Heat shield and air film cooling method for enhancing heat exchange between double walls

Abstract

The present application relates to a kind of heat exchanger of reinforced double-wall heat transfer heat shield, including air film hole plate and impact hole plate, multiple support trusses are arranged in the cavity between air film hole plate and impact hole plate in matrix, the support truss is by four truss rods, one end of four truss rods is crossed to form a intersection point, intersection point and the other end of four truss rods are connected with air film hole plate and impact hole plate respectively;Support truss is disturbed to impact jet and wall jet and forms complex flow and vortex C4, and the upper surface of air film hole plate is strengthened convective heat transfer, support truss forms support effect to impact hole plate and air film hole plate on the one hand, on the other hand, it plays the role of heat conduction heat transfer, increase the convective heat transfer area in channel.The present application strengthens internal heat exchange, and also promotes air film cooling effect, i.e. it can simultaneously improve the effect of internal cooling and external cooling.

Description

Technical Field

[0001] This invention belongs to the field of gas turbine engines, and particularly relates to a double-walled heat shield with a truss sandwich structure and a film cooling method. Background Technology

[0002] During aircraft startup, climb, and emergency maneuvers, aero engines require afterburner combustion to generate additional thrust. In afterburner mode, the temperature of the exhaust gases flowing through the afterburner and exhaust nozzle exceeds 2000K, far exceeding the heat resistance limit of usable high-temperature materials. Therefore, effective thermal protection is essential for the load-bearing structures of the afterburner and exhaust nozzle.

[0003] Heat shields are widely used as a form of thermal protection for afterburners and exhaust nozzles. Several heat shields for afterburners have been previously disclosed, including a porous corrugated plate heat shield (US 005465572A). Its corrugated structure's elasticity effectively prevents the effects of thermal deformation caused by vibration of the exhaust nozzle, and the cooling jets through discrete film cooling holes on the corrugated plate provide film cooling to the high-temperature combustion gas side of the heat shield. However, precisely because of the corrugated structure, the cooling film jets cannot cover the entire surface, resulting in excessively high local wall temperatures and preventing effective film coverage and heat exchange. Another type is a divergent cooling heat shield structure with turbulence columns (US 20140096527A1). This structure forms a film covering on the wall surface through divergent cooling, blocking direct contact with high-temperature combustion gas. Simultaneously, the turbulence column structure on the cold gas side of the heat shield can turbulently mix the cold gas, enhancing convective heat transfer and allowing the cold gas to carry away more heat, thus reducing the wall temperature. However, a simple divergent cooling method is insufficient to make the turbulence column work better, and the cooling flow mixing is not strong enough to improve its cooling efficiency.

[0004] Based on the above experience, and combining traditional methods such as film cooling and impact cooling, patent (CN 103968418A) discloses a double-walled heat shield for an afterburner. This structure includes a wall surface with film cooling holes near the combustion gas side, a wall surface with impact holes near the cold gas side, and a trapezoidal reinforcing frame between the film cooling plate and the impact cooling plate. This forms a composite cooling system combining impact cooling on the cold gas side, internal convection heat transfer, and film cooling coverage of the combustion gas side. This structure can remove the transferred heat through convection heat transfer, improving the utilization rate of the cold gas, and also has good mechanical properties. However, this structure does not consider the flow resistance introduced by the trapezoidal reinforcing frame during internal convection heat transfer.

[0005] With the development of advanced high-performance gas turbine engines, the temperature of the gas flowing through the afterburner and exhaust nozzle is constantly increasing. In addition, the increased airflow required for mainstream combustion leads to a decrease in the airflow available for cooling. Therefore, it is necessary to apply heat shield structures with high-efficiency cooling capabilities, that is, to achieve better cooling effect with as little cooling air as possible. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a heat insulation screen and air film cooling method that can effectively reduce the use of cold air and efficiently cool the wall surface, thereby enhancing the heat exchange between the two layers of walls.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a heat insulation screen for enhancing heat exchange between double-layer walls, comprising an air film perforated plate and an impact perforated plate, wherein multiple supporting trusses are arranged in a matrix within the cavity between the air film perforated plate and the impact perforated plate, wherein the supporting trusses are composed of four truss rods, one end of the four truss rods intersects each other to form an intersection point, and the intersection point and the other end of the four truss rods are respectively connected to the air film perforated plate and the impact perforated plate;

