axial turbine

Abstract

An axial turbine has: a turbine shaft; a turbine rotating blade row; and a turbine casing having an exhaust chamber on a downstream side of the turbine rotating blade row, the turbine casing including a flow guide portion having an inner peripheral side wall surface that forms a diffuser flow path for guiding working fluid that has passed through the turbine rotating blade row to a radially outer side between an inner wall of the exhaust chamber, a shortest distance between a trailing edge end and a negative pressure surface of an adjacent other turbine rotating blade is set as a throat (s), a pitch of the plurality of turbine rotating blades is set as (t), a blade height position of a blade root is set as 0%, a blade height position of a blade tip is set as 100%, in a distribution of a throat pitch ratio in the blade height direction when the blade height position of the blade root is set as 0% and the blade height position of the blade tip is set as 100%, a throat pitch ratio at a 25% blade height position is smaller than a line segment connecting the blade root and a central portion in the blade height direction, and a throat pitch ratio at a 75% blade height position is smaller than a line segment connecting the central portion and the blade tip portion.

Description

Technical Field

[0001] This invention relates to an axial flow turbine.

[0002] This application claims priority based on Japanese Patent Application No. 2023-210277, filed with the Japan Patent Office on December 13, 2023, the contents of which are incorporated herein by reference. Background Technology

[0003] To save space, a diffuser flow path is formed in the axial turbine to guide the exhaust gas that has passed through the turbine's rotating blades to the radially outward side (see Patent Document 1).

[0004] Previous technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2016-84730 Summary of the Invention

[0005] The technical problem to be solved by the invention Typically, the turbine blades of axial flow turbines are designed with the aim of improving the efficiency of the turbine blades themselves. However, it is difficult to say that this design approach will necessarily achieve an overall improvement in the efficiency of the axial flow turbine.

[0006] In view of the above, the object of at least one embodiment of the present invention is to provide an axial turbine that can improve the overall efficiency of an axial turbine.

[0007] means for solving technical problems At least one embodiment of the axial turbine according to the present invention includes: Turbine shaft; A turbine blade array, mounted on the turbine shaft and composed of a plurality of turbine blades arranged in an array circumferentially on the turbine shaft; and The turbine housing rotatably houses a row of turbine blades and has an exhaust chamber on the downstream side of the row of turbine blades. The turbine housing includes a flow guide section having an inner circumferential sidewall surface. This inner circumferential sidewall surface forms a diffuser flow path between itself and the inner wall of the exhaust chamber, for guiding the working fluid that has passed through the turbine's rotating blade array to the radially outward side. The throat is defined as 's' when the shortest distance between the trailing edge of the turbine blade and the negative pressure surface of the other adjacent turbine blades is defined as 't', the spacing between the plurality of turbine blades arranged in a row is defined as 't', and the blade height position of the blade root in the blade height direction from the blade root to the blade tip is defined as 0%, and the blade height position of the blade tip is defined as 100%. The distribution of the throat spacing ratio s / t in the blade height direction of the turbine rotating blades is as follows: The throat spacing ratio s / t at the 25% blade height position is less than the line segment connecting the throat spacing ratio s / t of the blade root including the blade root and the throat spacing ratio s / t of the central portion of the turbine rotating blade in the blade height direction, and, The throat spacing ratio s / t at 75% blade height position is less than the line segment connecting the throat spacing ratio s / t of the central portion and the throat spacing ratio s / t of the blade tip portion including the blade tip.

[0008] Invention Effects According to at least one embodiment of the present invention, an axial flow turbine capable of improving the overall efficiency of an axial flow turbine is provided. Attached Figure Description

[0009] Figure 1 This is a schematic half-sectional view of an axial flow turbine according to an embodiment of the present invention.

[0010] Figure 2 This is a schematic cross-sectional view of a turbine rotating blade in one embodiment of the present invention.

[0011] Figure 3 This is an explanatory diagram illustrating the distribution of the throat spacing ratio of turbine rotating blades relative to the blade height position in one embodiment of the present invention.

[0012] Figure 4 This is an explanatory diagram illustrating the distribution of the throat spacing ratio of turbine rotating blades relative to the blade height position in one embodiment of the present invention.

[0013] Figure 5 This is an explanatory diagram illustrating the distribution of the throat spacing ratio of turbine rotating blades relative to the blade height position in one embodiment of the present invention.

[0014] Figure 6 This is a schematic half-sectional view of the axial flow turbine involved in the comparative example, cut along the axial direction.

[0015] Figure 7 This is a schematic cross-sectional view of an axial flow turbine according to an embodiment of the present invention.

[0016] Figure 8 This is a schematic cross-sectional view of an axial turbine orthogonal to the axial direction according to an embodiment of the present invention.

[0017] Figure 9 This is an explanatory diagram illustrating the distribution of the axial length of the guide portion relative to the circumferential position in one embodiment of the present invention.

[0018] Figure 10 This is a schematic cross-sectional view of an axial flow turbine according to an embodiment of the present invention.

[0019] Figure 11 This is an explanatory diagram illustrating the distribution of the tilt angle of the trailing edge of the guide portion relative to the axial direction relative to the circumferential position in one embodiment of the present invention.

[0020] Figure 12 This is a schematic cross-sectional view of an axially oriented turbocharger according to an embodiment of the present invention. Detailed Implementation

[0021] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, and relative arrangements of the constituent parts described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0022] (Axial flow turbine) Figure 1 This is a schematic half-sectional view taken along the axial direction of an axial flow turbine according to one embodiment of the present invention. Figure 1 As shown, in some embodiments, the axial turbine 1 includes a turbine shaft 2 extending along the rotation center axis LA, a turbine blade row 3, and a turbine housing 4.

