Design method of heat shield for aviation aircraft wheel

Abstract

The invention discloses a design method of a heat shield for an aviation airplane wheel, and belongs to the technical field of civil aviation brake airplane wheels. The heat insulation screen is of a three-layer composite structure and sequentially comprises a hot end metal force bearing layer, a middle nanometer aerogel heat insulation layer and a cold end metal packaging layer from the hot end to the cold end. The design method comprises the following design steps: designing a bionic vein flow channel structure in the middle nano aerogel heat insulation layer; designing a micropore array and a locking lug on the hot end metal layer; and a radial heat-conducting rib array is designed on the cold-end metal packaging layer. And a vacuum sealing cavity is formed through high-temperature brazing. And performing quantitative calculation based on the geometric parameters of the hub. According to the invention, the cold end temperature is reduced by more than 50%, the weight is reduced by 32.9%, the thermal fatigue life is prolonged by 2.5 times, and the method is suitable for various aviation aircraft wheels with high braking energy.

Description

Technical Field

[0001] This invention belongs to the field of civil aviation brake wheel technology, specifically relating to a design method for a heat shield for aircraft wheels. Background Technology

[0002] Modern civil aircraft, especially large transport and passenger aircraft, primarily employ multi-disc carbon braking systems for efficient braking. During landing, takeoff aborts, or taxiing, kinetic energy is converted into heat through friction between the brake discs. This process causes the brake disc assembly temperature to rise rapidly, generating a large amount of heat, with brake disc temperatures reaching over 1000°C. To protect the wheel hubs and tires from high-temperature heat damage, aircraft wheel assemblies typically incorporate heat shields located between the brake discs and the hubs. These shields reflect heat radiation, block heat convection, and slow heat conduction, keeping the hub area operating temperature below a safe threshold (usually no higher than 200°C) to prevent tire fires, hub overheating leading to tire blowouts, and other safety incidents. Simultaneously, the heat shields guide cooling airflow through the braking system, assisting in rapid heat dissipation during flight intervals and preparing for the next landing.

[0003] For a long time, aviation heat shields have mainly adopted single-layer metal structures (such as stainless steel and titanium alloy plates) or multi-layer metal reflective screens. However, with the continuous increase in aircraft braking energy density, traditional metal heat shields have gradually revealed the following technical limitations: 1. Bottleneck in thermal insulation performance: Metallic materials have high thermal conductivity (titanium alloy approximately 7 W / (m·K), stainless steel approximately 15 W / (m·K)), at 1.5 MW / m 2 Under the above peak heat flux, the cold end temperature of a single-layer metal screen generally exceeds 220℃, with a temperature difference fluctuation of more than ±18℃, which is difficult to meet the safe temperature requirements of the wheel hub; although multi-layer metal reflective screens can improve the heat insulation effect through air layers, their performance improvement space is limited by structural thickness and weight constraints.

[0004] 2. Risk of thermal stress damage: The drastic and rapid temperature change of the brake disc (from -55℃ to above 1000℃) causes the heat shield to be subjected to periodic thermal shocks. The interfacial stress generated by the thermal expansion of the metal material is prone to thermal fatigue cracks. The thermal fatigue life of traditional heat shields is generally less than 1500 cycles, and the thermal insulation efficiency decay rate exceeds 25%, affecting the reliability of service.

[0005] In summary, existing civil aviation thermal insulation technology is insufficient to meet the comprehensive requirements of "high-efficiency thermal insulation, lightweight, long lifespan, and high reliability." There is an urgent need for a new thermal insulation design method that can fully leverage the thermal insulation advantages of aerogel while overcoming its application bottlenecks. Summary of the Invention

[0006] The technical problem to be solved: To avoid the shortcomings of existing technologies, this invention provides a design method for a heat shield for aircraft wheels. Through the collaborative design of a metal-aerogel-metal three-layer composite structure, biomimetic leaf vein flow channel, microporous array and heat-conducting ribs, and the establishment of a quantitative parameter calculation method based on wheel hub geometry, the comprehensive performance of the heat shield under extreme working conditions is achieved.

[0007] The technical solution of the present invention is: a design method for a heat shield for aircraft wheels, wherein the heat shield is installed between the brake disc assembly and the wheel hub, comprising the following steps: A three-layer composite structure is constructed, which consists of a hot-end metal load-bearing layer, a middle nano-aerogel heat insulation layer, and a cold-end metal encapsulation layer. A biomimetic leaf vein flow channel structure is designed in the middle nano-aerogel insulation layer. The biomimetic leaf vein flow channel structure includes a primary main vein arranged circumferentially along the insulation screen, and secondary branch veins that are radially connected to the primary main vein. A micropore array and locking lugs are designed on the hot-end metal load-bearing layer. The micropore array is used to release thermal stress and promote convective heat transfer, and the locking lugs are used to fix it to the wheel hub. A radial heat-conducting rib array is designed on the cold-end metal encapsulation layer, and the heat-conducting ribs are embedded in the middle nano-aerogel insulation layer to disperse heat radially. Determine the thickness matching and connection process of the three-layer composite structure to achieve the desired total thickness. d The thickness is controlled between 1.6mm and 3.2mm, and the hot-end metal load-bearing layer and the cold-end metal encapsulation layer are vacuum-sealed at the circumferential edge by high-temperature brazing or diffusion welding to form a vacuum-sealed cavity that encapsulates the middle nano-aerogel insulation layer. Quantitative design of key dimensions of the heat insulation screen based on hub geometry parameters, wherein the key dimensions include at least the axial reference length of the heat insulation screen. L Axial length of hot-end metal load-bearing layer L hot Axial length of cold end metal packaging layer L cold And the single-layer thickness of the hot-end metal load-bearing layer or the cold-end metal encapsulation layer. t ; Establish thermal-mechanical coupling design criteria and performance verification thresholds for thermal insulation screens. The thermal-mechanical coupling design criteria shall include at least a peak heat flux of not less than 1.5 MW / m². 2 The maximum temperature of the cold end should not exceed 200℃, and the temperature rise rate should be less than 50℃ / s. A further technical solution of the present invention is: the axial reference length of the heat insulation screen L Determined by the following formula:

[0008] Where h is the geometric depth of the hub, in mm; This is a reference area for the effective heat transfer zone of the wheel hub, in mm. 2 .

