Thermal shield and film forming method for a thrust chamber based on a roof truss structure

Abstract

The application relates to a force-added combustion chamber heat shield based on a roof truss type truss structure, which comprises a film hole plate with matrix-arranged film holes on the plate surface and an impingement hole plate with matrix-arranged impingement holes on the plate surface; a roof truss type truss is arranged in the cavity between the film hole plate and the impingement hole plate; the film hole plate, the impingement hole plate and the roof truss type truss constitute the heat shield; meanwhile, a film forming method with the heat shield of the roof truss type truss is provided; the structure and the method provided by the application strengthen internal heat exchange and improve film cooling effect, that is, the internal heat exchange and the external film cooling effect of the heat shield and the coupling working effect of the two are simultaneously improved, and the structure has good mechanical properties.

Description

Technical Field

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

[0002] During startup, climb, and emergency maneuvers, aircraft engines require additional thrust through re-ignition combustion in the afterburner. 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 existing high-temperature resistant 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 film cooling and impingement cooling methods, CN103968418A discloses a double-walled heat shield for afterburners. This structure includes a wall surface with film cooling holes near the combustion gas side, a wall surface with impingement holes near the cold gas side, and a trapezoidal reinforcing frame between the film cooling plate and the impingement plate. This forms a composite cooling system combining impingement cooling on the cold gas side, internal convection heat transfer, and film cooling covering 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, which inevitably leads to a continuous increase in the amount of cooling air required. The large amount of compressed high-pressure gas extracted for cooling purposes will inevitably have an adverse effect on the overall engine performance. Therefore, it is necessary to develop heat shield structures with high-efficiency cooling capabilities, that is, to achieve better cooling effects 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 for a stressed combustion chamber and a method for forming an air film based on a roof truss structure.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a heat insulation screen for a combustion chamber based on a roof truss structure, comprising a perforated plate with a matrix arrangement of perforated air film holes on its surface and a perforated plate with a matrix arrangement of perforated impact holes on its surface; a roof truss is provided in the cavity between the perforated air film plate and the perforated impact plate, and the perforated air film plate, the perforated impact plate and the roof truss constitute the heat insulation screen; The roof truss includes multiple matrix-arranged normal flow-around supports, with both ends of the normal flow-around supports fixed to the air film perforated plate and the impact perforated plate in a lattice configuration; it also includes inclined turbulence columns, with one end of at least two inclined turbulence columns connected to the end of the normal flow-around support on one side of the impact perforated plate, and the other end of the inclined turbulence columns connected to the air film perforated plate to form a connection point. A unit formed by the axial and circumferential spacing of the normal flow-around support pillars in the cavity is a matrix unit, and the air film holes and impact holes are alternately arranged on the air film or impact hole plates of the continuous matrix units. The air film hole is a hole arranged around the connection point. It is a discontinuous annular hole composed of at least two fan-ring holes and a fan-ring partition for connecting the two fan-ring holes. The inner diameter of the discontinuous annular hole is the same as the diameter of the connection point, and the center point of the discontinuous annular hole coincides with the center point of the connection point.

[0008] Furthermore, the matrix arrangement of the multiple normal flow-around supports is specifically as follows: with S x S represents the axial spacing of the normal flow-around supports. z Let H be the circumferential spacing of the normal flow-around supports, H be the distance between the film gas orifice plate and the impact orifice plate, D' be the diameter of the normal flow-around supports, and d' be the diameter of the circular hole with the same area as the fan ring hole. Then: H≥S x ≥2D'、H≥S z ≥2D'; π·(d' / 2) 2 / S x ×S z =0.4~4%; Multiple normal flow-around supports based on S x and S z The resulting matrix units are arranged axially and circumferentially between the air film orifice plate and the impact orifice plate.