[0023] The following will be the direction in which the rotation center axis LA of the turbine shaft 2 is extended ( Figure 1 The axial direction of the turbine shaft 2 (axial turbine 1) is defined as the left-right direction. The radial direction of the turbine shaft 2 (axial turbine 1) is defined as the direction orthogonal to the rotation center axis LA. The circumferential direction around the rotation center axis LA is defined as the circumferential direction of the turbine shaft 2 (axial turbine 1). In this invention, the axial, radial, and circumferential directions of the turbine shaft 2 are sometimes simply referred to as axial, radial, and circumferential, respectively. In addition, "along a certain direction" in this invention includes not only a certain direction, but also a direction inclined within ±15° relative to a certain direction.

[0024] (Turbine rotating blade array) The turbine blade row 3 is composed of a plurality of turbine blades 30 mounted on the turbine shaft 2 and arranged in a row along the circumference of the turbine shaft 2. In the illustrated embodiment, the turbine shaft 2 has a disc portion 22 that protrudes radially outward from the outer peripheral surface 21 of the turbine shaft 2. Each of the plurality of turbine blades 30 has: a blade root portion 31, including a blade root 311 connected to the outer peripheral surface 23 of the disc portion 22 of the turbine shaft 2; and a blade tip portion 32, including a blade tip (tip) 321 that is further radially outward from the turbine shaft 2 than the blade root 311 relative to the rotation center axis LA. The turbine blade row 3 can be integrally formed with the turbine shaft 2, or it can be separate from the turbine shaft 2 and fixed to the turbine shaft 2 by welding or the like.

[0025] Figure 2 This is a schematic cross-sectional view of the turbine rotating blade 30 according to one embodiment of the present invention. Figure 2 As shown, the plurality of turbine rotating blades 30 each have a leading edge end 301, a trailing edge end 302, a pressure surface 303, and a negative pressure surface 304. The pressure surface 303 has a concave curved surface on one side of the turbine shaft 2 in the circumferential direction, with one end connected to the leading edge end 301 and the other end connected to the trailing edge end 302. The negative pressure surface 304 has a convex curved surface on the other side of the turbine shaft 2 in the circumferential direction, with one end connected to the leading edge end 301 and the other end connected to the trailing edge end 302. The plurality of turbine rotating blades 30 are respectively configured such that the pressure surface 303 is positioned opposite the negative pressure surface 304, which is arranged adjacent to the turbine rotating blade 30A (30) on the aforementioned side of the turbine shaft 2 in the circumferential direction, with a circumferential gap between them.

[0026] (Turbine casing) The turbine housing 4 is configured to rotatably house the turbine shaft 2 and the turbine blade array 3. The turbine housing 4 includes: an annular inner annular portion 41 that covers the outer peripheral side (radially outer side) of the outer peripheral surface 21 of the turbine shaft 2 with a radial clearance; and an annular outer annular portion 42 that covers the outer peripheral side (radially outer side) of the outer peripheral surface 411 of the inner annular portion 41 with a radial clearance.

[0027] An annular flow path 43 extending axially along 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 used to direct the working fluid from one side of the turbine shaft 2 axially. Figure 1 (left side) to the other side ( Figure 1 The flow path is guided by the right side of the middle section. The turbine rotating blade row 3 is arranged in the annular flow path 43. Multiple turbine rotating blades 30 are respectively arranged so that the blade front end 321 is opposite to the inner circumferential surface 421 of the outer annular portion 42 through a radial gap.

[0028] The axial turbine 1 may include a turbine fixed blade row 5, which is disposed upstream of the working fluid flow direction of the annular flow path 43, i.e., on the axial side, compared to the turbine rotating blade row 3. The turbine fixed blade row 5 is composed of a plurality of turbine fixed blades 50 arranged in a row in the circumferential direction of the turbine shaft 2. In the illustrated embodiment, the plurality of turbine fixed blades 50 are respectively configured such that their outer peripheral ends are connected to the inner peripheral surface 421 of the outer annular portion 42, and their inner peripheral ends are connected to the outer peripheral surface 411 of the inner annular portion 41.

[0029] (Exhaust chamber) like Figure 1 As shown, the turbine housing 4 has an exhaust chamber 6 downstream of the turbine blade row 3 in the direction of fluid flow. The exhaust chamber 6 (turbine housing 4) includes an inner wall 61, a side wall 62, and a side wall 63. The inner wall 61 has at least a portion of a convex bend that protrudes radially inward with increasing distance (radial distance) from the rotation center axis LA toward the other side in the axial direction toward the turbine shaft 2. The side wall 62 and the other side wall 63 extend radially along the turbine shaft 2. The other side wall 63 is located on the other side in the axial direction of the turbine shaft 2, closer to the other side than the side wall 62, and is opposed to the side wall 62 by an axial clearance. An exhaust chamber flow path 64 for guiding the working fluid toward the radially outward is formed between the side wall 62 and the other side wall 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 63.

