Countersunk groove air film hole cooling structure with non-uniform groove depth

Abstract

The invention relates to a non-uniform groove depth sinking groove air film hole cooling structure. The non-uniform groove depth sinking groove air film hole cooling structure comprises an inclined cylindrical air film hole, a first-stage groove and a second-stage groove. An inclined cylindrical gas film hole is formed in a to-be-cooled wall surface base body, an inlet and an outlet of the cylindrical gas film hole are oval, a first-stage groove is formed in the outlet of the cylindrical gas film hole, the length of the first-stage groove is equal to the long diameter of the oval of the outlet of the gas film hole, and second-stage grooves with the same length as the first-stage groove are formed in the two sides of the first-stage groove. And the depth of the first-stage groove is smaller than that of the second-stage groove. The two-stage grooves are formed beside the cylindrical air film hole, the sinking groove air film hole with the non-uniform groove depth is constructed, stronger turbulent flow is formed in the grooves, a larger air film covering area is formed on the downstream of the holes, and the air film cooling performance can be remarkably improved. The device is simple in structure and easy to process and manufacture.

Description

Technical Field

[0001] The invention relates to an air film hole cooling technology, in particular to a sinking air film hole cooling structure with a non-uniform groove depth. Background Art

[0002] The overall performance of an aircraft engine depends largely on the high-pressure turbine inlet temperature. The turbine inlet temperature of advanced aircraft engines has reached as high as 2000K, far exceeding the melting point of the turbine blade material. To protect the turbine blades from high-temperature erosion and extend their service life, effective thermal protection technologies are required. Turbine designers are committed to improving existing thermal protection technologies or developing new cooling technologies to achieve even better thermal protection.

[0003] Film cooling is widely used for thermal protection of turbine blades. Its working principle is: cold air is injected into the high-temperature mainstream through holes or slits in the solid wall. The interaction between the cold air and the mainstream forms a lower-temperature air film that adheres to the wall, thereby cooling the solid material. In film cooling, cylindrical film holes are the most basic hole type. They have advantages such as few geometric parameters, simple shape, and easy processing. Therefore, the flow characteristics and cooling effect of cylindrical film holes have been widely studied over the past fifty years. The results show that when the cold air jet from the cylindrical film hole is injected into the mainstream, kidney-shaped vortices are formed downstream. As the blowing ratio increases, the intensity of the kidney-shaped vortex increases, which will cause the film to rise or even detach from the solid wall. In other words, the film cooling effect is significantly reduced.

[0004] In order to overcome the shortcomings of the cooling characteristics of cylindrical film holes, researchers have designed a variety of special-shaped film holes. Compared with cylindrical film holes, these special-shaped film holes usually have an enlarged hole outlet area, which reduces the jet momentum at the hole outlet, thereby weakening the strength of the kidney-shaped vortex and helping the film to adhere to the solid wall. However, the vast majority of special-shaped film holes are geometrically complex and difficult to process. In view of this, the researchers proposed a groove film hole design, which makes the outlet of the cylindrical film hole at the bottom of the groove, which is easy to process and implement. The groove film hole helps to weaken the strength of the kidney-shaped vortex, and the downstream wall of the groove can block part of the cold air jet, enhance the mixing of the cold air and the mainstream in the groove, and thus improve the downstream film cooling efficiency. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention aims to provide a sinking air film hole cooling structure with non-uniform groove depth. By constructing two-level grooves, stronger turbulent flow is formed inside the grooves, which can significantly improve the air film cooling performance.

[0006] The present invention is achieved through the following technical solutions.

[0007] A cooling structure for a sinking air film hole with a non-uniform groove depth comprises an inclined cylindrical air mold hole, a first-level groove, and a second-level groove. The inclined cylindrical air mold hole is opened on a substrate of a wall surface to be cooled. The inlet and outlet shapes of the cylindrical air film hole are both elliptical. A first-level groove is provided at the outlet of the cylindrical air film hole. Second-level grooves with the same length as the first-level groove are provided on both sides of the first-level groove. The first-level groove and the second-level groove constitute a sinking groove with a non-uniform groove depth. The groove depth of the first-level groove (i.e., the vertical distance between the bottom plane of the first-level groove and the wall surface to be cooled on the substrate of the wall surface to be cooled) is less than the groove depth of the second-level groove (i.e., the vertical distance between the bottom plane of the second-level groove and the wall surface to be cooled on the substrate of the wall surface to be cooled).

