Air film cooling structure with asymmetric center and turbine blade

Abstract

The invention provides a central asymmetrical air film cooling structure and turbine blade, including: a plurality of air film holes, each air film hole including a cold air inlet, a straight section cold air channel, an expansion section cold air channel and a cold air outlet, one end of the straight section cold air channel being communicated with the cold air inlet, the other end being communicated with one end of the expansion section cold air channel, and the other end being communicated with the cold air outlet; the other end of the expansion section cold air channel is communicated with the cold air outlet; the cross section, perpendicular to the cold air flowing direction, of the straight section cold air channel is of a center asymmetric structure. In the flow direction of the cold air, the expansion section cold air channel gradually expands towards the two sides along the cross section perpendicular to the flow direction of the cold air. Due to the fact that the center is asymmetric, cooling air is transversely and unevenly distributed at a hole inlet, in the expansion section, due to the fact that the cooling air is distributed in the asymmetric center, a separation area of a downstream wall outlet is not located on the center line, then the center of an outlet air film is asymmetric, and the effect similar to composite inclination is generated. And meanwhile, the inverted kidney-shaped vortex pair with asymmetric strength and size can transport the gas film to a farther downstream.

Description

Technical Field

[0001] The invention relates to the technical field of gas turbines, and in particular to a central asymmetric air film cooling structure and a turbine blade. Background Art

[0002] Gas turbines are widely used in the fields of ship propulsion, aerospace propulsion, industrial power generation, etc., and are an indispensable power device for a country's development. For gas turbines, increasing the turbine inlet temperature is an effective way to improve the performance of gas turbines, so the increase in turbine inlet temperature is an inevitable trend in the development of gas turbines. At present, the turbine inlet temperature has far exceeded the melting point of the alloy material used for the blades. The improvement of the temperature resistance of high-temperature alloys and the development of thermal barrier coating technology can no longer meet the needs of improving the efficiency of gas turbines. Therefore, advanced blade cooling technology has become a key determinant for the stable operation of gas turbines and further improvement of efficiency.

[0003] Gas turbine cooling can be divided into internal cooling and external cooling. External cooling is film cooling. Its basic principle is to extract low-temperature air from the compressor and transport it to the high-temperature parts of the turbine that need to be cooled. The low-temperature air flows out through discrete film holes and covers the wall surface, isolating the wall surface from the high-temperature mainstream while taking away part of the heat, thereby achieving the purpose of reducing the wall temperature and realizing the safe operation of the gas turbine.

[0004] At present, the most widely used hole type in film cooling technology is cylindrical hole. The cylindrical hole has a small outlet area, a small downstream lateral film coverage area, a large cold air jet momentum, and is easily blown away from the wall under high blowing ratios. Due to the above limitations, cylindrical holes cannot meet the growing cooling needs caused by the performance improvement of gas turbines. Based on this, a variety of new film cooling hole structures such as expansion holes, sister holes, double jet holes, and contraction slit holes have been proposed. The new film cooling hole structure has improved the film cooling performance to a certain extent, but due to the complex structure, high processing difficulty, and high processing cost, only the expansion hole has been actually used in advanced gas turbine turbines. However, the existing film holes are mainly based on circular cross-sections and are mostly symmetrical structures. The film cooling performance needs to be further improved. Summary of the invention

[0005] In view of this, the present invention provides a central asymmetric film cooling structure and a turbine blade, which are used to solve the problem that the film cooling performance of the existing symmetrical structure film holes needs to be further improved.

[0006] The first aspect of an embodiment of the present invention provides a central asymmetric air film cooling structure, comprising: a plurality of air film holes, each air film hole comprising a cold air inlet, a straight cold air channel, an expansion cold air channel and a cold air outlet, one end of the straight cold air channel is connected to the cold air inlet, and the other end is connected to one end of the expansion cold air channel, and the other end of the expansion cold air channel is connected to the cold air outlet; the straight cold air channel is a central asymmetric structure along the cross section perpendicular to the direction of the cold air flow; along the flow direction of the cold air, the expansion cold air channel gradually expands to both sides along the cross section perpendicular to the direction of the cold air flow.