[0030] (Flow diversion section) like Figure 1 As shown, the turbine housing 4 includes a guide section 7. The guide section 7 has an inner peripheral sidewall 71, which forms a diffuser flow path 70 between itself and the inner wall 61 of the exhaust chamber 6 for guiding the working fluid passing through the turbine rotating blade row 3 toward the radially outward side. The guide section 7 is disposed inside the exhaust chamber 6. The guide section 7 is an annular body covering the outer peripheral side (radially outward) of the inner wall 61 via the diffuser flow path 70, and the inner peripheral sidewall 71 is opposed to the inner wall 61 via the aforementioned diffuser flow path 70. The inner peripheral sidewall 71 has a convex bend in at least a portion, which protrudes radially inward as the distance (radial distance) from the rotation center axis LA increases toward the other side in the axial direction toward the turbine shaft 2.

[0031] The outlet (outlet opening) 73 of the diffuser flow path 70 is formed by the shortest distance between the rear edge 72 of the guide section 7 and the rear edge 72 of the inner wall 61. The diffuser flow path 70 is connected to the exhaust chamber flow path 64 on the downstream side of the diffuser flow path 70 via the outlet 73.

[0032] (Laryngeal distance ratio) like Figure 2 As shown, the shortest distance between the trailing edge 302 of the turbine blade 30 and the negative pressure surface 304 of another turbine blade 30A adjacent to the turbine blade 30 is defined as the throat s, and the spacing between the multiple turbine blades 30, 30A arranged in a row is defined as t. The throat spacing ratio s / t is obtained by dividing the throat s by the spacing t.

[0033] Figures 3-5 These are explanatory diagrams illustrating the distribution of the throat spacing ratio s / t of the turbine rotating blades 30 relative to the blade height position in one embodiment of the present invention. Figure 6 This is a schematic half-sectional view taken along the axial direction of the axial turbine 01 involved in the comparative example. (See attached image.) Figure 6 As shown, the axial turbine 01 involved in the comparative example has the same structure as the axial turbine 1 of the present invention, except for the turbine rotating blades 30. Figures 3-5 The graph shows a plot where the blade height position is set on the horizontal axis and the throat spacing ratio s / t is set on the vertical axis. Figures 3-5 The diagram shows broken lines L1, L2, and L3 representing the distribution of throat spacing ratio s / t relative to blade height position in two specific examples of the axial turbine 1 of the present invention, and a straight line L4 representing the distribution of throat spacing ratio s / t relative to blade height position in the axial turbine 01 involved in the comparative example.

[0034] The direction from the blade root 31 (blade root 311) of the turbine rotating blade 30 toward the blade tip 32 (blade tip 321) 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 height position of the blade root 31 is in the range of 0% or more and 10% or less, and the blade height position of the blade tip 32 is in the range of 90% or more and 100% or less. Furthermore, the blade height position of the central portion 33 in the blade height direction of the turbine rotating blade 30 is in the range of 40% or more and 60% or less.

[0035] exist Figures 3-5 The figure shows line segment LS1 connecting the throat spacing ratio s / t in the blade root 31 (0% blade height position, blade root 311 in the example) to the throat spacing ratio s / t in the central part 33 (50% blade height position in the example), and line segment LS2 connecting the throat spacing ratio s / t in the central part 33 (50% blade height position in the example) to the throat spacing ratio s / t in the blade tip 32 (100% blade height position, blade tip 321 in the example).

[0036] like Figures 3-5As shown by line L4, the throat spacing ratio s / t of the axial turbine 01 involved in the comparative example decreases monotonically with respect to the blade tip 321 side in the blade height direction. In this case, as... Figure 6 As shown, it is possible for the working fluid to be stripped from the flow of the inner wall 61 forming the diffuser flow path 70, resulting in pressure loss within the diffuser flow path 70.

[0037] In some embodiments of the axial turbine 1, such as Figures 3-5 As shown, the distribution of the throat spacing ratio s / t in the blade height direction of the turbine rotating blade 30 is configured as follows: the throat spacing ratio s / t at the 25% blade height position is less than the line segment LS1 connecting the throat spacing ratio s / t of the blade root 31 and the throat spacing ratio s / t of the central portion 33, and the throat spacing ratio s / t at the 75% blade height position is less than the line segment LS2 connecting the throat spacing ratio s / t of the central portion 33 and the throat spacing ratio s / t of the blade leading edge 32.

[0038] By setting the throat spacing ratio s / t of the turbine rotating blade 30 at the 25% and 75% blade height positions, respectively, to be smaller than line segments LS1 and LS2, and by making the throat spacing ratio s / t of the blade root 31 and blade leading edge 32 of the turbine rotating blade 30 relatively large, the flow velocity on the inner wall 61 side and the inner peripheral sidewall 71 side of the diffuser flow path 70 can be increased. This suppresses the stripping of the working fluid from the inner wall 61 and the inner peripheral sidewall 71 forming the diffuser flow path 70, thereby suppressing the overall efficiency reduction of the axial turbine 1. Furthermore, by making the throat spacing ratio s / t of the central portion 33 of the turbine rotating blade 30 in the blade height direction relatively large, the flow velocity distribution from the inner wall 61 side to the inner peripheral sidewall 71 side in the outlet 73 of the diffuser flow path 70 can be made relatively uniform (see reference). Figure 1 Therefore, it is possible to improve the pressure recovery performance of the exhaust chamber 6 and the overall efficiency of the axial turbine 1.

[0039] In some embodiments of the axial turbine 1, such as Figure 3 , Figure 4 As shown by the broken lines L1 and L2, the turbine rotating blade 30 is configured such that the distribution of the throat spacing ratio s / t in the blade height direction of the turbine rotating blade 30 has 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.

