Axial flow compressor

Abstract

An axial flow compressor capable of suppressing a decrease in performance of the axial flow compressor caused by a wake generated from the trailing edge of a final stage stator vane interfering with an outlet guide vane. [Solution] An axial flow compressor is provided with an outlet guide vane provided downstream of a final stage stator vane, and in a cross section perpendicular to the blade height direction of the final stage stator vane, the straight line obtained by extending the camber line of the final stage stator vane from the trailing edge of the final stage stator vane is called the camber line extension line, and if the shortest distance between the camber line extension line and the suction surface of the outlet guide vane is Dmin and the chord length of the outlet guide vane is C, the final stage stator vane and the outlet guide vane satisfy 0.07≦Dmin / C≦0.20 over the entire range in the blade height direction of the final stage stator vane.

Description

[Technical Field]

[0001] The present disclosure relates to an axial flow compressor. [Background technology]

[0002] Patent Document 1 discloses an axial flow compressor for compressing a fluid, which has a two-stage stator vane structure and includes an outlet guide vane on the downstream side of the final stage stator vane in the direction of fluid flow. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-249811 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the findings of the present inventors, in an axial flow compressor equipped with an outlet guide vane downstream of a final stage stator vane, if a wake (vortex) generated from the trailing edge of the final stage stator vane interferes with the outlet guide vane, flow separation occurs on the surface of the outlet guide vane, resulting in a deterioration in the performance of the axial flow compressor.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide an axial flow compressor that can suppress performance degradation of the axial flow compressor caused by wake generated from the trailing edge of a final stage stator vane interfering with an outlet guide vane. [Means for solving the problem]

[0006] In order to achieve the above object, an axial flow compressor according to at least one embodiment of the present disclosure comprises: 1. An axial flow compressor for compressing a fluid, comprising: The final stage stator blade, an outlet guide vane provided downstream of the final stage vane in the flow direction of the fluid; Equipped with In a cross section perpendicular to the blade height direction of the final stage stator vane, a straight line obtained by extending the camber line of the final stage stator vane from the trailing edge of the final stage stator vane is referred to as a camber line extension line, and the shortest distance between the camber line extension line and the suction surface of the outlet guide vane is Dmin, and the chord length of the outlet guide vane is C, then the final stage stator vane and the outlet guide vane satisfy the following formula (a) over the entire range in the blade height direction of the final stage stator vane: 0.07≦Dmin / C≦0.20 …(a) [Effects of the Invention]

[0007] According to at least one embodiment of the present disclosure, there is provided an axial flow compressor that can suppress performance degradation of the axial flow compressor caused by the wake generated from the trailing edge of the final stage stator vane interfering with the outlet guide vane. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic cross section along the axial direction of an axial flow compressor 2 according to one embodiment. [Figure 2] 1 is a diagram showing a cross section perpendicular to the blade height direction at a position Po belonging to an outer end 16fo in the blade height direction of the final stage stator vane 16f and the outlet guide vane 20 of the axial flow compressor 2. FIG. [Figure 3] 1 is a diagram showing a cross section perpendicular to the blade height direction at a position Pm belonging to a central portion 16fm in the blade height direction of the final stage stator vane 16f and an outlet guide vane 20 of the axial flow compressor 2. FIG. [Figure 4] 1 is a diagram showing a cross section perpendicular to the blade height direction at a position Pi belonging to an end 16fi on the inner side in the blade height direction of the final stage stator vane 16f and the outlet guide vane 20 of the axial flow compressor 2. FIG. [Figure 5A] FIG. 10 is a diagram showing the flow velocity distribution on the suction surface 46 of the outlet guide vane 20 in a comparative example. [Figure 5B] FIG. 10 is a diagram showing the flow velocity distribution on the suction surface 46 of the outlet guide vane 20 in a comparative example. [Figure 5C]FIG. 10 is a diagram showing the flow velocity distribution on the suction surface 46 of the outlet guide vane 20 in a comparative example. [Figure 6] FIG. 4 is a diagram showing a flow velocity distribution on a suction surface 46 of an outlet guide vane 20 in one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the invention. For example, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement exactly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. On the other hand, the expressions "comprise," "include," "have," "includes," or "have" of one element are not exclusive expressions that exclude the presence of other elements.

