaust side can be made larger than that of the anti-exhaust side. Thereby, the exhaust loss of the axial flow turbine (1) can be more effectively reduced.

[0064] 7) In some embodiments, it is the axial flow turbine (1) described in 5) or 6) above, wherein the flow guide portion (7) is, the inclination angle (θU) with respect to the axial direction of the trailing edge (72) of the flow guide portion (7) in at least a part of the exhaust side is larger than the inclination angle (θL) with respect to the axial direction of the trailing edge of the flow guide portion (7) in the anti-exhaust side.

[0065] According to the configuration of 7) above, by making the inclination angle (θU) on the exhaust side of the flow guide portion (7) larger than the inclination angle (θL) on the anti-exhaust side, the area ratio on the exhaust side can be made larger than that on the anti-exhaust side. Thereby, the exhaust loss of the axial flow turbine (1) can be more effectively reduced.

[0066] 8) In some embodiments, it is the axial flow turbine (1) described in any one of 1) to 7) above, The turbine moving blade row (3) provided in the axial flow turbine (1) is single-stage.

[0067] According to the configuration of 8) above, when the turbine moving blade row (3) provided in the axial flow turbine (1) is single-stage, the improvement in efficiency in the diffuser flow path (70) and the exhaust chamber (6) has a greater impact on the improvement in the overall efficiency of the axial flow turbine (1) than the improvement in efficiency in the turbine moving blade row (3). By making the distribution of the throat pitch ratio s / t in the blade height direction of the turbine moving blade (30) smaller than the respective line segments (LS1, LS2) at the 25% blade height position and the 75% blade height position, or by making it a shape having a maximum value (E1), a minimum value (E2) on the blade root side, and a minimum value (E3) on the blade tip side, and improving the efficiency in the diffuser flow path (70) and the exhaust chamber (6), the overall efficiency of the axial flow turbine (1) can be effectively improved.

[0068] 9) In some embodiments, it is the axial flow turbine (1) described in any one of 1) to 8) above, The axial flow turbine (1) is mounted on a supercharger (100).

[0069] According to the configuration of 9) above, since there is a demand to make the size of the axial flow turbine (1) mounted on the supercharger (100) compact, it has a diffuser flow path (70) for guiding the working fluid to the outer side in the radial direction. The axial flow turbine (1) having such a diffuser flow path (70) can improve the overall efficiency of the axial flow turbine (1) by having the configuration described in any one of 1) to 7) above.

Description of reference numerals

[0070] 1,01 Axial flow turbine 2 Turbine shaft 3 Turbine rotor blade row 4 Turbine housing 5 Turbine stator blade row 6 Exhaust chamber 7 Flow guide section 30, 30A Turbine rotor blade 31 Blade root 32 Blade tip 33 Central part 41 Inner annular part 42 Outer annular part 43 Annular flow path 50 Turbine stator blade 61 Inner wall 64 Exhaust chamber flow path 65 Outlet 70 Diffuser flow path 71 Inner peripheral side wall surface 72 Trailing edge end 73 Outlet 100 Supercharger 101 Centrifugal compressor 311 Blade root 312 Blade tip E1 Maximum value E2 Minimum value on blade root side E3 Minimum value on blade tip side

Claims

1. a turbine shaft; a turbine blade row configured by a plurality of turbine moving blades attached to the turbine shaft and arranged in a row in the circumferential direction of the turbine shaft; a turbine housing that rotatably accommodates the turbine blade row and has an exhaust chamber on the downstream side of the turbine blade row; and the turbine housing includes a flow guide portion having an inner circumferential side wall surface that forms a diffuser flow path for guiding the working fluid that has passed through the turbine blade row to the outside in the radial direction between the inner wall of the exhaust chamber; defining the shortest distance between the trailing edge of the turbine moving blade and the suction surface of another turbine moving blade adjacent to the turbine moving blade as a throat s, defining the pitch of the plurality of turbine moving blades arranged in a row as t, defining the blade height position of the blade root in the blade height direction from the blade root to the blade tip of the turbine moving blade as 0%, and defining the blade height position of the blade tip as 100%; in this case, the distribution of the throat - pitch ratio s / t in the blade height direction of the turbine moving blade the throat - pitch ratio s / t at the 25% blade height position is smaller than the line segment connecting the throat - pitch ratio s / t of the blade root portion including the blade root and the throat - pitch ratio s / t of the central portion in the blade height direction of the turbine moving blade, and the throat - pitch ratio s / t at the 75% blade height position is configured to be smaller than the line segment connecting the throat - pitch ratio s / t of the central portion and the throat - pitch ratio s / t of the blade tip portion including the blade tip, an axial - flow turbine.

2. the distribution of the throat - pitch ratio s / t in the blade height direction of the turbine moving blade has a maximum value formed between the blade root portion and the blade tip portion, a blade - root - side minimum value formed between the blade root portion and the maximum value, and a blade - tip - side minimum value formed between the maximum value and the blade tip portion, The axial - flow turbine according to Claim 1.

3. the turbine moving blade is configured such that the throat - pitch ratio s / t has a maximum value at the blade root, The axial - flow turbine according to Claim 1 or 2.

4. the turbine moving blade is configured such that the maximum value of the throat - pitch ratio s / t is formed within a range where the blade height position is 40% or more and 60% or less, The axial - flow turbine according to Claim 2.

5. The turbine housing has an outlet of the exhaust chamber formed in a part of the circumferential direction for discharging the working fluid from the exhaust chamber. In the circumferential direction, when the side where the outlet of the exhaust chamber is located is defined as the exhaust side with respect to a reference line passing through the rotation center of the turbine shaft and parallel to the outlet of the exhaust chamber, and the side separated from the outlet of the exhaust chamber with respect to the reference line is defined as the anti-exhaust side. The flow guide portion is configured such that an outlet area of the diffuser flow path in at least a part of the exhaust side is larger than an outlet area of the diffuser flow path in the anti-exhaust side. The axial flow turbine according to claim 1 or 2.

6. The flow guide portion has an axial length of the flow guide portion in at least a part of the exhaust side smaller than an axial length of the flow guide portion in the anti-exhaust side. The axial flow turbine according to claim 5.

7. The flow guide portion has an inclination angle of a trailing edge end of the flow guide portion in at least a part of the exhaust side with respect to the axial direction larger than an inclination angle of the trailing edge end of the flow guide portion in the anti-exhaust side with respect to the axial direction. The axial flow turbine according to claim 5.

8. The turbine moving blade row included in the axial flow turbine is single-stage. The axial flow turbine according to claim 1 or 2.

9. The axial flow turbine is mounted on a supercharger. The axial flow turbine according to claim 1 or 2.

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