[0009] A further technical solution of the present invention is: the axial length of the hot-end metal load-bearing layer L hot Equal to the axial reference length of the heat insulation screen L ; Axial length of the cold-end metal encapsulation layer L cold Determined by the following formula:

[0010] in, This is the indentation amount, ranging from 6mm to 8mm.

[0011] A further technical solution of the present invention is: the single-layer thickness of the hot-end metal load-bearing layer or the cold-end metal encapsulation layer. t， Simply put, it refers to the thickness of a single metal layer. t The selection rules are as follows:

[0012] Where P is the area-to-hole ratio of the hub, which is the ratio of the total area of ​​the hub surface relief holes to the apparent area of ​​the hub; h is the geometric depth of the hub. A further technical solution of the present invention is: the thickness of the intermediate nano-aerogel insulation layer d aero Based on total thickness d and the thickness of a single metal layer t Sure: d aero = d -2 t and satisfy d aero Within the range of 1.0mm to 2.0mm, and d aero >2 t . A further technical solution of the present invention is: in the biomimetic leaf vein flow channel structure, the cross-section of the primary main vein flow channel is rectangular, with a width of 0.5mm to 2.0mm and a depth of 60% to 80% of the thickness of the intermediate nano-aerogel insulation layer; the width of the secondary branch vein flow channel is 0.2mm to 0.8mm.

[0013] A further technical solution of the present invention is: the dimensional parameters of the biomimetic leaf vein flow channel structure are based on the axial reference length. L Dynamic matching: When the axial reference length of the heat insulation screen LWhen the width is >200mm, the width of the primary main vein should be 1.5mm to 2.0mm, and the density of secondary branch veins should be increased by 30% accordingly; when d aero When the thickness is ≥1.5mm, the depth of the secondary branch channel should be 70% to 80% of the thickness of the intermediate nano-aerogel insulation layer.

[0014] A further technical solution of the present invention is: the diameter of the micropores in the micropore array is 50μm to 200μm, and the porosity is controlled at 10% to 25%; and the micropore parameters are based on the thickness of a single metal layer. t Match: When t When the diameter is 0.3 mm, the micropore diameter is taken as 80 μm to 120 μm, and the porosity is taken as 18% to 22%; when t When the diameter is 0.6 mm, the micropore diameter is taken as 150 μm to 200 μm, and the porosity is taken as 22% to 25%.

[0015] A further technical solution of the present invention is: the width of a single heat-conducting rib in the radial heat-conducting rib array is 1mm to 3mm, and the height of a single heat-conducting rib is consistent with the thickness of the intermediate nano-aerogel insulation layer; and the size of the heat-conducting rib is based on the axial length of the cold-end metal encapsulation layer. L cold and the thickness of the intermediate nano-aerogel insulation layer d aero Compatible with: When L cold When the diameter is <100mm, the width of a single heat-conducting fin should be 2mm to 3mm; when d aero When the thickness is greater than 1.5mm, the rib height is increased simultaneously to match the thickness of the intermediate nano-aerogel insulation layer.

[0016] A heat shield for aircraft wheels, installed between the brake disc assembly and the wheel hub, includes: A hot-end metal bearing layer is positioned facing the heat source of the brake disc. The hot-end metal bearing layer is provided with a micropore array and a locking lug. The micropore array has a micropore diameter of 50μm to 200μm and a porosity of 10% to 25%. The locking lug is used to fix it to the wheel hub. The intermediate nano-aerogel insulation layer is stacked on the side of the hot-end metal load-bearing layer away from the brake disc. It has a biomimetic leaf vein flow channel structure. The biomimetic leaf vein flow channel structure includes a primary main vein arranged around the circumference of the insulation screen and secondary branch veins connected to it. The cross-section of the primary main vein flow channel is rectangular, with a width of 0.5mm to 2.0mm and a depth of 60% to 80% of the thickness of the intermediate nano-aerogel insulation layer. The width of the secondary branch vein flow channel is 0.2mm to 0.8mm. The cold end metal encapsulation layer is stacked on the side of the middle nano-aerogel insulation layer away from the hot end metal load-bearing layer and facing the hub. A radial heat-conducting rib array is provided on it. The radial heat-conducting rib array is embedded in the middle nano-aerogel insulation layer. The width of a single heat-conducting rib is 1mm to 3mm, and the height of a single heat-conducting rib is the same as the thickness of the middle nano-aerogel insulation layer. The total thickness of the heat insulation screen d The thickness ranges from 1.6mm to 3.2mm, where the thickness of the hot-end metal load-bearing layer is... d hot The thickness of the intermediate nano-aerogel insulation layer is 0.3mm to 0.6mm. d aero The thickness of the cold-end metal encapsulation layer is 1.0mm to 2.0mm. d cold It is 0.3mm to 0.6mm, and d aero >2 d hot ; The hot-end metal load-bearing layer and the cold-end metal encapsulation layer are sealed and welded at the circumferential edge to form a vacuum-sealed cavity that encloses the intermediate nano-aerogel insulation layer.

[0017] Beneficial effects The beneficial effects of this invention are as follows: 1. Leapfrog Thermal Insulation Configuration: The "metal-aerogel-metal" composite configuration combines the strength of metal with the excellent thermal insulation of aerogel, achieving a leapfrog improvement in thermal insulation performance. Traditional metal thermal insulation screens have a maximum cold end temperature exceeding 220℃ under a heat flux of 1.5MW / m², with temperature fluctuations of over ±18℃. This invention utilizes nano-aerogel (thermal conductivity ≤0.018W / (m·K)) in conjunction with flow channels and micropores for synergistic heat dissipation, achieving a cold end temperature of only 156℃, a temperature reduction of over 30%, and a temperature difference reduced to ±3℃, effectively avoiding local overheating problems.

[0018] 2. Active Thermal Management: The biomimetic leaf vein flow channel achieves active thermal management through heat absorption, heat storage, and heat equalization. The flow channel design optimizes the heat flow path. Traditional metal screens lack active heat dissipation and moisture absorption protection, and the aerogel's single structure is mechanically weak with a water absorption rate exceeding 18%. This invention's vacuum encapsulation reduces the water absorption rate to 0.6%, constructing an integrated system of "heat insulation-heat equalization-heat dissipation," reducing the thermal response speed from 60s to 22s, achieving a leap from "passive heat insulation" to "active thermal management."

