Axial flow compressor and moving blade thereof

Abstract

A moving blade (20) of an axial flow compressor has an airfoil part (22) of which the cross section forms an airfoil shape and which extends in a blade height direction perpendicular to the cross section. A leading edge part (23) including a leading edge (23l), a trailing edge part (24) including a trailing edge (24t), a negative pressure surface (25), and a positive pressure surface (26) are included. The shape of the outer edge on a virtual plane perpendicular to the blade height direction in the trailing edge part is an arc. Provided that the maximum blade height (W) is the maximum interval corresponding to a position in the blade height direction between the positive pressure surface and the negative pressure surface, the ratio of the arc radius (Rtc) of the trailing edge part to the maximum blade width (Wc) at the end on the tip side is greater than the ratio of the arc radius (Rtm) of the trailing edge part to the maximum blade width (Wm) at the midpoint in the blade height direction.

Description

Axial flow compressor and its rotor blades

[0001] This application claims priority to Japanese Patent Application No. 2024-069438, filed on April 23, 2024, the contents of which are incorporated herein by reference.

[0002] The axial flow compressor includes a rotor rotatable about an axis, a casing covering the outer periphery of the rotor, and a plurality of stator blade rows. The rotor has a rotor shaft rotationally symmetrical about the axis, and a plurality of moving blade rows attached to the rotor shaft and aligned in the axial direction along which the axis extends. Each of the plurality of moving blade rows has a plurality of moving blades aligned in the circumferential direction about the axis. One of the plurality of stator blade rows is arranged axially downstream of each of the plurality of moving blade rows. Each stator blade row is attached inside the casing. Each stator blade row is composed of a plurality of stator blades aligned in the circumferential direction.

[0003] Patent Document 1 below discloses a rotor blade for an axial flow turbine, in which the thickness of the trailing edge of the rotor blade gradually decreases toward the tip side on the radially outer side relative to the axis.

[0004] Japanese Patent Application Laid-Open No. 2004-263602

[0005] In an axial flow compressor that compresses gas containing non-gaseous particles such as liquid particles and solid particles, erosion by non-gaseous particles is more likely to progress on the rotor blades that rotate in the gas flow path than on the stator vanes. If the chord length of the rotor blades becomes shorter due to erosion, the possibility of surging occurring increases.

[0006] Therefore, an object of the present disclosure is to provide a technique capable of suppressing the occurrence of surging in an axial flow compressor that compresses gas containing non-gaseous particles such as liquid particles and solid particles.

[0007] In one aspect of the invention to achieve the above object, a rotor blade for an axial flow compressor includes: an airfoil portion having an airfoil cross section and extending in a blade height direction perpendicular to the cross section, a platform defining a part of an edge of a gas flow path, and a connecting portion located between the airfoil portion and the platform in the blade height direction and connecting the platform to the hub side of the airfoil portion in the blade height direction. The airfoil portion has a leading edge portion including a leading edge, a trailing edge portion including a trailing edge, a suction surface connecting the leading edge and the trailing edge, and a pressure surface connecting the leading edge and the trailing edge and being back-to-back with the suction surface. The leading edge portion, the trailing edge portion, the suction surface, and the pressure surface all extend in the blade height direction and have the hub-side end and the tip-side end. The shape of the outer edge of the trailing edge portion on an imaginary plane perpendicular to the blade height direction is an arc, and the trailing edge is located on the arc of the trailing edge portion. When the maximum distance between the pressure surface and the suction surface according to the position in the blade height direction is defined as the maximum blade width, the ratio of the arc radius of the trailing edge portion to the maximum blade width at the tip end is larger than the ratio of the arc radius of the trailing edge portion to the maximum blade width at an intermediate position in the blade height direction.

[0008] In an axial compressor that compresses gas containing non-gaseous particles such as liquid particles and solid particles, erosion by non-gaseous particles is more likely to progress in the rotor blades that rotate in the gas flow path than in the stator vanes. In particular, because the peripheral speed around the axis is higher at the tip side of the airfoil section than at the hub side, erosion is more likely to progress at the tip side of the airfoil section. Furthermore, since the lateral width of the leading edge increases toward the downstream side of the axis, the chord length of the rotor blade does not change significantly even if erosion progresses at this leading edge. On the other hand, since the lateral width of the trailing edge decreases toward the downstream side of the axis, progression of erosion at this trailing edge shortens the chord length of the rotor blade compared to when erosion progresses at the leading edge.

[0009] As the chord length of the blades decreases, the likelihood of surging increases.

