A composite cooling structure inside the trailing edge of a turbine blade

Abstract

A composite cooling structure for the trailing edge of a turbine blade belongs to the field of high-temperature turbine blade cooling technology. This invention addresses the problem that existing trailing edge cooling structures cannot simultaneously utilize cross-ribs to enhance heat transfer within the channel and employ swirling flow to increase the turbulence of the cooling medium, thus limiting the cooling effect at the blade trailing edge. The invention includes an inlet straight section, a cross-rib channel, a first swirling nozzle, a swirling chamber, a second swirling nozzle, and an outlet straight section. The outlet of the inlet straight section is connected to the inlet of the cross-rib channel; the outlet of the cross-rib channel is connected to the inlet of the first swirling nozzle; the outlet of the first swirling nozzle is connected to the inlet of the swirling chamber; the outlet of the swirling chamber is connected to the inlet of the second swirling nozzle; the medium outlet of the second swirling nozzle is connected to the medium inlet of the outlet straight section; and the gas section at the turbine blade trailing edge is connected to the outlet straight section. This invention is primarily used for cooling the trailing edge of turbine blades.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature blade cooling technology for gas turbines, and particularly relates to a composite cooling structure inside the trailing edge of a turbine blade. Background Technology

[0002] As the demands for output power and thermal efficiency in gas turbines continue to increase, turbine inlet temperatures are also gradually rising. Currently, the turbine inlet temperature of fourth-generation aero-engines has reached nearly 2000K, and advanced heavy-duty gas turbines have reached 1600℃, both far exceeding the allowable temperature of blade materials. To ensure the safe operation of gas turbines, turbine blades often require highly efficient cooling treatment.

[0003] In turbine blades, the trailing edge region is most susceptible to high-temperature environments. Whether it's a stationary or moving blade, the trailing edge is the high-temperature zone and generally requires special attention during heat transfer design. Turbine blade trailing edge cooling often employs a composite cooling method combining internal cooling structures with external film cooling.

[0004] The internal cooling structure of the trailing edge is generally in the form of turbulence columns or cross ribs. Cross ribs are a special type of reinforced rib channel. Under the action of the upper and lower intersecting ribs, the internal cooling channel is divided into several sub-channels. Due to the large number of cross ribs increasing the heat transfer area in the channel, and under the angle impact surface formed by the upper and lower ribs, the cooling medium impacts the corner wall and then turns and rotates into the lower sub-channel, which enhances the turbulence of the cooling medium. This allows the cross ribs to significantly enhance the heat transfer in the channel.

[0005] Swirl cooling is a novel internal cooling structure with advantages such as good thermal uniformity and strong heat exchange capacity. Swirl cooling creates a swirling cavity at the blade trailing edge. Upon entering the swirling cavity, the cooling medium generates large vortices, thereby reducing the temperature of the inner wall surface. In the interaction between the cooling medium and the mainstream combustion gas, the swirling flow also inhibits the mixing of the cooling medium and the combustion gas, allowing the cooling medium to better adhere to the wall surface.

[0006] The trailing edge semi-slit structure removes part of the material from the pressure surface of the blade, thus forming a stepped flow channel to increase the trailing edge thickness and facilitate the arrangement of cooling structures. The trailing edge film cooling vents are characterized by slits, forming a film of air attached to the trailing step, providing efficient cooling to the trailing edge region of the blade.

[0007] Existing trailing edge internal cooling structures cannot simultaneously employ cross ribs to enhance heat transfer within the channels and use swirling flow to increase the turbulence of the cooling medium, resulting in limited cooling effect at the blade trailing edge. Summary of the Invention

[0008] To address the limitations of existing trailing edge cooling structures, which cannot simultaneously employ cross ribs to enhance heat transfer within the channels and use swirling flow to increase the turbulence of the cooling medium, resulting in limited cooling performance at the blade trailing edge, this invention provides a composite cooling structure for the turbine blade trailing edge. This structure combines cross rib channels with a swirling flow cooling structure within the blade trailing edge, significantly enhancing the heat transfer capacity of the trailing edge channels and further improving the film cooling efficiency of the step behind the trailing edge semi-slit, thus achieving highly efficient cooling of the turbine blade trailing edge region.