[0019] 3. Lightweight Design: Traditional metal heat shields with a diameter of 300mm weigh over 380g and have an impact resistance of ≤2.5J / cm², making them prone to deformation and cracking. This invention utilizes the lightweight properties of aerogel (density 1 / 10 that of metal), reducing the weight to 255g, a reduction of 32.9%. The rigid metal frame increases the impact resistance to 4.2J / cm², meeting the impact load requirements during high-speed rotation of aircraft wheels and aircraft landing.

[0020] 4. Excellent thermal stress release: The microporous array design at the hot end effectively releases braking thermal stress, extending the service life of the heat insulation screen. Traditional metal screens have a thermal fatigue life of ≤1500 cycles and a thermal insulation efficiency decay rate of over 25%; this invention absorbs 68% of the interfacial thermal stress through the microporous array, combined with vacuum sealing technology, extending the service life to 5200 cycles, with the decay rate controlled at 2.8%.

[0021] 5. Design-oriented precision and adaptability: Through quantitative calculations, the main dimensions of the heat insulation screen are directly linked to the objective parameters of the wheel hub, realizing a shift from experience-based design to precise design. The metal layer thickness selection rules can adapt to the heat dissipation potential of different wheel hubs, achieving optimal weight reduction while ensuring safety.

[0022] 6. Systematized design methodology: It provides a complete design methodology system from parameter calculation, microstructure design, material matching, process implementation to performance verification. It is highly instructive and can cover various application scenarios of high braking energy wheels. Attached Figure Description

[0023] Figure 1 This is a flowchart of the heat insulation screen design method in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the three-layer composite heat insulation screen in an embodiment of the present invention; Figure 3 This is a planar layout diagram of the biomimetic leaf vein flow channel structure of the intermediate nano-aerogel insulation layer in an embodiment of the present invention; Figure 4 This is a schematic diagram of the microporous array of the hot-end metal load-bearing layer and the single locking lug structure in an embodiment of the present invention; Figure 5 This is a schematic diagram of the heat-conducting rib structure of the cold-end metal encapsulation layer in an embodiment of the present invention; Figure 6 This is a schematic diagram showing the installation position of the heat insulation screen in the aircraft wheel in an embodiment of the present invention.

[0024] Explanation of reference numerals in the attached diagram: 1. Hot end metal load-bearing layer, 11. Micropore, 12. Locking lug; 2. Middle nano-aerogel insulation layer, 21. Primary main vein, 22. Secondary branch vein; 3. Cold end metal encapsulation layer, 31. Heat-conducting rib; 4. Heat insulation screen. Detailed Implementation

[0025] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0026] In recent years, nano-aerogel materials have attracted widespread attention in the field of thermal insulation due to their ultra-low thermal conductivity (down to below 0.018 W / (m·K)). However, the application of aerogels in the high-strength, high-dynamic, and extreme temperature difference conditions of aircraft wheels faces several key technical challenges: 1. Weak mechanical properties: Pure aerogel materials are brittle and have poor impact resistance. They cannot withstand impact loads of more than 1.5 times their own weight when an aircraft lands, and are prone to cracking and falling off under high-speed rotation of the wheels (speed exceeding 600 rpm). 2. Insufficient thermal stability: Traditional aerogels are prone to shrinkage and sintering at temperatures above 800℃, and the destruction of the pore structure leads to a sharp decline in thermal insulation performance, making it difficult to match the peak temperature environment of brake discs above 1000℃. 3. Poor interfacial compatibility: The thermal expansion coefficients of aerogels and metals differ significantly (approximately 1×10⁻⁶ for aerogels). -6 / ℃, metal approximately 10×10 -6 / ℃), which is prone to interfacial delamination during repeated thermal cycling; 4. Difficulties in molding and packaging: Aerogel is difficult to process directly into complex shapes that fit the contours of the wheel, and it is prone to moisture absorption and powdering, so the problems of sealing protection and precise molding need to be solved.

[0027] While existing technologies have attempted to use aerogel for thermal insulation of electronic devices (e.g., CN218830859U) or to place obstacles on the surface of thermal insulation screens to enhance convection (e.g., US10619690B2, CN107628236A), none have proposed a systematic solution to the aforementioned difficulties in the application of aerogel under aviation braking conditions. Although CN201154772Y and CN206579836U involve the structure of aviation brake wheel thermal insulation screens, they both adopt a single-layer metal design with limited functionality and do not involve aerogel composite material configurations or active thermal management designs.

[0028] Based on the problems existing in the prior art, this invention proposes a design method for a heat shield for aircraft wheels, wherein the heat shield is installed between the brake disc assembly and the wheel hub, and includes the following steps: A three-layer composite structure is constructed, which consists of a hot-end metal load-bearing layer, a middle nano-aerogel heat insulation layer, and a cold-end metal encapsulation layer. A biomimetic leaf vein flow channel structure is designed in the intermediate nano-aerogel insulation layer. The biomimetic leaf vein flow channel structure includes a primary main vein arranged circumferentially along the insulation screen, and secondary branch veins that are radially connected to the primary main vein. A micropore array and locking lugs are designed on the hot-end metal load-bearing layer. The micropore array is used to release thermal stress and promote convective heat transfer, and the locking lugs are used to fix it to the wheel hub. A radial heat-conducting rib array is designed on the cold-end metal encapsulation layer. The heat-conducting ribs are embedded in the middle nano-aerogel insulation layer to disperse heat radially. Determine the thickness matching and connection process of the three-layer composite structure to achieve the desired total thickness. d The thickness is controlled between 1.6mm and 3.2mm, and the hot-end metal load-bearing layer and the cold-end metal encapsulation layer are vacuum-sealed at the circumferential edge by high-temperature brazing or diffusion welding to form a vacuum-sealed cavity that encapsulates the middle nano-aerogel insulation layer. Quantitative design of key dimensions of the heat insulation screen based on hub geometry parameters, wherein the key dimensions include at least the axial reference length of the heat insulation screen. L Axial length of hot-end metal load-bearing layer L hot Axial length of cold end metal packaging layer L cold And the single-layer thickness of the hot-end metal load-bearing layer or the cold-end metal encapsulation layer. t ; Establish thermal-mechanical coupling design criteria and performance verification thresholds for thermal insulation screens. The thermal-mechanical coupling design criteria shall include at least a peak heat flux of not less than 1.5 MW / m². 2 The maximum temperature of the cold end should not exceed 200℃, and the temperature rise rate should be less than 50℃ / s. The present invention also proposes a heat shield for aircraft wheels, installed between the brake disc assembly and the wheel hub, comprising: A hot-end metal bearing layer is positioned facing the heat source of the brake disc. The hot-end metal bearing layer is provided with a micropore array and a locking lug. The micropore array has a micropore diameter of 50μm to 200μm and a porosity of 10% to 25%. The locking lug is used to fix it to the wheel hub. An intermediate nano-aerogel insulation layer is stacked on the side of the hot-end metal load-bearing layer away from the brake disc. It contains a biomimetic leaf vein flow channel structure, which includes a primary main vein arranged circumferentially along the insulation screen and secondary branch veins connected to it. The primary main vein flow channel has a rectangular cross-section with a width of 0.5mm to 2.0mm and a depth of 60% to 80% of the thickness of the intermediate nano-aerogel insulation layer. The secondary branch vein flow channel has a width of 0.2mm to 0.8mm. A cold-end metal encapsulation layer is stacked on the side of the middle nano-aerogel insulation layer away from the hot-end metal load-bearing layer and facing the hub. A radial heat-conducting rib array is provided on it. The heat-conducting ribs are embedded in the middle nano-aerogel insulation layer. The width of a single heat-conducting rib is 1mm to 3mm, and the rib height is consistent with the thickness of the middle nano-aerogel insulation layer. The total thickness of the heat insulation screen d The thickness ranges from 1.6mm to 3.2mm, where the thickness of the hot-end metal load-bearing layer is... d hot The thickness of the intermediate nano-aerogel insulation layer is 0.3mm to 0.6mm. d aero The thickness of the cold-end metal encapsulation layer is 1.0mm to 2.0mm. d cold It is 0.3mm to 0.6mm, and d aero >2 d hot ; The hot-end metal load-bearing layer and the cold-end metal encapsulation layer are sealed and welded at the circumferential edge to form a vacuum-sealed cavity that encloses the intermediate nano-aerogel insulation layer.

