Rear end structure of turbine or compressor

Abstract

To reduce a gas vortex flow in a main flow passage which would reduce the efficiency of a turbine or compressor.SOLUTION: A rear end structure of a platform surrounding a main flow passage of a turbine or compressor includes a rear edge at which the platform terminates and which borders an opening for introducing secondary air from the outside and does not include a plane perpendicular to an axis of the turbine or compressor, and a curved surface facing the main flow passage, continuously increasing in its curvature factor toward the rear edge, and terminating at the rear edge.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The following disclosure relates to the structure of a flow path for introducing secondary air into a turbine or a compressor, and in particular to the rear end structure of a platform that forms a flow path that can suppress pressure loss. [Background technology]

[0002] A turbofan engine is a type of jet engine that has a bypass duct around the core engine. Hot combustion gases generated by the combustor are introduced into a turbine located downstream to extract some of their energy, and then discharged through an exhaust nozzle to generate engine thrust. The extracted energy is used to drive a fan and compressor located upstream of the combustor. Part of the airflow generated by the fan is introduced into the compressor, compressed, and used for combustion, while the other part is ejected directly rearward through the bypass duct, contributing to increased engine thrust and improved energy efficiency.

[0003] Most of the compressed air produced by the compressor is sent to the combustor, but a significant amount is also bled into the internal air system. The secondary air that passes through the internal air system is used for purposes such as cooling the inside of the engine and preventing high-temperature gas from leaking out of the main flow path (sealing). Patent Documents 1 and 2 disclose technology related to the structure of a purge cavity that introduces secondary air into the main flow path for sealing purposes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2006-283755 [Patent Document 2] JP 2008-151138 A Summary of the Invention [Problem to be solved by the invention]

[0005] The secondary air introduced into the main flow path generates vortices in the gas within the main flow path, causing pressure loss and reducing the efficiency of the turbine or compressor. Until now, attempts to reduce vortices have been made by modifying the shape of the purge cavity or the shape of the blades or vanes further downstream. The inventors discovered that further vortices can be reduced by modifying the aft-end structure of the upstream platform, and came up with the aft-end structure disclosed below. [Means for solving the problem]

[0006] The rear end structure of a platform surrounding a main flow path of a turbine or compressor according to the present disclosure comprises a trailing edge where the platform terminates and borders an opening for introducing secondary air from the outside, the trailing edge not including a plane perpendicular to the axis of the turbine or compressor, and a curved surface facing the main flow path, the curvature of which continuously increases toward the trailing edge and which terminates at the trailing edge.

[0007] Preferably the trailing end structure further comprises an outer surface outwardly of said main flow path and terminating at said trailing edge, said outer surface being curved or straight towards said trailing edge. [Effects of the Invention]

[0008] A rear end structure is provided that improves the efficiency of the turbine or compressor. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic longitudinal sectional view of a turbofan engine. [Figure 2] FIG. 2 is a cross-sectional elevation view of a portion of a turbine. [Figure 3] FIG. 3 is a schematic cross-sectional elevation view of the aft end structure of the platform. [Figure 4] FIG. 4 is a cross-sectional elevation view of the flow channel and its surroundings, showing the flow around the rear end structure. [Figure 5]FIG. 5 is a cross-sectional elevation view of a flow path and its surroundings, schematically illustrating the flow around the rear end structure according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Several exemplary embodiments will be described below with reference to the accompanying drawings. It should be particularly noted that the drawings are not necessarily drawn to scale, and therefore the dimensional relationships between the drawings are not limited to those shown. Throughout the following description and the appended claims, unless otherwise specified, the axis refers to the central axis of a turbofan engine, and the axis also typically coincides with the rotational axis of a turbine and a compressor. The terms "axial," "radial," and "circumferential" are each defined relative to the axis. In addition, the intake side of an engine may be referred to as "forward" or "upstream," the exhaust side as "aft" or "downstream," the side facing the main flow path as "inner," and the opposite side as "outer."