[0040] exist Figure 3 and Figure 4In the embodiment shown, the throat spacing ratio s / t at the blade root 31 is greater than the throat spacing ratio s / t at the blade root lateral minimum E2, and the throat spacing ratio s / t gradually decreases in the blade height direction from the blade root 311 towards the blade root lateral minimum E2. Conversely, the throat spacing ratio s / t gradually increases in the blade height direction from the blade root lateral minimum E2 towards the maximum E1.

[0041] exist Figure 3 and Figure 4 In the illustrated embodiment, the throat spacing ratio s / t gradually decreases in the blade height direction from the maximum value E1 towards the minimum value E3 at the blade tip. The throat spacing ratio s / t at the blade tip 32 is greater than the throat spacing ratio s / t at the blade tip minimum value E3, and in the blade height direction, the throat spacing ratio s / t gradually increases from the blade tip minimum value E3 towards the blade tip 321. Furthermore, the blade root minimum value E2 can be greater than, less than, or the same as the blade tip minimum value E3. The throat spacing ratio s / t at the maximum value E1 can be greater than or less than the throat spacing ratio s / t at the blade root 31 and the blade tip 32.

[0042] By setting the throat spacing ratio s / t of the turbine rotating blade 30 in the blade height direction to a shape with a maximum value E1, a minimum value E2 at the blade root side, and a minimum value E3 at the blade tip side, and by making the throat spacing ratio s / t of the turbine rotating blade 30 at the blade root 31, the blade tip 32, and the central part 33 relatively large, the velocity distribution from the inner wall 61 side to the inner peripheral side wall 71 side in 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 overall efficiency of the axial turbine 1 can be improved.

[0043] In some implementations, such as Figure 3 and Figure 4 As shown, the maximum value E1 of the throat spacing ratio s / t of the turbine rotating blade 30 is formed in the range of 40% to 60% of the blade height. In the central part (40% to 60%) of the turbine rotating blade 30 in the blade height direction, by maximizing the throat spacing ratio s / t, the velocity distribution from the inner wall 61 side to the inner peripheral side wall 71 side in the outlet 73 of the diffuser flow path 70 can be made more uniform, thus more effectively improving the pressure recovery performance of the exhaust chamber 6 and the overall efficiency of the axial turbine 1.

[0044] like Figure 3 and Figure 4As shown, the root-side minimum value E2 of the throat spacing ratio s / t is preferably formed in the range of 20% to 30% of the blade height. The tip-side minimum value E3 of the throat spacing ratio s / t is preferably formed in the range of 70% to 80% of the blade height.

[0045] Furthermore, in some embodiments, the distribution of the throat spacing ratio s / t in the blade height direction of the turbine rotating blade 30 can be configured to not have a maximum value E1, a root-side minimum value E2, and a leading-edge-side minimum value E3. For example, in Figure 5 In the embodiment shown, the throat spacing ratio s / t at the 25% blade height position is greater than the throat spacing ratio s / t at the central portion 33 (specifically, at the 50% blade height position).

[0046] In some implementations, such as Figures 3-5 As shown, the turbine blade 30 described above is configured such that the throat spacing ratio s / t has a maximum value in the blade root 31 (blade root 311 in the example). Alternatively, the throat spacing ratio s / t can also have a maximum value at a blade height position other than blade root 311 in the blade root 31. In the structure of the axial flow turbine 1 that guides the working fluid to the radially outward side, it is easy for the working fluid to detach from the inner wall 61 on the side of the blade root 31 that forms the diffuser flow path 70. By maximizing the throat spacing ratio s / t in the blade root 31, the detachment of the working fluid from the inner wall 61 on the side of the blade root 31 that forms the diffuser flow path 70 can be more reliably suppressed.

[0047] Figure 7 This is a schematic cross-sectional view taken along the axial direction of an axial turbine 1 according to an embodiment of the present invention. Figure 8 This is a schematic cross-sectional view orthogonal to the axial direction of the axial turbine 1 according to one embodiment of the present invention. Figure 8 The middle section roughly shows along Figure 7 The cross-section shown is cut along line AB. (Example) Figure 8 As shown, the turbine housing 4 has an outlet 65 formed on a portion of its circumferential direction for discharging the working fluid from the exhaust chamber 6. Figure 8 As shown, in the circumferential direction, relative to the reference line LB which passes through the rotation center C of the turbine shaft 2 and is 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 relative to the reference line LB, the side away from the outlet 65 of the exhaust chamber 6 (the lower side in the figure) is defined as the reverse exhaust side.

[0048] In the illustrated embodiment, the outlet 65 of the exhaust chamber 6 is formed above the rotation center C of the turbine shaft 2 in the vertical direction, with the side above the rotation center C becoming the exhaust side and the side below the rotation center C becoming the reverse exhaust side. Figure 8 In the cross-sectional view shown, the baseline LB is orthogonal to the axis LC of the outlet 65 of the exhaust chamber 6. The exhaust chamber 6 includes... Figure 8 The cross-sectional view shown includes an arc-shaped reverse exhaust sidewall 66 on the reverse exhaust side and an exhaust sidewall 67 formed along the axis LC on the exhaust side.

[0049] Hereinafter, the circumferential angle positions of the two intersection points of the baseline LB and the wall of the exhaust chamber 6 are defined as 90° and 270°, respectively, and the range above 90° and below 270° is defined as the circumferential angle α on the exhaust side (refer to...). Figure 8 ).