[0029] This invention addresses the challenges of existing technologies through a synergistic structural design and process optimization of "metal material-aerogel-metal material," achieving the following effects: 1. Mechanical reinforcement and structural stability: The hot-end metal load-bearing layer and the cold-end metal encapsulation layer form a "rigid frame" that completely encapsulates the middle nano-aerogel insulation layer and fixes it through high-temperature brazing / diffusion welding. This protects the middle nano-aerogel insulation layer from direct impact and shear force, meeting the mechanical requirements of high-speed rotation of the wheel and landing impact.

[0030] 2. Wide temperature range insulation performance: High-temperature resistant nano-aerogel is selected as the core insulation layer. Combined with the thermal buffering effect of the metal layer, the pore structure of the middle nano-aerogel insulation layer can remain stable within a wide temperature range of -55℃ (high altitude low temperature) to 1000℃ (braking peak temperature). Compared with traditional insulation materials, it achieves high-efficiency insulation under all working conditions from "normal temperature to high temperature".

[0031] 3. Stress relief and long-term compatibility: The microporous array of the hot-end metal load-bearing layer and the thermally conductive rib array of the cold-end metal encapsulation layer form a "flexible-rigid" composite connection interface, which effectively absorbs the stress caused by the thermal expansion difference between the aerogel and the metal layer; the vacuum-sealed encapsulation design avoids the aerogel from absorbing moisture and turning into powder.

[0032] 4. Precise Molding and Functional Integration: Through a combination of molding (intermediate nano-aerogel insulation layer) and laser cutting (metal layer), the heat insulation screen and the wheel hub contour are precisely matched (dimensional tolerance ±0.1mm); at the same time, the heat conduction / heat dissipation structure of the intermediate nano-aerogel insulation layer and the metal layer work together to form an integrated function of "heat insulation-heat equalization-heat dissipation". Compared with the pure aerogel insulation structure, it can further reduce the cold end temperature and improve the thermal response speed.

[0033] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0034] In one embodiment, refer to Figure 2 As shown, a heat shield for aircraft wheels is installed between the brake disc assembly and the wheel hub. The heat shield has a three-layer composite structure, comprising, from the hot end (near the brake disc) to the cold end (near the hub): a hot-end metal load-bearing layer, a middle nano-aerogel heat insulation layer, and a cold-end metal encapsulation layer. The hot-end metal load-bearing layer and the cold-end metal encapsulation layer form a vacuum-sealed cavity at their circumferential edges through high-temperature brazing or diffusion welding, completely encapsulating the middle nano-aerogel heat insulation layer.

[0035] The total thickness of the heat insulation screen d The thickness is controlled between 1.6mm and 3.2mm, where the thickness of the hot-end metal load-bearing layer is... d hot The thickness of the intermediate nano-aerogel insulation layer is 0.3mm to 0.6mm. d aero The thickness of the cold-end metal encapsulation layer is 1.0mm to 2.0mm. d cold The thickness should be 0.3mm to 0.6mm, and it must meet the following requirements. d aero >2 d hot This ensures that the intermediate nano-aerogel insulation layer plays a dominant role in heat insulation.

[0036] In one embodiment, refer to Figure 1 As shown, the specific steps of a design method for a heat shield for aircraft wheels are as follows: Step 1: Design of the biomimetic leaf vein flow channel structure of the intermediate nano-aerogel insulation layer: like Figure 3 As shown, a biomimetic leaf vein-shaped microchannel cavity structure is prepared in the thickness direction of the intermediate nano-aerogel insulation layer using laser etching or molding methods. The microchannel includes a primary main vein and secondary branches: the primary main vein is arranged in a ring around the circumference of the insulation screen to form a rectangular trunk; the secondary branches are radially connected to the primary main vein, forming a "solid-gas phase change heat sink".

[0037] The primary main channel has a rectangular cross-section with a width of 0.5mm to 2.0mm and a depth of 60% to 80% of the thickness of the nano-aerogel insulation layer in the middle of the primary main channel; the secondary branch channels have a width of 0.2mm to 0.8mm.

[0038] The flow channel dimensions must be based on the axial reference length determined in step 5.1. L Perform dynamic matching: when LFor diameters greater than 200mm (corresponding to larger wheel hub depths and wider heat-affected zones), the width of the primary main vein should be 1.5mm to 2.0mm, and the density of the secondary branch veins should be increased by 30% compared to the conventional approach to ensure adequate flow channel coverage. L Corresponding heat load area matching; when d aero When the thickness is ≥1.5mm, the channel depth is taken as 70% to 80% of the thickness of the middle nano-aerogel insulation layer. By increasing the channel volume, the heat penetration caused by the thermal conductivity of the metal layer is compensated, and the phase change heat storage effect is enhanced.

