Intake duct, gas turbine engine, and aircraft

Abstract

To provide an intake duct that allows for better introduction of air into the compressor. [Solution] The intake duct 28 comprises a rear wall 30, a front wall, and a side wall 34. The duct space 36 defined by the rear wall 30, the front wall, and the side wall 34 includes a first partial space 36a and a second partial space 36b. The second partial space 36b is located on one side relative to the first partial space 36a, and at least a portion of the partial side wall 34a, which is part of the side wall 34, is located on the other side relative to the first partial space 36a. The shape of at least a portion of the partial side wall 34a is spiral in a view in the axial direction of the gas turbine engine.

Description

Technical Field

[0001] The present disclosure relates to an intake duct, a gas turbine engine, and an aircraft.

Background Art

[0002] Japanese Patent No. 6661323 discloses an intake structure of a compressor incorporated in a gas turbine engine. An intake port that opens in a direction away from the central axis of the compressor is formed in the intake duct provided in the intake structure.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is desired to introduce air into the compressor more favorably.

[0005] The present disclosure aims to solve the above-described problems.

Means for Solving the Problems

[0006] A first aspect of the present disclosure is an intake duct for guiding air to a compressor of a gas turbine engine, comprising: a rear wall having an opening formed therein through which an introduction passage for introducing air into the compressor is provided; a front wall facing the rear wall; and a side wall connecting the rear wall and the front wall, wherein the duct space defined by the rear wall, the front wall and the side wall includes a first partial space including the center of the opening and a second partial space that guides air flowing in through the intake port into the first partial space, the second partial space being located on one side of the first partial space, at least a portion of the partial side wall being part of the side wall being located on the other side of the first partial space, and the shape of at least a portion of the partial side wall being spiral in a view in the axial direction of the gas turbine engine.

[0007] A second aspect of this disclosure is a gas turbine engine comprising an intake duct according to the first aspect.

[0008] A third aspect of this disclosure is an aircraft having a plurality of gas turbine engines according to the second aspect, wherein the plurality of gas turbine engines are arranged in parallel inside the aircraft. [Effects of the Invention]

[0009] According to this disclosure, it is possible to introduce air into the compressor effectively. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a perspective view of the power generation unit. [Figure 2] Figure 2 is a plan view of the power generation unit. [Figure 3] Figure 3 is a side view of the power generation unit. [Figure 4] Figure 4 is a cross-sectional view taken along line IV-IV of Figure 3. [Figure 5] Figure 5 is a cross-sectional view of the VV section of Figure 3. [Figure 6] Figure 6 illustrates the shape of a partial side wall in an axial view. [Figure 7]Figure 7 shows the allowable range for the partial sidewall. [Figure 8] Figure 8 shows the airflow in the intake duct. [Figure 9] Figure 9 shows other base circles. [Figure 10] Figure 10 is a schematic diagram of the aircraft. [Modes for carrying out the invention]

[0011] In a gas turbine engine, air (outside air) flows from the intake port into the intake duct and is guided by the intake duct to the inlet (also called the intake port) of the air supply path to the compressor. However, uneven intake of air in the compressor can cause a decrease in the output of the gas turbine engine and engine stall. Uneven intake of air in the compressor is particularly noticeable in gas turbine engines with a side air intake structure.

[0012] In a gas turbine engine with a side air intake structure, the intake port opens in one direction (referred to as the +d direction) perpendicular to the axis of the gas turbine engine. The inlet is formed in an annular shape centered on the axis of the gas turbine engine. Air flows from the intake port towards the inlet through the intake duct along a plane perpendicular to the axis of the gas turbine engine. Furthermore, the air that reaches the inlet changes its direction of flow by approximately 90 degrees and flows through the inlet passage along the axis of the gas turbine engine. In this way, the air is introduced to the compressor.