[0009] Furthermore, in the S x and S z Within the formed matrix unit, there are at least four normal flow-around pillars, and the enclosed space is a rectangular or square space; The four normal flow-around pillars and the eight inclined flow-disrupting pillars together constitute a heat exchange unit, and at least two fan-shaped holes in the air film holes of each inclined flow-disrupting pillar are arranged in the heat exchange unit.

[0010] 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-ring hole. Therefore, B < 0.5D; the air film holes include 2 to 6 fan-ring holes.

[0011] Furthermore, the fan-shaped hole is a normal through hole or a normal backward expansion hole of the air film perforated plate; Furthermore, when the air film orifice plate has a normal through hole, the cross-section of the air film orifice is correspondingly set with a pair of inclination angles α1=α2=90°. When the air film orifice plate is a normal backward expansion orifice, the sum of a pair of inclination angles corresponding to the cross section of the air film orifice is 90 degrees, and: 45°≤α1≤90°, 45°≤α2≤90°.

[0012] Furthermore, the fan-shaped partition 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.

[0013] Furthermore, the impact hole is a normal through hole of the impact hole plate; the diameter of the impact hole is 0.7~1.5mm; the opening area of ​​the air film hole is 1~3 times the opening area of ​​the impact hole.

[0014] Furthermore, given that the diameter of the normal flow-around support column of the supporting truss is D', the diameter of the circular hole with equal area of ​​the fan-shaped annulus hole is d', and the distance between the air film orifice plate and the impact orifice plate is H, then: D' / d' = 0.5~2; H / d' = 0.1~20.

[0015] Furthermore, the present invention also provides a method for forming an air film in a stressed combustion chamber heat shield based on a roof truss structure, comprising the following steps: The cooling airflow in the cold air bypass duct is injected perpendicularly to the impact target surface along the axis of the impact hole, forming an impact jet A1. The impact jet A1 stops upon impacting the target surface and then turns 90° to form a wall-attached jet A6. The wall-attached jet A6 accelerates and then decelerates along the direction away from the stagnation point, forming a local high heat transfer zone near the impact stagnation point. After a portion of the wall-attached jet A6 collides with the normal flow support, it spreads upward along the surface of the support and then detaches from the surface of the normal flow support to form a rotating vortex. A pair of primary counter-rotating vortices A2 are formed between adjacent impact jets A1. A pair of secondary counter-rotating vortices opposite to the primary counter-rotating vortices A2 are formed below the inclined turbulence column near the target surface. A portion of the wall-attached jet A6 develops into a spiral airflow A3 towards the film cooling hole and collides with the inclined baffle column for heat exchange. The airflow A4 below the inclined baffle column near the film cooling hole is compressed by the inclined baffle column and undergoes high-intensity heat exchange with the target surface while merging into the film cooling hole along the direction of the inclined baffle column, thus reducing the area of ​​the low heat exchange zone and simultaneously improving the film cooling efficiency and the surface heat exchange of the target surface. Another portion of the wall-attached jet A6 is directly drawn into the film cooling hole along the straight direction from the impact hole to the film cooling hole. After the airflow A5 near the film gas orifice undergoes enhanced heat exchange through the turbulence of the normal flow support and the inclined turbulence column, the cold air A7 flows out through the discontinuous annular orifice, reducing the gas temperature near the wall and forming a cold air covering film on the outer wall of the film gas orifice plate, blocking the transfer of gas heat to the heat insulation screen cylinder. Due to the increased spanwise coverage area of ​​the film gas of the discontinuous annular orifice and the flow resistance of the turbulence structure itself, the normal momentum of the outflow from the film gas orifice is weakened, and the adhesion of the film gas to the wall is improved, thus significantly improving the cooling efficiency of the film gas on the surface of the heat insulation screen.