[0039] This biomimetic flow channel structure utilizes air convection to accelerate the lateral diffusion of heat within the intermediate nano-aerogel insulation layer, preventing localized heat accumulation. On the other hand, it forms a heat sink effect through the hierarchical connection of the main and branch channels, absorbing some heat under transient thermal shock and delaying the transfer of heat to the cold end.

[0040] Step 2: Design of hot-end metal load-bearing layer locking and microporous heat release structure: like Figure 4 As shown, the hot-end metal load-bearing layer faces the brake disc heat source and is made of high-temperature alloy materials (such as titanium alloy TC4, stainless steel, etc.). A micropore array is formed on the front side (hot end face) of the hot-end metal load-bearing layer using laser drilling. The micropore diameter Φ is 50μm~200μm, and the porosity is controlled between 10% and 25%. The micropore array has the following functions: Increase the surface area for thermal radiation and promote convective heat transfer of air inside the micropores during hub rotation; Releases thermal stress caused by drastic temperature changes during braking and inhibits crack initiation; The cooling airflow is guided to scour the surface of the intermediate nano-aerogel insulation layer, thereby reducing the surface temperature of the aerogel and delaying high-temperature sintering aging.

[0041] Locking lug: A locking lug is designed at one end of the hot-end metal load-bearing layer. The locking lug has a mounting hole for fixing to the hub, so as to achieve overall anti-rotation locking of the heat insulation screen.

[0042] The micropore parameters need to be based on the metal layer thickness determined in step 5.3. t Perform a match: when t When the thickness is 0.3 mm (thin metal layer), micropores with a diameter of 80 μm to 120 μm and a porosity of 18% to 22% are selected to ensure heat dissipation efficiency while controlling the strength loss of the metal layer to within 10%. when t When the thickness of the metal layer is 0.6 mm, the diameter of the micropores can be increased to 150 μm to 200 μm, and the porosity can be increased to 22% to 25%. The heat dissipation capacity of the wheel hub itself can be used to compensate for the influence of the micropores on the strength, while further improving the convective heat dissipation effect.

[0043] Key technical challenges and verification of micropore arrays: This invention optimizes the micropore design through experiments, solving the following challenges: 1. Thermal stress release test: A rapid thermal shock + in-situ stress testing method was adopted. The test conditions were -55℃ (holding temperature for 5 min) to 1000℃ (holding temperature for 5 min), with a thermal shock rate of 100℃ / min. Simultaneously, the interface stress was monitored in-situ using a built-in fiber optic grating sensor. The results showed that the non-porous metal layer developed a through-crack after 85 thermal shocks (stress peak 320 MPa, threshold 300 MPa); the 10% porosity microporous layer developed microcracks after 170 thermal shocks (stress peak 295 MPa, threshold 290 MPa); while the 20% porosity, 100 μm diameter microporous layer used in this invention maintained a stable stress peak of 220 MPa after 200 thermal shocks, with no cracks, achieving a stress absorption efficiency of 68% (compared to only 23% for the non-porous layer).

[0044] 2. Enhanced Heat Dissipation Synergy Test: Under simulated wheel rotation at 600 rpm, a peak heat flux of 1.5 MW / m² was applied to test the heat conduction and cold-end temperature of different structures. The results showed that the heat conduction from the hot end of the non-porous metal layer to the intermediate nano-aerogel insulation layer was 860 W / m²; the heat conduction of the 20% porosity microporous layer (designed in this invention) was 668 W / m², a reduction of 22.3%; the highest cold-end temperature was 238℃ for the non-porous layer and 189℃ for the microporous layer; the thermal response time (from room temperature to 150℃) was shortened from 42 s to 28 s, demonstrating a significant heat dissipation synergy effect.

[0045] 3. Structural strength retention test: Tensile strength tests were conducted on 0.3 mm thick titanium alloy (TC4) plates. The tensile strength of the non-porous plate was 950 MPa; the tensile strength of the microporous plate (designed in this invention) with a porosity of 20% and a diameter of 100 μm was 872 MPa, a decrease of only 8.2%; if randomly distributed micropores were used, the tensile strength decreased to 798 MPa, a decrease of 16%. In the impact strength test, the impact energy of the microporous plate designed in this invention was 4.2 J / cm², and that of the non-porous plate was 4.5 J / cm², with the decrease controlled within 6.7%.

[0046] 4. High-Temperature Compatibility Test: The microporous material was kept at a constant temperature of 1050℃ for 2 hours, and the edge condition of the micropores was tested. The microporous material without edge treatment had an oxide layer thickness of 8μm and microcracks appeared. The material of this invention, after plasma polishing to remove the oxide layer and applying a 0.05mm rounded corner treatment, had an oxide layer thickness of only 1.2μm and no cracks. After 10 consecutive high-temperature holding-room-temperature cooling cycles, the oxide layer thickness did not increase significantly, and the structural integrity remained good.

[0047] Step 3: Thermal conductivity enhancement structure design for the cold-end metal encapsulation layer: like Figure 5 As shown, the cold-end metal encapsulation layer faces the hub and is made of titanium alloy or aluminum alloy. An array of radially extending heat-conducting ribs is designed on its inner surface (near the middle nano-aerogel insulation layer). Each heat-conducting rib is 1mm to 3mm wide, and its height is equal to the thickness of the middle nano-aerogel insulation layer. d aero Consistent. The heat-conducting ribs are embedded in the middle nano-aerogel insulation layer, which quickly disperses the heat that may penetrate to the cold end in the radial direction, avoiding the formation of local hot spots.

[0048] The dimensions of the heat-conducting fins need to be based on the axial length of the cold-end metal encapsulation layer determined in step 5.2. L cold And the thickness of the intermediate nano-aerogel insulation layer determined in step 5.4 d aero Adaptation: when L cold When the length is less than 100mm, the width of a single heat-conducting fin is 2mm to 3mm to compensate for the heat loss caused by the shortened length by increasing the heat-conducting area. when d aero When the thickness is greater than 1.5mm, the rib height is increased to match the thickness of the intermediate nano-aerogel insulation layer to ensure full contact between the heat-conducting rib and the intermediate nano-aerogel insulation layer, so as to quickly dissipate the deep-penetrated heat and avoid the accumulation of heat at the aerogel-metal interface.