[0013] In the intake duct, a part of the air flows into the air introduction passage from the +d direction. Also, in the intake duct, another part of the air circulates along the periphery of the inlet and flows into the introduction passage from a direction other than the +d direction. For example, another part of the air bypasses the inlet by 180 degrees and flows into the introduction passage from the direction opposite to the +d direction (referred to as the -d direction). There is a tendency for a bias to occur between the flow rate of the air flowing into the introduction passage from the +d direction and the flow rate of the air flowing into the introduction passage from the -d direction. For these reasons, in a gas turbine engine with a side air intake structure, intake bias in the compressor is likely to occur.

[0014] According to the embodiment described below, in a gas turbine engine with a side air intake structure, it is possible to suppress intake bias in the compressor.

[0015] [Power generation unit 10] FIG. 1 is a perspective view of the power generation unit 10. FIG. 2 is a plan view of the power generation unit 10. FIG. 3 is a side view of the power generation unit 10. In this specification, for the sake of convenience of explanation, directions such as front and rear, up and down, and left and right are used. Further, in this specification, the power generation unit 10 in which the axis A of the power generation unit 10 extends in the front-rear direction is described. That is, the axial direction of the power generation unit 10 coincides with the front-rear direction. However, the axial direction of the power generation unit 10 is not limited to the front-rear direction. That is, the attitude of the power generation unit 10 is not limited to a specific attitude.

[0016] The power generation unit 10 includes a generator 12 and a gas turbine engine 14 with a side air intake structure. The generator 12 is arranged in front of the gas turbine engine 14. Each of the rotating shaft (not shown) of the generator 12 and the shaft 26 (FIG. 5) of the gas turbine engine 14 is arranged on the axis A of the power generation unit 10. The axis A of the power generation unit 10 is also the axis of each of the generator 12 and the gas turbine engine 14. In this specification, the axis of the generator 12 and the axis of the gas turbine engine 14 are referred to as the axis A. The rotating shaft of the generator 12 is connected to the shaft 26 (FIG. 5) of the gas turbine engine 14. When the shaft 26 of the gas turbine engine 14 rotates, the rotating shaft of the generator 12 rotates. Thereby, the generator 12 generates electricity.

[0017] [2 Gas turbine engine 14] As shown in FIGS. 2 and 3, the gas turbine engine 14 includes a compressor 20, a combustor 22, and a turbine 24. FIGS. 1 to 3 show the compressor 20, the combustor 22, and the turbine 24 covered by the cover 16. The compressor 20, the combustor 22, and the turbine 24 are arranged along the front-rear direction. The compressor 20 is arranged in front of the combustor 22. The combustor 22 is arranged in front of the turbine 24. When the turbine 24 rotates, the shaft 26 (FIG. 5) of the gas turbine engine 14 rotates.

[0018] [3 Intake duct 28] For example, as shown in FIGS. 2 and 3, the gas turbine engine 14 includes an intake duct 28. The intake duct 28 is arranged in front of the compressor 20 and behind the generator 12. The intake duct 28 is connected to each of the compressor 20 and the generator 12. The intake duct 28 includes a rear wall 30, a front wall 32, and side walls 34. Each of the rear wall 30, the front wall 32, and the side walls 34 is a casing member that defines a duct space 36 serving as an air flow path inside the intake duct 28.

[0019] Figure 4 is a cross-sectional view taken along line IV-IV of Figure 3. Figure 5 is a cross-sectional view taken along line VV of Figure 3. The rear wall 30 intersects with axis A. An opening 38 is formed in the rear wall 30, centered on axis A. A bell mouth 48, which will be described later, is attached to the opening 38.

[0020] As shown in Figure 2, the front wall 32 is positioned in front of the rear wall 30. The front wall 32 includes a partial front wall 32a located on the right side and a partial front wall 32b located on the left side. Partial front wall 32a intersects axis A. Partial front wall 32a runs along the rear wall 30 and faces the rear wall 30. On the other hand, partial front wall 32b is partially curved. Partial front wall 32b extends diagonally forward to the left, starting from the connection point with partial front wall 32a.