[0050] In some implementations, such as Figure 7 As shown, the aforementioned guide section 7 is configured such that the outlet area AU of the diffuser flow path 70 in at least a portion of the exhaust side is larger than the outlet area AL of the diffuser flow path 70 on the reverse exhaust side. Figure 7 As shown, the opening area in the trailing edge 312 of the blade root 311 of the turbine rotating blade 30 is set as the inlet area A1 of the diffuser flow path 70. The opening area of ​​the diffuser flow path 70 increases as it moves towards the downstream side of the diffuser flow path 70.

[0051] The diffuser flow path 70 is a deceleration flow path used to slow down the working fluid. Therefore, within a range that does not cause the working fluid to detach from the wall forming the diffuser flow path 70, by increasing the ratio of the outlet area to the inlet area of ​​the diffuser flow path 70 (i.e., the area ratio), the discharge velocity of the working fluid from the diffuser flow path 70 can be reduced, thereby reducing the exhaust losses of the axial turbine 1. By increasing the respective flow velocities on the inner wall 61 side and the inner peripheral wall 71 side at the outlet 73 of the diffuser flow path 70, the detachment of the working fluid from the wall forming the diffuser flow path 70 is more biased towards the high area ratio side, thus effectively reducing the exhaust losses of the axial turbine 1. Moreover, the exhaust side with a high detachment margin can have a larger area ratio than the reverse exhaust side, thereby more effectively reducing the exhaust losses of the axial turbine 1.

[0052] In some implementations, such as Figure 7 As shown, the axial length LFU of at least a portion of the guide section 7 on the exhaust side is less than the axial length LFL of the guide section 7 on the reverse exhaust side.

[0053] Figure 9 This is an explanatory diagram illustrating the distribution of the axial length LF of the guide portion 7 relative to the circumferential position in one embodiment of the present invention. Figure 9The curve L6 shown represents Figure 7 The distribution of the axial length LF of the guide portion 7 relative to the circumferential position in the illustrated embodiment. Figure 9 The straight line L7 shown represents the case where the axial length LF of the guide section 7 is set to constant. For example... Figure 9 As shown, the axial length LF (LFU) is smallest in the central part of the exhaust side (where the circumferential angle α is 160° or more and 200° or less), and the axial length LF (LFL) is largest in the central part of the reverse exhaust side (where the circumferential angle α is 0° or more and 20° or 340° or more and 360° or less). The axial length LF gradually increases from the central part of the exhaust side towards the central part of the reverse exhaust side. Figure 9 In the illustrated embodiment, the axial length LF (LFU) is minimum when the circumferential angle α is 180°, and the axial length LF (LFL) is maximum when the circumferential angle α is 0°. In one embodiment, the minimum length of the axial length LF is at most 5% shorter than the maximum length. Furthermore, in one embodiment, when the axial length from the trailing edge 312 of the blade root 311 of the turbine rotating blade 30 to one side wall 62 is defined as L5, the axial length LF of the guide section 7 is 50% or more and 70% or less relative to L5 over the entire circumference.

[0054] By making the axial length LFU of the exhaust side of the guide section 7 smaller than the axial length LFL of the reverse exhaust side, the area ratio of the exhaust side can be made larger than that of the reverse exhaust side. As a result, the exhaust losses of the axial turbine 1 can be reduced more effectively.

[0055] Figure 10 This is a schematic cross-sectional view taken along the axial direction of an axial flow turbine 1 according to one embodiment of the present invention. In some embodiments, such as Figure 10 As shown, in the above-mentioned guide section 7, the rear edge end 72 of the guide section 7 on the exhaust side has an inclination angle θU relative to the axial direction that is greater than the rear edge end 72 of the guide section 7 on the reverse exhaust side has an inclination angle θL relative to the axial direction.

[0056] Figure 11 This is an explanatory diagram illustrating the distribution of the tilt angle θ of the trailing edge 72 of the guide portion 7 relative to the axial direction relative to the circumferential position in one embodiment of the present invention. Figure 11 The curve L8 shown represents Figure 10 The distribution of the tilt angle θ of the trailing edge 72 of the guide portion 7 relative to the axial direction relative to the circumferential position in the embodiment shown. Figure 11 The straight line L9 shown represents the case where the tilt angle θ is set to a constant. For example... Figure 11As shown, the tilt angle θ (θU) is largest in the central part of the exhaust side (where the circumferential angle α is 160° or more and 200° or less), and smallest in the central part of the reverse exhaust side (where the circumferential angle α is 0° or more and 20° or 340° or more and 360° or less). The tilt angle θ gradually decreases from the central part of the exhaust side towards the central part of the reverse exhaust side. Figure 11 In the illustrated embodiment, the tilt angle θ (θU) is at its maximum when the circumferential angle α is 180°, and the axial length tilt angle θ (θL) is at its minimum when the circumferential angle α is 0°. In one embodiment, the maximum tilt angle θ is more than 5° greater than the minimum tilt angle.

[0057] By making the tilt angle θU of the exhaust side of the guide section 7 greater than the tilt angle θL of the reverse exhaust side, the area ratio of the exhaust side can be made greater than that of the reverse exhaust side. This allows for a more effective reduction in exhaust losses of the axial turbine 1. Furthermore, in some embodiments, the axial length LFU of the exhaust side of the guide section 7 can be made smaller than the axial length LFL of the reverse exhaust side, and the tilt angle θU of the exhaust side of the guide section 7 can be made greater than the tilt angle θL of the reverse exhaust side.