[0010] FIG. 1 is a diagram showing a schematic cross section along the axial direction of an axial flow compressor 2 according to one embodiment. 1, the axial flow compressor 2 includes a rotor 4 and a casing 6 that houses the rotor 4. Between the rotor 4 and the casing 6, a flow path 7 is formed through which a fluid to be compressed flows.

[0011] The rotor 4 includes a rotating shaft 8 and a plurality of rows of rotating blades 10 provided on the outer peripheral surface of the rotating shaft 8. The plurality of rows of rotating blades 10 are arranged at intervals in the axial direction. In this specification, unless otherwise specified, the term "axial direction" refers to the axial direction of the axial compressor 2, i.e., the axial direction of the rotating shaft 8; the term "radial direction" refers to the radial direction of the axial compressor 2, i.e., the radial direction of the rotating shaft 8; and the term "circumferential direction" refers to the circumferential direction of the axial compressor 2, i.e., the circumferential direction of the rotating shaft 8, unless otherwise specified. In this specification, the term "upstream side" refers to the upstream side in the flow direction of the fluid flowing through the flow passage 7, i.e., the upstream side in the axial direction, and the term "downstream side" refers to the downstream side in the flow direction of the fluid flowing through the flow passage 7, i.e., the downstream side in the axial direction, unless otherwise specified.

[0012] Each of the plurality of rotor blade rows 10 includes a plurality of rotor blades 12 provided at intervals in the circumferential direction along a circular arc on the outer peripheral surface of the rotary shaft 8 .

[0013] The axial flow compressor 2 also includes a plurality of stator blade rows 14 provided on the inner circumferential surface of the casing 6. The plurality of stator blade rows 14 are arranged at intervals in the axial direction. The rotor blade rows 10 and the stator blade rows 14 are arranged alternately in the axial direction. The stator blade rows 14 include a plurality of stator vanes 16 provided on the inner circumferential surface of the casing 6 along an arc at intervals in the circumferential direction.

[0014] Here, the rotor blade row 10 and the stator blade row 14 arranged adjacent to the rotor blade row 10 on the downstream side of the rotor blade row 10 constitute one stage 18 of the axial compressor 2, and the axial compressor 2 includes a plurality of stages 18 arranged in series in the axial direction. Here, the stage located most downstream among the plurality of stages 18 will be referred to as the final stage 18f, the stator blade row 14 belonging to the final stage 18f will be referred to as the final stage stator blade row 14f, and each of the stator blades 16 constituting the final stage stator blade row 14f will be referred to as the final stage stator blade 16f. Furthermore, in this specification, unless otherwise specified, the "blade height direction" refers to the blade height direction of the final stage stator blade 16f, the "outside" in the blade height direction means the outside in the radial direction (the side toward the casing 6 in the blade height direction), and the "inside" in the blade height direction means the inside in the radial direction (the side toward the rotating shaft 8 in the blade height direction).

[0015] The axial flow compressor 2 includes a plurality of outlet guide vanes 20 that are provided at intervals in the circumferential direction along a circular arc on the inner peripheral surface of the casing 6. Each of the outlet guide vanes 20 is provided in one-to-one correspondence with each of the plurality of final stage stator vanes 16 f, and is disposed adjacent to the corresponding final stage stator vane 16 f on the downstream side of each of the plurality of final stage stator vanes 16 f.

[0016] 2 to 4 are diagrams illustrating examples of the arrangement of the final stage stator vane 16f and the outlet guide vane 20 downstream of the final stage stator vane 16f in a cross section perpendicular to the blade height direction. Fig. 2 shows a cross section perpendicular to the blade height direction at a position Po belonging to an outer end 16fo (see Fig. 1) of the final stage stator vane 16f in the blade height direction, Fig. 3 shows a cross section perpendicular to the blade height direction at a position Pm belonging to a central portion 16fm (see Fig. 1) of the final stage stator vane 16f in the blade height direction, and Fig. 4 shows a cross section perpendicular to the blade height direction at a position Pi belonging to an inner end 16fi (see Fig. 1) of the final stage stator vane 16f in the blade height direction. The end 16fo is located outward in the blade height direction from the central portion 16fm, and the end 16fi is located inward in the blade height direction from the central portion 16fm.