[0021] As shown in Figures 1 to 3, the side wall 34 is positioned between the rear wall 30 and the front wall 32 in the front-rear direction. The side wall 34 connects a portion of the periphery of the rear wall 30, excluding the left portion, and a portion of the periphery of the front wall 32, excluding the left portion. As shown in Figures 2 and 4, the portion of the side wall 34 located on the right side (a part of the side wall 34) is referred to as the partial side wall 34a.

[0022] As shown in Figure 4, the intake duct 28 is equipped with a plurality of struts 40. The struts 40 have an airfoil shape. An example of an airfoil shape is the NACA0012 shape. The plurality of struts 40 are arranged inside the duct space 36. The plurality of struts 40 are arranged at intervals from each other on a predetermined circle centered on axis A. The predetermined circle is the base circle 68 (Figure 6) of the involute curve 66, which will be described later. In an axial view, the struts 40 are arranged along the radial direction of the base circle 68. In an axial view, the struts 40 are arranged outside the opening 38. The struts 40 connect the rear wall 30 and the front wall 32 (partial front wall 32a).

[0023] As shown in Figure 4, the intake duct 28 is equipped with a pair of guide vanes 42. The pair of guide vanes 42 are arranged inside the duct space 36. One guide vane 42 is positioned above the other guide vane 42. The guide vanes 42 are positioned between the opening 38 (and the base circle 68 shown in Figure 6) and the intake port 44. The guide vanes 42 rectify the air flowing into the duct space 36 from the intake port 44. The guide vanes 42 are connected to the rear wall 30 and the front wall 32 (partial front wall 32a).

[0024] As shown in Figure 4, an intake port 44 opening to the left is formed on the left side of the intake duct 28. The duct space 36 communicates with the outside space through the intake port 44. The duct space 36 includes a first partial space 36a and a second partial space 36b. The first partial space 36a is located on the right side (the other side) of the duct space 36. In an axial view, the first partial space 36a includes the center of the opening 38 located on axis A. The second partial space 36b is located on the left side (the other side) of the duct space 36. The second partial space 36b is adjacent to the intake port 44. The second partial space 36b guides the air flowing in through the intake port 44 into the first partial space 36a.

[0025] In this specification, the boundary between the first partial space 36a and the second partial space 36b lies between the leftmost strut 40 among the multiple struts 40 and the guide vane 42. That is, each strut 40 is located inside the first partial space 36a. Each guide vane 42 is located inside the second partial space 36b.

[0026] The dimension D1 (Figure 1) of the second partial space 36b in the vertical direction decreases as it moves away from the first partial space 36a. On the other hand, the dimension D2 (Figure 1) of the second partial space 36b in the front-to-back direction (axial direction) increases as it moves away from the first partial space 36a. In this embodiment, in at least a portion of the second partial space 36b, the amount of change in the cross-sectional area of ​​the second partial space 36b in response to the change in dimension D1 is made substantially the same as the amount of change in the cross-sectional area of ​​the second partial space 36b in response to the change in dimension D2. In other words, in at least a portion of the second partial space 36b, the cross-sectional shape of the second partial space 36b changes as it moves away from the first partial space 36a, while the cross-sectional area of ​​the second partial space 36b remains constant. Note that the cross-section referred to here is the cross-section along the front-to-back direction and the vertical direction.

[0027] As shown in Figure 5, a bell mouth 48 is attached to an opening 38 formed in the rear wall 30. The bell mouth 48 comprises an outer shroud 50 and an inner shroud 54. The connection between the inner edge portion of the rear wall 30 around the opening 38 and the outer edge portion of the outer shroud 50 is sealed. The tip 52 of the outer shroud 50 is located inside the first partial space 36a. The base end (not shown) of the outer shroud 50 is fixed to a rearward-positioned member (not shown). The tip 56 of the inner shroud 54 is located in front of the tip 52 of the outer shroud 50. The tip 56 of the inner shroud 54 is located inside the first partial space 36a and is fixed to the partial front wall 32a. The base end (not shown) of the inner shroud 54 is fixed to a rearward-positioned member (not shown).