[0009] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0010] A composite cooling structure for the trailing edge of a turbine blade is disclosed. The composite cooling structure is disposed inside the trailing edge of the turbine blade and conforms to the suction and pressure surfaces of the turbine blade. The composite cooling structure includes an inlet straight section, a cross-rib channel, several first swirling nozzles, a swirling chamber, several second swirling nozzles, and an outlet straight section. The medium outlet of the inlet straight section is connected to several medium inlets of the cross-rib channel. Each medium outlet of the cross-rib channel corresponds to one of the first swirling nozzles and is connected to the medium inlet of the first swirling nozzle. The medium outlets of the first swirling nozzles correspond to and are connected to several medium inlets on the swirling chamber. Each medium outlet on the swirling chamber corresponds to one of the second swirling nozzles and is connected to the medium inlet of the second swirling nozzle. The medium outlet of the second swirling nozzle is connected to the medium inlet of the outlet straight section. The gas combustion section at the trailing edge of the turbine blade is connected to the outlet straight section.

[0011] Preferably, the cross-rib channel is composed of two rows of intersecting rib sub-channels, with one end of the upper row of ribs connected to one end of the corresponding lower row of ribs, forming a bend impact surface at the connection; the cross-sectional shape of the upper rib in the cross-rib channel along the flow direction is trapezoidal.

[0012] Preferably, the rib inclination angle α of each rib in the cross rib channel is 45°, the ratio of rib width r to rib spacing s is r / s = 1, and the ratio of the suction surface end height H1 to the pressure surface end height of the cross rib channel is H1 / H2 = 1.5~3.

[0013] Preferably, the number of the first swirling nozzles is 2N, and the 2N first swirling nozzles are arranged in two groups, upper and lower, and respectively on the suction surface and pressure surface of the cross rib channel. The N first swirling nozzles in each group are arranged at equal intervals along the length of the swirling cavity.

[0014] Preferably, the number of the second swirling nozzles is N, and the N second swirling nozzles are arranged at equal intervals along the length of the swirling cavity, and are symmetrically arranged on the left and right sides of the swirling cavity with the N first swirling nozzles located on the pressure surface of the cross rib channel.

[0015] Preferably, the first swirling nozzle and the second swirling nozzle have the same structure; one end of the first swirling nozzle is a vertical, flush cut, and the other end is an arc-shaped cut. The arc-shaped cut of the first swirling nozzle is connected to the medium inlet of the swirling cavity, and the cooling medium ejected from the first swirling nozzle enters tangentially along the inner wall of the swirling cavity; the cooling medium flowing out of the swirling cavity enters tangentially along the inner wall of the second swirling nozzle.

[0016] Preferably, the axial cross-sectional shape of the first or second swirl nozzle is rectangular, the width-to-height ratio of the first or second swirl nozzle is a / b = 3 to 5, and the ratio of the rib height H1 of the suction surface of the cross rib channel to the height b of the first or second swirl nozzle is H1 / b = 5 to 8.

[0017] Preferably, the axial cross-sectional shape of the swirling cavity is capsule-like, comprising two arc-shaped surfaces on both sides and a straight section in the middle, with the two arc-shaped surfaces symmetrically arranged on both sides of the straight section and protruding outward.

[0018] Preferably, the arc-shaped surface is a semicircle with a radius R = (H1 + H2) / 2 and the width of the straight section is equal to the diameter of the semicircle.

[0019] Preferably, the arc-shaped cut ends of the first and second swirling nozzles are connected to the arc-shaped surface of the swirling cavity. The cooling medium flows out from the medium outlet of the first swirling nozzle and flows along the straight section and arc-shaped surface of the swirling cavity to generate swirling flow.