[0049] By using a middle nano-aerogel insulation layer to block heat conduction, a flow channel and micropores to accelerate heat convection, and heat-conducting ribs to evenly disperse residual heat, the synergistic effect of these three elements can significantly reduce the temperature difference of local hot spots and improve the overall thermal uniformity.

[0050] Step 4: Thickness matching and connection process of the three-layer composite structure: Thickness of hot and cold end metal layers t In principle, the same value should be used to ensure structural symmetry and process consistency. Total thickness d Within the range of 1.6mm to 3.2mm, dynamically adjust according to the calculation results in step 5.4: when L When >200mm, d aero Take a thickness of 1.5mm to 2.0mm. d Use a thickness of 2.5mm to 3.2mm to enhance thermal barrier properties by increasing the thickness of the insulation layer; when L When <100mm, d aero Take a thickness of 1.0mm to 1.5mm. d A thickness of 1.6mm to 2.2mm is used to achieve weight reduction while meeting thermal insulation requirements.

[0051] Connection process: High-temperature brazing or diffusion welding is used to vacuum seal the hot-end metal load-bearing layer and the cold-end metal encapsulation layer at the circumferential edge, wrapping and fixing the middle nano-aerogel heat insulation layer to form an overall vacuum-sealed cavity.

[0052] Vacuum sealing solves the problem of aerogel absorbing moisture and turning into powder (the water absorption rate is reduced from more than 18% without encapsulation to 0.6%). At the same time, it complements the flow channel + microporous structure – the sealed cavity prevents external moisture from entering, and the flow channel + microporous structure solves the problem of internal heat dissipation after sealing.

[0053] Step 5: Design and calculation of key parameters for the heat shield based on wheel hub geometry: To ensure the compatibility between the heat shield and the wheel hub and achieve the optimal balance between protective performance and weight, this invention proposes a quantitative design method based on the key geometric parameters of the wheel hub.

[0054] Step 5.1: Axial reference length of the heat insulation screen L The determination; Axial length of heat insulation screen L The heat-affected zone of the wheel hub needs to be fully covered. The calculation formula is as follows:

[0055] in: L : Axial design reference length of heat insulation screen (mm); h: Geometric depth of the hub structure (mm), characterizing the potential influence range of the heat source along the axial direction; Reference area of ​​the effective heat transfer zone of the wheel hub (mm²) 2 The square root of represents the area effect of the heat load.

[0056] This formula quantifies the combined impact of hub depth (positively correlated) and area (negatively correlated via the square root) on the required coverage length of the heat shield. It applies to three types of hubs (h=230mm / 193.4mm / 115mm). A hub =623.4mm 2 / 490mm 2 / 385mm 2 Verification, calculation L The dimensions are 229.6mm / 190.3mm / 117.2mm respectively, with an error of ≤2.8% compared to the actual measured lengths (203mm / 193.4mm / 115mm).

[0057] Step 5.2: Determining the axial length of the hot-end metal load-bearing layer and the cold-end metal encapsulation layer; Based on the axial reference length of the heat insulation screen L The hot-end metal load-bearing layer and the cold-end metal encapsulation layer adopt a "stepped" length design to adapt to different requirements of high heat load and installation interface: Axial length of hot-end metal load-bearing layer This ensures complete isolation from axial thermal radiation and heat conduction; Axial length of cold end metal packaging layer ,in The indentation is 6mm to 8mm, meaning that the cold end metal encapsulation layer is shortened by 6mm to 8mm at both ends compared to the hot end metal load-bearing layer.

[0058] The design has the following advantages: ① Optimized thermal protection: The full-length hot end layer provides maximum thermal insulation barrier; ② Weight reduction and reduced stress concentration: The shortened cold end metal encapsulation layer reduces the amount of metal used and avoids edge alignment to reduce interlayer shear stress; ③ Adaptable installation space: Allows for operation space for bolts and bosses on the wheel hub.

[0059] Step 5.3: Metal Layer Thickness t Selection rules; The thickness of the heat insulation screen body t Specifically refers to the thickness of a single layer of the hot-end metal load-bearing layer or the cold-end metal encapsulation layer, or simply the thickness of a single metal layer. t The choice of thickness depends on the material type and the structural characteristics of the wheel hub.

[0060] in: P: The "area-to-hole ratio" of the wheel hub, which is the ratio of the total area of ​​the light-reducing holes on the wheel hub surface to the apparent area of ​​the wheel hub (expressed as a decimal). h: Hub depth (mm).

[0061] Judgment Logic: The core of the rule lies in assessing the heat dissipation capacity of the wheel hub itself. Only when both conditions are met simultaneously (1) high thermal strength but heavier stainless steel is used and (2) the wheel hub itself has a high overall heat dissipation potential (P·h≥2.0), a thicker (0.6mm) metal layer is allowed to obtain better structural strength and heat capacity. In all other cases, a thinner (0.3mm) design is used to prioritize weight reduction requirements.

[0062] Relationship with the three-layer configuration: the single-layer thickness of the hot-end metal load-bearing layer and the cold-end metal encapsulation layer t In principle, the same value should be used to ensure structural symmetry and process consistency. The thickness of the intermediate nano-aerogel insulation layer... d aeroBased on the total thickness constraint d Match the thickness range in step 4.

[0063] Step 5.4: Design calculation process integration; 1) Input hub geometry parameters: depth h, reference area A hub Area opening ratio P; 2) Calculate the axial reference length according to the formula in step 5.1. L ; 3) Determine the length of the metal layer: Let the axial length of the hot-end metal load-bearing layer be... Determine the indentation amount (Preferred length 6mm), calculate the axial length of the cold-end metal encapsulation layer. ; 4) Material Selection and Metal Layer Thickness: Based on mechanical, temperature resistance, and cost requirements, select the metal substrate material. Combine P and h, and determine the thickness of each metal layer according to rule 5.3. t ; 5) Determine the thickness of the intermediate nano-aerogel insulation layer: based on the total thickness target. d Values ​​are taken within the range of 1.6mm to 3.2mm, combined with the selected... t Calculate and determine the thickness of the intermediate nano-aerogel insulation layer. d aero = d -2 t and satisfy d aero Within the range of 1.0mm to 2.0mm, and d aero >2 t ; 6) In L hot , L cold , t , d aero Within this framework, detailed structural design steps 1-4 are performed, and based on... L , t , d aero The specific dimensions of the flow channel, micropores, and heat-conducting ribs are dynamically matched with parameters.