[0016] The beneficial effects of this invention are as follows: The beam-shaped truss structure proposed in this invention, as an internal cooling structure, can adjust its structural parameters to meet the optimal arrangement of impact cooling and film cooling. Furthermore, it enhances convective heat transfer with lower flow resistance. The spanwise coverage area of ​​the film cooling system through the four 1 / 4 discontinuous annular holes is increased, and the film's adhesion to the wall is improved, significantly enhancing the film cooling efficiency, effectively reducing wall temperature, and increasing the utilization rate of cooled air. Simultaneously, the roof-truss structure provided by this invention has the advantage that, without interfering with the impact stagnation point and the wall-adhering jet, the inclined columns enhance the heat transfer of the spiral airflow and compress the gas below the inclined columns to enhance heat transfer with the target surface, reducing the area of ​​the low heat transfer zone. This achieves a simultaneous improvement in film cooling efficiency and target surface convective heat transfer, thereby enhancing the overall cooling efficiency of the heat shield structure. In other words, it improves the internal heat transfer and external film cooling effects of the heat shield, as well as the coupling effect of the two. In addition, the fixed impact perforated plate-film perforated plate double-wall structure of the beam-shaped truss array structure has good mechanical properties. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the heat exchange unit of the present invention; Figure 3 This is a schematic diagram of the projected structure of the heat exchange unit of the present invention; Figure 4 This is a schematic cross-sectional view of the air film pore structure of the present invention; Figure 5 This is a top view schematic diagram of the air film pore structure of the present invention; Figure 6 This is a schematic diagram of the three-dimensional cooling flow lines inside the heat insulation screen of the present invention; Figure 7 This is a schematic diagram of the heat flow and streamline distribution on the impact target surface of the heat insulation screen of the present invention; Figure 8 This is a schematic diagram showing the Nusselt number distribution of the impact target surface compared to a heat insulation screen with a cylindrical turbulence layer, according to the present invention. Figure (a) shows the Nusselt number distribution on the impact target surface of a heat shield with a cylindrical turbulence layer. Figure (b) is a schematic diagram of the Nusselt number distribution on the impact target surface of the heat exchange unit of the present invention; Figure 9 This is a schematic diagram showing the air film cooling efficiency of the present invention compared to a heat insulation screen with a cylindrical turbulence layer. Figure (a) is a schematic diagram of the cooling efficiency of the heat-insulating shielding film with a cylindrical turbulence layer. Figure (b) is a schematic diagram of the air film cooling efficiency of the heat exchange unit of the present invention; Figure 10 This is a comparison diagram of the spanwise average cooling effect of the heat insulation screen of the present invention and the heat insulation screen with a cylindrical turbulence layer. Detailed Implementation

[0018] 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.

[0019] To achieve the above objectives, the present invention provides the following specific embodiments: Example 1: As Figure 1-5 and Figure 7-10As shown, a heat shield for an afterburner based on a roof truss structure includes a film perforated plate 1 with film perforations 5 arranged in a matrix on its surface and an impact perforated plate 2 with impact holes 6 arranged in a matrix on its surface; a roof truss 3 is provided in the cavity between the film perforated plate 1 and the impact perforated plate 2. The film perforated plate 1, the impact perforated plate 2 and the roof truss 3 form a heat shield. The impact perforated plate 2 forms a cold air duct with the outer wall of the afterburner, and the film perforated plate 1 is the inner wall of the afterburner cylinder, which is in direct contact with the mainstream combustion gas. The impact perforated plate and the film perforated plate form a convective heat exchange channel. The roof truss 3 includes multiple matrix-arranged normal flow-around supports 31, with both ends of the normal flow-around supports 31 fixed to the film perforated plate 1 and the impact perforated plate 2 in a lattice configuration; it also includes inclined turbulence columns 32, with one end of at least two inclined turbulence columns 32 connected to the end of the normal flow-around supports 31 on one side of the impact perforated plate 2, and the other end of the inclined turbulence columns 32 connected to the film perforated plate 1 to form a connection point 4; A matrix unit is formed by the axial and circumferential spacing of the normal flow-around support column 31 in the cavity. Then, the air film hole 5 and the impact hole 6 are alternately arranged on the air film hole plate 1 or the impact hole plate 2 of the continuous matrix unit. The matrix arrangement of multiple normal flow-around supports 31 is specifically as follows: with S x S represents the axial spacing of the normal flow-around supports 31. z Let H be the circumferential spacing of the normal flow-around support columns 31, H be the distance between the film gas orifice plate 1 and the impact orifice plate 2, D' be the diameter of the normal flow-around support columns 31, and d' be the diameter of the circular hole with the same area as the fan ring hole. Then we have: H≥S x ≥2D'、H≥S z ≥2D'; π·(d' / 2) 2 / S x ×S z =0.4~4%; Multiple normal flow-around supports 31 according to S x and S z The resulting matrix units are arranged axially and circumferentially between the air film orifice plate 1 and the impact orifice plate 2.