[0008] Of the four truss members, two of the four connection points on the impact perforated plate are located on a straight line in front of the intersection along the airflow direction, and the other two connection points are located on a straight line in the rear of the intersection along the airflow direction, with each straight line being equidistant from the intersection; impact holes are provided on the impact perforated plate; the impact holes are located outside the four connection points and on the line connecting the intersection and the center point of the four connection points.

[0009] Air film holes are provided on the air film perforated plate; the air film holes are holes arranged around the intersection, and are discontinuous annular holes composed of at least two fan-ring holes and fan-ring partitions for connecting the two fan-ring holes. The inner diameter of the discontinuous annular holes is the same as the diameter of the intersection, and the center point of the discontinuous annular holes coincides with the center point of the intersection.

[0010] Furthermore, the matrix arrangement of the multiple supporting trusses is specifically as follows: with Sx as the axial spacing of the supporting trusses, Sz as the circumferential spacing of the supporting trusses, H as the distance between the air film perforated plate and the impact perforated plate, D' as the diameter of the supporting truss, and d' as the diameter of the circular hole with the same area as the fan-shaped hole, then:

[0011] H≥Sx≥2 D', H≥Sz≥2 D';

[0012] π·(d' / 2) 2 / Sx×Sz=0.4~4%;

[0013] The supporting truss extends sequentially along the axial and circumferential directions of the cavity between the air film perforated plate and the impact perforated plate at predetermined distances.

[0014] Furthermore, the diameter of the inner ring formed by the air film holes is d, the diameter of the outer ring is D, and the distance between the outer ring and the inner ring is the width B of the fan-shaped hole. Therefore, B < 0.5 D.

[0015] Furthermore, the air film pores include 2 to 6 fan-shaped pores.

[0016] Furthermore, the fan-shaped hole is a normal through hole or a normal backward expansion hole of the air film perforated plate;

[0017] When the hole is a normal through hole of an air film orifice plate, the cross-section of the air film orifice is provided with a pair of inclination angles α1=α2=90°.

[0018] When the air film orifice is a normal backward expansion orifice, the sum of a pair of inward inclination angles corresponding to the cross-section of the orifice is 90 degrees, and:

[0019] 45°≤α1≤90°, 45°≤α2≤90°.

[0020] Furthermore, the fan-shaped partition has a pair of arc-shaped connecting edges and a pair of parallel or inclined edges; when it is a parallel edge, the distance L between the two edges is 0.1~0.2mm; when it is an inclined edge, the central angle corresponding to the inclined edge is θ, and θ ranges from 10 to 30 degrees.

[0021] Furthermore, the impact hole is a normal through hole in the impact hole plate; the diameter of the impact hole is 0.7~1.5mm;

[0022] The opening area of ​​the air film pore is 1 to 3 times that of the opening area of ​​the impact pore.

[0023] Furthermore, given that the diameter of the supporting truss is D', the diameter of the circular hole with equal area of ​​the fan-shaped hole is d', and the distance between the air film perforated plate and the impact perforated plate is H, then:

[0024] D' / d' = 0.5~2;

[0025] H / d' = 0.1~20.

[0026] Furthermore, the normal angle between the supporting truss and the wall surface of the impact plate is θ, where θ is 30~60°; the length of the truss members constituting the supporting truss is... l H is the distance between the film gas plate and the impact plate. l=H / cos θ.