[0007] According to an embodiment of the present invention, the cross-section of the straight section of the cold air channel along the cross-section perpendicular to the direction of the cold air flow is composed of a central trapezoid and semicircular arcs on both sides, and the semicircular arcs on both sides have different diameters; the expansion section of the cold air channel is formed based on the semicircular arcs on both sides and gradually expands to both sides along the cross-section perpendicular to the direction of the cold air flow.

[0008] According to an embodiment of the present invention, the diameter of the semicircular arc is 0.4 to 1 times the diameter of the cross section of the standard cylindrical hole.

[0009] According to an embodiment of the present invention, the cross-sectional area of ​​the straight section cold air passage is equal to the cross-sectional area of ​​the standard cylindrical hole.

[0010] According to an embodiment of the present invention, the expansion section cold air channel expands toward both sides at an angle of 10° to 20° based on the semicircular arcs on both sides along a direction perpendicular to the cold air flow.

[0011] According to an embodiment of the present invention, the width of the cross section of the straight cold air passage along a direction perpendicular to the cold air flow direction and perpendicular to the bottom of the central trapezoid is 1 to 2 times the diameter of the cross section of the standard cylindrical hole.

[0012] According to an embodiment of the present invention, the total length of the air film holes is 4 to 8 times the diameter of the standard cylindrical hole cross section, and the ratio of the hole spacing between two adjacent air film holes to the diameter of the standard cylindrical hole cross section is not less than 5.

[0013] According to an embodiment of the present invention, the ratio of the length of the straight section of the cold air passage to the total length of the air film holes is 1 / 4 to 1 / 2.

[0014] According to an embodiment of the present invention, the angle between the flow direction of the cold air blown out of the cold air outlet and the cooled surface is between 30° and 60°.

[0015] A first aspect of an embodiment of the present invention provides a turbine blade for a gas turbine, comprising the above-mentioned central asymmetric air film cooling structure, wherein the central asymmetric air film cooling structure is arranged on the pressure surface, suction surface and end wall of the turbine blade, and is used to cool the pressure surface, suction surface and end wall.

[0016] The central asymmetric film cooling structure and turbine blade provided by the embodiments of the present invention can at least achieve the following technical effects:

[0017] The central asymmetric film cooling structure changes the traditional circular cross-section of the film cooling hole into a central asymmetric structure. Due to the central asymmetry, the cooling gas forms a laterally uneven distribution at the cold air inlet. In the expansion section of the cold air channel, the central asymmetric cooling gas distribution causes the separation zone of the downstream wall outlet to be not located on the center line, thereby forming a central asymmetry of the cold air outlet film, producing an effect similar to compound tilt. At the same time, the anti-kidney vortex pairs with asymmetric strength and scale can transport the air film to a farther downstream, thereby improving the film cooling performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0019] Figure 1 The geometric structure diagram of a conventional air film cooling structure based on fan-shaped holes is schematically shown.

[0020] Figure 2A The geometric structure diagram of the central asymmetric air film cooling structure according to an embodiment of the present invention is schematically shown.

[0021] Figure 2B Schematically shows an embodiment of the present invention Figure 2A AA cross-sectional view of the straight section of the cooling air channel in the central asymmetric film cooling structure shown.

[0022] Figure 2C Schematically shows an embodiment of the present invention Figure 2A The lateral spacing between two adjacent air film holes in the central asymmetric air film cooling structure is shown.

[0023] Figure 3 The structure of a turbine blade for a gas turbine provided by an embodiment of the present invention is schematically shown.

[0024] Figure 4 A diagram schematically shows a comparison between the effect of the central asymmetric film cooling structure provided by an embodiment of the present invention and the film cooling effect of a traditional fan-shaped hole.

