Turbine blades

Abstract

The object of the present invention is to provide a turbine moving blade, which has a cooling structure and can improve the cooling effect of the blade tip. To achieve the above object, the turbine moving blade has a blade tip and a blade trailing edge cold air cavity located inside the blade body, the blade tip includes a bottom cover plate, a pressure side rib and a suction side rib that form a groove, an air film slit is arranged at the tail of the bottom cover plate of the groove, and the tail area of ​​the pressure side rib has a notch, which extends to the trailing edge of the blade tip, and the angle between the center line of the air film slit and the surface of the bottom cover plate of the groove is an acute angle, the air film slit connects the blade trailing edge cold air cavity with the tail area of ​​the blade tip, so that under the pressure and pumping effect of the blade trailing edge cold air cavity, cold air flows out from the blade trailing edge cold air cavity through the air film slit and covers the tail area of ​​the suction side rib.

Description

Technical Field

[0001] The invention relates to a turbine blade, and in particular to a cooling structure of the turbine blade. Background Art

[0002] Economy, reliability, safety and maintainability are important bases for evaluating commercial aircraft engines. A gas turbine is a rotating machine that converts the internal energy in high-temperature and high-pressure fuel gas into mechanical energy. It is one of the most critical components in an aircraft gas turbine, and its performance has a direct impact on the performance of the aircraft gas turbine. The high-pressure turbine blades of commercial aircraft engines work in a high-temperature, high-pressure, and high-speed environment. They are subject to very large thermal and mechanical loads, and the temperature and speed vary in a wide range. The blades have a certain elongation, and the tip clearance has a certain range of variation. Tip leakage losses account for about 30% of the total loss of the turbine stage. The tip temperature is high, difficult to cool, and prone to ablation. Therefore, the high-pressure turbine tip greatly affects the economy, reliability, safety, and maintainability of commercial aircraft engines.

[0003] There is a circumferential and axial dominant pressure difference in the tip area of ​​the turbine blade. The circumferential pressure difference causes the high-pressure combustion gas on the pressure surface to flow to the suction surface through the tip gap, forming a tip gap leakage flow. The leakage flow seriously deviates from the magnitude and direction of the mainstream velocity of the flow channel, which has a very large impact on the turbine gas thermal performance. The leakage flow and leakage vortex also increase the difficulty of heat transfer cooling near the turbine blade tip, and greatly affect the unsteadiness of the downstream flow field.

[0004] In order to meet the increasing demand for turbine inlet gas temperature, avoid exposure of hot end components to high-temperature gas environment, and prevent severe thermal stress caused by insufficient or uneven cooling, which can lead to thermal fatigue damage and failure, advanced cooling technologies (film cooling and impingement cooling) have developed rapidly despite the slow development of advanced materials.

[0005] The Chinese patent specification with the announcement number CN207093147U records the tip cooling structure of the turbine rotor blade. The pressure surface of the blade near the tip is concave from the pressure surface side to the suction surface side to form a pressure surface platform. Air film holes are arranged on the pressure surface platform. The pressure surface is provided with a partition along the main flow direction of the blade guide, and the partition is also provided with air film holes. Multiple partitions divide the pressure surface platform 1 into multiple sections. In the height direction of the partition, its top is flush with the top surface of the blade tip, and the surface of the pressure surface side of the partition is a continuation of the pressure surface of the blade. The outlet of the air film hole is located on the pressure surface of the partition.

[0006] The Chinese patent specification with announcement number CN207554113U records another tip cooling structure of a turbine blade. A cooling air hole can be set on the tip boss. Cooling gas is ejected from the cooling air hole set on the tip boss, impacting the casing to form an air film covering the inner surface of the casing, forming impact cooling and air film cooling for the casing and its area. The cooling air film flowing to the pressure side blocks the leakage flow and exchanges heat, and can also reduce the leakage flow to a certain extent. The reduction in leakage flow allows more fuel gas to do useful work and effectively reduces the strength of the leakage vortex system, thereby reducing leakage losses and improving the aerodynamic and heat exchange performance of the turbine.