[0011] Referring primarily to FIG. 1 , a turbofan engine 1 generally includes a core 9 having a compressor 3, a combustor 5, and a turbine 7. A mixture of fuel and air is burned in the combustor 5 to generate energy, and a portion of this energy is extracted by the turbine 7 to drive the compressor 3 and a fan in front of it. At least a portion of the outside air introduced by the fan becomes an intake flow f, which is guided into a main flow path 3W surrounding the compressor 3, compressed, and used for combustion in the combustor 5. A high-temperature gas flow F generated from the combustor 5 is guided into a main flow path 7W of the turbine 7 to drive it, and is further discharged rearward through an exhaust nozzle EN to generate thrust.

[0012] The intake air flow f is compressed by the compressor 3 and reaches a high temperature, and the high-temperature gas flow F passing through the turbine 7 is, of course, also at a high temperature. To confine these high-temperature gases within the main flow paths 3W and 7W, secondary air flows fa1, fa2, and fa3 are introduced from the internal air system to the compressor 3 and the turbine 7. The rear end structure of this embodiment can be suitably used in a flow path for introducing secondary air into the turbine 7 or the compressor 3. An example of application to the turbine 7 will be mainly described below, but it goes without saying that it can also be easily applied to the compressor 3.

[0013] Referring to FIG. 2 in combination with FIG. 1, the turbine 7 includes, for example, a high-pressure turbine rotor 11, a low-pressure turbine stator 13, and a low-pressure turbine rotor 15 arranged in sequence from the upstream side.

[0014] With regard to the high-pressure turbine rotor 11, each segment includes, for example, an inner platform 21 connected to the shaft, blades 23 extending radially outward from the platform 21, and an outer platform 25 located close to the outer side of the blades 23 in the radial direction. A plurality of segments are arranged in the circumferential direction to form an annulus, thereby constituting the high-pressure turbine rotor 11. The blades 23 are airfoils inclined with respect to the axial direction, and can extract energy from the high-temperature gas flow F passing through it, convert it into rotational energy about the axis X, and transmit it to the high-pressure compressor via the shaft.

[0015] The low-pressure turbine stator 13 similarly consists of a plurality of segments arranged in the circumferential direction, and each segment has an inner platform 27 and an outer platform 31 fixed to the engine core, and a vane 29 extending therebetween, the vane 29 also being an airfoil.

[0016] The low-pressure turbine rotor 15 similarly consists of a plurality of segments arranged in the circumferential direction, and each segment has an inner platform 33, blades 35 which are airfoils extending radially outward from the platform 33, and an outer platform 37 which is integral with the blades 35. The low-pressure turbine rotor 15 also converts part of the energy of the high-temperature gas flow F into rotational energy about the axis X and transmits it to the low-pressure compressor via the shaft.

[0017] Circumferentially adjacent platforms are smoothly connected to each other to enclose an annular space around the axis X, and the front and rear platforms are also smoothly connected to each other, so that all of these platforms enclose a main flow path 7W through which a high-temperature gas flow F passes. The platforms are very close to each other, and their edges form a labyrinth to seal the high-temperature gas flow F, but some gaps are open to form purge flow paths 27P, 31P that introduce secondary air flows fa2, fa3.

[0018] Taking the purge flow path 27P as an example, its structure will be described with reference to Figure 3 in combination with Figures 1 and 2. The rear end 27R of the platform 27 terminates at a trailing edge 41, and together with the platform 33 downstream thereof, the rear end 27R borders the flow path 27P. The inner surface 45 of the platform 27 facing the main flow path 7W may be a surface that approximates a plane or may have a constant profile, but forms a curved surface 45C toward the trailing edge 41 and curves in a direction that deviates outward from the main flow path 7W.

[0019] The structure of the trailing edge 27R will be described in more detail with reference to Figures 4 and 5 in combination with Figure 3. Referring primarily to Figure 4, when the high-temperature gas flow Fa2 of the high-temperature gas flow F flows along the inner surface 45 and reaches the trailing edge 41, it creates a flow that turns around the rear surface of the trailing edge 41, inducing the generation of a separated flow ft. The generation of the separated flow ft destabilizes the merger with the secondary air flow fa2 further downstream and promotes the development of vortices in the mixed flow Fv. Therefore, in this embodiment, the generation of the separated flow ft is suppressed by eliminating flat surfaces from the trailing edge 41, thereby suppressing the generation of vortices. More preferably, the trailing edge 41 does not include a flat surface perpendicular to the axis X.