[0020] In S x and S z Within the formed matrix unit, there are at least four normal flow-around pillars 31, and the enclosed space is a rectangular or square space; like Figure 2 As shown, four normal flow-around pillars 31 and eight inclined flow-disrupting pillars 32 together constitute a heat exchange unit, and each inclined flow-disrupting pillar 32 corresponds to at least two fan-shaped holes in the air film hole 2 and is arranged in the heat exchange unit.

[0021] The air film hole 5 is a hole set around the connection point 4. It is a discontinuous annular hole composed of at least two fan-ring holes and a fan-ring partition for connecting the two fan-ring holes. The inner diameter of the discontinuous annular hole is the same as the diameter of the connection point 4, and the center point of the discontinuous annular hole coincides with the center point of the connection point 4.

[0022] like Figure 4 As shown, the diameter of the inner ring formed by the air film orifice 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-shaped annular hole. Therefore, B < 0.5D. The air film orifice 5 includes 2 to 6 fan-shaped annular holes. The fan-shaped annular holes are normal through holes or normal backward expansion holes of the air film orifice plate 1. Furthermore, when the air film orifice plate 1 has a normal through hole, the cross section of the air film orifice 2 is correspondingly provided with a pair of inclination angles α1=α2=90°; When the air film orifice plate 1 is a normal backward expansion orifice, the sum of the two inclination angles corresponding to the cross section of the air film orifice 2 is 90 degrees, and: 45°≤α1≤90°, 45°≤α2≤90°.

[0023] like Figure 5 As shown, the fan-shaped partition 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 the side is inclined, the central angle corresponding to the inclined side is θ, and the range of θ is 10~30 degrees.

[0024] Impact hole 6 is a normal through hole of impact hole plate 2; the diameter of impact hole 6 is 0.7~1.5mm; the opening area of ​​air film hole 5 is 1~3 times the opening area of ​​impact hole 6.

[0025] The diameter of the normal flow support 31 of the roof truss 3 is D', the diameter of the circular hole with the same area as the fan ring hole is d', and the distance between the air film orifice plate 1 and the impact orifice plate 2 is H. Then: D' / d' = 0.5~2; H / d' = 0.1~20.

[0026] See Figures 1-3 This embodiment is a double-walled heat shield for an afterburner, including a film perforated plate 1, an impact perforated plate 2, and a roof truss 3. The film perforated plate 1 on the gas side forms the inner wall of the afterburner cylinder, with the main high-temperature gas flow of the afterburner on the inner side. The impact perforated plate 2 on the cold gas side has secondary cold gas flow on the outer side. The roof truss 3 is provided between the impact perforated plate 2 and the film perforated plate 1, together forming a double-walled heat shield. like Figure 3As shown, in the heat exchange unit, a normal flow support 31 is arranged at the center of the projection position of two adjacent air film holes 5. An inclined turbulence column 32 is formed by extending from the vertex where the normal flow support 31 connects with the impact plate 2 towards the air film hole 5. The normal flow support 31 and the connected inclined turbulence column 32 together constitute a roof truss 3. The air film holes 5 are distributed around the bottom circular cross section of the inclined turbulence column 32.