[0007] The tip of the turbine blade is exposed to high-temperature combustion gas. Due to the difficulty of blade tip cooling design, the cooling effect of the cold air flowing in from the blade root on the blade tip is significantly weakened after heat exchange with the blade body, making the blade tip structure very easy to be ablated. Therefore, how to further optimize the structure and cooling method of such blade tips to achieve better leakage prevention and cooling effects has become a problem of great concern. Summary of the invention

[0008] The object of the present invention is to provide a turbine rotor blade having a cooling structure which can improve the cooling effect of the blade tip.

[0009] To achieve the above purpose, a turbine blade has a blade tip and a blade trailing edge cooling air cavity located inside the blade body, the blade tip including a bottom cover plate, a pressure side rib and a suction side rib forming a groove, an air film slit is arranged at the tail of the bottom cover plate of the groove, and the tail area of ​​the pressure side rib has a notch, which extends to the trailing edge of the blade tip, and the angle between the center line of the air film slit and the surface of the bottom cover plate of the groove is an acute angle, the air film slit connects the blade trailing edge cooling air cavity with the tail area of ​​the blade tip, so that under the action of the pressure and pumping effect of the blade trailing edge cooling air cavity, cold air flows out from the blade trailing edge cooling air cavity through the air film slit and covers the tail area of ​​the suction side rib.

[0010] In one embodiment, the ratio of the length to the width of the air film slit is between 1.5 and 8.

[0011] In one embodiment, the angle between the center line of the air film slit and the upper surface of the blade tip is 10° to 50°.

[0012] In one embodiment, the air film slit is an expansion type slit along the flow direction of the cold air.

[0013] In one embodiment, the air film slit separates the groove bottom cover plate into a cover plate main body portion and a cover plate trailing edge portion, and the cover plate trailing edge portion is configured to be a slope.

[0014] In one embodiment, the angle between the slope and the center line is 0° to 40°.

[0015] In one embodiment, the air film slit has a front edge and a rear edge opposite to the front edge, and the angle between the front edge or the rear edge and the center line is 0° to 20°.

[0016] In one embodiment, the air film slit has a front edge and a rear edge opposite to the front edge, and the connection between the rear edge and the slope is smoothly transitioned.

[0017] Cooling the trailing edge of the blade tip is a difficult point in cooling turbine blades. By setting an air film hole in the limited space at the tail of the blade tip, the air film hole is specifically arranged at the tail of the blade top cover plate, and the angle between the center line of the air film hole and the surface of the cover plate at the bottom of the groove is an acute angle. The air film hole connects the cold air cavity at the trailing edge of the blade with the tail area of ​​the blade tip. Under the action of the pressure in the cold air cavity at the trailing edge of the blade and the pumping effect, cold air flows out from the cold air cavity at the trailing edge of the blade through the cold air hole and covers the tail area of ​​the suction side rib tip. In this way, the tail of the turbine blade tip is cooled, the temperature of the tail of the turbine blade tip is reduced, the heat exchange characteristics of the blade tip are improved, and the life of the turbine blade tip is increased. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0019] Figure 1 is a schematic diagram of a turbine blade assembly;

[0020] Figure 2 is a schematic diagram of a turbine blade;

[0021] Figure 3 It is a schematic diagram of the tip of a turbine rotor blade partially cut away;

[0022] Figure 4 It is a schematic diagram showing another perspective of the tip of a partially cut-away turbine rotor blade;

[0023] Figure 5 It is the streamline diagram of the air film slit simulation;

[0024] Figure 6 yes Figure 3 A partial enlarged schematic diagram of the portion corresponding to the middle circle 54.

[0025] Fig. 7A In one embodiment, it is a figure formed by the intersection of an auxiliary plane perpendicular to the center line of the air film slit and the surface of the air film slit.

[0026] Figure 7B In another embodiment, it is a figure formed by the intersection of an auxiliary plane perpendicular to the center line of the air film slit and the surface of the air film slit.

[0027] Figure 7CIn another embodiment, it is a figure formed by the intersection of an auxiliary plane perpendicular to the center line of the air film slit and the surface of the air film slit.