[0010] In this embodiment, the relative size of the arc radius of the trailing edge with respect to the maximum blade span is larger at the tip end than at the intermediate position. Therefore, even if erosion of the trailing edge progresses to some extent, shortening of the chord length of the rotor blade can be suppressed. Therefore, in this embodiment, the occurrence of surging in an axial flow compressor that compresses gas containing non-gas particles can be suppressed.

[0011] An axial compressor according to one aspect of the invention for achieving the above object includes: a rotor rotatable about an axis; and a casing covering an outer periphery of the rotor. The rotor has a rotor shaft rotationally symmetrical about the axis; and a plurality of blade rows attached to the rotor shaft and aligned in an axial direction along which the axis extends. Each of the plurality of blade rows has a plurality of blades aligned in a circumferential direction about the axis. The plurality of blades included in at least some of the plurality of blade rows are all blades of the axial compressor according to the above aspect. The blade height direction is a radial direction relative to the axis. The tip side is a radially outer side relative to the axis. The hub side is a radially inner side relative to the axis.

[0012] According to one aspect of the present disclosure, it is possible to suppress the occurrence of surging in an axial flow compressor that compresses gas containing non-gaseous particles such as liquid particles and solid particles.

[0013] Fig. 3 is a schematic cross-sectional view of an axial flow compressor in an embodiment according to the present disclosure; Fig. 4 is a perspective view of a rotor blade in an embodiment according to the present disclosure; Fig. 5 is a side view of a rotor blade in an embodiment according to the present disclosure; Fig. 6 is a cross-sectional view taken along line IV-IV in Fig. 3; Fig. 7 is an explanatory view showing dimensions of each part in multiple cross sections of a rotor blade in an embodiment according to the present disclosure.

[0014] Hereinafter, embodiments of an axial flow compressor and rotor blades thereof according to the present disclosure will be described in detail with reference to the drawings.

[0015] [Embodiment of Axial Flow Compressor] An axial flow compressor according to this embodiment will be described with reference to FIG.

[0016] The axial flow compressor 10 in this embodiment is a compressor that compresses Blast Furnace Gas (BFG) from a blast furnace 1 in a steelworks. The BFG contains gases such as nitrogen and carbon monoxide, which is a combustible component, as well as solid particles such as slag.

[0017] The axial flow compressor 10 includes a rotor 11 that can rotate about an axis Ar, a casing 14 that covers the rotor 11, and a plurality of stator vane rows 16. In the following description, the direction in which the axis Ar extends is referred to as the axial direction Da, one side in the axial direction Da is referred to as the axial upstream side Dau, and the other side in the axial direction Da is referred to as the axial downstream side Dad. The circumferential direction centered on the axis Ar is simply referred to as the circumferential direction Dc. The direction perpendicular to the axis Ar is referred to as the radial direction Dr, and the side of the radial direction Dr that approaches the axis Ar is referred to as the radially inner side Dri, and the opposite side is referred to as the radially outer side Dro.

[0018] The rotor 11 has a rotor shaft 12 that extends in the axial direction Da in rotational symmetry about the axis Ar, and a plurality of rotor blade rows 13 attached to the rotor shaft 12. A rotor of an electric motor or turbine 3 that rotates the rotor 11 is connected to an end of the rotor shaft 12. The plurality of rotor blade rows 13 are aligned in the axial direction Da. Each rotor blade row 13 is composed of a plurality of rotor blades aligned in the circumferential direction Dc. One of the plurality of stator blade rows 16 is arranged on the axial downstream side Dad of each of the plurality of rotor blade rows 13. Each stator blade row 16 is attached inside the casing 14. Each stator blade row 16 is composed of a plurality of stator blades aligned in the circumferential direction Dc.

[0019] The annular space between the outer periphery of the rotor shaft 12 and the inner periphery of the casing 14 forms a gas flow path 15 through which the BGF flows.

[0020] An inlet 14i for introducing gas into the casing 14 is formed on the axial upstream side Dau of the casing 14. The BFG line 2 extending from the blast furnace 1 is connected to the inlet 14i of the casing 14. In addition, an outlet 14o for discharging compressed gas is formed at the end of the axial downstream side Dad of the casing 14.

[0021] [Embodiment of Rotor Blade] The rotor blade in this embodiment will be described with reference to Figures 2 to 5. Note that the rotor blade in this embodiment is a rotor blade included in at least some of the rotor blade rows 13 described above.

[0022] As shown in FIGS. 2 and 3 , the rotor blade 20 in this embodiment includes a blade body 21 , a connection portion 27 , a platform 28 , and a blade root 29 .