[0058] In some embodiments of the axial turbine 1, such as Figure 1 , Figure 7 , Figure 10 As shown, the turbine blade row 3 of the axial flow turbine 1 is a single stage. Figure 1 , Figure 7 , Figure 10 In the illustrated embodiment, the turbine fixed blade row 5 of the axial turbine 1 is also a single stage. When the turbine rotating blade row 3 of the axial turbine 1 is a single stage, the efficiency improvement in the diffuser path 70 or the exhaust chamber 6 has a greater impact on the overall efficiency improvement of the axial turbine 1 than the efficiency improvement in the turbine rotating blade row 3. By setting the distribution of the throat spacing ratio s / t in the blade height direction of the turbine rotating blades 30 to a shape where the 25% and 75% blade height positions are smaller than line segments LS1 and LS2, respectively, or a shape with a maximum value E1, a minimum value E2 at the blade root side, and a minimum value E3 at the blade tip side, the efficiency improvement in the diffuser path 70 or the exhaust chamber 6 can be achieved, thereby effectively improving the overall efficiency of the axial turbine 1.

[0059] Figure 12 This is a schematic cross-sectional view of the supercharger 100 of the axial-flow turbine 1 according to one embodiment of the present invention, taken along the axial direction. In some embodiments, such as Figure 12As shown, the aforementioned axial turbine 1 is mounted on a turbocharger 100. The turbocharger 100 includes the axial turbine 1 and a centrifugal compressor 101 mounted on the turbine shaft 2 of the axial turbine 1. The centrifugal compressor 101 is configured to be driven in conjunction with the rotation of the turbine shaft 2 of the axial turbine 1, which is driven by exhaust gas (working fluid) discharged from an internal combustion engine (not shown), and to compress and guide the exhaust gas supplied to the aforementioned internal combustion engine.

[0060] The axial turbine 1 mounted on the turbocharger 100 has a diffuser flow path 70 for guiding the exhaust gas, which is the working fluid, radially outward due to the requirement of compact size. By making the axial turbine 1 with such a diffuser flow path 70 the axial turbine 1 involved in some of the above embodiments, the overall efficiency of the axial turbine 1 can be improved.

[0061] In this specification, expressions such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" that indicate relative or absolute configuration not only strictly indicate such configuration, but also indicate the state of relative displacement of angle or distance with tolerance or to the extent that the same function can be obtained.

[0062] For example, expressions such as "same," "equal," and "homogeneous" that indicate things are in the same state not only mean that they are the same in a strict sense, but also that there are differences in the degree to which they can achieve the same function.

[0063] Furthermore, in this specification, the description of shapes such as quadrilaterals or cylinders refers not only to shapes such as quadrilaterals or cylinders in a strict geometric sense, but also to shapes such as concave or convex parts or chamfered parts within the range where the same effect can be obtained.

[0064] Furthermore, in this specification, expressions such as "possessing," "including," or "having" a constituent element are not exclusive expressions that exclude the existence of other constituent elements.

[0065] The present invention is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments or appropriate combinations thereof.

[0066] The contents described in some of the above embodiments are as follows.

[0067] 1) The axial turbine 1 according to at least one embodiment of the present invention comprises: Turbine shaft 2; A turbine blade row 3 is mounted on the turbine shaft 2 and consists of a plurality of turbine blades 30 arranged in a row along the circumference of the turbine shaft 2; and The turbine housing 4 rotatably houses the turbine blade array 3 and has an exhaust chamber 6 on the downstream side of the turbine blade array 3. The turbine housing 4 includes a flow guide 7, which has an inner peripheral sidewall 71. The inner peripheral sidewall 71 forms a diffuser flow path 70 between itself and the inner wall 61 of the exhaust chamber 6 to guide the working fluid that has passed through the turbine blade row 3 to the radially outward side. The throat is defined as s when the shortest distance between the trailing edge 302 of the turbine rotating blade 30 and the negative pressure surface 304 of the other turbine rotating blades 30A adjacent to the turbine rotating blade 30 is defined as t; the spacing between the plurality of turbine rotating blades 30, 30A arranged in a row is defined as t; and the blade height position of the blade root 311 in the blade height direction from the blade root 311 of the turbine rotating blade 30 toward the blade tip 321 is defined as 0%, and the blade height position of the blade tip 321 is defined as 100%. The distribution of the throat spacing ratio s / t in the blade height direction of the turbine rotating blade 30 is as follows: The throat spacing ratio s / t at the 25% blade height position is less than the line segment LS1 connecting the throat spacing ratio s / t of the blade root 31 including the blade root 311 and the throat spacing ratio s / t of the central portion 33 in the blade height direction of the turbine rotating blade 30, and, The throat spacing ratio s / t at 75% of the blade height position is less than the line segment LS2 connecting the throat spacing ratio s / t of the central portion 33 and the throat spacing ratio s / t of the blade leading end portion 32 including the blade leading end portion 321.

[0068] Based on the structure described in 1) above, by setting the 25% and 75% blade height positions of the throat spacing ratio s / t distribution in the blade height direction of the turbine rotating blade 30 to be smaller than line segments LS1 and LS2, respectively, and by making the throat spacing ratio s / t of the blade root 31 and the blade leading end 32 of the turbine rotating blade 30 relatively large, the flow velocity on the inner wall 61 side and the inner peripheral sidewall 71 side of the diffuser flow path 70 can be increased. This suppresses the stripping of the working fluid from the inner wall 61 and the inner peripheral sidewall 71 forming the diffuser flow path 70, thereby suppressing the overall efficiency reduction of the axial turbine 1. Furthermore, by making the throat spacing ratio s / t of the central portion 33 in the blade height direction of the turbine rotating blade 30 relatively large, the velocity distribution from the inner wall 61 side to the inner peripheral sidewall 71 side at the outlet 73 of the diffuser flow path 70 can be made relatively uniform, thus improving the pressure recovery performance of the exhaust chamber 6 and the overall efficiency of the axial turbine 1.

