A structure for enhancing the effect of turbine blade cooling by leakage flow from a casing

Abstract

The present application belongs to the field of turbine blade cooling technology of an aero-engine, and particularly relates to a structure for enhancing the cooling effect of a turbine blade by leakage flow of a casing, comprising an inner casing, an outer casing coaxially arranged outside the inner casing, a front outer casing coaxially arranged at the front end of the outer casing, a leakage flow inlet arranged between the front outer casing and the outer casing, and a flow guide assembly fixed to the inner edge of the front outer casing and close to the leakage flow inlet. In use, the flow guide assembly weakens the mixing between the main flow and the leakage flow, so that the leakage flow can better adhere to the blade tip of the turbine blade, thereby achieving better cooling effect.

Description

Technical Field

[0001] This invention belongs to the field of turbine blade cooling technology for aero-engines, and particularly relates to a structure that enhances the cooling effect of casing leakage flow on turbine blades. Background Technology

[0002] Based on the fundamental principles of the Brayton cycle, increasing the turbine inlet temperature directly improves the ideal cycle work and thermal cycle efficiency of an aero-engine. A higher temperature increase ratio results in greater ideal cycle work and higher cycle power ratio, thereby reducing fuel consumption, increasing range, and lowering operating costs in the aviation industry. To ensure the normal operation of gas turbine blades at high temperatures, cooling designs are necessary. As rotating components, turbine blades must withstand enormous centrifugal and aerodynamic forces at high temperatures. A well-designed cooling structure can extend the lifespan of the turbine blades and improve aero-engine performance.

[0003] Turbine blades are typically cooled by a relatively cool airflow drawn from the compressor components. For turbine blades, the cooling gas generally enters the blade from the blade root through the inner casing, passes through the internal cooling channel, and then merges into the mainstream through film cooling holes on the blade surface. Although film cooling holes are provided at the blade tip, there is often a lack of effective cooling design at the blade tip leading edge. Furthermore, the leading edge of the blade is subjected to intense thermal loads from the high-temperature fluid, making it highly susceptible to ablation. Therefore, the cooling design of the blade tip is crucial. Summary of the Invention

[0004] The purpose of this invention is to provide a structure that enhances the cooling effect of the casing leakage flow on the turbine blades, so as to solve the above-mentioned problems and achieve the goal of improving the cooling of the blade tips.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A structure for enhancing the cooling effect of the leakage flow from the casing on the turbine blades includes an inner casing, a rear outer casing coaxially disposed on the outer side of the inner casing, a front outer casing circumferentially disposed at the front end of the rear outer casing, a leakage flow inlet disposed between the front outer casing and the rear outer casing, and a flow guide assembly circumferentially fixed at the inner edge of the front outer casing, the flow guide assembly being close to the leakage flow inlet.

[0007] Preferably, the flow guiding component includes a leakage flow front outer casing profile, which is fixedly connected to the inner edge of the leakage flow front outer casing and is coaxially arranged with the leakage flow front outer casing.

[0008] Preferably, a plurality of turbine blades are fixedly connected to the outer edge of the inner casing, and the plurality of turbine blades are equally spaced along the circumference of the inner casing, with a gap between the end of the turbine blade away from the inner casing and the inner diameter of the outer casing after leakage.

[0009] Preferably, the outer diameter of the outer casing profile before the leakage flow is the same as the inner diameter of the outer casing profile after the leakage flow, and the inner diameter of the outer casing profile before the leakage flow is smaller than the inner diameter of the outer casing profile after the leakage flow.

[0010] Preferably, the inner diameter of the outer casing before the leakage flow is the same as the inner diameter of the outer casing after the leakage flow, and the outer diameter of the outer casing before the leakage flow is the same as the outer diameter of the outer casing after the leakage flow.

[0011] Preferably, the distance between the inner and outer diameters of the outer casing profile before the leakage flow is less than the gap between the turbine blade and the inner diameter of the outer casing after the leakage flow.

[0012] Preferably, the side of the axial section of the outer casing surface before the leakage flow is curved near the axis of the outer casing surface before the leakage flow, and one of the tangents of the curved edge is parallel to the inner wall of the outer casing after the leakage flow near the inner casing, and the tangent is located at the leakage flow inlet.