[0023] The blade body 21 has an airfoil section 22 that has an airfoil-shaped cross section and extends in a blade height direction Dr perpendicular to the cross section. The airfoil section 22 has a leading edge section 23 including a leading edge 23l, a trailing edge section 24 including a trailing edge 24t, a suction surface 25 connecting the leading edge section 23 and the trailing edge section 24, and a pressure surface 26 connecting the leading edge section 23 and the trailing edge section 24 and back-to-back with the suction surface 25. The leading edge section 23, the trailing edge section 24, the suction surface 25, and the pressure surface 26 all extend in the blade height direction Dr and have a hub-side end Dri and a tip-side end Dro. Note that, hereinafter, one side in the blade height direction Dr is referred to as the tip side Dro, and the other side in the blade height direction Dr is referred to as the hub side Dri.

[0024] The connecting portion 27 is located between the airfoil portion 22 and the platform 28 in the blade height direction Dr, and connects the platform 28 to the hub side Dri of the airfoil portion 22 .

[0025] The platform 28 extends in a direction perpendicular to the blade height direction Dr from the end of the hub side Dri of the connecting portion 27. The surface of the platform 28 facing the tip side Dro is a gas path surface 28p that defines part of the edge of the gas flow path 15 (see FIG. 1) described above.

[0026] The blade root 29 fits into the blade root groove 12g (see FIG. 1) of the rotor shaft 12 and serves to attach the rotor blade 20 to the rotor shaft 12. The blade root 29 has a portion whose width in the lateral direction Dc, which is the direction in which the suction surface 25 and the pressure surface 26 are aligned, gradually increases toward the hub side Dri.

[0027] 3 and 4, the hub-side end Dri of the airfoil portion 22 coincides with the hub-side end Dri of the airfoil body 21. The width of the connecting portion 27 in the lateral direction Dc gradually increases toward the hub-side Dri. However, the rate of change in the width of the connecting portion 27 in the lateral direction Dc with respect to a change in position in the blade height direction Dr is greater than the rate of change in the width of the airfoil portion 22 in the lateral direction Dc with respect to a change in position in the blade height direction Dr. In other words, when considering a function of the width in the lateral direction Dc with the position in the blade height direction Dr as a parameter, the boundary between the airfoil portion 22 and the connecting portion 27 in the blade height direction Dr becomes an inflection point.

[0028] In this embodiment, the end of the tip side Dro of the airfoil portion 22 does not coincide with the end of the tip side Dro of the airfoil body 21. Specifically, the airfoil body 21 has a tip side portion 21c that is located closer to the tip side Dro than the end of the tip side Dro of the airfoil portion 22. The width of this tip side portion 21c in the lateral direction Dc gradually decreases toward the tip side Dro. However, the rate of change in the width of the tip side portion 21c in the lateral direction Dc with respect to a change in position in the blade height direction Dr is greater than the rate of change in the width of the airfoil portion 22 in the lateral direction Dc with respect to a change in position in the blade height direction Dr. In other words, when considering a function of the width in the lateral direction Dc with the position in the blade height direction Dr as a parameter, the boundary between the airfoil portion 22 and the tip side portion 21c in the blade height direction Dr becomes an inflection point.

[0029] As described above, the portion on the hub side Dri of the airfoil portion 22 where the width in the lateral direction Dc suddenly increases does not constitute the airfoil portion 22 but the connecting portion 27. Also, the portion on the tip side Dro of the airfoil portion 22 where the width in the lateral direction Dc suddenly decreases does not constitute the airfoil portion 22 but the tip side portion 21c of the airfoil body 21.

[0030] The above-described rotor blade 20 is attached to the rotor shaft 12 (see FIG. 1 ) as previously described. When the rotor blade 20 is attached to the rotor shaft 12, the blade height direction Dr becomes the radial direction Dr, the tip-side Dro becomes the radially outer side Dro, and the hub-side Dri becomes the radially inner side Dri. Furthermore, the lateral direction Dc becomes the circumferential direction Dc. The suction surface 25 faces one side in the circumferential direction Dc, and the pressure surface 26 faces the other side in the circumferential direction Dc.

[0031] As shown in FIG. 5, the shape of the outer edge of the leading edge portion 23 on an imaginary plane perpendicular to the blade height direction Dr is an arc. The leading edge 23l is located on this arc. The shape of the outer edge of the trailing edge portion 24 on an imaginary plane perpendicular to the blade height direction Dr is also an arc. The trailing edge 24t is located on this arc. Note that in FIG. 5, Va indicates the cross section taken along line Va-Va in FIG. 3 (a cross section at the end of the tip side Dro of the airfoil portion 22). Also in FIG. 5, Vb indicates the cross section taken along line Vb-Vb in FIG. 3 (a cross section at the middle position in the blade height direction Dr of the airfoil portion 22), and Vc indicates the cross section taken along line Vc-Vc in FIG. 3 (a cross section at the end of the hub side Dri of the airfoil portion 22).