[0017] 2 to 4 , the final stage stator vane 16f includes a leading edge 30, a trailing edge 32, a pressure surface 34 connecting the leading edge 30 and the trailing edge 32, and a suction surface 36 connecting the leading edge 30 and the trailing edge 32. The outlet guide vane 20 also includes a leading edge 40, a trailing edge 42, a pressure surface 44 connecting the leading edge 40 and the trailing edge 42, and a suction surface 46 connecting the leading edge 40 and the trailing edge 42.

[0018] As shown in Figures 2 to 4, in each cross section perpendicular to the blade height direction, the straight line extending the camber line Lc of the final stage stator vane 16f from the trailing edge 32 of the final stage stator vane 16f is called the camber line extension line Le, the shortest distance between the camber line extension line Le and the suction surface 46 of the outlet guide vane 20 is Dmin, and the chord length of the outlet guide vane 20 is C. The final stage stator vane 16f and the outlet guide vane 20 are configured to satisfy the following formula (a) over the entire range in the blade height direction of the final stage stator vane 16f. 0.07≦Dmin / C≦0.20 …(a)

[0019] The "camber line Lc of the final stage stator vane 16f" refers to a line that passes through the leading edge 30 and the trailing edge 32 and connects the center of the thickness of the final stage stator vane 16 (a line that connects positions equidistant from the pressure surface 34 and the suction surface 36). The "straight line extending the camber line Lc of the final stage stator vane 16f from the trailing edge 32 of the final stage stator vane 16f" refers to a straight line extending the camber line Lc from the trailing edge 32 of the final stage stator vane 16f along the direction of the tangent to the camber line Lc at the trailing edge 32. The "shortest distance between the camber line extension line Le and the suction surface 46 of the outlet guide vane 20" refers to the distance between the tangent line Lt and the extension line Le, where Lt is a tangent that is parallel to the camber line extension line Le and tangent to the suction surface 46. Furthermore, "the entire range in the blade height direction of the final stage stator vane 16f" means the range from the outer end of the final stage stator vane 16f in the blade height direction to the inner end of the final stage stator vane 16f, and "the entire range in the blade height direction of the final stage stator vane 16f satisfies the following formula (a)" means that the above cross section (cross section perpendicular to the blade height direction) at all positions from the outer end of the final stage stator vane 16f in the blade height direction to the inner end of the final stage stator vane 16f satisfies the above formula (a).

[0020] The effect obtained by satisfying the above formula (a) will now be described with reference to Figures 5A to 5C and 6. Figures 5A to 5C show flow velocity distributions on the suction surface 46 of the outlet guide vane 20 for several comparative embodiments. Figure 5A shows a case where the ratio Dmin / C in a cross section perpendicular to the blade height direction at position Pm belonging to the central portion 16fm is 0.056. Figure 5B shows a case where the ratio Dmin / C in a cross section at position Pm belonging to the central portion 16fm is 0.066. Figure 5C shows a case where the ratio Dmin / C in a cross section at position Pm belonging to the central portion 16fm is 0.069. Figure 6 shows a flow velocity distribution on the suction surface 46 of the outlet guide vane 20 in one embodiment. Figure 6 shows a case where the ratio Dmin / C in a cross section at position Pm belonging to the central portion 16fm is 0.11.

[0021] In the comparative example shown in Fig. 5A, flow separation occurs in a range S near the outer end 20o in the blade height direction on the suction surface 46 of the outlet guide vane 20. According to the findings of the present inventors, such separation on the suction surface 46 of the outlet guide vane 20 occurs when a wake (vortex) generated from the trailing edge 32 of the final stage stator vane 16f interferes with the outlet guide vane 20, resulting in a decrease in performance of the axial flow compressor 2. Furthermore, as shown in Figs. 5A to 5C, as the ratio Dmin / C decreases, the range S of separation on the suction surface 46 of the outlet guide vane 20 shrinks, and it can be seen that no flow separation occurs on the suction surface 46 of the outlet guide vane 20 in the embodiment shown in Fig. 6.

[0022] As a result of intensive studies by the present inventors, it has been found that when the ratio Dmin / C satisfies the above formula (a) over the entire range in the blade height direction of the final stage stator vane 16f, an appropriate distance is ensured between the wake (vortex) generated from the trailing edge 32 of the final stage stator vane 16f and the outlet guide vane, the wake can be prevented from interfering with the outlet guide vane 20, and separation on the suction surface 46 of the outlet guide vane 20 can be prevented compared to the comparative configurations shown in Figures 5A to 5C. Therefore, when the ratio Dmin / C satisfies the above formula (a) over the entire range in the blade height direction of the final stage stator vane 16f, it is possible to prevent a decrease in performance of the axial flow compressor 2 caused by the wake generated from the trailing edge 32 of the final stage stator vane 16f interfering with the outlet guide vane 20.