[0027] As the truss angle changes, the truss length changes, the thermal conductivity changes, and the flow resistance to the fluid also changes; the increase or decrease in diameter affects the solids ratio and the change in the contact area with the fluid, and the diameter affects the changes in flow resistance and heat transfer performance.

[0028] Figure 7 The heat flow and streamline distribution of the double-walled impact target surface of the beam-shaped truss sandwich structure are shown. As can be seen from the figure, after the wall-attached jet of the beam-shaped plate collides with the straight column at the center of the adjacent impact hole, it merges into the spiral flow and moves towards the air film hole 5. A secondary high heat flow zone appears below the inclined column near the air film hole.

[0029] Figure 8 The Nusselt number cloud maps of the impact target surface and the turbulence structure surface of the heat shield unit with the existing cylindrical turbulence layer and the heat shield unit of the present invention were compared. Compared with the heat shield with cylindrical turbulence layer, the heat shield of the present invention has a larger impact stagnation point area and a larger high heat transfer area of ​​the wall jet, the wall jet is not disturbed, and the low heat transfer area on the impact target surface is distributed on both sides of the inclined turbulence column in a cross shape. As for the turbulence surface, the heat shield with cylindrical turbulence layer has a heat transfer maximum value on the turbulence column at the center of the impact hole and the air film hole, while the turbulence surface of the heat shield of the present invention does not have a heat transfer maximum value, but the area of ​​the second highest heat transfer area is larger.

[0030] Experimental Example: Based on the same air film plate opening ratio and consistent flow parameters (momentum ratio I = 0.08), and with identical structural parameters for each model, the cooling efficiency of the cylindrical turbulence structure and cylindrical air film holes in the heat insulation screen of the traditional cylindrical turbulence layer was compared with that of the roof truss 3 and annular air film holes 5 provided by this invention. The cooling efficiency cloud diagram is shown below. Figure 9 As shown, the spanwise average film cooling effect is compared to... Figure 10 As shown.

[0031] Figure 9 Compared with the cylindrical turbulence structure, the spanwise gas film coverage area of ​​each exhaust film hole 5 of the heat exchange unit of the present invention is increased, and under the superposition effect, the difference between the exhaust flow of each hole to the gas film coverage area is not obvious. In addition, the high cooling efficiency zone of the discontinuous annular hole of the present invention is more discrete, and part of the gas film acts on the solid domain in the center of the annular hole, which effectively reduces the area of ​​the local low cooling efficiency zone.

[0032] Figure 10In each flow direction, the air film cooling efficiency of the cylindrical turbulence structure is less than that of the roof truss 3, and the average air film cooling efficiency of the heat exchange unit of the present invention is increased by 6.4%.