[0032] In this embodiment, the arc radius Rlm of the leading edge portion 23 at the intermediate position in the blade height direction Dr of the airfoil portion 22 is smaller than the arc radius Rlh of the leading edge portion 23 at the hub-side Dri end of the airfoil portion 22. Also, the arc radius Rlc of the leading edge portion 23 at the tip-side Dro end of the airfoil portion 22 is smaller than the arc radius Rlm of the leading edge portion 23 at the intermediate position in the blade height direction Dr of the airfoil portion 22. That is, in this embodiment, the arc radius Rl of the leading edge portion 23 gradually decreases from the hub-side Dri end to the tip-side Dro end.

[0033] Here, the maximum distance between the pressure surface 26 and the suction surface 25 in the blade height direction Dr is defined as the maximum blade width W. In this embodiment, the maximum blade width Wm at the intermediate position in the blade height direction Dr of the airfoil portion 22 is smaller than the maximum blade width Wh at the end of the hub side Dri of the airfoil portion 22. Also, the maximum blade width Wc at the end of the tip side Dro of the airfoil portion 22 is smaller than the maximum blade width Wm at the intermediate position in the blade height direction Dr of the airfoil portion 22. That is, in this embodiment, the maximum blade width W gradually decreases from the end of the hub side Dri to the end of the tip side Dro toward the tip side Dro.

[0034] In this embodiment, the arc radius Rth of the trailing edge portion 24 at the hub-side end Dri of the airfoil portion 22, the arc radius Rtm of the trailing edge portion 24 at the intermediate position in the blade height direction Dr of the airfoil portion 22, and the arc radius Rtc of the trailing edge portion 24 at the tip-side end Dro of the airfoil portion 22 are all the same. That is, in this embodiment, the arc radius Rt of the trailing edge portion 24 is the same at any position in the blade height direction Dr. Furthermore, the arc radius Rtc of the trailing edge portion 24 at the tip-side end Dro is the same as the arc radius Rlc of the leading edge portion 23 at the tip-side end Dro.

[0035] Therefore, in this embodiment, the ratio (Rtc / Wc) of the arc radius Rtc of the trailing edge 24 to the maximum blade width Wc at the tip-side end Dro is greater than the ratio (Rtm / Wm) of the arc radius Rtm of the trailing edge 24 to the maximum blade width Wm at the midpoint in the blade height direction Dr. In other words, Rtc / Wc>Rtm / Wm.

[0036] In this embodiment, the ratio (Rtm / Wm) of the arc radius Rtm of the trailing edge 24 to the maximum blade width Wm at the midpoint in the blade height direction Dr is greater than the ratio (Rth / Wh) of the arc radius Rth of the trailing edge 24 to the maximum blade width Wth at the end of the hub-side Dri. In other words, Rtm / Wm>Rth / Wh.

[0037] Moreover, in this embodiment, the ratio (Rt / W) of the arc radius Rt of the trailing edge portion 24 to the maximum blade width W gradually increases from the end of the hub side Dri to the end of the tip side Dro, toward the tip side Dro. Therefore, in this embodiment, the ratio (Rt / W) of the arc radius Rt of the trailing edge portion 24 to the maximum blade width W gradually increases from the middle position in the blade height direction Dr to the end of the tip side Dro, toward the tip side Dro.

[0038] In an axial flow compressor 10 that compresses BFG containing solid particles such as slag, erosion by solid particles is more likely to progress in the rotor blades 20 rotating in the gas flow path 15 than in the stator vanes. In particular, because the peripheral speed around the axis Ar is higher in the tip-side Dro portion of the airfoil section 22 than in the hub-side Dri portion, erosion is more likely to progress in the tip-side Dro portion of the airfoil section 22. Furthermore, since the width of the leading edge 23 in the lateral direction Dc increases toward the axial downstream side Dad, even if erosion of the leading edge 23 progresses, the chord length of the rotor blade 20 does not change significantly. On the other hand, the width of the trailing edge 24 in the lateral direction Dc decreases toward the axial downstream side Dad. Therefore, if erosion of the trailing edge 24 progresses, the chord length of the rotor blade 20 becomes shorter than if erosion of the leading edge 23 progressed.

[0039] As the chord length of the rotor blades 20 decreases, the likelihood of surging occurring increases.