[0027] This invention also provides a method for enhancing the film cooling effect of the heat insulation screen with enhanced double-wall heat exchange. In the cooling gas duct, the cooling airflow C1 enters the cavity between the film cooling perforated plate and the perforated plate through the impact holes on the perforated plate, impacting and cooling the inner wall surface of the film cooling perforated plate to form an impact jet C2 and a wall-attached jet C3. The supporting truss disturbs the impact jet and the wall-attached jet, forming complex flow around the perforated plate and vortex C4, which enhances convective heat transfer on the upper surface of the film cooling perforated plate. The supporting truss provides support for the impact jet and the film cooling perforated plate and also plays a role in heat conduction and transfer, increasing the convective heat transfer area in the channel. Simultaneously, the flow around the perforated plate and vortex C4 either flow into or are drawn into the film cooling perforation to form a film outflow C5, which mixes with the high-temperature mainstream C6 on the outer side of the film cooling perforated plate, reducing the gas temperature near the wall surface and forming a film covering layer on the outer wall surface of the film cooling perforated plate, blocking the direct scouring of the gas.

[0028] The beneficial effects of this invention are as follows: This invention proposes a double-walled heat shield with a pyramidal truss sandwich structure for afterburners and exhaust nozzles. The structure includes a gas-side film cooling perforated plate, a cold-gas-side impact cooling perforated plate, and a pyramidal truss array connecting the film cooling perforated plate and the impact cooling perforated plate. The impact cooling perforated plate forms a cold-gas duct with the outer wall of the afterburner or exhaust nozzle, while the film cooling perforated plate forms the inner wall of the cylinder of the afterburner or exhaust nozzle, directly contacting the mainstream gas flow. The impact cooling perforated plate and the film cooling perforated plate form a convective heat transfer channel. The pyramidal truss structure, as an internal cooling structure, can adjust its structural parameters to optimize the arrangement of impact cooling and film cooling. Furthermore, it enhances convective heat transfer with relatively low flow resistance, increases the heat transfer area, improves film cooling efficiency, effectively reduces wall temperature, and improves cold gas utilization. The outstanding advantage of this structure is that it enhances both internal heat transfer and film cooling efficiency, thus simultaneously improving both internal and external cooling effects. In addition, the double-walled structure of the impact plate-air film plate fixed by the pyramid truss array structure has good mechanical properties. Attached Figure Description

[0029] Figure 1 This is a top view of the double-walled heat insulation screen structure of the present invention;

[0030] Figure 2 This is a top view cross-sectional structural diagram of the present invention;

[0031] Figure 3 This is a schematic diagram of the side cross-sectional structure of the present invention;

[0032] Figure 4 This is a schematic cross-sectional view of the air film pore structure of the present invention;

[0033] Figure 5 This is another schematic diagram of the top view structure of the air-supported membrane panel of the present invention;

[0034] in, Figure 5(a) is a structural diagram of Example 4. Figure 5 (b) is a structural diagram of Example 5;

[0035] Figure 6 This is a flow diagram of the internal structure of the double-layered wall of the pyramid truss of the present invention.

[0036] Figure 7 This is a comparison diagram of the spanwise average film cooling effect of the present invention;

[0037] Figure 8 This is a comparison chart of the overall cooling efficiency of the present invention in the spanwise direction;

[0038] Figure 9 This is a heat transfer cloud diagram of the double-walled target surface of the present invention;

[0039] (a) is a heat transfer cloud map of the target surface of the straight column air film hole turbulence double-walled target, and (b) is a heat transfer cloud map of the target surface of the pyramid truss double-walled target.

[0040] In the diagram: 1. Film membrane orifice plate; 2. Impact orifice plate; 3. Support truss; 4. Casing; 5. Film membrane orifice; 51. Fan ring orifice; 52. Fan ring partition; 6. Impact hole; 7. Four connection points; 8. Intersection point; A. Mainstream high-temperature combustion gas; B. Cooling airflow; C1. Impact jet; C2. Reverse airflow generated by the collision of adjacent impact jets; C3. Wall-attached jet directly drawn in by the film membrane orifice; C4. Airflow around the pyramid truss; C5. Film membrane outflow. Detailed Implementation

[0041] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0042] To achieve the above objectives, the present invention provides the following specific embodiments:

[0043] Example 1: As Figure 1-5 As shown, a heat insulation screen for enhancing heat exchange between double-walled structures includes an air-film perforated plate 1 and an impact perforated plate 2. Multiple support trusses 3 are arranged in a matrix within the cavity between the air-film perforated plate 1 and the impact perforated plate 2. Each support truss 3 is composed of four truss rods. One end of each of the four truss rods intersects to form an intersection point 8. The intersection point 8 and the other ends of the four truss rods are respectively connected to the air-film perforated plate 1 and the impact perforated plate 2.