[0025] Figure 5 A schematic diagram showing a comparison of the lateral average cooling effect distribution of the central asymmetric air film cooling structure provided by an embodiment of the present invention and the traditional fan-shaped holes.

[0026] Figure 6 A schematic diagram shows a comparison of the cooling effects of the central asymmetric film cooling structure provided by an embodiment of the present invention and the traditional fan-shaped holes applied to turbine blades.

[0027] Figure 7 A schematic diagram shows a comparison of the lateral average cooling effect distribution of the central asymmetric film cooling structure provided by an embodiment of the present invention and the traditional fan-shaped holes on the turbine moving blade. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0030] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] In the description of the present invention, it should be understood that the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the subsystem or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0032] Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present invention. The shapes, sizes, and positional relationships of the components in the drawings do not reflect the actual size, proportion, and actual positional relationship. In addition, in the present invention, any reference symbol between brackets should not be constructed as a limitation to the present invention.

[0033] Similarly, in order to simplify the present invention and help understand one or more of the various disclosed aspects, in the above description of exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0035] Figure 1 The geometric structure diagram of a conventional air film cooling structure based on fan-shaped holes is schematically shown.

[0036] like Figure 1 As shown in the figure, the fan-shaped hole expands the rear half of the film hole laterally on the basis of the cylindrical hole. The fan-shaped hole can be divided into a straight section and an expansion section along the flow direction of the cold air. The total length of the film hole is L, of which the length of the straight section is Lt. The cross-sectional shape of the straight section of the fan-shaped hole is consistent with that of the simple cylindrical hole, which is a circle with a diameter of D. The lateral expansion angle of the expansion section is γ. After expansion, the outlet width of the film hole increases, the outlet area becomes larger, the outlet momentum of the cold air jet decreases, and it is not easy to break away from the wall under high blowing ratios. Compared with the simple cylindrical hole, the fan-shaped hole structure enhances the flow of the cold air jet to both sides and increases the coverage area of ​​the cold air in the lateral direction. The outlet expansion structure of the film hole improves the film cooling effect to a certain extent and has been successfully applied on turbine blades. Although the increase in the outlet width of the film hole based on the film cooling structure of the fan-shaped hole is beneficial to the improvement of the film cooling effect, the cross-section of the existing film holes is mostly a symmetrical structure, the distance of the film transport is limited, and the cooling effect needs to be further improved.

[0037] Based on this, an embodiment of the present invention provides a central asymmetric air film cooling structure, including: a plurality of air film holes, each air film hole includes a cold air inlet, a straight cold air channel, an expansion cold air channel and a cold air outlet, one end of the straight cold air channel is connected to the cold air inlet, and the other end is connected to one end of the expansion cold air channel, and the other end of the expansion cold air channel is connected to the cold air outlet. The straight cold air channel is a central asymmetric structure along the cross section perpendicular to the cold air flow direction. Along the flow direction of the cold air, the expansion cold air channel gradually expands to both sides along the cross section perpendicular to the cold air flow direction. The central asymmetric air film cooling structure is described below in conjunction with specific embodiments.

[0038] Figure 2A The geometric structure diagram of the central asymmetric air film cooling structure according to an embodiment of the present invention is schematically shown.

[0039] Figure 2B Schematically shows an embodiment of the present invention Figure 2A AA cross-sectional view of the straight section of the cooling air channel in the central asymmetric film cooling structure shown.

[0040] Figure 2C Schematically shows an embodiment of the present invention Figure 2A The lateral spacing between two adjacent air film holes in the central asymmetric air film cooling structure is shown.

[0041] like Figure 2A to Figure 2C As shown, the central asymmetric air film cooling structure includes a plurality of air film holes, each of which is composed of a connected straight cold air channel 1 and an expansion cold air channel 2, wherein the straight cold air channel 1 is located on the cold air side and is connected to the cold air inlet, and the expansion cold air channel 2 is located on the gas side and is connected to the cold air outlet. The straight cold air channel 1 is a central asymmetric structure along the cross section perpendicular to the cold air flow direction, and along the cold air flow direction, the expansion cold air channel 2 gradually expands to both sides along the cross section perpendicular to the cold air flow direction.