[0033] Example 2: Figure 6 As shown, the present invention also provides a method for forming a film of gas in an afterburner heat shield based on a roof truss structure, comprising the following steps: the cooling airflow in the cold air bypass duct is injected perpendicularly to the impact target surface along the axis of the impact hole 6 to form an impact jet A1. The impact jet A1 impacts the target surface and stops, and then turns 90° to form a wall-attached jet A6. The wall-attached jet A6 accelerates and then decelerates along the direction away from the stagnation point to form a local high heat transfer zone near the impact stagnation point. After a portion of the wall-attached jet A6 collides with the normal flow support 31, it spreads upward along the surface of the column and then detaches from the surface of the normal flow support 31 to form a rotating vortex. A pair of main counter-rotating vortices A2 are formed between adjacent impact jets A1. A pair of secondary counter-rotating vortices opposite to the main counter-rotating vortices A2 are formed below the inclined turbulence column 32 near the target surface. A portion of the wall-attached jet A6 develops into a spiral airflow A3 towards the film cooling hole and collides with the inclined baffle column 32 for heat exchange. The airflow A4 below the inclined baffle column 32 near the film cooling hole 5 is compressed by the inclined baffle column 32 and undergoes high-intensity heat exchange with the target surface while flowing into the film cooling hole 5 along the direction of the inclined baffle column 32, reducing the area of ​​the low heat exchange zone and simultaneously improving the film cooling efficiency and the surface heat exchange of the target surface. Another portion of the wall-attached jet A6 is directly drawn into the film cooling hole 5 along the straight direction from the impact hole 6 to the film cooling hole 5. After the airflow A5 near the air film hole 5 undergoes enhanced heat exchange through the turbulence of the normal flow support 31 and the inclined turbulence column 32, the cold air A7 flows out through the discontinuous annular hole, reducing the gas temperature near the wall and forming a cold air covering film on the outer wall of the air film perforated plate 1, blocking the transfer of gas heat to the heat insulation screen cylinder. Due to the increased spanwise coverage area of ​​the air film of the discontinuous annular hole and the flow resistance of the turbulence structure itself, the normal momentum of the air film outflow is weakened, and the adhesion of the air film to the wall is improved, thus significantly improving the air film cooling efficiency on the surface of the heat insulation screen.

[0034] 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 a stressed combustion chamber based on a roof truss structure, characterized in that, It includes an air-film perforated plate (1) with air-film holes (5) arranged in a matrix on the plate surface and an impact perforated plate (2) with impact holes (6) arranged in a matrix on the plate surface; a roof truss (3) is provided in the cavity between the air-film perforated plate (1) and the impact perforated plate (2), and the air-film perforated plate (1), the impact perforated plate (2) and the roof truss (3) constitute the heat insulation screen; The roof truss (3) includes multiple matrix-arranged normal flow support columns (31), the two ends of which are fixed to the air film perforated plate (1) and the impact perforated plate (2) in a dot matrix form; it also includes inclined turbulence columns (32), one end of at least two inclined turbulence columns (32) is connected to the end of the normal flow support column (31) on one side of the impact perforated plate (2), and the other end of the inclined turbulence columns (32) is connected to the air film perforated plate (1) and forms a connection point (4). A matrix unit is formed by the axial and circumferential spacing of the normal flow support (31) in the cavity. Then, the air film holes (5) and impact holes (6) are alternately arranged on the air film orifice plate (1) or impact orifice plate (2) of the continuous matrix unit. The air film hole (5) is a hole set around the connection point (4). It is a discontinuous annular hole composed of at least two fan ring holes and a fan ring partition for connecting the two fan ring holes. The inner diameter of the discontinuous annular hole is the same as the diameter of the connection point (4), and the center point of the discontinuous annular hole coincides with the center point of the connection point (4).

2. The afterburner heat insulation screen based on a roof truss structure as described in claim 1, characterized in that, The matrix arrangement of the multiple normal flow-around supports (31) is specifically as follows: with S x S is the axial spacing of the normal flow-around support (31). z Let H be the circumferential spacing of the normal flow support (31), H be the distance between the film gas orifice plate (1) and the impact orifice plate (2), D' be the diameter of the normal flow support (31), and d' be the diameter of the circular hole with the same area as the fan ring hole. Then we have: H≥S x ≥2D’、H≥S z ≥2D’; π·(d' / 2) 2 / S x ×S z =0.4~4%; Multiple normal flow-around supports (31) according to S x and S z The resulting matrix units are arranged axially and circumferentially between the air film orifice plate (1) and the impact orifice plate (2).

3. The heat insulation screen for the stressed combustion chamber based on a roof truss structure as described in claim 2, characterized in that, In the S x and S z Within the formed matrix unit, there are at least four normal flow-around pillars (31), and the enclosed space is a rectangular or square space; The four normal flow-around pillars (31) and the eight inclined flow-disrupting pillars (32) together constitute a heat exchange unit, and each inclined flow-disrupting pillar (32) has at least two fan-shaped holes in the air film hole (5) arranged in the heat exchange unit.