[0028] The outer shroud 50 and the inner shroud 54 define an annular inlet passage 58 for introducing air into the compressor 20. The inlet passage 58 connects the duct space 36 with the internal space of the compressor 20 (the space where the impeller is located).

[0029] [4 Shape of the partial side wall 34a] Figure 6 is a diagram illustrating the shape of the partial side wall 34a in an axial view. The shape of the partial side wall 34a in an axial view will be described below. Here, we assume a first imaginary line 62 extending in the left-right direction and perpendicular to axis A, and a second imaginary line 64 extending in the up-down direction and perpendicular to axis A. The side wall 34 in this embodiment has a shape that is symmetrical with respect to the first imaginary line 62 as the axis. Here, we will describe the shape of the partial side wall 34a located above the first imaginary line 62, and omit the description of the partial side wall 34a located below the first imaginary line 62.

[0030] With respect to the first subspace 36a, the second subspace 36b is located to the left of the first subspace 36a. Also, with respect to the first subspace 36a, at least a portion of the sub-sidewall 34a is located to the right of the first subspace 36a. At least a portion of the sub-sidewall 34a has a spiral shape. The spiral shape is, for example, an involute curve 66. The center of the base circle 68 of the involute curve 66 is located on axis A. The base circle 68 of the involute curve 66 passes through the maximum thickness portion of each strut 40, where the wall thickness is greatest. The starting point 70 of the involute curve 66 is located at the intersection of the first imaginary line 62 and the base circle 68.

[0031] The partial side wall 34a follows a portion of the involute curve 66. The portion of the involute curve 66 that the partial side wall 34a follows is referred to as the partial involute curve 66a. In this embodiment, the partial involute curve 66a is defined as follows: The first virtual line 62 is assumed to be the x-axis, the second virtual line 64 is assumed to be the y-axis, and the position of axis A is assumed to be the origin. Furthermore, the range located to the right of the origin is assumed to be the positive range of x, and the range located to the left of the origin is assumed to be the negative range of x. The range located above the origin is assumed to be the positive range of y, and the range located below the origin is assumed to be the negative range of y. The x-axis direction is the first direction, and the y-axis direction is the second direction. In this embodiment, the starting point 72 of the partial involute curve 66a is defined as the point where the magnitude of the x component (first direction component) of the radial element 80 of the involute curve 66 is maximum in the involute curve 66 with an involute angle θ from 0 to 180 degrees. In this embodiment, the ending point 76 of the partial involute curve 66a is defined as the point where the magnitude of the y component (second direction component) of the radial element 80 of the involute curve 66 is maximum in the involute curve 66 with an involute angle θ from 0 to 180 degrees. The partial involute curve 66a includes a point (part 74) where the magnitude of the x component of the involute curve 66 is 0. The positions of the starting point 72 and the ending point 76 of the partial involute curve 66a can be set arbitrarily. In an axial view, the overall shape of the partial side wall 34a may coincide with the shape of the involute curve 66.

[0032] Note that the shape of at least a portion of the partial side wall 34a does not need to perfectly match the shape of the involute curve 66. At least a portion of the partial side wall 34a only needs to follow the involute curve 66. For example, as shown in Figure 7, the curve drawn by the first radial vector 82, which is 2% longer than the radial vector 80 of the involute curve 66, is called the first virtual curve 84. The curve drawn by the second radial vector 86, which is 2% shorter than the radial vector 80 of the involute curve 66, is called the second virtual curve 88. The portion of the partial side wall 34a between the portion corresponding to the starting point 72 of the partial involute curve 66a and the portion corresponding to the ending point 76 of the partial involute curve 66a only needs to be located between the first virtual curve 84 and the second virtual curve 88.