[0044] Of the four truss members connected at four points 7 on the perforated plate 2, two points are located on a straight line in front of the intersection along the airflow direction, and the other two points are located on a straight line behind the intersection along the airflow direction, with each line equidistant from the intersection. An impact hole 6 is provided on the perforated plate 2. The impact hole 6 is located outside the four connection points 7 and on the line connecting the intersection 8 and the center point of the four connection points 7. The impact hole 6 is a normal through hole in the perforated plate 2, and its diameter is 0.7~1.5mm.

[0045] Air film holes 5 are provided on the air film orifice plate 1. The air film holes 5 are holes arranged around the intersection point 8, and are discontinuous annular holes composed of at least two fan-ring holes 51 and fan-ring partitions 52 for connecting the two fan-ring holes 51. The inner diameter of the discontinuous annular holes is the same as the diameter of the intersection point 8, and the center point of the discontinuous annular holes coincides with the center point of the intersection point 8. The opening area of ​​the air film holes 5 is 1 to 3 times the opening area of ​​the impact holes 6.

[0046] The air film hole 5 is a discontinuous annular hole consisting of at least two fan ring holes 51 and fan ring partitions 52 for connecting two fan ring holes 51; the air film hole 5 includes 2 to 6 fan ring holes 51.

[0047] The diameter of the inner ring formed by the air film hole 5 is d, the diameter of the outer ring is D, and the distance between the outer ring and the inner ring is the width B of the fan ring hole 51. Therefore, B < 0.5 D.

[0048] The fan-shaped hole 51 is a normal through hole or a normal backward expansion hole of the air film orifice plate 1;

[0049] When the air film orifice plate 1 is a normal through hole, the cross section of the air film orifice 2 is provided with a pair of inclination angles α1=α2=90°.

[0050] When the air film orifice 2 is a normal backward expansion orifice, the sum of the two corresponding inward inclination angles of the cross-section is 90 degrees, and:

[0051] 45°≤α1≤90°, 45°≤α2≤90°.

[0052] The fan-shaped partition 52 has a pair of arc-shaped connecting edges and a pair of parallel or inclined edges; when they are parallel edges, the distance L between the two edges is 0.1~0.2mm; when they are inclined edges, the central angle corresponding to the inclined edge is θ, and the range of θ is 10~30 degrees.

[0053] The matrix arrangement of multiple supporting trusses 3 is as follows: with Sx as the axial spacing of the supporting trusses 3, Sz as the circumferential spacing of the supporting trusses 3, H as the distance between the air film perforated plate 1 and the impact perforated plate 2, D' as the diameter of the supporting truss, and d' as the diameter of the circular hole with the same area as the fan ring hole 51, then:

[0054] H≥Sx≥2 D', H≥Sz≥2 D';

[0055] π·(d' / 2) 2 / Sx×Sz=0.4~4%.

[0056] The supporting truss 3 extends sequentially in the axial and circumferential directions of the cavity between the air film perforated plate 1 and the impact perforated plate 2 according to the set distance.

[0057] The diameter of the supporting truss is D', the diameter of the circular hole with equal area of ​​the fan ring hole 51 is d', and the distance between the air film perforated plate 1 and the impact perforated plate 2 is H. Then:

[0058] D' / d' = 0.5~2;

[0059] H / d' = 0.1~20.

[0060] The normal angle between the supporting truss 3 and the wall of the impact plate 2 is θ, where θ is 30~60°; the length of the truss members constituting the supporting truss 3 is... l H is the distance between the air film orifice plate 1 and the impact orifice plate 2. l=H / cos θ.