[0069] 2) In some embodiments, it is the axial flow turbine 1 described in 1) above, wherein, The distribution of the throat spacing ratio s / t in the blade height direction of the turbine rotating blade 30 is configured as follows: The maximum value E1 is formed between the root 31 of the blade and the tip 32 of the blade; The leaf root lateral minimum E2 is formed between the leaf root 31 and the maximum value E1; and The blade tip minimum E3 is formed between the maximum value E1 and the blade tip 32.

[0070] Based on the structure described in 2), by setting the distribution of the throat spacing ratio s / t in the blade height direction of the turbine rotating blade 30 to a shape with a maximum value E1, a minimum value E2 at the blade root side, and a minimum value E3 at the blade tip side, and by making the throat spacing ratio s / t of the blade root 31, the blade tip 32, and the central part 33 of the turbine rotating blade 30 relatively large, the velocity distribution from the inner wall 61 to the inner peripheral side wall 71 in 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 overall efficiency of the axial turbine 1 can be improved.

[0071] 3) In some embodiments, it is the axial flow turbine 1 described in 1) or 2) above, wherein, The turbine rotating blades 30 are configured as follows: The throat spacing ratio s / t at the root 31 of the blade has a maximum value.

[0072] Based on the structure described in 3) above, the axial turbine 1, with its structure that guides the working fluid radially outward, is prone to experience flow stripping of the working fluid from the wall surface (inner wall 61) on the side of the blade root 31 that forms the diffuser flow path 70. By setting the throat spacing ratio s / t in the blade root 31 to the maximum, the flow stripping of the working fluid from the wall surface (inner wall 61) on the side of the blade root 31 that forms the diffuser flow path 70 can be suppressed more reliably.

[0073] 4) In some embodiments, it is the axial flow turbine 1 described in 2) above, wherein, The turbine rotating blades 30 are configured as follows: The maximum value E1 of the throat spacing ratio s / t is formed when the blade height position is in the range of 40% or more and 60% or less.

[0074] According to the structure described in 4), by setting the throat spacing ratio s / t to the maximum in the central part (a range of 40% to 60%) of the blade height direction of the turbine rotating blade 30, the velocity distribution from the inner wall 61 side to the inner peripheral side wall 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 overall efficiency of the axial turbine 1 can be improved more effectively.

[0075] 5) In some embodiments, the axial flow turbine 1 is any one of 1) to 4) above, wherein, The turbine housing 4 has an outlet 65 in a circumferential portion for discharging working fluid from the exhaust chamber 6. In the circumferential direction, with respect to the reference line LB that passes through the rotation center C of the turbine shaft 2 and is parallel to the outlet 65 of the exhaust chamber 6, the side containing the outlet 65 of the exhaust chamber 6 (the upper side in the figure) is defined as the exhaust side, and with respect to the reference line LB, the side away from the outlet 65 of the exhaust chamber 6 (the lower side in the figure) is defined as the reverse exhaust side. The flow guide 7 is configured such that, The outlet area AU of the diffuser flow path 70 in at least a portion of the exhaust side is greater than the outlet area AL of the diffuser flow path 70 on the reverse exhaust side.

[0076] According to the structure described in 5) above, the diffuser flow path 70 is a deceleration flow path used to slow down the working fluid. Therefore, within a range that does not cause the working fluid to detach from the wall forming the diffuser flow path 70, by increasing the ratio of the outlet area to the inlet area of ​​the diffuser flow path 70 (i.e., the area ratio), the discharge velocity of the working fluid from the diffuser flow path 70 can be reduced, thereby reducing the exhaust loss of the axial turbine 1. By increasing the respective flow velocities on the inner wall 61 side and the inner peripheral wall 71 side at the outlet of the diffuser flow path 70, the detachment of the working fluid from the wall forming the diffuser flow path 70 is more biased towards the high area ratio side, thus effectively reducing the exhaust loss of the axial turbine 1. Moreover, the exhaust side with a high detachment margin can have a larger area ratio than the reverse exhaust side, thereby more effectively reducing the exhaust loss of the axial turbine 1.

[0077] 6) In some embodiments, it is the axial flow turbine 1 described in 5) above, wherein, The flow guide 7 is configured such that, The axial length LFU of the inner peripheral sidewall 71 in at least a portion of the exhaust side is less than the axial length LFL of the inner peripheral sidewall 71 in the reverse exhaust side.

[0078] Based on the structure described in 6) above, by making the axial length LFU of the exhaust side of the guide section 7 smaller than the axial length LFL of the reverse exhaust side, the area ratio of the exhaust side can be set to be greater than that of the reverse exhaust side. This allows for a more effective reduction in the exhaust losses of the axial turbine 1.

[0079] 7) In some embodiments, it is the axial flow turbine 1 described in 5) or 6) above, wherein, The flow guide 7 is configured such that, The rear edge end 72 of the guide portion 7 in at least a portion of the exhaust side has an inclination angle θU relative to the axial direction that is greater than the inclination angle θL of the rear edge end of the guide portion 7 in the reverse exhaust side relative to the axial direction.