[0033] [5. Airflow in the intake duct 28] Figure 8 shows the airflow in the intake duct 28. Partial air 90, which is a portion of the air flowing into the duct space 36 from the intake port 44, flows through a relatively short path and enters the introduction passage 58 from the left. Partial air 92, which is a portion of the air flowing into the duct space 36 from the intake port 44, flows through a longer path than the path through which partial air 90 flows and enters the introduction passage 58 from above (or below). Partial air 94, which is a portion of the air flowing into the duct space 36 from the intake port 44, flows through a longer path than the path through which partial air 92 flows and enters the introduction passage 58 from the right.

[0034] The length of the paths through which some of the air 90 and some of the air 92 flow is relatively short. Therefore, some of the air 90 and some of the air 92 easily flow into the inlet path 58. On the other hand, the length of the path through which some of the air 94 flows is relatively long. Furthermore, some of the air 94 is subjected to resistance from the side wall 34. Therefore, under normal circumstances, some of the air 94 does not easily flow into the inlet path 58.

[0035] In this embodiment, at least a portion of the partial side wall 34a follows the involute curve 66. This reduces the resistance that the partial air 94 receives from the side wall 34, thereby reducing the pressure loss of the partial air 94. As a result, the partial air 94 flows smoothly along the side wall 34.

[0036] Thus, according to this embodiment, a portion of the air 94 can be smoothly guided to the position furthest from the intake port 44. As a result, the air intake is less uneven in each part of the introduction passage 58 in the circumferential direction. In other words, according to this embodiment, the air intake unevenness in the compressor 20 can be suppressed, and as a result, the introduction of air into the compressor 20 can be improved in the gas turbine engine 14 with a side air intake structure.

[0037] Furthermore, since the cross-sectional area of ​​the second partial space 36b is constant, turbulence of the air flowing into the first partial space 36a can be suppressed. As a result, separation of the air from the guide vane 42 can be suppressed. Therefore, the air straightening effect of the guide vane 42 can be improved.

[0038] [6 Other Embodiments] Figure 9 shows another base circle 68. The base circle 68 of the involute curve 66 may be set based on the bell mouth 48. For example, as shown in Figure 5, the base circle 68 of the involute curve 66 may be the outer circle of the tip 52 of the outer shroud 50 and the outer circle of the tip 56 of the inner shroud 54, whichever has the larger radius. Figure 5 shows a configuration in which the radius r1 of the outer circle of the tip 52 of the outer shroud 50 is larger than the radius r2 of the outer circle of the tip 56 of the inner shroud 54. In this case, as shown in Figure 9, the outer circle of the tip 52 of the outer shroud 50 is made the base circle 68 of the involute curve 66. According to this embodiment, the base circle 68 can be set for an intake duct 28 that does not have a strut 40.

[0039] [7 Flying Objects] Figure 10 is a schematic diagram of the aircraft 100. The aircraft 100 is an electric vertical take-off and landing (eVTOL) aircraft. The aircraft 100 is equipped with eight VTOL rotors 102. The VTOL rotors 102 generate upward thrust relative to the airframe 104. The aircraft 100 is equipped with eight electric motors 106. One electric motor 106 drives one VTOL rotor 102. The aircraft 100 has two cruise rotors 108. The cruise rotors 108 generate forward thrust relative to the airframe 104. The aircraft 100 is equipped with four electric motors 110. Two electric motors 110 drive one cruise rotor 108.

[0040] The aircraft 100 is equipped with multiple power generation units 10. The multiple power generation units 10 are arranged in parallel inside the aircraft body 104. That is, the multiple gas turbine engines 14 are arranged in parallel inside the aircraft body 104. Each gas turbine engine 14 is arranged so that its axis A is aligned in the front-rear direction. Furthermore, the intake ports 44 of each intake duct 28 are located on the walls of the aircraft body 104. The electricity generated by the generators 12 of the power generation units 10 is supplied to the electric motors 106 and 110.

[0041] [8 Note] The following additional information is disclosed regarding the above embodiment.