[0042] In the embodiment of the present invention, the straight section cold air passage 1 is composed of a central trapezoid 3 and semicircular arcs 4 and 5 on both sides. The expansion section cold air passage 2 is formed by the semicircular arcs 4 and 5 on both sides of the runway shape 3 in the straight section cross section expanding at a certain angle in the lateral direction. The semicircular arcs 4 and 5 on both sides have different diameters D1 and D2, and a corresponding center asymmetric structure is formed at the cold air outlet. Considering the machining accuracy and structural strength limitations, the diameters D1 and D2 of the semicircular arcs 4 and 5 on both sides are 0.4 to 1 times the diameter D of the standard cylindrical hole cross section.

[0043] It should be noted that the standard cylindrical hole can be understood as an ordinary cylindrical hole in the existing air film structure. The geometric dimensions of the central asymmetric air film cooling structure of the embodiment of the present invention are all converted to the cylindrical aperture D. A correlation can be established between the usual hole type and the non-circular cross-section hole for easy comparison.

[0044] Furthermore, the cross-sectional area of ​​the straight section of the cold air passage 1 is equal to the cross-sectional area of ​​the standard cylindrical hole. When the diameters D1 and D2 of the semicircular arcs 4 and 5 on both sides are 0.4 to 1 times the diameter D of the cross-sectional area of ​​the standard cylindrical hole, the width W of the cross-sectional area of ​​the straight section of the cold air passage 1 along the direction perpendicular to the cold air flow direction and along the direction perpendicular to the bottom of the central trapezoid is 1 to 2 times the diameter D of the cross-sectional area of ​​the standard cylindrical hole.

[0045] Continue reading Figure 2A In the embodiment of the present invention, the total length L of the air film hole is 4 to 8 times the diameter D of the cross section of the standard cylindrical hole. The ratio of the length Lt of the straight cold air passage 1 to the total length L of the air film hole is 1 / 4 to 1 / 2. The expansion section cold air passage 2 is based on the semicircular arcs on both sides and expands to both sides perpendicular to the cold air flow direction at angles of γ1 and γ2, respectively, and both γ1 and γ2 are 10° to 20°.

[0046] Furthermore, the angle between the flow direction of the cold air blown out of the cold air outlet and the cooled surface is between 30° and 60°. In practical application, the spray angle α of the air film hole in the embodiment of the present invention can be adjusted according to specific needs depending on the application position of the air film hole.

[0047] Stay Engaged Figure 2C When multiple air film holes of the central asymmetric air film cooling structure of the embodiment of the present invention are arranged in a row, due to the large hole outlet width, the ratio between the hole spacing P of two adjacent air film holes when arranged in a row and the diameter D of the cross section of the standard cylindrical hole is not less than 5.

[0048] Figure 3 The structure of a turbine blade for a gas turbine provided by an embodiment of the present invention is schematically shown.

[0049] like Figure 3 As shown, the turbine blade for a gas turbine has a ribbed cooling channel structure inside the turbine blade, which may include the central asymmetric film cooling structure described above, wherein the central asymmetric film cooling structure is arranged on the pressure surface, suction surface and end wall of the turbine blade, and is used to cool the pressure surface, suction surface and end wall, especially the moving blade channel with uneven inlet flow or with an inlet cross-flow channel. The specific details are not repeated here.

[0050] In order to further illustrate the advantages of the central asymmetric air film cooling structure provided by the embodiment of the present invention, the following data are given below to prove it.

[0051] Figure 4 A diagram schematically shows a comparison between the effect of the central asymmetric film cooling structure provided by an embodiment of the present invention and the film cooling effect of a traditional fan-shaped hole.