[0064] Step 6: Thermo-Mechanical Coupling Design Criteria and Performance Verification Thresholds This embodiment establishes the following design criteria and verification thresholds: 1. Heat flux threshold: The heat insulation screen must withstand a peak heat flux of not less than 1.5MW / m² for a duration equal to the maximum energy braking cycle; 2. Cold end temperature limit: In the standard maximum braking energy test, the maximum temperature of the cold end (the side in contact with the wheel hub) of the heat shield shall not exceed 200℃, and the temperature rise rate shall be less than 50℃ / s; 3. Structural integrity: Under simulated maximum landing impact load, no plastic deformation, delamination, or cracking shall occur; the natural frequency shall be kept within ±20% of the main vibration frequency of the wheel to prevent resonance.

[0065] In one embodiment, taking a main landing gear wheel of an aircraft as an example, the wheel hub parameters are: depth h = 150 mm, reference area... =500mm 2 The area-to-opening ratio P = 0.15.

[0066] 1. Calculate key parameters: Calculate the reference length L : L =0.519×150+2.554× -74.1≈112.74mm.

[0067] Determine the length of the metal layer: Take the indentation amount =6mm.

[0068] Axial length of hot-end metal load-bearing layer: .

[0069] Axial length of cold-end metal encapsulation layer: .

[0070] Material selection and metal layer thickness: Considering weight reduction requirements, titanium alloy (TC4) is selected as the metal substrate material. The calculated heat dissipation coefficient P·h = 0.15 × 150 = 22.5 ≥ 2.0. Since the material is not stainless steel, the single-layer thickness of the metal layer is selected according to the rules. t =0.3mm.

[0071] Determine the thickness of the intermediate nano-aerogel insulation layer: Set a target total thickness. d =2.0mm, then the thickness of the middle nano-aerogel insulation layer is... d aero = d -2 t =1.4mm. Verification: d aero =1.4mm>2 t =0.6mm, and within the range of 1.0mm to 2.0mm, which meets the requirements.

[0072] 2. Detailed structural design: Bionic flow channel: The flow channel is laser-etched on the intermediate nano-aerogel insulation layer with a thickness of 1.4mm. The width of the primary main pulse is W1=1.0mm and the width of the secondary branch pulse is W2=0.3mm. Hot-end metal load-bearing layer structure: The hot-end titanium alloy plate (thickness 0.3mm, length 112.74mm) has a locking lug designed at a set position on its outer periphery for positioning and anti-rotation, and the front side adopts a laser-drilled micro-hole array (Φm=100μm, porosity 20%). Cold-end metal encapsulation layer structure: Cold-end titanium alloy plate (thickness 0.3mm, length 100.74mm) with an in-plane radial heat-conducting rib array (each heat-conducting rib is 1.0mm wide and 100.74mm high). d aero Consistent); Connection process: Vacuum diffusion welding is used to seal the three-layer edge to form a whole, wherein the hot end metal load-bearing layer and the cold end metal encapsulation layer form a stepped difference at both ends.

[0073] 3. Performance verification experiment: To verify the heat insulation and heat dissipation performance of the structure of this invention, a comparative experiment was conducted: Experimental groups: Group A is a traditional single-layer titanium alloy plate (thickness 0.6mm); Group B is a three-layer structure of titanium alloy-aerogel-titanium alloy (no flow channel, no micropores); Group C is the structure of this invention (including biomimetic leaf vein flow channel structure + hot end micropore array + cold end heat-conducting rib array).

[0074] Heat source simulation: The hot end is heated to 600℃ at a constant temperature (simulating braking conditions), and the cold end is forced to be cooled by air (flow rate 5m / s).

[0075] Measurement indicators: Steady-state cold end temperature (°C): reflects thermal insulation performance; Temperature equalization time (s, the time it takes for the temperature at the center point of the cold end surface to stabilize when the hot end surface of the specimen is rapidly heated and maintained at 600℃ while the cold end surface is subjected to air cooling at 5m / s): reflects the heat diffusion efficiency. Temperature uniformity at the hot end face (temperature difference ΔT between the highest and lowest points): reflects the heat dissipation capacity. Experimental results are as follows: Experimental results:

[0076] Experimental data analysis: (1) The cold end temperature of the structure of the present invention (Group C) is 74.4% lower than that of the traditional single-layer screen (Group A) and 50.3% lower than that of the ordinary three-layer structure (Group B), indicating that the biomimetic flow channel and microporous array significantly enhance the synergistic effect of heat insulation and heat dissipation; (2) The temperature equalization time was shortened by 54.2% compared with Group B, indicating that the flow channel design promoted gas convection in the middle nano-aerogel insulation layer and accelerated the uniform transfer of heat to the cold end. (3) The temperature of the hot end face ΔT is only 35℃, which is 83.3% lower than that of group A and 70.8% lower than that of group B, proving that the bionic flow channel optimizes the heat flow distribution and avoids local overheating.

[0077] In conclusion, the design method for heat shields for aircraft wheels provided by this invention systematically solves the heat insulation problem under high braking heat flux through an innovative three-layer composite structure, biomimetic thermal management design, and quantitative parameter calculation. It features high efficiency, lightweight, and high reliability, and is of great significance for improving the safety and reliability of aircraft braking systems.

[0078] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A design method for a heat shield for an aircraft wheel, wherein the heat shield is installed between the brake disc assembly and the wheel hub, characterized in that, Includes the following steps: A three-layer composite structure is constructed, which consists of a hot-end metal load-bearing layer, a middle nano-aerogel heat insulation layer, and a cold-end metal encapsulation layer. A biomimetic leaf vein flow channel structure is designed in the middle nano-aerogel insulation layer. The biomimetic leaf vein flow channel structure includes a primary main vein arranged circumferentially along the insulation screen, and secondary branch veins that are radially connected to the primary main vein. A micropore array and locking lugs are designed on the hot-end metal load-bearing layer. The micropore array is used to release thermal stress and promote convective heat transfer, and the locking lugs are used to fix it to the wheel hub. A radial heat-conducting rib array is designed on the cold-end metal encapsulation layer. The heat-conducting rib array is embedded in the middle nano-aerogel insulation layer to disperse heat radially. Determine the thickness matching and connection process of the three-layer composite structure to achieve the desired total thickness. δ The thickness is controlled between 1.6mm and 3.2mm, and the hot-end metal load-bearing layer and the cold-end metal encapsulation layer are vacuum-sealed at the circumferential edge by high-temperature brazing or diffusion welding to form a vacuum-sealed cavity that encapsulates the middle nano-aerogel insulation layer. Quantitative design of key dimensions of the heat insulation screen based on hub geometry parameters, wherein the key dimensions include at least the axial reference length of the heat insulation screen. L Axial length of hot-end metal load-bearing layer L hot Axial length of cold end metal packaging layer L cold And the single-layer thickness of the hot-end metal load-bearing layer or the cold-end metal encapsulation layer. t ; Establish thermal-mechanical coupling design criteria and performance verification thresholds for thermal insulation screens. The thermal-mechanical coupling design criteria shall include at least a peak heat flux of not less than 1.5 MW / m². 2 The maximum temperature of the cold end should not exceed 200℃, and the temperature rise rate should be less than 50℃ / s.