[0042] (Note 1) The intake duct (28) of the present disclosure is an intake duct for guiding air to a compressor (20) of a gas turbine engine (14), and comprises a rear wall (30) having an opening (38) in which an introduction passage (58) for introducing air into the compressor is provided, a front wall (32) facing the rear wall, and a side wall (34) connecting the rear wall and the front wall, wherein the duct space (36) defined by the rear wall, the front wall and the side wall includes a first partial space (36a) including the center of the opening, and a second partial space (36b) that guides air flowing in through an intake port (44) into the first partial space, wherein the second partial space is located on one side of the first partial space, and at least a portion of a partial side wall (34a), which is part of the side wall, is located on the other side of the first partial space, and the shape of at least a portion of the partial side wall is spiral in a view in the axial direction of the gas turbine engine.

[0043] (Note 2) In the intake duct described in Appendix 1, at least a portion of the partial side wall is formed along an involute curve (66) in the axial direction view of the gas turbine engine, and the center of the base circle (68) of the involute curve may be located on the axis (A) of the gas turbine engine.

[0044] (Note 3) In the intake duct described in Appendix 2, a plurality of struts (40) are provided connecting the rear wall and the front wall, and in the axial view of the gas turbine engine, the plurality of struts are arranged on the base circle at intervals from each other, and the base circle may pass through the portion of each strut that has the maximum wall thickness.

[0045] (Note 4) In the intake duct described in Appendix 2, the portion of the partial side wall formed along the involute curve is at least along a partial involute curve (66a) which is a part of the involute curve, and when the direction from the center of the base circle toward the starting point (70) of the involute curve is taken as the first direction, the starting point (72) of the partial involute curve may be the point where the magnitude of the component of the involute curve in the first direction is maximum.

[0046] (Note 5) In the intake duct described in Appendix 4, the partial involute curve may reach at least as far as the point (74) where the magnitude of the first directional component of the involute curve becomes zero.

[0047] (Note 6) In the intake duct described in Appendix 4 or 5, when the direction perpendicular to the first direction is defined as the second direction, the partial involute curve may reach the point (76) where the magnitude of the second-direction component of the involute curve is maximum.

[0048] (Note 7) In the intake duct described in Appendix 6, in the axial view of the gas turbine engine, a portion of the partial side wall may be located between a first virtual curve (84) drawn by a first radial (82) which is 2% longer than the length of the radial (80) of the involute curve, and a second virtual curve (88) drawn by a second radial (86) which is 2% shorter than the length of the radial of the involute curve, between a portion of the partial side wall corresponding to the starting point of the partial involute curve and a portion corresponding to the ending point (76) of the partial involute curve.

[0049] (Note 8) In the intake duct described in Appendix 1, the dimension (D2) of the second partial space in the axial direction of the gas turbine engine may increase as it moves away from the first partial space.

[0050] (Note 9) In the intake duct described in Appendix 1, in at least a portion of the second partial space, the cross-sectional shape of the second partial space changes as it moves away from the first partial space, while the cross-sectional area of ​​the second partial space remains constant.

[0051] (Note 10) In the intake duct described in Appendix 1, a guide vane (42) may be provided, which is located between the opening and the intake port in the axial view of the gas turbine engine and is connected to the rear wall and the front wall.

[0052] (Note 11) In the intake duct described in Appendix 2, an outer shroud (50) and an inner shroud (54) are provided, and a bell mouth (48) is attached to the opening, wherein the base circle may be the outer circle of the larger radius between the outer circle of the tip portion (52) of the outer shroud and the outer circle of the tip portion (56) of the inner shroud.

[0053] (Note 12) The gas turbine engine of this disclosure comprises an intake duct as described in any one of appendices 1 to 11.

[0054] (Note 13) The aircraft (100) of this disclosure is an aircraft equipped with a plurality of gas turbine engines as described in any of Appendix 1 to Appendix 12, wherein the plurality of gas turbine engines are arranged in parallel inside the aircraft (104).