[0023] In some embodiments, if the shortest distance Dmin in the cross section shown in Figure 2 (cross section at position Po belonging to the outer end 16fo in the blade height direction of the final stage stator vane 16f) is Dmino, the shortest distance Dmin in the cross section shown in Figure 3 (cross section at position Pm belonging to the central part 16fm in the blade height direction of the final stage stator vane 16f) is Dminm, and the shortest distance Dmin in the cross section shown in Figure 4 (cross section at position Pi belonging to the inner end 16fi in the blade height direction of the final stage stator vane 16f) is Dmini, the final stage stator vane 16f and the outlet guide vane 20 are configured to satisfy the following formula (b): Domino <Dminm<Dmini …(b)

[0024] If the outlet guide vane 20 has a twisted shape such that the shortest distance Dmin decreases outward in the blade height direction, the above formula (b) is satisfied, but in such a case, the shortest distance Dmino is likely to be small, and therefore the above-mentioned separation is likely to occur near the outer end 20o of the outlet guide vane 20 in the blade height direction, as shown in Fig. 5A. Even in such a case, by satisfying the above formula (a) over the entire range of the final stage stator vane 16f in the blade height direction, it is possible to suppress a deterioration in performance of the axial flow compressor 2 caused by the wake generated from the trailing edge 32 of the final stage stator vane 16f interfering with the outlet guide vane 20.

[0025] In some embodiments, when the chord length C of the outlet guide vane 20 in the cross section shown in Figure 2 (cross section at position Po belonging to the outer end 16fo in the blade height direction of the final stage stator vane 16f) is Co, the chord length C of the outlet guide vane 20 in the cross section shown in Figure 3 (cross section at position Pm belonging to the central part 16fm in the blade height direction of the final stage stator vane 16f) is Cm, and the chord length C of the outlet guide vane 20 in the cross section shown in Figure 4 (cross section at position Pi belonging to the inner end 16fi in the blade height direction of the final stage stator vane 16f) is Ci, the final stage stator vane 16f and the outlet guide vane 20 are configured to satisfy the following formula (c): Cm <Ci<Co …(c)

[0026] Even in such a case, by satisfying the above formula (a) over the entire range in the blade height direction of the final stage stator vane 16f, it is possible to suppress the performance degradation of the axial flow compressor 2 caused by the wake generated from the trailing edge 32 of the final stage stator vane 16f interfering with the outlet guide vane 20.

[0027] In some embodiments, when the ratio Dmin / C in the cross section shown in FIG. 2 (a cross section at a position Po belonging to the outer end 16fo in the blade height direction of the final stage stator vane 16f) is Eo, the ratio Dmin / C in the cross section shown in FIG. 3 (a cross section at a position Pm belonging to the central part 16fm in the blade height direction of the final stage stator vane 16f) is Em, and the ratio Dmin / C in the cross section shown in FIG. 4 (a cross section at a position Pi belonging to the inner end 16fi in the blade height direction of the final stage stator vane 16f) is Ei, the final stage stator vane 16f and the outlet guide vane 20 are configured to satisfy the following formula (d): Eo <Em<Ei …(d)

[0028] When the above formula (d) is satisfied, the above-described separation may be more likely to occur near the outer end 20o in the blade height direction of the outlet guide vane 20. Even in such a case, by satisfying the above formula (a) over the entire range of the final stage stator vane 16f in the blade height direction, it is possible to suppress a deterioration in the performance of the axial flow compressor 2 caused by the wake generated from the trailing edge 32 of the final stage stator vane 16f interfering with the outlet guide vane 20.

[0029] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0030] For example, in some embodiments, the final stage stator vane 16f and the outlet guide vane 20 may be configured to satisfy the above formula (e). 0.09≦Dmin / C≦0.18 …(e) In this case as well, the deterioration in performance of the axial flow compressor 2 caused by the wake generated from the trailing edge 32 of the final stage stator vane 16f interfering with the outlet guide vane 20 can be suppressed.

[0031] The contents described in each of the above embodiments can be understood, for example, as follows.