2. The design method of a heat shield for aircraft wheels according to claim 1, characterized in that: The axial reference length of the heat insulation screen L Determined by the following formula: Where h is the geometric depth of the hub, in mm; This is a reference area for the effective heat transfer zone of the wheel hub, in mm. 2 .

3. The design method of a heat shield for aircraft wheels according to claim 2, characterized in that: The axial length of the hot-end metal load-bearing layer L hot Equal to the axial reference length of the heat insulation screen L ; Axial length of cold end metal packaging layer L cold Determined by the following formula: in, This is the indentation amount, ranging from 6mm to 8mm.

4. The design method of a heat shield for aircraft wheels according to claim 3, characterized in that: The single-layer thickness of the hot-end metal load-bearing layer or the cold-end metal encapsulation layer t， Simply put, it refers to the thickness of a single metal layer. t， The selection rules are as follows: Where P is the area-to-hole ratio of the hub, which is the ratio of the total area of ​​the hub surface relief holes to the apparent area of ​​the hub; h is the geometric depth of the hub.

5. The design method of a heat shield for aircraft wheels according to claim 4, characterized in that: Thickness of intermediate nano-aerogel insulation layer δ aero Based on total thickness δ and the thickness of a single metal layer t Sure: δ aero = δ -2 t and satisfy δ aero Within the range of 1.0mm to 2.0mm, and δ aero >2 t .

6. The design method of a heat shield for aircraft wheels according to claim 5, characterized in that: In the biomimetic leaf vein flow channel structure, the primary main vein flow channel has a rectangular cross-section with a width of 0.5mm to 2.0mm and a depth of 60% to 80% of the thickness of the intermediate nano-aerogel insulation layer; the secondary branch vein flow channel has a width of 0.2mm to 0.8mm.

7. The design method of a heat shield for aircraft wheels according to claim 6, characterized in that: The dimensional parameters of the biomimetic leaf vein flow channel structure are based on the axial reference length of the heat insulation screen. L Dynamic matching: when L When the width is >200mm, the width of the primary main vein is 1.5mm to 2.0mm, and the density of secondary branch veins increases by 30%; when δ aero When the thickness is ≥1.5mm, the channel depth is taken as 70% to 80% of the thickness of the intermediate nano-aerogel insulation layer.

8. The design method of a heat shield for aircraft wheels according to claim 7, characterized in that: The micropores in the micropore array have a diameter of 50 μm to 200 μm and a porosity controlled between 10% and 25%; and the micropore parameters are based on the thickness of a single metal layer. t Match: When t When the diameter is 0.3 mm, the micropore diameter is taken as 80 μm to 120 μm, and the porosity is taken as 18% to 22%; when t When the diameter is 0.6 mm, the micropore diameter is taken as 150 μm to 200 μm, and the porosity is taken as 22% to 25%.

9. The design method of a heat shield for aircraft wheels according to claim 8, characterized in that: The width of a single thermal rib in the radial thermal rib array is 1mm to 3mm, and the height of a single thermal rib is consistent with the thickness of the intermediate nano-aerogel insulation layer; and the size of the thermal rib is based on the axial length of the cold-end metal encapsulation layer. L cold and the thickness of the intermediate nano-aerogel insulation layer δ aero Compatible with: When L cold When the diameter is <100mm, the width of a single heat-conducting fin should be 2mm to 3mm; when δ aero When the thickness is greater than 1.5mm, the height of a single heat-conducting rib increases synchronously to match the thickness of the intermediate nano-aerogel insulation layer.

10. A heat shield for aircraft wheels, obtained by the design method of the heat shield for aircraft wheels according to any one of claims 1-9, characterized in that, include: A hot-end metal bearing layer is positioned facing the heat source of the brake disc. The hot-end metal bearing layer is provided with a micropore array and a locking lug. The micropore array has a micropore diameter of 50μm to 200μm and a porosity of 10% to 25%. The locking lug is used to fix it to the wheel hub. The intermediate nano-aerogel insulation layer is stacked on the side of the hot-end metal load-bearing layer away from the brake disc. It has a biomimetic leaf vein flow channel structure. The biomimetic leaf vein flow channel structure includes a primary main vein arranged around the circumference of the insulation screen and secondary branch veins connected to it. The cross-section of the primary main vein flow channel is rectangular, with a width of 0.5mm to 2.0mm and a depth of 60% to 80% of the thickness of the intermediate nano-aerogel insulation layer. The width of the secondary branch vein flow channel is 0.2mm to 0.8mm. The cold end metal encapsulation layer is stacked on the side of the middle nano-aerogel insulation layer away from the hot end metal load-bearing layer and facing the hub. A radial heat-conducting rib array is provided on it. The radial heat-conducting rib array is embedded in the middle nano-aerogel insulation layer. The width of a single heat-conducting rib is 1mm to 3mm, and the height of a single heat-conducting rib is the same as the thickness of the middle nano-aerogel insulation layer. The total thickness of the heat insulation screen δ The thickness ranges from 1.6mm to 3.2mm, where the thickness of the hot-end metal load-bearing layer is... δ hot The thickness of the intermediate nano-aerogel insulation layer is 0.3mm to 0.6mm. δ aero The thickness of the cold-end metal encapsulation layer is 1.0mm to 2.0mm. δ cold It is 0.3mm to 0.6mm, and δ aero >2 δ hot ; The hot-end metal load-bearing layer and the cold-end metal encapsulation layer are sealed and welded at the circumferential edge to form a vacuum-sealed cavity that encloses the middle nano-aerogel heat insulation layer.

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