4. The afterburner heat insulation screen based on a roof truss structure as described in claim 1, characterized in that, The inner ring of the air film hole (5) has a diameter of d, the outer ring has a diameter of D, and the distance between the outer ring and the inner ring is the width B of the fan ring hole. Therefore, B < 0.5D. The air film hole (5) includes 2 to 6 fan ring holes.

5. The afterburner heat insulation screen based on a roof truss structure as described in claim 1, characterized in that, The fan-shaped hole is a normal through hole or a normal backward expansion hole of the air film perforated plate (1); Furthermore, when the normal through hole of the air film perforated plate (1) is in the cross section of the air film hole (5), a pair of inclination angles α1=α2=90° are set accordingly. When the air film perforated plate (1) is a normal backward expansion hole, the sum of a pair of inclination angles corresponding to the cross section of the air film hole (5) is 90 degrees, and: 45°≤α1≤90°, 45°≤α2≤90°.

6. The afterburner heat insulation screen based on a roof truss structure as described in claim 1, characterized in that, The fan-shaped partition 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.

7. The afterburner heat insulation screen based on a roof truss structure 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 1~3 times the opening area of ​​the impact hole (6).

8. The afterburner heat insulation screen based on a roof truss structure as described in claim 1, characterized in that, The diameter of the normal flow support (31) of the roof truss (3) is D', the diameter of the circular hole with the same area as the fan ring hole is d', and the distance between the air film perforated plate (1) and the impact perforated plate (2) is H. Then: D' / d' = 0.5~2; H / d' = 0.1~20.

9. The method for forming an air film in a stressed combustion chamber heat shield based on a roof truss structure as described in claim 1, characterized in that, Includes the following steps: The cooling airflow in the cold air bypass is injected perpendicularly to the impact target surface along the axis of the impact hole (6) to form an impact jet A1. The impact jet A1 stops when it hits the target surface, and then turns 90° to form a wall-attached jet A6. The wall-attached jet A6 accelerates and then decelerates along the direction away from the stagnation point to form a local high heat transfer zone near the impact stagnation point. After a portion of the wall-attached jet A6 collides with the normal flow support (31), it spreads upward along the surface of the column and then separates from the surface of the normal flow support (31) to form a rotating vortex. A pair of main counter-rotating vortices A2 are formed between adjacent impact jets A1. A pair of secondary counter-rotating vortices opposite to the main counter-rotating vortices A2 are formed below the inclined turbulence column (32) near the target surface. A portion of the wall-attached jet A6 develops into a spiral airflow A3 towards the film film hole and collides with the inclined baffle column (32) for heat exchange. The airflow A4 below the inclined baffle column (32) near the film film hole (5) is compressed by the inclined baffle column (32) and undergoes high-intensity heat exchange with the target surface while flowing into the film film hole (5) along the direction of the inclined baffle column (32), reducing the area of ​​the low heat exchange zone and achieving simultaneous improvement of film cooling efficiency and surface heat exchange with the target surface. Another portion of the wall-attached jet A6 is directly drawn into the film film hole (5) along the straight direction from the impact hole (6) to the film film hole (5). After the airflow A5 near the air film hole (5) is turbulent and heat-exchanged by the normal flow support (31) and the inclined turbulence column (32), the cold air A7 flows out through the discontinuous annular hole, which reduces the gas temperature near the wall and forms a cold air covering film on the outer wall of the air film perforated plate (1), blocking the transfer of gas heat to the heat insulation screen cylinder. Due to the increased longitudinal coverage area of ​​the air film of the discontinuous annular hole and the flow resistance of the turbulence structure itself, the normal momentum of the air film outflow is weakened, and the adhesion of the air film to the wall is improved, thus significantly improving the air film cooling effect on the surface of the heat insulation screen.

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