[0061] Based on the same opening ratio of the air film plate, the opening ratio of the impact plate, and the diameter of the turbulence column, while maintaining consistent flow parameters, this pyramid truss sandwich double-wall structure is compared with a traditional circular straight-column turbulence double-wall structure. The air film cooling efficiency, overall cooling efficiency, and heat transfer distribution of the impact target surface are as follows: Figure 7 , 8 As shown in the figure, compared with the circular straight column air film hole double-wall structure, the pyramid truss sandwich double-wall structure has a significantly higher air film cooling efficiency and overall cooling efficiency.

[0062] like Figure 9 As shown, for target surface heat transfer, Figure 9 (a) In the case of a straight column with a porous membrane, there are low heat transfer zones on both sides of the turbulent tail, while the present invention provides... Figure 9 (b) Pyramid truss turbulence structure. As can be seen from the figure, the structure of the present invention effectively avoids the occurrence of this low heat exchange zone and can achieve efficient heat exchange and cooling.

[0063] Example 2: As Figure 4 As shown in (a), it is the same as in Example 1, except that: the air film hole 5 is a pair of inward inclination angles α1=α2=90° corresponding to the cross section of the air film hole 5, which is the normal through hole of the air film plate 1.

[0064] Example 3: As Figure 4 As shown in (b), the method is the same as in Example 1, except that: the air film hole 5 is a rearward expansion hole of the air film perforated plate 1, and the sum of the two pairs of inward inclination angles corresponding to the cross-section of the air film hole 5 is 90 degrees, and:

[0065] 45°≤α1≤90°, 45°≤α2≤90°.

[0066] Example 4: Figure 5 As shown in (a), it is the same as in Example 1, except that the fan ring partition 52 has a pair of arc-shaped connecting edges and a pair of parallel edges, and the distance L between the two edges is 0.1~0.2mm.

[0067] Example 5: Figure 5 As shown in (b), it is the same as in Example 1, except that the fan ring partition 52 has a pair of arc-shaped connecting edges and a pair of inclined edges, and the central angle corresponding to the inclined edges is θ, with θ ranging from 10 to 30 degrees.

[0068] Example 6: As Figure 6 As shown, the present invention also provides a method for enhancing the air film cooling effect of a heat insulation screen that strengthens heat transfer between double-walled structures. Cooling airflow C1 in the outer duct of the cooling air enters the cavity between the air film perforated plate 1 and the perforated plate 2 through the impact holes 6 on the perforated plate 2, impacting and cooling the inner wall surface of the air film perforated plate to form an impact jet C2 and a wall-attached jet C3. The supporting truss 3 disturbs the impact jet and the wall-attached jet, forming complex flow around and vortex C4, thus enhancing convective heat transfer on the upper surface of the air film perforated plate 1. The supporting truss, on the one hand, affects the heat transfer between the impact jet 2 and the air film... The orifice plate 1 provides support and also serves as a heat conductor, increasing the convective heat transfer area in the channel. Simultaneously, the surrounding flow and eddy current C4 either flow into or are drawn into the film gas orifice 5 to form film gas outflow C5, which mixes with the high-temperature mainstream C6 on the outside of the film gas orifice plate 1, reducing the gas temperature near the wall and forming a film gas covering layer on the outer wall of the film gas orifice plate 1, blocking the direct scouring of the gas. Due to the increased longitudinal coverage area of ​​the film gas in the annular film gas orifice and the better adhesion of the film gas to the wall, the film gas cooling efficiency is significantly improved.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heat insulation screen for enhancing heat transfer between double-layer walls, characterized in that, It includes an air film perforated plate (1) and an impact perforated plate (2). Multiple support trusses (3) are arranged in a matrix in the cavity between the air film perforated plate (1) and the impact perforated plate (2). The support trusses (3) are composed of four truss rods. One end of the four truss rods intersects each other to form an intersection point (8). The intersection point (8) and the other end of the four truss rods are respectively connected to the air film perforated plate (1) and the impact perforated plate (2). Of the four truss rods, two of the four connection points (7) on the impact hole plate (2) are located on a straight line in front of the intersection along the airflow direction, and the other two connection points are located on a straight line in the rear of the intersection along the airflow direction, and each straight line is equidistant from the intersection; an impact hole (6) is provided on the impact hole plate (2); the impact hole (6) is located outside the four connection points (7) and on the line connecting the intersection (8) and the center point of the four connection points (7); An air film hole (5) is provided on the air film perforated plate (1); the air film hole (5) is a hole arranged around the intersection (8), and is a discontinuous annular hole composed of at least two fan ring holes (51) and a fan ring partition (52) for connecting the two fan ring holes (51). The inner diameter of the discontinuous annular hole is the same as the diameter of the intersection (8), and the center point of the discontinuous annular hole coincides with the center point of the intersection (8).