[0013] Compared with the prior art, the present invention has the following advantages and technical effects:

[0014] The flow guiding component of this invention reduces the mixing between the mainstream and the leakage flow, enabling the leakage flow to be cooled better. The simple structure of this invention can better utilize the lower temperature leakage flow, improve its cooling efficiency on the turbine blade tip, and reduce the temperature of the turbine blade tip. This flow guiding structure can improve the cooling system of aero-engines and is of great significance to the design of aero-engine turbines. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of the present invention;

[0017] Figure 2 for Figure 1 Enlarged view of section B in the image;

[0018] Figure 3 This is a schematic diagram of the structure of the two moving blade units of the present invention;

[0019] Figure 4 for Figure 3 Cross-sectional view along the AA direction;

[0020] Figure 5 for Figure 4 Enlarged view of a section at point C;

[0021] Figure 6 A cross-sectional view of a conventional purging structure with leakage flow cooling;

[0022] Figure 7 This is a magnified view of part D in his 6th section;

[0023] Figure 8 The distribution of average cooling efficiency is shown for both the conventional purging structure and the structure of this invention.

[0024] Among them, 1. Outer casing before leakage flow; 2. Turbine blade; 3. Main stream; 4. Inner casing; 5. Leakage flow inlet; 6. Blade tip; 7. Outer casing after leakage flow; 8. Leakage flow; 9. Outer casing profile before leakage flow; 10. Curve. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Reference Figures 1-8 The present invention provides a structure for enhancing the cooling effect of the leakage flow of the casing on the turbine blades, including an inner casing 4, a leakage flow rear outer casing 7 coaxially disposed on the outer side of the inner casing 4, a leakage flow front outer casing 1 circumferentially disposed at the front end of the leakage flow rear outer casing 7, a leakage flow inlet 5 disposed between the leakage flow front outer casing 1 and the leakage flow rear outer casing 7, and a flow guiding component circumferentially fixed at the inner edge of the leakage flow front outer casing 1, the flow guiding component being close to the leakage flow inlet 5.

[0028] The flow guiding component of the present invention reduces the mixing between the main flow 3 and the leakage flow 8, allowing the leakage flow 8 to better adhere to the tip of the turbine blade 2, resulting in better cooling. The present invention has a simple structure, can better utilize the lower temperature leakage flow 8, improve its cooling efficiency on the tip of the turbine blade 2, and reduce the tip temperature of the aero-engine blade. This flow guiding structure can improve the aero-engine cooling system and is of great significance to the design of aero-engine turbines.

[0029] The scheme is further optimized. The flow guiding component includes the leakage flow front outer casing surface 9, which is fixedly connected to the inner edge of the leakage flow front outer casing 1. The leakage flow front outer casing surface 9 and the leakage flow front outer casing 1 are coaxially arranged.

[0030] In a further optimized design, a number of turbine blades 2 are fixed to the outer edge of the inner casing 4. The turbine blades 2 are evenly spaced along the circumference of the inner casing 4. A gap is left between the end of the turbine blade 2 away from the inner casing 4 and the inner diameter of the outer casing 7 after leakage.

[0031] One end of the turbine blade 2 is fixed to the outer wall of the inner casing 4, and the other end of the turbine blade 2 is called the blade tip 6. The distance between the blade tip 6 and the outer casing is defined as h in this invention.

[0032] The scheme is further optimized so that the outer diameter of the outer casing surface 9 before the leakage flow is the same as the inner diameter of the outer casing 7 after the leakage flow, and the inner diameter of the outer casing surface 9 before the leakage flow is smaller than the inner diameter of the outer casing 7 after the leakage flow.

[0033] The diameter of the outer casing profile 9 before the leakage flow at the inlet position of the main flow 3 is the same as the inner diameter of the outer casing 7 after the leakage flow. The diameter of the outer casing profile 9 at its downstream end along the main flow 3 is smaller than the inner diameter of the outer casing 7 after the leakage flow. This invention defines the difference in radii as g.

[0034] The scheme is further optimized so that the inner diameter of the outer casing 1 before the leakage flow is the same as the inner diameter of the outer casing 7 after the leakage flow, and the outer diameter of the outer casing 1 before the leakage flow is the same as the outer diameter of the outer casing 7 after the leakage flow.