[0032] [1] An axial flow compressor according to at least one embodiment of the present disclosure comprises: An axial compressor for compressing a fluid (e.g., the axial compressor 2 described above), A final stage vane (for example, the above-mentioned final stage vane 16f), an outlet guide vane (for example, the above-mentioned outlet guide vane 20) provided downstream of the final stage vane in the flow direction of the fluid; Equipped with In a cross section perpendicular to the blade height direction of the final stage stator vane, a straight line extending from the trailing edge of the camber line of the final stage stator vane (for example, the above-mentioned camber line Lc) is referred to as a camber line extension line (for example, the above-mentioned camber line extension line Le), and the shortest distance between the camber line extension line and the suction surface of the outlet guide vane is Dmin and the chord length of the outlet guide vane is C, then the final stage stator vane and the outlet guide vane satisfy the following formula (a) over the entire range in the blade height direction of the final stage stator vane: 0.07≦Dmin / C≦0.20 …(a)

[0033] According to the axial flow compressor described in [1] above, it is possible to appropriately ensure the distance between the wake (vortex) generated from the trailing edge of the final stage stator vane and the outlet guide vane, thereby suppressing interference of the wake with the outlet guide vane. This makes it possible to suppress separation on the suction surface of the outlet guide vane, thereby suppressing a decrease in performance of the axial flow compressor caused by interference of the wake generated from the trailing edge of the final stage stator vane with the outlet guide vane.

[0034] [2] In some embodiments, in the axial flow compressor according to [1] above, Let Dmino be the shortest distance in the cross section at a first position (e.g., the above-mentioned position Po) belonging to an outer end portion (e.g., the above-mentioned end portion 16fo) of the final stage stator vane in the blade height direction, Dminm be the shortest distance in the cross section at a second position (e.g., the above-mentioned position Pm) belonging to a central portion (e.g., the above-mentioned central portion 16fm) of the final stage stator vane in the blade height direction, and Dmini be the shortest distance in the cross section at a third position (e.g., the above-mentioned position Pi) belonging to an inner end portion (e.g., the above-mentioned end portion 16fi) of the final stage stator vane in the blade height direction, then the final stage stator vane and the outlet guide vane satisfy the following formula (b): Domino <Dminm<Dmini …(b)

[0035] If the outlet guide vane has a twisted shape so that the shortest distance Dmin decreases outward in the blade height direction, the above formula (b) is satisfied as described in [2] above. However, in such a case, the shortest distance Dmino tends to be small, and the above-mentioned separation tends to occur near the outer end of the outlet guide vane in the blade height direction. Even in such a case, by satisfying the above formula (a) over the entire range of the final stage stator vane in the blade height direction, it is possible to suppress a deterioration in the performance of the axial flow compressor caused by the wake generated from the trailing edge of the final stage stator vane interfering with the outlet guide vane.

[0036] [3] In some embodiments, in the axial flow compressor according to [1] or [2] above, Let Co be the chord length in the cross section at a first position (e.g., the above-mentioned position Po) belonging to an outer end portion (e.g., the above-mentioned end portion 16fo) of the final stage stator vane in the blade height direction, Cm be the chord length in the cross section at a second position (e.g., the above-mentioned position Pm) belonging to a central portion (e.g., the above-mentioned central portion 16fm) of the final stage stator vane in the blade height direction, and Ci be the chord length in the cross section at a third position (e.g., the above-mentioned position Pi) belonging to an inner end portion (e.g., the above-mentioned end portion 16fi) of the final stage stator vane in the blade height direction, then the final stage stator vane and the outlet guide vane satisfy the following formula (c): Cm <Ci<Co …(c)

[0037] Even in such a case, by satisfying the above formula (a) over the entire range of the final stage stator vane in the blade height direction, it is possible to suppress the degradation of the performance of the axial flow compressor caused by the wake generated from the trailing edge of the final stage stator vane interfering with the outlet guide vane.