[0020] The beneficial effects of this invention compared to the prior art are:

[0021] In this application, the cooling medium flows into the upper row of ribs (sub-channels) of the cross-rib channel through the straight inlet section. Under the impact surface formed by the angle between the upper and lower ribs, the cooling medium impacts the corner wall and then rotates into the lower sub-channel, enhancing the turbulence of the cooling medium and significantly improving heat transfer capacity, effectively reducing the wall temperature at the blade trailing edge. The cooling medium then flows out of the cross-rib channel and tangentially into the swirling nozzle and swirling chamber, forming a swirling flow within the swirling chamber. It then flows again through the swirling nozzle into the rear step region of the straight outlet section, simultaneously mixing with the gas entering from the combustion gas section. The swirling flow generated by the interaction between the cooling medium and the mainstream combustion gas inhibits the mixing of the cooling medium and the combustion gas, allowing the cooling medium to better adhere to the wall surface, protecting the semi-slit structure at the blade trailing edge from erosion by the high-temperature combustion gas, and achieving efficient cooling of the turbine blade trailing edge region. This invention is reliable in operation, simple in structure, and suitable for internal cooling of the semi-slit structure at the trailing edge of gas turbine blades. Attached Figure Description

[0022] The accompanying drawings, which form part of this application, are provided to further illustrate the invention.

[0023] Figure 1 This is a schematic diagram of the arrangement of the trailing edge semi-slit cooling structure in the blade.

[0024] Figure 2 This is a three-dimensional structural diagram of the fluid domain of the trailing edge semi-slit cooling structure.

[0025] Figure 3 This is a front view of the fluid domain of the trailing edge semi-slit cooling structure.

[0026] Figure 4 for Figure 3 A magnified view of a section at point C.

[0027] Figure 5 for Figure 3 Cross-sectional view at point AA.

[0028] Figure 6 for Figure 3 Cross-sectional view at point BB.

[0029] Figure 7 This is a schematic diagram of the structure of the first swirling nozzle.

[0030] Figure 8 This is a schematic diagram of the vortex cavity.

[0031] Explanation of reference numerals in the attached drawings: 1-Inlet straight section; 2-Cross-ribbed channel; 3-First swirl nozzle; 4-Swirl chamber; 5-Second swirl nozzle; 6-Outlet straight section; 7-Gas section; 301-Flat cut; 302-Arc-shaped cut; 401-Arc-shaped surface; 402-Straight section. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0033] See Figure 1 This application provides a composite cooling structure inside the trailing edge of a turbine blade. The composite cooling structure is disposed inside the trailing edge of the turbine blade and conforms to the suction and pressure surfaces of the turbine blade. The composite cooling structure includes an inlet straight section 1, a cross-rib channel 2, a plurality of first swirling nozzles 3, a swirling cavity 4, a plurality of second swirling nozzles 5, and an outlet straight section 6. The medium outlet of the inlet straight section 1 is connected to a plurality of medium inlets of the cross-rib channel 2. The plurality of medium outlets of the cross-rib channel 2 are correspondingly arranged with a plurality of the first swirling nozzles 3 and are connected to the medium inlets of the first swirling nozzles 3. The medium outlets of the first swirling nozzles 3 are correspondingly arranged with a plurality of medium inlets on the swirling cavity 4 and are connected. The plurality of medium outlets on the swirling cavity 4 are correspondingly arranged with a plurality of the second swirling nozzles 5 and are connected to the medium inlets of the second swirling nozzles 5. The medium outlets of the second swirling nozzles 5 are connected to the medium inlets of the outlet straight section 6. The gas section 7 at the trailing edge of the turbine blade is connected to the outlet straight section 6.

[0034] In this embodiment, the cooling medium flows sequentially through the inlet straight section 1, the cross-rib channel 2, several first swirling nozzles 3, and the swirling chamber 4, and then enters the rear step region of the outlet straight section 6 through the second swirling nozzle 5. The gas enters the outlet straight section 6 directly from the gas section 7 and mixes with the cooling medium, after which the mixed gas is discharged from the outlet straight section 6. This application incorporates a swirling cooling structure based on the trailing edge semi-slit cross-rib structure, featuring enhanced heat transfer capacity, uniform gas film distribution, and good cooling effect. It can be applied to the cooling structure of the trailing edge semi-slit of gas turbine blades.