[0052] like Figure 4 As shown, the upper part of the picture is a schematic diagram of the cooling effect of the central asymmetric air film cooling structure in the embodiment of the present invention, and the lower part is a schematic diagram of the cooling effect of the traditional fan-shaped hole. In the figure, x represents the distance in the X-axis direction, y represents the distance in the Y-axis direction, and D is the cross-sectional diameter of the fan-shaped hole. Figure 4 The depth of the color in the figure represents the air film cooling efficiency. The lighter the color, the higher the cooling efficiency, and the darker the color, the lower the cooling efficiency. From the comparison results, it can be seen that, compared with the traditional fan-shaped holes, the flow coverage distance of the two is equivalent, and the lateral coverage area of ​​the air film holes in the embodiment of the present invention is increased.

[0053] Figure 5 A schematic diagram showing a comparison of the lateral average cooling effect distribution of the central asymmetric air film cooling structure provided by an embodiment of the present invention and the traditional fan-shaped holes.

[0054] like Figure 5 As shown in the figure, 0.5-0.6-L1-deg14 is an example of the air film hole provided by the embodiment of the present invention. From the comparison results, it can be seen that the hole type provided by the embodiment of the present invention improves the air film cooling effect compared with the fan-shaped hole, which is improved by about 12% overall.

[0055] Figure 4 and Figure 5 The aperture D simulated by the flat plate model used in the test is 4 mm, and the simulated hole spacing P is 6D. The density ratio of cold air to mainstream is DR=1.5, and the blowing ratio is M=2.0. The diameters D1 and D2 of the circles corresponding to the arc structures at both ends of the cross-section of the hole type provided by the present invention are 0.6D and 0.5D, respectively. The expansion angle and injection angle of the fan-shaped hole and the air film hole provided by the present invention are consistent, the lateral expansion angle γ of the expansion section is 14°, and the air film hole injection angle α is 30°. The total length L of the air film holes of the two hole types is 6D, and the ratio of the straight section length to the total length of the air film hole Lt / L is 1 / 3.

[0056] Figure 6 A schematic diagram shows a comparison of the cooling effects of the central asymmetric film cooling structure provided by an embodiment of the present invention and the traditional fan-shaped holes applied to turbine blades.

[0057] like Figure 6 As shown, the left part of the picture is a cooling effect diagram of the air film holes of the embodiment of the present invention, and the right part is a cooling effect diagram of the fan-shaped holes. The vertical coordinate Z in the figure represents the distance along the blade height direction, and the horizontal coordinate S represents the distance along the blade flow direction. The depth of the color in the figure represents the air film cooling efficiency. The lighter the color, the higher the cooling efficiency, and the darker the color, the lower the cooling efficiency. The spacing between the air film holes is 7.5D, and a total of 16 air film holes are set along the blade height direction. In order to more clearly see the comparison of the cooling effects of the two air film holes, Figure 6The cooling effect of four air film holes in the middle of the blade is shown in the figure. By comparing the cooling efficiency of the two holes, it can be seen that the air film holes in the embodiment of the present invention have a large lateral coverage area, and the outflow is more uniform in the case of cross flow, the cooling double peaks are of similar size, and the cooling outflow of the fan-shaped holes is obviously skewed.

[0058] Figure 7 A schematic diagram shows a comparison of the lateral average cooling effect distribution of the central asymmetric film cooling structure provided by an embodiment of the present invention and the traditional fan-shaped holes on the turbine moving blade.

[0059] like Figure 7 As shown, the hole type of the embodiment of the present invention has a certain degree of improvement in the film cooling effect near the downstream and far downstream, and the overall improvement is about 18.3%. The above results show that the hole type of the embodiment of the present invention has advantages in improving the cooling effect. By optimizing the hole type parameters, the hole type of the embodiment of the present invention can further obtain a high cooling effect, such as: adjusting the size of the arc structure at both ends of the cross section, changing the expansion angle of the air film hole, etc.