[0008] Furthermore, the axial inclination angle α of the cylindrical air film hole to the mainstream flow is 30°, the length of the cylindrical air film hole is L1, the diameter of the cylindrical air film hole is D, the length of the first-level groove is L2, and the major diameter of the outlet ellipse of the cylindrical air film hole is equal to the length L2 of the first-level groove.

[0009] Furthermore, L2=2D, the groove depth of the first-level groove is H1=0.5D, the groove depth of the second-level groove is H2=1D, the minimum distance between the edge of the first-level groove in the width direction and the edge of the cylindrical air mold hole outlet is W1, W1=0.25D, and the maximum distance between the edge of the first-level groove in the width direction and the edge of the second-level groove in the width direction is W2, W2=2.25D.

[0010] Compared with existing technologies, the present invention offers the following advantages: by providing two-stage grooves adjacent to the cylindrical film holes, creating submerged film holes with uneven depths, this creates stronger turbulent flow within the grooves and a larger air film coverage area downstream of the holes, significantly improving film cooling performance. The present invention also has a simple structure and is easy to manufacture. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is an axonometric view of the present invention;

[0012] Figure 2 A top view of the present invention;

[0013] Figure 3 It is a front view of the present invention;

[0014] Figure 4 This is a schematic diagram of a cylindrical air mold hole of the present invention;

[0015] Figure 5 for Figure 2 A partial enlarged view of

[0016] Figure 6 for Figure 3 A partial enlarged view of

[0017] Figure 7A comparison diagram of the flow characteristics of a cylindrical air film hole, a uniform groove depth air film hole, and a non-uniform groove depth air film hole of the present invention;

[0018] Figure 8 Cooling efficiency cloud diagrams of cylindrical film holes, uniform groove depth submerged groove film holes, and non-uniform groove depth submerged groove film holes of the present invention;

[0019] Figure 9 This is a comparison chart of the spanwise average cooling efficiency of cylindrical film holes, uniform groove depth submerged groove film holes, and the non-uniform groove depth submerged groove film holes of the present invention;

[0020] Figure 10 Schematic diagram of cylindrical air film hole;

[0021] Figure 11 This is a schematic diagram of the air film hole in the uniform groove depth;

[0022] In the figure: 1, cylindrical air mold hole, 2, first-level groove, 3, second-level groove, 4, wall substrate to be cooled;

[0023] α is the inclination angle of the axial direction of the cylindrical air film hole and the mainstream flow, L1 is the length of the cylindrical air film hole, D is the diameter of the cylindrical air film hole, L2 is the length of the first-level groove, H1 is the groove depth of the first-level groove, H2 is the groove depth of the second-level groove, W1 is the minimum distance between the edge of the first-level groove in the width direction and the edge of the cylindrical air film hole outlet, W2 is the maximum distance between the edge of the first-level groove in the width direction and the edge of the second-level groove in the width direction. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0025] like Figure 1 refer to Figure 6 As shown, a sinking groove air film hole cooling structure with non-uniform groove depth includes an inclined cylindrical air mold hole 1, a first-level groove 2, and a second-level groove 3. The inclined cylindrical air mold hole 1 is opened on the wall surface substrate 4 to be cooled. The inlet and outlet shapes of the cylindrical air film hole 1 are both elliptical. A first-level groove 2 is provided at the outlet of the cylindrical air film hole 1. Second-level grooves 3 with the same length as the first-level groove 2 are provided on both sides of the first-level groove 2. The first-level groove 2 and the second-level groove 3 form a sinking groove with non-uniform groove depth. The groove depth of the first-level groove 2 (that is, the vertical distance between the bottom plane of the first-level groove 2 and the wall surface to be cooled on the wall surface substrate 4 to be cooled) is smaller than the groove depth of the second-level groove 3 (that is, the vertical distance between the bottom plane of the second-level groove 3 and the wall surface to be cooled on the wall surface substrate 4 to be cooled).