[0020] Furthermore, if a separated flow ft occurs, the high-temperature gas flow Fa2 loses its outward pressure, and the mixed flow Fv is pushed by the secondary air flow fa2 and tends to flow inward into the main flow passage 7W. As a result, the generated vortex flow is directed inward. Therefore, in order to direct the high-temperature gas flow Fa2 outward and counteract the inward flow of the mixed flow, the inner surface of the rear end 27R is made into a curved surface 45C that is curved in a direction that deviates outward from the main flow passage 7W.

[0021] 5, the trailing edge 41 does not include a plane perpendicular to the axis X, and the curved surface 45C continues directly to the trailing edge 41, where it terminates. With this structure, no significant separated flow occurs, and the flow generated by the merging of the two flows becomes a stable flow Fc that does not include significant vortices, and flows along the downstream inner platform 33, causing no pressure loss in the vanes 29 or blades 35. Even with this structure, the secondary air flow fa2 can still effectively confine the high-temperature gas flow F within the main flow path 7W.

[0022] The curved surface 45C may have a constant curvature, i.e., may describe a circular arc in cross section, but preferably has a curvature that continuously increases (the radius of curvature continuously decreases) toward the trailing edge 41. Examples of such cross sections include, but are not limited to, quadratic curves such as ellipses and parabolas.

[0023] The shape of the outer surface 43 opposite the inner surface 45 is not particularly limited, and may be a straight plane toward the trailing edge 41 as shown in the figure. Alternatively, the shape can be freely selected depending on the convenience of the internal air system or the convenience of connection with the adjacent platform. Furthermore, the outer surface 43 may be curved according to the curved surface 45C and protrude outward, for the purpose of preventing the trailing end 27R from being locally thin. Note that unless the outer surface 43 is curved in the opposite direction to that described above, the trailing edge 41 will necessarily have a contour that forms a right angle or an acute angle in its cross section.

[0024] As can be seen from the above explanation, the curved surface 45C is clearly different from small-scale curved surfaces such as chamfers, and differs in that it continues at least to the trailing edge 41. Unlike a profiled outer surface for rectifying the secondary air, or a cooperation between the upstream structure and the downstream structure, advantageous effects can be obtained simply by the inner surface of the upstream platform having a curved surface at its aft end. Contrary to expectations based on common technical knowledge, this curved surface reduces vortices in the main flow path 7W and confines the high-temperature gas flow F within the main flow path 7W, thereby improving the effectiveness of the secondary air.

[0025] Although several embodiments have been described, modifications or variations of the embodiments can be made based on the above disclosure. [Industrial Applicability]

[0026] A rear end structure is provided that improves the efficiency of the turbine or compressor. [Explanation of symbols]

[0027] 1 turbofan engine 3 Compressor 3W main channel 5. Combustor 7 Turbine 7W main channel 9 cores 27 Inner Platform 27P Purge flow path 27R rear end 33 Inner Platform 41 Trailing edge 43 Exterior 45 Inner 45C curved surface f Intake flow fa1, fa2, fa3 Secondary air flow ft separated flow F hot gas flow Fa2 High temperature gas flow Fc stable flow Fv mixed flow X-axis

Claims

1. An aft end structure of a platform surrounding a main flow path of a turbine or a compressor, a trailing edge at which the platform terminates and which borders an opening for introducing secondary air from the outside, the trailing edge not including a plane perpendicular to an axis of the turbine or the compressor; a curved surface facing the main flow path, the curvature of which continuously increases toward the trailing edge and which terminates at the trailing edge; Rear end structure equipped with

2. an outer surface outwardly of the main flow path and terminating at the trailing edge, the outer surface being curved or straight toward the trailing edge; The rear end structure of claim 1 further comprising:

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