2. The heat insulation screen for enhanced inter-wall heat exchange as described in claim 1, characterized in that, The diameter of the inner ring formed by the air film hole (5) is d, the diameter of the outer ring is D, and the distance between the outer ring and the inner ring is the width B of the fan ring hole (51). Therefore, B < 0.5 D.

3. The heat insulation screen for enhanced inter-wall heat exchange as described in claim 2, characterized in that, The air film pore (5) includes 2 to 6 fan-shaped pores (51).

4. The heat insulation screen for enhanced inter-wall heat exchange as described in claim 2, characterized in that, The fan-shaped hole (51) is a normal through hole or a normal backward expansion hole of the air film perforated plate (1); When it is a normal through hole of the air film perforated plate (1), the cross section of the air film hole (5) is provided with a pair of inclination angles α1=α2=90°. When the air film hole (5) is a normal backward expansion hole, the sum of the two inward inclination angles corresponding to the cross-section of the air film hole (5) is 90 degrees, and: 45°≤α1≤90°，45°≤α2≤90°。 5. The heat insulation screen for enhanced inter-wall heat exchange as described in claim 2, characterized in that, The fan-shaped partition (52) has a pair of arc-shaped connecting edges and a pair of parallel or inclined edges; When the sides are parallel, the distance L between the two sides is 0.1~0.2mm; When it is the inclined side, the central angle corresponding to the inclined side is θ, and the range of θ is 10~30 degrees.

6. The heat insulation screen for enhanced inter-wall heat exchange as described in claim 1, characterized in that, The impact hole (6) is a normal through hole of the impact hole plate (2); the diameter of the impact hole (6) is 0.7~1.5mm; The opening area of ​​the air film hole (5) is 1 to 3 times the opening area of ​​the impact hole (6).

7. The heat insulation screen for enhanced double-wall heat exchange as described in any one of claims 1-6, characterized in that, The normal angle between the supporting truss (3) and the impact plate (2) is θ, where θ is 30~60°; the length of the truss rods constituting the supporting truss (3) is... l H is the distance between the air film orifice plate (1) and the impact orifice plate (2), then l=H / cos θ.

8. The method for enhancing the air-film cooling effect of a heat insulation screen for double-wall heat exchange as described in any one of claims 1-6, characterized in that, The cooling airflow C1 in the cold air bypass enters the cavity between the air film perforated plate (1) and the air film perforated plate (2) through the impact hole (6) on the impact perforated plate (2), and performs impact cooling on the inner wall surface of the air film perforated plate to form an impact jet C2 and a wall-attached jet C3. The supporting truss (3) disturbs the impact jet and the wall-attached jet, forming complex flow around and eddy currents C4, which enhance convective heat transfer on the upper surface of the film perforated plate (1). The supporting truss (3) provides support for the impact perforated plate (2) and the film perforated plate (1) on the one hand, and plays a role in heat conduction and heat transfer on the other hand, increasing the convective heat transfer area in the channel. At the same time, the flow around and eddy currents C4 either flow into or are drawn into the film perforation (5) to form film outflow C5, which mixes with the high-temperature mainstream C6 on the outside of the film perforated plate (1), reducing the gas temperature near the wall and forming a film covering layer on the outer wall of the film perforated plate (1), blocking the direct scouring of the gas.

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