[0040] In this embodiment, the relative size of the arc radius Rt of the trailing edge portion 24 with respect to the maximum blade span W is larger at the tip-side end Dro than at the hub-side end Dri or the middle position. Therefore, even if erosion of the trailing edge portion 24 progresses to some extent, shortening of the chord length of the rotor blade 20 can be suppressed. Therefore, in this embodiment, the occurrence of surging in the axial flow compressor 10 that compresses BFG containing fixed particles can be suppressed.

[0041] As described above, in this embodiment, the ratio (Rt / W) of the arc radius Rt of the trailing edge 24 to the maximum blade width W gradually increases from the end of the hub-side Dri to the end of the tip-side Dro toward the tip-side Dro. Therefore, in this embodiment, the change in chord length due to erosion in response to changes in position in the blade height direction Dr can be suppressed compared to when the ratio (Rt / W) of the arc radius Rt of the trailing edge 24 to the maximum blade width W suddenly increases or increases or decreases at any position in the blade height direction Dr. Furthermore, in this embodiment, the performance of the blade 20 can be improved and the blade 20 can be easily manufactured compared to when the ratio (Rt / W) of the arc radius Rt of the trailing edge 24 to the maximum blade width W suddenly increases or increases or decreases at any position in the blade height direction Dr.

[0042] Furthermore, in this embodiment, the arc radius Rt of the trailing edge portion 24 is the same at any position in the blade height direction Dr, and therefore, from this perspective as well, the rotor blade 20 can be easily manufactured.

[0043] "Modification" In the above embodiment, the blade body 21 has a tip side portion 21c that is located closer to the tip side Dro than the end of the tip side Dro of the blade-shaped portion 22. However, the blade body 21 does not have to have this tip side portion 21c. In this case, the entire blade-shaped portion 22 becomes the entire blade body 21.

[0044] In the above embodiment, the arc radius Rl of the leading edge portion 23 gradually decreases from the end of the hub side Dri to the end of the tip side Dro. However, the arc radius Rl of the leading edge portion 23 may increase or decrease in any region in the blade height direction Dr.

[0045] In the above embodiment, the ratio (Rt / W) of the arc radius Rt of the trailing edge portion 24 to the maximum wing span W gradually increases from the end of the hub-side Dri to the end of the tip-side Dro toward the tip-side Dro. However, the ratio (Rt / W) of the arc radius Rt of the trailing edge portion 24 to the maximum wing span W may increase or decrease in any region of the wing height direction Dr. However, even in this case, the ratio (Rtc / Wc) of the arc radius Rtc of the trailing edge portion 24 to the maximum wing span Wc at the end of the tip-side Dro must be greater than the ratio (Rtm / Wm) of the arc radius Rtm of the trailing edge portion 24 to the maximum wing span Wm at the middle position in the wing height direction Dr.

[0046] In the above embodiments, the arc radius Rt of the trailing edge portion 24 is the same at any position in the blade height direction Dr. However, the arc radius Rt of the trailing edge portion 24 may increase or decrease in any region in the blade height direction Dr. For example, if the rate of change of the arc radius Rt of the trailing edge portion 24, which gradually decreases toward the tip side Dro, is small relative to the rate of change of the maximum blade width W, which gradually decreases toward the tip side Dro, the arc radius Rt of the trailing edge portion 24 may gradually decrease toward the tip side Dro. That is, in any of the above cases, it is sufficient that the ratio (Rtc / Wc) of the arc radius Rtc of the trailing edge portion 24 to the maximum blade width Wc at the end of the tip side Dro is greater than the ratio (Rtm / Wm) of the arc radius Rtm of the trailing edge portion 24 to the maximum blade width Wm at the intermediate position in the blade height direction Dr.

[0047] In the above embodiment, the arc radius Rtc of the trailing edge 24 at the end of the tip side Dro is the same as the arc radius Rlc of the leading edge 23 at the end of the tip side Dro. However, the arc radius Rtc of the trailing edge 24 at the end of the tip side Dro may be smaller or larger than the arc radius Rlc of the leading edge 23 at the end of the tip side Dro. However, considering the effects of erosion, it is preferable that the arc radius Rtc of the trailing edge 24 at the end of the tip side Dro be equal to or larger than the arc radius Rlc of the leading edge 23 at the end of the tip side Dro.

[0048] The axial flow compressor 10 in this embodiment is a compressor that compresses BFG from a blast furnace 1 in a steelworks. However, the axial flow compressor may be any axial flow compressor that compresses gas containing non-gaseous particles such as liquid particles and solid particles.

[0049] The present disclosure is not limited to the above-described embodiments and modifications, and various additions, modifications, substitutions, partial deletions, etc. are possible within the scope of the conceptual idea and spirit of the present invention as derived from the content defined in the claims and their equivalents.