[0035] Further optimization of the scheme: the distance between the inner and outer diameters of the outer casing surface 9 before leakage flow is smaller than the gap between the turbine blade 2 and the inner diameter of the outer casing 7 after leakage flow.

[0036] By guiding the main stream 3 through the outer casing profile 9 before the leakage flow, the mixing of the main stream 3 between the leakage flow inlet 5 and the leakage flow 8 is reduced, allowing the leakage flow 8 to better adhere to the tip of the moving blade 6 and achieve a better cooling effect.

[0037] For a further optimized solution, the side of the axial section of the front outer casing profile 9 of the leakage flow close to the axis of the front outer casing profile 9 of the leakage flow is a curved edge 10, and one of the tangents of the curved edge 10 is parallel to the inner wall of the rear outer casing 7 of the leakage flow close to the inner casing 4, and the tangent is located at the leakage flow inlet 5.

[0038] The tangent of the curve 10 at the leakage flow inlet 5 is parallel to the inner wall of the rear outer casing 7 of the leakage flow close to the inner casing 4 to reduce the flow loss of the main flow 3.

[0039] The present invention requires that the outer diameter of the front outer casing profile 9 of the leakage flow is greater than the outer diameter of the turbine moving blade 2, that is, the diameter of the most downstream end of the front outer casing profile 9 of the leakage flow along the direction of the main flow 3 is greater than the diameter of the blade tip 6, that is, g < h. This can enable the front outer casing profile 9 of the leakage flow to guide the main flow to avoid both the area with intense mixing with the leakage flow 8 and completely cover the position where the turbine moving blade 2 is impacted, achieving the function of turbine energy conversion.

[0040] The working process of the present invention is as follows:

[0041] In this embodiment, the blade tip clearance h is 0.8 mm, and the difference g between the radius of the most downstream end of the front outer casing profile 9 of the leakage flow along the direction of the main flow 3 and the radius of the rear outer casing 7 of the leakage flow is 0.5 mm. Figure 4 For the case of using a common purge structure for leakage flow cooling, it will be used for comparison with the cooling effect of the present invention. In this embodiment, the total inlet temperature of the guide vane is 709 K; the static temperature of the leakage flow is 300 K; the Mach number at the outlet of the moving blade is about 0.7; the mass flow rate of the leakage flow 8 accounts for about 1% of the mass flow rate of the main flow 3; the rotational speed of the turbine moving blade 2 is 8450 r / min.

[0042] To ensure the comparability of the results, the parameters of the main flow 3 and the corresponding structural parameters without leakage flow cooling, using a common purge structure for leakage flow cooling, and using the structure of the present invention for leakage flow cooling are exactly the same, and the only difference is whether there is a leakage flow 8 and the structure of the front outer casing profile 9 of the leakage flow. It should be noted that the cooling efficiency mentioned in the present invention is the calculation result under adiabatic wall conditions (all the walls are set as adiabatic walls) and rotational periodic boundary conditions. The specific processing formula is as follows:

[0043]

[0044] Among them, η is the adiabatic cooling efficiency, used to measure the quality of the cooling effect; Tin is the wall recovery temperature without leakage flow, Tc is the leakage flow inlet temperature, and Tw is the wall adiabatic temperature. Naturally, the larger the value of η, the better the cooling effect of the cooling structure design.

[0045] Refer to Figure 8The figure represents the average circumferential cooling efficiency of the blade tip, distributed along the flow direction, compared to leakage flow cooling using a conventional blow-through structure and leakage flow cooling using the structure of this invention. The horizontal axis represents the dimensionless distance x / c along the axis, where c is the axial chord length of the moving blade. The vertical axis represents the average circumferential cooling efficiency. x / c = 0 represents the leading edge of the blade, and x / c = 1 represents the trailing edge of the moving blade.