[0055] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the intent of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of Symbols]

[0056] 14...Gas turbine engine 20...Compressor 28... Intake duct 30... Rear wall 32...Front wall 34...Side wall 34a...Partial side wall 36...Duct space 36a...first subspace 36b...second subspace 38…Opening 40…Strut 42... Guide vane 44... Air intake 48... Bellmouth 50... Outer shroud 52, 56...Tip section 54...Inner shroud 58...Introduction path 66...Involute curve 66a...Partial involute curve 68...Base circle 74...part (location) 80...radius 82...First radial vector 84...First virtual curve 86...Second radial vector 88...Second virtual curve 70, 72... Starting point 100... Flying object 104...Aircraft A...Axis D1, D2... Dimensions

Claims

1. An intake duct that guides air to the compressor of a gas turbine engine, The rear wall has an opening formed in which an introduction passage for introducing air into the compressor is provided, The front wall opposite the aforementioned rear wall, A side wall connecting the rear wall and the front wall, Equipped with, The duct space defined by the rear wall, the front wall, and the side wall includes a first partial space including the center of the opening, and a second partial space that guides the air flowing in through the intake into the first partial space. The second subspace is located on one side of the first subspace, At least a portion of the partial side wall, which is part of the aforementioned side wall, is located on the other side with respect to the first partial space. An intake duct in which at least a portion of the shape of the aforementioned side wall is spiral in a view in the axial direction of the gas turbine engine.

2. In the intake duct according to claim 1, At least a portion of the aforementioned side wall is formed along an involute curve in the axial view of the gas turbine engine, The center of the base circle of the involute curve is located on the axis of the gas turbine engine, in the intake duct.

3. In the intake duct according to claim 2, The rear wall and the front wall are connected by a plurality of struts, In the axial view of the gas turbine engine, the plurality of struts are arranged on the base circle at intervals from each other, and the base circle is an intake duct through which the thickest part of each strut passes.

4. In the intake duct according to claim 2, The portion of the aforementioned side wall formed along the involute curve is at least along a partial involute curve which is a part of the involute curve, An intake duct in which, when the direction from the center of the base circle toward the starting point of the involute curve is defined as the first direction, the starting point of the partial involute curve is the point where the magnitude of the component of the involute curve in the first direction is maximum.

5. In the intake duct according to claim 4, An intake duct wherein the partial involute curve extends at least to a point where the magnitude of the first directional component of the involute curve becomes zero.

6. In the intake duct according to claim 4, An intake duct in which, when the direction perpendicular to the first direction is taken as the second direction, the partial involute curve reaches the point where the magnitude of the second-direction component of the involute curve is maximum.

7. In the intake duct according to claim 6, In an intake duct, in an axial view of the gas turbine engine, a portion of the partial side wall is located between a first virtual curve drawn by a first radial length 2% longer than the radial length of the involute curve and a second virtual curve drawn by a second radial length 2% shorter than the radial length of the involute curve, between the portion of the partial side wall corresponding to the starting point of the partial involute curve and the portion corresponding to the ending point of the partial involute curve.

8. In the intake duct according to claim 1, An intake duct in which the dimensions of the second partial space in the axial direction of the gas turbine engine increase as it moves away from the first partial space.

9. In the intake duct according to claim 1, An intake duct in which, in at least a portion of the second partial space, the cross-sectional shape of the second partial space changes as it moves away from the first partial space, while the cross-sectional area of ​​the second partial space remains constant.

10. In the intake duct according to claim 1, An intake duct, located between the opening and the intake port in the axial view of the gas turbine engine, and comprising guide vanes connected to the rear wall and the front wall.

11. In the intake duct according to claim 2, It comprises an outer shroud and an inner shroud, and a bell mouth attached to the opening, The base circle is the outer circumference of the outer shroud tip, which has the larger radius, and is the outer circumference of the inner shroud tip, in the intake duct.

12. A gas turbine engine comprising an intake duct according to any one of claims 1 to 11.

13. An aircraft comprising a plurality of gas turbine engines as described in claim 12, Multiple gas turbine engines are arranged in parallel inside the aircraft body of the aircraft.

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