[0060] Figure 6 and Figure 7 The diameters D1 and D2 of the circles corresponding to the arc structures at both ends of the cross-section of the hole type used in the blade model used in the test are 0.6D and 0.5D respectively, the hole spacing P is 7.5D, and D is the diameter of the fan-shaped hole 1mm. The density ratio of cold air to mainstream is DR=1.5, and the blowing ratio is M=2.0. The lateral expansion angle γ of the expansion section of the two hole types is 14°, the total length L of the air film hole is 6D, and the ratio of the straight section length to the total length of the air film hole Lt / L is 1 / 3.

[0061] In summary, the central asymmetric air film cooling structure provided by the embodiment of the present invention can improve the cooling effect of discrete air film holes.

[0062] The above is only a specific embodiment of the present invention, but the protection scope of this application is not limited thereto. Any changes or substitutions made within the spirit and principle of the present invention should be included in the protection scope of this application. Therefore, the protection scope of this application should be based on the protection scope of the claims.

Claims

1. A central asymmetric air film cooling structure, comprising: A plurality of air film holes, each of which comprises a cold air inlet, a straight cold air channel, an expansion cold air channel and a cold air outlet, one end of the straight cold air channel is connected to the cold air inlet, the other end of the straight cold air channel is connected to one end of the expansion cold air channel, and the other end of the expansion cold air channel is connected to the cold air outlet; The straight cold air passage has a central asymmetric structure along a cross section perpendicular to the cold air flow direction; Along the flow direction of the cold air, the expansion section cold air channel gradually expands toward both sides along a cross section perpendicular to the flow direction of the cold air.

2. The central asymmetric air film cooling structure according to claim 1, wherein: The cross section of the straight section of the cold air channel along the direction perpendicular to the cold air flow consists of a central trapezoid and semicircular arcs on both sides, and the semicircular arcs on both sides have different diameters; the expansion section of the cold air channel is formed by gradually expanding toward both sides along the direction perpendicular to the cold air flow based on the semicircular arcs on both sides.

3. The central asymmetric air film cooling structure according to claim 2, wherein: The diameter of the semicircular arc is 0.4 to 1 times the diameter of the cross section of the standard cylindrical hole.

4. The central asymmetric air film cooling structure according to claim 3, wherein: The cross-sectional area of ​​the straight cold air passage is equal to the cross-sectional area of ​​the standard cylindrical hole.

5. The central asymmetric air film cooling structure according to claim 2, wherein: The expansion section cold air channel is based on the semicircular arcs on both sides and expands to both sides perpendicular to the cold air flow direction at an angle of 10° to 20°.

6. The central asymmetric air film cooling structure according to claim 2, wherein: The width of the cross section of the straight cold air channel along the direction perpendicular to the cold air flow direction and along the direction perpendicular to the bottom of the central trapezoid is 1 to 2 times the diameter of the cross section of the standard cylindrical hole.

7. The central asymmetric film cooling structure according to claim 1, wherein: The total length of the air film holes is 4 to 8 times the diameter of the cross section of a standard cylindrical hole, and the ratio of the hole spacing between two adjacent air film holes to the diameter of the cross section of the standard cylindrical hole is not less than 5.

8. The central asymmetric air film cooling structure according to claim 1 or 7, wherein: The ratio of the length of the straight cold air channel to the total length of the air film holes is 1 / 4 to 1 / 2.

9. The central asymmetric film cooling structure according to claim 1, wherein: The angle between the flow direction of the cold air blown out of the cold air outlet and the cooled surface is between 30° and 60°.

10. A turbine blade for a gas turbine, comprising the central asymmetric film cooling structure according to any one of claims 1 to 9, wherein: The central asymmetric air film cooling structure is arranged on the pressure surface, suction surface and end wall of the turbine blade, and is used to cool the pressure surface, suction surface and end wall.

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