[0026] Furthermore, the axial inclination angle α of the cylindrical air film hole 1 to the mainstream flow is 30°, the length of the cylindrical air film hole 1 is L1, the diameter of the cylindrical air film hole 1 is D, the length of the first-level groove 2 is L2, and the major diameter of the outlet ellipse of the cylindrical air film hole 1 is equal to the length L2 of the first-level groove 2.

[0027] Furthermore, L2=2D, the groove depth of the first-level groove 2 is H1=0.5D, the groove depth of the second-level groove 3 is H2=1D, the minimum distance between the width edge of the first-level groove 2 and the outlet edge of the cylindrical air mold hole 1 is W1, W1=0.25D, and the maximum distance between the width edge of the first-level groove 2 and the width edge of the second-level groove 3 is W2, W2=2.25D.

[0028] Through numerical simulation, the cylindrical air film hole (referring to the traditional cylindrical air film hole, such as Figure 10 As shown), uniform groove depth sinking air film hole (refers to the traditional cylindrical air film hole and a groove of equal depth, such as Figure 11 ) and the flow characteristics and film cooling effect of the non-uniform groove depth sinking groove air film hole of the present invention (see Figure 7 、 Figure 8 、 Figure 9 ).from Figure 7 It can be seen that compared with the cylindrical air film hole, the cold air flow line downstream of the uniform groove deep groove air film hole covers a wider area and adheres to the wall surface; compared with the uniform groove deep groove air film hole, the turbulent flow inside the groove of the non-uniform groove deep groove air film hole is stronger, and the cold air is more fully mixed with the mainstream. Figure 8 It can be seen that the uniform groove depth submerged groove air film hole has a larger air film coverage area downstream of the hole than the cylindrical air film hole, and the non-uniform groove depth submerged groove air film hole has a more uniform distribution of cold air inside the groove than the uniform groove depth submerged groove air film hole, and the air film coverage downstream of the hole is more sufficient. Figure 9 It can be seen that the spanwise average cooling efficiency of the uniform groove depth submerged groove film hole is more than twice that of the cylindrical air film hole, and the spanwise average cooling efficiency of the non-uniform groove depth submerged groove film hole is improved by 15.8% overall compared with the uniform groove depth submerged groove film hole.

[0029] The above description is only a preferred embodiment of the present invention and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A cooling structure of a submerged film hole with a non-uniform groove depth, characterized in that: The invention comprises an inclined cylindrical air film hole (1), a first-level groove (2), and a second-level groove (3). The inclined cylindrical air film hole (1) is opened on a wall substrate (4) to be cooled. The inlet and outlet shapes of the cylindrical air film hole (1) are both elliptical. A first-level groove (2) is provided at the outlet of the cylindrical air film hole (1). Second-level grooves (3) having the same length as the first-level groove (2) are provided on both sides of the first-level groove (2). The first-level groove (2) and the second-level groove (3) form a sink groove with a non-uniform groove depth. The groove depth of the first-level groove (2) is less than the groove depth of the second-level groove (3).

2. The cooling structure of the submerged film hole with non-uniform groove depth according to claim 1, characterized in that: The inclination angle α between the axial direction of the cylindrical air film hole (1) and the main flow is 30°, the length of the cylindrical air film hole (1) is L1, the diameter of the cylindrical air film hole (1) is D, the length of the first-stage groove (2) is L2, and the major diameter of the outlet ellipse of the cylindrical air film hole (1) is equal to the length L2 of the first-stage groove (2).

3. The cooling structure of the submerged film hole with non-uniform groove depth according to claim 2, characterized in that: L2=2D, the groove depth of the first-level groove (2) is H1=0.5D, the groove depth of the second-level groove (3) is H2=1D, the minimum distance between the width edge of the first-level groove (2) and the outlet edge of the cylindrical air mold hole (1) is W1, W1=0.25D, and the maximum distance between the width edge of the first-level groove (2) and the width edge of the second-level groove (3) is W2, W2=2.25D.

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