[0080] Based on the structure described in 7), by making the tilt angle θU of the exhaust side of the guide section 7 greater than the tilt angle θL of the reverse exhaust side, the area ratio of the exhaust side can be set to be greater than the area ratio of the reverse exhaust side. This allows for a more effective reduction in the exhaust losses of the axial turbine 1.

[0081] 8) In some embodiments, the axial flow turbine 1 is any one of 1) to 7) above, wherein, The turbine blade row 3 of the axial flow turbine 1 is a single stage.

[0082] Based on the structure described in 8) above, when the turbine blade row 3 of the axial turbine 1 is a single stage, the efficiency improvement in the diffuser path 70 or the exhaust chamber 6 has a greater impact on the overall efficiency improvement of the axial turbine 1 than the efficiency improvement in the turbine blade row 3. By setting the distribution of the throat spacing ratio s / t in the blade height direction of the turbine blades 30 to a shape where the 25% and 75% blade height positions are smaller than line segments LS1 and LS2, respectively, or setting it to a shape with a maximum value E1, a minimum value E2 at the blade root side, and a minimum value E3 at the blade tip side, the efficiency improvement in the diffuser path 70 or the exhaust chamber 6 can be achieved, thereby effectively improving the overall efficiency of the axial turbine 1.

[0083] 9) In some embodiments, the axial flow turbine 1 is any one of 1) to 8) above, wherein, The axial turbine 1 is mounted on the turbocharger 100.

[0084] According to the structure described in 9), the axial turbine 1 mounted on the supercharger 100 is required to be compact in size, therefore it has a diffuser flow path 70 for guiding the working fluid to the radially outward side. By having the structure described in any one of 1) to 7), the axial turbine 1 with this diffuser flow path 70 can improve the overall efficiency of the axial turbine 1.

[0085] Symbol Explanation 1. 01-Axial flow turbine, 2-Turbine shaft, 3-Turbine rotating blade row, 4-Turbine housing, 5-Turbine fixed blade row, 6-Exhaust chamber, 7-Guide section, 30, 30A-Turbine rotating blade, 31-Blade root, 32-Blade leading edge, 33-Central part, 41-Inner annular part, 42-Outer annular part, 43-Annular flow path, 50-Turbine fixed blade, 61-Inner wall, 64-Exhaust chamber flow path, 65-Outlet, 70-Diffuser flow path, 71-Inner peripheral side wall, 72-Trail edge, 73-Outlet, 100-Intensifier, 101-Centrifugal compressor, 311-Blade root, 312-Blade leading edge, E1-Maximum value, E2-Blade root side minimum value, E3-Blade leading edge side minimum value.

Claims

1. An axial flow turbine, comprising: Turbine shaft; A turbine blade array, mounted on the turbine shaft and composed of a plurality of turbine blades arranged in an array circumferentially on the turbine shaft; and The turbine housing rotatably houses the turbine blade array and has an exhaust chamber on the downstream side of the turbine blade array. The turbine housing includes a flow guide section having an inner circumferential sidewall surface. This inner circumferential sidewall surface forms a diffuser flow path between itself and the inner wall of the exhaust chamber, for guiding the working fluid that has passed through the turbine's rotating blade array to the radially outward side. The throat is defined as 's' when the shortest distance between the trailing edge of the turbine blade and the negative pressure surface of the other adjacent turbine blades is defined as 't', the spacing between the plurality of turbine blades arranged in a row is defined as 't', and the blade height position of the blade root in the blade height direction from the blade root to the blade tip is defined as 0%, and the blade height position of the blade tip is defined as 100%. The distribution of the throat spacing ratio s / t in the blade height direction of the turbine rotating blades is as follows: The throat spacing ratio s / t at the 25% blade height position is less than the line segment connecting the throat spacing ratio s / t of the blade root including the blade root and the throat spacing ratio s / t of the central portion of the turbine rotating blade in the blade height direction, and, The throat spacing ratio s / t at 75% of the blade height position is less than the line segment connecting the throat spacing ratio s / t of the central portion and the throat spacing ratio s / t of the blade tip portion including the blade tip.

2. The axial flow turbine according to claim 1, wherein, The distribution of the throat spacing ratio s / t in the blade height direction of the turbine rotating blades is configured as follows: The maximum value formed between the root of the blade and the leading edge of the blade; The leaf root lateral minimum formed between the leaf root and the maximum value; and The blade tip-side minimum is formed between the maximum value and the blade tip.

3. The axial flow turbine according to claim 1 or 2, wherein, The turbine rotating blades are configured as follows: The throat spacing ratio s / t at the root of the blade has a maximum value.

4. The axial flow turbine according to claim 2, wherein, In the turbine rotating blades The maximum value of the throat spacing ratio s / t is formed when the blade height position is in the range of 40% or more and 60% or less.

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

6. The axial flow turbine according to claim 5, wherein, In the guide section, the axial length of the guide section in at least a portion of the exhaust side is less than the axial length of the guide section in the reverse exhaust side.

7. The axial flow turbine according to claim 5, wherein, In the guide section, the rear edge of the guide section on the exhaust side has a greater tilt angle relative to the axial direction than the rear edge of the guide section on the reverse exhaust side has a greater tilt angle relative to the axial direction.

8. The axial flow turbine according to claim 1 or 2, wherein, The turbine blades of the axial flow turbine are arranged in a single stage.

9. The axial flow turbine according to claim 1 or 2, wherein, The axial turbine is mounted on the turbocharger.

Images