[0028] Figure 8 This is a schematic diagram of the trailing edge of the turbine blade tip. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with specific embodiments and drawings. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description herein. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0030] It should be noted that these and other subsequent drawings are only examples and are not drawn to scale, and should not be used to limit the actual scope of protection required by the present invention.

[0031] like Figure 1 As shown, a plurality of turbine blades are mounted on the turbine blade assembly 100 around the engine axis. Figure 2 As shown, the turbine moving blade includes a tenon 1, an edge plate 2, and a blade body 3. The blade body 3 has a concave pressure surface 31 and a convex suction surface 32. The pressure surface 31 and the suction surface 32 extend between the leading edge 35 and the trailing edge 36 of the blade and between the blade root 4 and the blade tip 5. The pressure surface is also called the blade basin, the suction surface is also called the blade back, and the blade tip is also called the blade top. The blade profile is similar to a dolphin, a crescent, etc., and its thickness gradually increases from the leading edge 35 to the maximum thickness, and then gradually decreases to the trailing edge 36. The blade body 3 can be formed by stacking blades of different design cross-sections according to a certain linear rule. The surface of the blade body 3 is a spatial curved surface with three-dimensional characteristics. The pressure surface 31 and the suction surface 32 make the fluid flowing through its surface produce different speed and pressure distributions. The pressure difference on the blade surface drives the turbine moving blade, and the turbine moving blade drives the turbine moving blade assembly 100, which realizes the conversion from internal energy to kinetic energy.

[0032] Figure 3 This is an enlarged schematic diagram of a section of the trailing edge area of ​​the pressure side blade tip according to an embodiment of the present invention, which shows the blade tip 5 and the blade trailing edge cooling air cavity 60 located inside the blade body. The blade tip 5 includes a bottom cover plate 55, a pressure side rib 51 and a suction side rib 52 that form a groove. A blade tip tail slit 56 is provided at the trailing edge. In practice, the blade tip tail slit 56 cannot effectively cover the tail of the blade tip with an air film, and the cooling effect is not ideal.

[0033] An air film slit 57 is provided on the bottom cover plate 55 of the groove, and the air film slit 57 connects the cold air cavity 60 at the trailing edge of the blade and the tail area 54 of the blade tip. Under the pressure of the cold air cavity 60 at the trailing edge of the blade and the pumping effect, the cold air in the cold air cavity 60 at the trailing edge of the blade flows out along the air film slit 57 and covers the tail part 53 of the suction side rib of the blade tip. Figure 5 and Figure 8 As shown, the tail region of the pressure side rib 51 has a notch 510 , which extends all the way to the trailing edge of the blade tip.

[0034] Continue to refer to Figure 5 , Figure 5 The figure mainly shows the numerical simulation streamlines of the air film slit. Figure 8 The notch 510 exposes the tail 53 of the suction side rib of the blade tip, and the cold air 58 flowing out of the air film slit 57 can cover the tail 53 of the suction side rib of the blade tip. The cold air 58 flows into the mainstream along the notch 510, thereby cooling the tail of the turbine rotor blade tip, reducing the temperature of the tail of the turbine rotor blade tip, improving the heat exchange characteristics of the blade tip, and increasing the life of the turbine rotor blade tip. The notch separates the pressure side rib 51 and the suction side rib 52 on the pressure side of the blade tip tail area 54, and does not affect the thickness of the pressure side rib 51 and the suction side rib 52, so the strength of the blade tip trailing edge area 54 is basically not affected by the notch.

[0035] from Figure 5 It can be seen that the air film slit only passes through the bottom cover of the groove, the air film slit has little effect on the strength of the ribs on both sides, and the coverage area of ​​the air film formed by the cold air is larger and more uniform.