[0035] See Figure 1 The cross rib channel 2 is composed of two rows of intersecting rib sub-channels. One end of the upper row of ribs is connected to one end of the corresponding lower row of ribs, and a folded impact surface is formed at the connection. The cross-sectional shape of the upper rib in the cross rib channel 2 along the flow direction is trapezoidal, and is consistent with or similar to the outline of the turbine blade trailing edge.

[0036] Furthermore, in the cross-rib channel 2, the rib inclination angle α of each rib is 45°, the ratio of rib width r to rib spacing s is r / s = 1, and the ratio of the suction surface end height H1 to the pressure surface rib end height of the cross-rib channel 2 is H1 / H2 = 1.5~3, preferably H1 / H2 = 2.

[0037] In this embodiment, the difference between the suction surface end height H1 and the pressure surface end height H2 of the cross-rib channel 2 depends on the structural characteristics of the turbine blade trailing edge. The curvature of the turbine blade's pressure surface changes significantly, while the curvature of the suction surface changes less. Therefore, the pressure surface rib height of the cross-rib structure will be smaller than the suction surface rib height. Generally, the ratio of the rib heights on both sides of the simulated cross-rib is around 2 to simulate the real trailing edge cross-rib structure.

[0038] In this embodiment, the upper part of the cross rib channel 2 is set to fit the pressure surface of the turbine blade, so the curvature of the upper part of the cross rib channel 2 changes significantly, forming an inclined state; the lower part of the cross rib channel 2 is set to fit the suction surface of the turbine blade, so the curvature of the lower part of the cross rib channel 2 does not change much, forming a planar state, and the area between the main stream section and the cross rib area is the pressure surface solid domain.

[0039] See Figure 1 There are 6 first swirling nozzles 3. The 6 first swirling nozzles 3 are arranged in two groups, upper and lower, and respectively on the suction surface and pressure surface of the cross rib channel 2. The 3 first swirling nozzles 3 in each group are arranged at equal intervals along the length of the swirling cavity 4.

[0040] See Figure 1 There are three second swirling nozzles 5. The three second swirling nozzles 5 are arranged at equal intervals along the length of the swirling cavity 4 and are symmetrically arranged on the left and right sides of the swirling cavity 4 with the three first swirling nozzles 3 located on the suction surface of the cross rib channel 2.

[0041] See Figure 1 The first swirling nozzle 3 and the second swirling nozzle 5 have the same structure. One end of the first swirling nozzle 3 is a vertical flush cut 301, which is tangentially connected to the cross rib channel 2. The other end of the first swirling nozzle 3 is an arc-shaped cut 302, which is connected to the medium inlet of the swirling cavity 4. The cooling medium ejected from the first swirling nozzle 3 enters tangentially along the inner wall of the swirling cavity 4. The flush cut of the second swirling nozzle 5 is connected to the straight outlet section 6, and the arc-shaped cut of the second swirling nozzle 5 is connected to the medium outlet of the swirling cavity 4. The cooling medium flowing out of the swirling cavity 4 enters tangentially along the inner wall of the second swirling nozzle 5.

[0042] In this embodiment, if the first swirling nozzle 3 is only arranged on the suction surface of the swirling cavity 4 at the medium inlet side, most of the fluid will directly rush out of the swirling cavity 4 and enter the second swirling nozzle 5 without swirling. Only a small portion of the cooling working fluid will generate swirling in the swirling cavity, and the swirling motion trend will be small, which cannot achieve the purpose of suppressing the mixing of cooling working fluid and gas. If the first swirling nozzle 3 is only arranged on the pressure surface of the swirling cavity 4 at the medium inlet side, although most of the fluid can achieve swirling in the swirling cavity 4, the working fluid will be concentrated in the three swirling nozzles at the top of the rectifying section, which may cause excessive local stress. Therefore, in order to achieve a reasonable distribution of pressure and flow rate, the first swirling nozzle 3 is arranged on both the pressure surface and the suction surface of the swirling cavity 4 to achieve a balance between the two.