[0046] The results show that:

[0047] When using a conventional purging structure for leak flow cooling, the adiabatic temperature of the moving blade tip 6 surface will decrease significantly, and its adiabatic cooling efficiency will increase significantly within the range where x / c is less than 0.6. Combined with temperature contour maps and streamline analysis, the moving blade tip 6 is protected by low-temperature gas cooling near the leading edge; while in the middle and near the trailing edge, due to the higher pressure on the pressure surface and the lower pressure on the suction surface, a secondary flow is formed, and the leak flow 8 is drawn into the suction surface side. Therefore, when x / c > 0.63, the leak flow almost loses its cooling effect. Overall, using a conventional purging structure for leak flow cooling can play a certain cooling role.

[0048] Using the structure of this invention for leak flow cooling significantly improves the adiabatic cooling efficiency, substantially enhancing the cooling effect of the casing leak flow 8 on the turbine blade tip 6. Especially upstream of the blade tip 6, the outer casing profile 9 of the leak flow in this invention effectively guides the mainstream flow, reducing mixing between the mainstream flow 3 and the leak flow 8. Compared to conventional purging structures for leak flow cooling, the increase in adiabatic cooling efficiency of the cooling structure and method of this invention remains stable until x / c < 0.63. Particularly at x / c close to 0.59, where the adiabatic cooling efficiency is already low, this invention still maintains a good cooling enhancement effect.

[0049] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0050] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A structure for enhancing the cooling effect of casing leakage flow on turbine blades, characterized in that, The device includes an inner casing (4), a rear outer casing (7) coaxially disposed on the outer side of the inner casing (4), a front outer casing (1) circumferentially disposed at the front end of the rear outer casing (7), a leakage inlet (5) disposed between the front outer casing (1) and the rear outer casing (7), and a flow guide assembly circumferentially fixed at the inner edge of the front outer casing (1), the flow guide assembly being close to the leakage inlet (5). The flow guiding assembly includes a front outer casing profile (9) for the leakage flow, and the distance between the inner and outer diameters of the front outer casing profile (9) for the leakage flow is less than the gap between the turbine blade (2) and the inner diameter of the rear outer casing (7) for the leakage flow. By guiding the main stream (3) through the outer casing profile (9) of the leakage flow, the mixing of the main stream (3) between the leakage flow inlet (5) and the leakage flow (8) is reduced, so that the leakage flow (8) can better adhere to the tip of the moving blade (6) and obtain a better cooling effect. The axial section of the outer casing surface (9) before the leakage flow is curved (10) on the side of the outer casing surface (9) before the leakage flow. One of the tangents of the curved (10) is set parallel to the inner wall of the outer casing (7) after the leakage flow near the inner casing (4). The tangent is located at the leakage flow inlet (5). The tangent of the curved edge (10) at the leakage inlet (5) is parallel to the inner wall of the outer casing (7) after the leakage flow near the inner casing (4) to reduce the flow loss of the main stream (3).

2. The structure for enhancing the cooling effect of casing leakage flow on turbine blades according to claim 1, characterized in that, The leakage flow front outer casing surface (9) is fixedly connected to the inner edge of the leakage flow front outer casing (1), and the leakage flow front outer casing surface (9) is coaxially arranged with the leakage flow front outer casing (1).

3. The structure for enhancing the cooling effect of casing leakage flow on turbine blades according to claim 1, characterized in that, A plurality of turbine blades (2) are fixed to the outer edge of the inner casing (4). The plurality of turbine blades (2) are arranged at equal intervals along the circumference of the inner casing (4). A gap is left between the end of the turbine blade (2) away from the inner casing (4) and the inner diameter of the outer casing (7) after leakage.

4. The structure for enhancing the cooling effect of casing leakage flow on turbine blades according to claim 2, characterized in that, The outer diameter of the front outer casing profile (9) of the leakage flow is the same as the inner diameter of the rear outer casing (7) of the leakage flow, and the inner diameter of the front outer casing profile (9) of the leakage flow is smaller than the inner diameter of the rear outer casing (7) of the leakage flow.

5. The structure for enhancing the cooling effect of casing leakage flow on turbine blades according to claim 1, characterized in that, The inner diameter of the front outer casing (1) of the leakage flow is the same as the inner diameter of the rear outer casing (7) of the leakage flow, and the outer diameter of the front outer casing (1) of the leakage flow is the same as the outer diameter of the rear outer casing (7) of the leakage flow.

Images