[0036] There is a tip gap leakage flow in the tip area of ​​the turbine rotor blade. The leakage flow seriously deviates from the magnitude and direction of the mainstream velocity of the flow channel. The leakage flow reduces the mainstream flow rate and basically does no useful work, which reduces the work done by the gas on the blade. The leakage flow mixes with the mainstream to form a leakage vortex, which dissipates and affects the airflow angle at the outlet of the blade grid. At the same time, the leakage flow and the leakage vortex block the mainstream channel. These aspects increase the aerodynamic loss of the turbine. For a modern high-pressure turbine, the turbine stage loss caused by it is as high as 30% of the total aerodynamic loss. The above scheme evenly covers the cooling gas on the trailing edge of the blade tip, which is more conducive to cooling the tail area of ​​the turbine blade tip, reducing the tail temperature of the turbine blade tip, improving the blade tip heat exchange characteristics, and increasing the life of the turbine blade tip.

[0037] Figure 6 The air film slit is different from the hole. It can be understood that the air film slit is perpendicular to the center line 575 of the slit to form an auxiliary plane. The auxiliary plane intersects with the surface around the air film slit to form a rectangle or a rounded rectangle or a racetrack shape, etc. 7A to 7C As shown, the ratio of length a (maximum length) to width b (maximum width) is usually between 1.5 and 8.

[0038] Preferably, Figure 6 As shown in the diagram of the film slit direction, the angle θ between the center line 575 of the film slit 57 and the upper surface of the blade tip ranges from 10° to 50°.

[0039] Preferably, the air film slit 57 is an expansion type slit.

[0040] Preferably, the angle α between the seam edge 571 and the center line 575 of the air film slit 57 is in the range of 0° to 20°.

[0041] Preferably, the angle β between the seam edge 572 and the center line 575 of the air film slit 57 is in the range of 0° to 20°.

[0042] like Figure 4 As shown, the air film slit 57 separates the groove bottom cover plate 55 into a cover plate main body portion 550 and a cover plate trailing edge portion 573, and the cover plate trailing edge portion 573 is arranged to be inclined.

[0043] Preferably, the angle γ between the trailing edge portion 573 of the cover plate and the center line 575 of the air film slit 57 is in the range of 0° to 40°.

[0044] Preferably, the connection between the seam edge 572 and the cover plate trailing edge portion 573 has a smooth transition.

[0045] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. A turbine rotor blade, comprising a blade tip and a blade trailing edge cold air cavity located inside the blade body, wherein the blade tip comprises a groove bottom cover plate, a pressure side rib and a suction side rib forming a groove, characterized in that: An air film slit is arranged at the tail of the groove bottom cover plate, and the tail area of ​​the pressure side rib has a notch, which extends to the trailing edge of the blade tip to expose the tail of the suction side rib. The angle between the center line of the air film slit and the surface of the groove bottom cover plate is an acute angle. The air film slit connects the cold air cavity at the trailing edge of the blade with the tail area of ​​the blade tip, so that under the action of the pressure and pumping effect of the cold air cavity at the trailing edge of the blade, cold air flows out from the cold air cavity at the trailing edge of the blade through the air film slit and covers the tail area of ​​the suction side rib, thereby cooling the tail of the turbine blade tip, and the cold air merges into the mainstream along the notch.

2. The turbine impeller according to claim 1, characterized in that: The ratio of the length to the width of the air film slit is between 1.5 and 8.

3. The turbine rotor blade according to claim 1, characterized in that: The angle between the center line of the air film slit and the upper surface of the blade tip is 10° to 50°.

4. The turbine impeller according to claim 1, characterized in that: The air film slit is an expansion type slit along the flow direction of the cold air.

5. The turbine impeller according to claim 1, characterized in that: The air film slit separates the groove bottom cover plate into a cover plate main body portion and a cover plate trailing edge portion, and the cover plate trailing edge portion is arranged to be a slope.

6. The turbine impeller according to claim 5, characterized in that: The included angle between the slope and the center line is 0° to 40°.

7. The turbine impeller according to claim 1, characterized in that: The air film slit has a front edge and a rear edge opposite to the front edge, and the angle between the front edge or the rear edge and the center line is 0° to 20°.

8. The turbine impeller according to claim 5, characterized in that: The air film slit has a front edge and a rear edge opposite to the front edge, and the connection between the rear edge and the slope is smoothly transitioned.

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