[0050] "Additional Notes" The rotor blades 20 of the axial compressors in the above embodiments and modified examples can be understood, for example, as follows: (1) The rotor blades 20 of the axial compressor 10 in a first aspect include an airfoil portion 22 having an airfoil-shaped cross section and extending in a blade height direction Dr perpendicular to the cross section, a platform 28 that defines a part of the edge of the gas flow path 15, and a connection portion 27 that is located between the airfoil portion 22 and the platform 28 in the blade height direction Dr and connects the platform 28 to the hub side Dri of the airfoil portion 22 in the blade height direction Dr. The airfoil portion 22 has a leading edge portion 23 including a leading edge 23l, a trailing edge portion 24 including a trailing edge 24t, a suction surface 25 connecting the leading edge portion 23 and the trailing edge portion 24, and a pressure surface 26 connecting the leading edge portion 23 and the trailing edge portion 24 and in a back-to-back relationship with the suction surface 25. The leading edge portion 23, the trailing edge portion 24, the suction surface 25, and the pressure surface 26 all extend in the blade height direction Dr and have an end on the hub-side Dri and an end on the tip-side Dro. The shape of the outer edge of the trailing edge portion 24 on an imaginary plane perpendicular to the blade height direction Dr is an arc, and the trailing edge 24t is located on the arc of the trailing edge portion 24. If the maximum distance between the positive pressure surface 26 and the negative pressure surface 25 according to the position in the blade height direction Dr is defined as the maximum blade width W, the ratio (Rtc / Wc) of the arc radius Rtc of the trailing edge portion 24 to the maximum blade width Wc at the end of the tip side Dro is greater than the ratio (Rtm / Wm) of the arc radius Rtm of the trailing edge portion 24 to the maximum blade width Wm at the intermediate position in the blade height direction Dr.

[0051] In an axial flow compressor 10 that compresses gas containing non-gaseous particles such as liquid particles and solid particles, erosion by non-gaseous particles is more likely to progress in the rotor blades 20 rotating in the gas flow path 15 than in the stator vanes. In particular, because the peripheral speed around the axis Ar is higher in the tip-side Dro portion of the airfoil section 22 than in the hub-side Dri portion, erosion is more likely to progress in the tip-side Dro portion of the airfoil section 22. Furthermore, since the width of the leading edge 23 in the lateral direction Dc increases toward the axial downstream side Dad, even if erosion of this leading edge 23 progresses, the chord length of the rotor blade 20 does not change significantly. On the other hand, the width of the trailing edge 24 in the lateral direction Dc decreases toward the axial downstream side Dad. Therefore, when erosion of this trailing edge 24 progresses, the chord length of the rotor blade 20 becomes shorter than when erosion of the leading edge 23 progresses.

[0052] As the chord length of the rotor blades 20 decreases, the likelihood of surging occurring increases.

[0053] In this embodiment, the relative size of the arc radius Rt of the trailing edge portion 24 with respect to the maximum blade span W is larger at the tip end Dro than at the intermediate position. Therefore, even if erosion of the trailing edge portion 24 progresses to some extent, it is possible to prevent shortening of the chord length of the rotor blade 20. Therefore, in this embodiment, it is possible to prevent surging from occurring in the axial flow compressor 10 that compresses gas containing non-gaseous particles.

[0054] (2) In the rotor blade 20 of the axial compressor 10 in the second aspect, in the rotor blade 20 in the first aspect, the ratio (Rt / W) of the arc radius Rt of the trailing edge portion 24 to the maximum blade width W gradually increases from the middle position in the blade height direction Dr to the end of the tip side Dro, toward the tip side Dro.

[0055] Compared to a case where the ratio (Rt / W) of the arc radius Rt of the trailing edge 24 to the maximum blade width W suddenly increases or increases or decreases between the intermediate position in the blade height direction Dr and the end of the tip side Dro, this embodiment can suppress changes in chord length due to erosion in this region. Furthermore, compared to a case where the ratio (Rt / W) of the arc radius Rt of the trailing edge 24 to the maximum blade width W suddenly increases or increases or decreases between the intermediate position in the blade height direction Dr and the end of the tip side Dro, this embodiment can improve the performance of the blade 20 and make it easier to manufacture the blade 20.

[0056] (3) In the third aspect of the rotor blade 20 of the axial compressor 10, in the rotor blade 20 of the first or second aspect, the arc radius Rt of the trailing edge portion 24 is the same at any position from the middle position in the blade height direction Dr to the end of the tip side Dro.