[0038] [4] In some embodiments, in the axial flow compressor according to any one of [1] to [3] above, Let Eo be the ratio Dmin / C in the cross section at a first position (e.g., the above-mentioned position Po) belonging to the outer end of the final stage stator vane in the blade height direction (e.g., the above-mentioned end 16fo), Em be the ratio Dmin / C in the cross section at a second position (e.g., the above-mentioned position Pm) belonging to the central portion of the final stage stator vane in the blade height direction (e.g., the above-mentioned central portion 16fm), and Ei be the ratio Dmin / C at a third position (e.g., the above-mentioned position Pi) belonging to the inner end of the final stage stator vane in the blade height direction (e.g., the above-mentioned end 16fi), then the final stage stator vane and the outlet guide vane satisfy the following formula (d): Eo <Em<Ei …(d)

[0039] When the above formula (d) is satisfied, the above-mentioned separation may be more likely to occur near the outer end of the outlet guide vane in the blade height direction. However, even in such a case, by satisfying the above formula (a) over the entire range of the final stage stator vane in the blade height direction, it is possible to suppress the degradation of the performance of the axial flow compressor caused by the wake generated from the trailing edge of the final stage stator vane interfering with the outlet guide vane.

[0040] [5] In some embodiments, in the axial flow compressor according to any one of [1] to [4] above, The final stage stator vane and the outlet guide vane satisfy the following formula (e) over the entire range in the blade height direction of the final stage stator vane. 0.09≦Dmin / C≦0.18 …(e)

[0041] According to the axial flow compressor described in [5] above, it is possible to suppress the deterioration of the performance of the axial flow compressor caused by the wake generated from the trailing edge of the final stage stator vane interfering with the outlet guide vane. [Explanation of symbols]

[0042] 2. Axial flow compressor 4 rotors 6 Casing 7 Flow path 8 Rotation Axis 10 Moving blade row 12 Moving blade 14 Stator blade row 14f final stage stator blade row 16 Stator blade 16f final stage stationary blade 16fi,16fo,20o end 18 paragraphs 18f Final paragraph 20 Exit guide vane 36,46 suction surface 30,40 leading edge 32,42 Trailing edge 34,44 Pressure surface 46 Suction surface C, Co, Cm, Ci cord length Dmin,Dmino,Dminm,Dmini Shortest distance Lc camber line Le Camber line extension Lt tangent Pi,Pm,Po position S range

Claims

1. 1. An axial flow compressor for compressing a fluid, comprising: The final stage stator blade, an outlet guide vane provided downstream of the final stage vane in the flow direction of the fluid; Equipped with a leading edge of the outlet guide vane is located downstream of a trailing edge of the final stage stator vane in the axial direction of the axial flow compressor, an axial flow compressor in which, in a cross section perpendicular to a blade height direction of the final stage stator vane, a straight line obtained by extending a camber line of the final stage stator vane from a trailing edge of the final stage stator vane is called a camber line extension line, the shortest distance between the camber line extension line and a suction surface of the outlet guide vane is Dmin, and the chord length of the outlet guide vane is C, the final stage stator vane and the outlet guide vane satisfy the following formula (a) over an entire range in the blade height direction of the final stage stator vane: 0.11≦Dmin / C≦0.20…(a)

2. 2. The axial flow compressor according to claim 1, wherein the shortest distance in the cross section at a first position belonging to an outer end of the final stage stator vane in the blade height direction is Dmino, the shortest distance in the cross section at a second position belonging to a central portion of the final stage stator vane in the blade height direction is Dminm, and the shortest distance in the cross section at a third position belonging to an inner end of the final stage stator vane in the blade height direction is Dmini, the final stage stator vane and the outlet guide vane satisfy the following formula (b): Dmino<Dminm<Dmini…(b)

3. 2. The axial flow compressor according to claim 1, wherein the outlet guide vane satisfies the following formula (c): Co is the chord length in the cross section at a first position belonging to an outer end of the final stage stator vane in the blade height direction, Cm is the chord length in the cross section at a second position belonging to a central portion of the final stage stator vane in the blade height direction, and Ci is the chord length in the cross section at a third position belonging to an inner end of the final stage stator vane in the blade height direction. Cm<Ci<Co...(c)

4. 2. The axial flow compressor according to claim 1, wherein the final stage stator vane and the outlet guide vane satisfy the following formula (d): Eo is a ratio Dmin / C in the cross section at a first position belonging to an outer end of the final stage stator vane in the blade height direction, Em is a ratio Dmin / C in the cross section at a second position belonging to a central portion of the final stage stator vane in the blade height direction, and Ei is a ratio Dmin / C in the cross section at a third position belonging to an inner end of the final stage stator vane in the blade height direction. Eo<Em<Ei...(d)

Images