[0043] See Figure 6 The axial cross-sectional shape of the first swirl nozzle 3 or the second swirl nozzle 5 is rectangular. The aspect ratio a / b of the first swirl nozzle 3 or the second swirl nozzle 5 is 3 to 5. The aspect ratio can be determined according to the heat load on the trailing edge of the turbine blade during operation and the adaptability of the swirl structure. The ratio of the rib height H1 of the suction surface of the cross rib channel 2 to the height b of the first swirl nozzle 3 or the second swirl nozzle 5 is: H1 / b = 5 to 8 (if this ratio is too large, the cooling medium at the trailing edge half-slit outlet may not adhere well to the blade surface, reducing the film cooling efficiency; if it is too small, it may cause excessive stress at the connection between the rectifier section outlet and the first swirl nozzle 3, resulting in unnecessary pressure loss, etc. Therefore, this ratio is considered appropriate). The length of the first swirl nozzle 3 or the second swirl nozzle 5 can be appropriately varied by the limitation of the blade trailing edge size.

[0044] See Figure 1 The axial cross-sectional shape of the swirling cavity 4 is capsule-like, which includes two arc-shaped surfaces 401 on both sides and a straight section 402 in the middle. The two arc-shaped surfaces 401 are symmetrically arranged on both sides of the straight section 402 and protrude outward.

[0045] Furthermore, the arc-shaped surface 401 is a semicircle with a radius R = (H1 + H2) / 2. The width of the straight section 402 is equal to the diameter of the semicircle, and the length of the straight section 402 can be freely changed according to the size requirements of the blade trailing edge.

[0046] See Figure 1 The arc-shaped cut end 302 of the first swirling nozzle 3 and the second swirling nozzle 5 is connected to the arc-shaped surface 401 of the swirling cavity 4. The cooling medium flows out from the medium outlet of the first swirling nozzle 3 and flows along the straight section 402 and the arc-shaped surface 401 of the swirling cavity 4 to generate swirling flow.

[0047] The following further explains the working process of the present invention to further demonstrate its working principle and advantages:

[0048] The cooling medium flows into the upper row of ribs (sub-channels) of the cross-rib channel through the straight inlet section. Under the impact surface formed by the angle between the upper and lower ribs, the cooling medium impacts the corner wall and then turns and rotates into the lower sub-channel, enhancing the turbulence of the cooling medium and significantly improving the heat transfer capacity within the channel, effectively reducing the wall temperature of the blade trailing edge. The cooling medium then flows out of the cross-rib channel and tangentially into the first swirling nozzle and swirling chamber, forming a swirling flow within the swirling chamber. It then flows again through the second swirling nozzle into the rear step area of ​​the straight outlet section. At the same time, the cooling medium mixes with the gas entering from the combustion gas section. The swirling flow generated by the interaction between the cooling medium and the mainstream gas at the rear step of the trailing edge of the straight outlet section inhibits the mixing of the cooling medium and the gas, allowing the cooling medium to better adhere to the wall of the rear step of the trailing edge, cooling the trailing edge area of ​​the turbine blade, ensuring that the semi-slit structure of the blade trailing edge is not eroded by the high-temperature gas, and achieving efficient cooling of the trailing edge area of ​​the turbine blade.