[0057] In this embodiment, the rotor blade 20 can be manufactured more easily than when the arc radius Rt of the trailing edge portion 24 changes between the middle position in the blade height direction Dr and the end of the tip side Dro.

[0058] (4) In a fourth aspect of the rotor blade 20 of the axial compressor 10, in the rotor blade 20 of any one of the first to third aspects, the ratio (Rtm / Wm) of the arc radius Rtm of the trailing edge portion 24 to the maximum blade width Wm at the intermediate position in the blade height direction Dr is greater than the ratio (Rth / Wh) of the arc radius Rth of the trailing edge portion 24 to the maximum blade width Wh at the end of the hub side Dri.

[0059] In this embodiment, the relative size of the arc radius Rt of the trailing edge 24 with respect to the maximum blade span W is larger at the middle position than at the end of the hub-side Dri. Therefore, even if erosion of the trailing edge 24 progresses to some extent, shortening of the chord length of the rotor blade 20 can be suppressed. Therefore, in this embodiment, it is possible to suppress the occurrence of surging in the axial flow compressor 10 that compresses gas containing non-gaseous particles.

[0060] (5) In the fifth aspect of the rotor blade 20 of the axial compressor 10, in the rotor blade 20 of any one of the first to fourth aspects, the ratio (Rt / W) of the arc radius Rt of the trailing edge portion 24 to the maximum blade width W gradually increases from the end of the hub side Dri to the end of the tip side Dro, toward the tip side Dro.

[0061] In this embodiment, the change in chord length due to erosion can be suppressed compared to when the ratio (Rt / W) of the arc radius Rt of the trailing edge 24 to the maximum blade width W suddenly increases or increases or decreases between the hub-side Dri end and the tip-side Dro end. Furthermore, in this embodiment, the performance of the rotor blade 20 can be improved and the rotor blade 20 can be manufactured more easily compared to when the ratio (Rt / W) of the arc radius Rt of the trailing edge 24 to the maximum blade width W suddenly increases or increases or decreases between the hub-side Dri end and the tip-side Dro end.

[0062] (6) In a sixth aspect of the axial compressor 10, the rotor blade 20 is the rotor blade 20 of any one of the first to fifth aspects, wherein the arc radius Rt of the trailing edge portion 24 is the same at any position in the blade height direction Dr.

[0063] This embodiment can be manufactured more easily than when the arc radius Rt of the trailing edge portion 24 changes between the end Dri on the hub side and the end Dro on the tip side.

[0064] (7) A seventh aspect of the rotor blade 20 of the axial compressor 10 is the rotor blade 20 of any one of the first to sixth aspects, wherein the shape of the outer edge of the leading edge portion 23 on an imaginary plane perpendicular to the blade height direction Dr is an arc, and the leading edge 23l is located on the arc of the leading edge portion 23. An arc radius Rtc of the trailing edge portion 24 at the end of the tip side Dro is equal to or greater than an arc radius Rlc of the leading edge portion 23 at the end of the tip side Dro.

[0065] In this embodiment, the arc radius Rtc of the trailing edge portion 24 at the end of the tip side Dro is equal to or greater than the arc radius Rlc of the leading edge portion 23 at the end of the tip side Dro. Therefore, even if erosion of the trailing edge portion 24 progresses to some extent, it is possible to prevent shortening of the chord length of the rotor blade 20. Therefore, in this embodiment, it is possible to prevent surging from occurring in the axial flow compressor 10 that compresses gas containing non-gaseous particles.

[0066] The axial compressor 10 in the above embodiments and modified examples can be understood as follows, for example. (8) An axial compressor 10 in an eighth aspect includes: a rotor 11 rotatable about an axis Ar; and a casing 14 covering an outer periphery of the rotor 11. The rotor 11 includes a rotor shaft 12 rotationally symmetric about the axis Ar; and a plurality of blade rows 13 attached to the rotor shaft 12 and aligned in an axial direction Da along which the axis Ar extends. Each of the plurality of blade rows 13 includes a plurality of blades aligned in a circumferential direction Dc relative to the axis Ar. Each of the plurality of blade rows 13 includes a plurality of blades aligned in a circumferential direction Dc relative to the axis Ar. The plurality of blades included in at least some of the plurality of blade rows 13 are the blades 20 of the axial compressor 10 in any one of the first to seventh aspects. The blade height direction Dr is a radial direction Dr relative to the axis Ar. The tip side Dro is a radially outer side Dro relative to the axis Ar. The hub side Dri is the radially inner side Dri with respect to the axis Ar.

[0067] According to one aspect of the present disclosure, it is possible to suppress the occurrence of surging in an axial flow compressor that compresses gas containing non-gaseous particles such as liquid particles and solid particles.