[0049] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A turbine blade trailing edge internal composite cooling structure, characterized by: The composite cooling structure is located inside the trailing edge of the turbine blade and is attached to the suction and pressure surfaces of the turbine blade. The composite cooling structure includes an inlet straight section (1), a cross-rib channel (2), several first swirling nozzles (3), a swirling chamber (4), several second swirling nozzles (5), and an outlet straight section (6). The medium outlet of the inlet straight section (1) is connected to several medium inlets of the cross-rib channel (2), and several medium outlets of the cross-rib channel (2) are correspondingly set with several of the first swirling nozzles (3). And connected to the medium inlet of the first swirling nozzle (3), the medium outlet of the first swirling nozzle (3) is correspondingly set to a plurality of medium inlets set on the swirling cavity (4) and connected; the plurality of medium outlets on the swirling cavity (4) are correspondingly set to a plurality of the second swirling nozzles (5) and connected to the medium inlet of the second swirling nozzles (5); the medium outlet of the second swirling nozzles (5) is connected to the medium inlet of the outlet straight section (6); the gas section (7) at the trailing edge of the turbine blade is connected to the outlet straight section (6); The first swirling nozzle (3) and the second swirling nozzle (5) have the same structure; one end of the first swirling nozzle (3) is a vertical flat cut (301), and the other end is an arc-shaped cut (302). The arc-shaped cut (302) of the first swirling nozzle (3) is connected to the medium inlet of the swirling cavity (4). The cooling medium sprayed out by the first swirling nozzle (3) enters tangentially along the inner wall of the swirling cavity (4); the cooling medium flowing out of the swirling cavity (4) enters tangentially along the inner wall of the second swirling nozzle (5). The axial cross-sectional shape of the first swirl nozzle (3) or the second swirl nozzle (5) is rectangular, the width-height ratio of the first swirl nozzle (3) or the second swirl nozzle (5) a / b = 3~5, the rib height of the suction surface of the cross rib channel (2) H 1 is in the ratio of: b H 1 / b = 5~8;​ The axial cross-sectional shape of the swirling cavity (4) is capsule-like, which includes two arc-shaped surfaces (401) on both sides and a straight section (402) in the middle. The two arc-shaped surfaces (401) are symmetrically arranged on both sides of the straight section (402) and protrude outward. The arc-shaped surface (401) is a semicircle, and the radius of the semicircle is... R=(H) 1 +H 2 ） / 2 The width of the straight segment (402) is equal to the diameter of the semicircle; The arc-shaped cut (302) ends of the first swirling nozzle (3) and the second swirling nozzle (5) are connected to the arc-shaped surface (401) of the swirling cavity (4). The cooling medium flows out from the medium outlet of the first swirling nozzle (3) and flows along the straight section (402) and the arc-shaped surface (401) of the swirling cavity (4) to generate swirling flow.

2. The composite cooling structure inside the trailing edge of a turbine blade according to claim 1, characterized in that: The cross rib channel (2) is composed of two rows of intersecting rib sub-channels. One end of the upper row of ribs is connected to one end of the corresponding lower row of ribs, and a folded impact surface is formed at the connection. The cross-sectional shape of the upper rib in the cross rib channel (2) along the flow direction is trapezoidal.

3. The composite cooling structure inside the trailing edge of a turbine blade according to claim 2, characterized in that: The rib inclination angle of each rib in the cross rib channel (2) α = 45°, rib width r Spacing between ribs s ratio r / s = 1, Height of the suction surface end of the cross rib channel (2) H The ratio of 1 to the height of the end of the pressure rib is: H 1 / H 2 = 1.5~3.

4. The composite cooling structure inside the trailing edge of a turbine blade according to claim 1, characterized in that: The number of the first swirling nozzles (3) is 2N. The 2N first swirling nozzles (3) are arranged in two groups, upper and lower, and respectively on the suction surface and pressure surface of the cross rib channel (2). The N first swirling nozzles (3) in each group are arranged at equal intervals along the length of the swirling cavity (4).

5. The composite cooling structure inside the trailing edge of a turbine blade according to claim 4, characterized in that: The number of the second swirling nozzles (5) is N. The N second swirling nozzles (5) are arranged at equal intervals along the length of the swirling cavity (4) and are symmetrically arranged on the left and right sides of the swirling cavity (4) with the N first swirling nozzles (3) located on the pressure surface of the cross rib channel (2).

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