[0068] 1: Blast furnace 2: BFG line 3: Electric motor or turbine 10: Axial compressor 11: Rotor 12: Rotor shaft 12g: Blade root groove 13: Rotor row 14: Casing 14i: Inlet 14o: Discharge port 15: Gas flow path 16: Stator row 20: Rotor blade 21: Blade body 21c: Tip side 22: Airfoil section 23: Leading edge 23l: Leading edge 24: Trailing edge 24t: Trailing edge 25: Suction surface 26: Pressure surface 27: Connection 28: Platform 28p: Gas path surface 29: Blade root Va, Vb, Vc: Cross section Rl: Arc radius of leading edge Rlc: Arc radius of leading edge at tip side end Rlm: Arc radius of leading edge at intermediate position Rlh: Arc radius of leading edge at hub side end Rt: Arc radius of the trailing edge Rtc: Arc radius of the trailing edge at the tip end Rtm: Arc radius of the trailing edge at the intermediate position Rth: Arc radius of the trailing edge at the hub end W: Maximum blade width Wc: Maximum blade width at the tip end Wm: Maximum blade width at the intermediate position Wh: Maximum blade width at the hub end Ar: Axis Da: Axial direction Dau: Axial upstream side Dad: Axial downstream side Dc: Lateral direction (or circumferential direction) Dr: Blade height direction (or radial direction) Dri: Hub side (or radially inner side) Dro: Tip side (or radially outer side)

Claims

1. An airfoil section having an airfoil cross section and extending in a blade height direction perpendicular to the cross section; a platform defining a part of the edge of a gas flow path; and a connecting section located between the airfoil section and the platform in the blade height direction, the connecting section connecting the platform to the hub side of the airfoil section in the blade height direction, the airfoil section having a leading edge section including a leading edge, a trailing edge section including a trailing edge, a suction surface connecting the leading edge section and the trailing edge section, and a pressure surface connecting the leading edge section and the trailing edge section and being back-to-back with the suction surface, the leading edge section, the trailing edge section, the suction surface and the pressure surface all extending in the blade height direction and having an end on the hub side and an end on the tip side, the shape of the outer edge of the trailing edge section on an imaginary plane perpendicular to the blade height direction is an arc, the trailing edge being located on the arc of the trailing edge section, a ratio of the arc radius of the trailing edge portion to the maximum blade width at the tip end is larger than a ratio of the arc radius of the trailing edge portion to the maximum blade width at an intermediate position in the blade height direction, when the maximum distance between the pressure surface and the suction surface according to the position in the blade height direction is defined as a maximum blade width.

2. A rotor blade for an axial flow compressor according to claim 1, wherein the ratio of the arc radius of the trailing edge to the maximum blade width gradually increases from the midpoint in the blade height direction to the tip end, moving towards the tip side.

3. A rotor blade for an axial flow compressor according to claim 1, wherein the arc radius of the trailing edge portion is the same at any position from the intermediate position in the blade height direction to the tip end.

4. A rotor blade for an axial flow compressor according to claim 1, wherein the ratio of the arc radius of the trailing edge to the maximum blade width at the intermediate position in the blade height direction is greater than the ratio of the arc radius of the trailing edge to the maximum blade width at the end on the hub side.

5. A rotor blade for an axial flow compressor according to claim 1, wherein the ratio of the arc radius of the trailing edge to the maximum blade width gradually increases from the end on the hub side to the end on the tip side, moving towards the tip side.

6. A rotor blade for an axial flow compressor according to claim 1, wherein the arc radius of the trailing edge portion is the same at any position in the blade height direction.

7. A rotor blade for an axial flow compressor according to claim 1, wherein the shape of the outer edge of the leading edge portion on an imaginary plane perpendicular to the blade height direction is an arc, the leading edge is located on the arc of the leading edge portion, and the arc radius of the trailing edge portion at the tip side end is equal to or greater than the arc radius of the leading edge portion at the tip side end.

8. An axial compressor comprising: a rotor rotatable about an axis; and a casing covering the outer periphery of the rotor, wherein the rotor has a rotor shaft rotationally symmetrical about the axis, and a plurality of rows of moving blades attached to the rotor shaft and aligned in the axial direction along which the axis extends, each of the plurality of rows of moving blades having a plurality of moving blades aligned in the circumferential direction about the axis, and wherein the plurality of moving blades owned by at least some of the plurality of rows of moving blades are all moving blades of an axial compressor according to any one of claims 1 to 7, wherein the blade height direction is a radial direction with respect to the axis, the tip side is a radially outer side with respect to the axis, and the hub side is a radially inner side with respect to the axis.

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