Fractal structure functional integration heat protection system containing composite phase change material

Abstract

The application discloses a fractal structure functional integration heat protection system containing composite phase change material, which comprises a fractal structure web plate fixedly arranged on the inner side of an outer plate, an inner plate fixedly arranged on the lower side of the fractal structure web plate, an intermediate partition plate fixedly arranged on the fractal structure web plate between the outer plate and the inner plate, a cavity between the intermediate partition plate and the outer plate filled with a heat insulation material, and a cavity between the intermediate partition plate and the inner plate filled with the composite phase change material. Through the synergistic effect of the nano wetting effect of the modified low-melting-point metal-based alloy and the micron-level framework of the expanded graphite, a "alloy-graphite" two-stage heat conduction network is constructed, the heat conduction coefficient is greatly improved, the heat of the fractal structure web plate can be quickly transmitted to the composite phase change material for storage, the problem of heat short circuit does not occur, the heat protection performance and temperature uniformity are improved, and a reliable guarantee is provided for the safe flight of the aircraft in the environment with serious aerodynamic heating.

Description

Technical Field

[0001] This invention relates to the field of thermal protection technology, and in particular to a fractal structure integrated thermal protection system containing composite phase change materials. Background Technology

[0002] When an aircraft flies at high speed, the temperature of the skin surface and its vicinity rises rapidly due to shock wave compression, boundary layer friction, and adiabatic stagnation effects. The rapidly rising aerodynamic heat can cause problems such as material failure, deformation of the airframe structure, electronic system failure, and communication interruption. In order to maintain the overall or local aerodynamic stability of the aircraft and the normal operation of internal electronic equipment and personnel within the allowable temperature range, it is of great significance to develop an efficient and reliable aerodynamic thermal protection system for high-speed aircraft.

[0003] Traditional corrugated plate integrated thermal protection systems combine load-bearing and heat protection functions, have high structural efficiency, and meet the design concepts of lightweight, low redundancy, and multi-functionality of future aircraft. However, they have a thermal short-circuit problem; that is, heat is always transferred to the interior of the aircraft through the web structure with high thermal conductivity, resulting in increased internal ambient temperature and aggravated temperature unevenness.

[0004] Phase change materials (PCMs) possess characteristics such as high latent heat, low density, and small volume change, making them suitable as heat-absorbing materials to alleviate thermal short-circuit problems in integrated thermal protection systems, thereby significantly improving the thermal insulation performance of these systems. However, while common PCMs can absorb heat through their latent heat, they suffer from low thermal conductivity, narrow phase change temperature ranges, and are prone to leakage at excessively high temperatures. Therefore, this invention proposes a fractal structure functional integrated thermal protection system containing composite PCMs to address the problems existing in the prior art. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to propose a fractal structure functional integrated thermal protection system containing composite phase change materials. This system utilizes the synergistic effect of the nano-wetting effect of modified low-melting-point metal-based alloys and the micron-scale framework of expanded graphite to construct an "alloy-graphite" dual-level thermal conductivity network, significantly improving the thermal conductivity. This allows for the rapid transfer of heat from the fractal structure's web to the composite phase change material for storage, preventing thermal short circuits and enhancing thermal protection performance and temperature uniformity. This provides a reliable guarantee for the safe flight of aircraft in environments with severe aerodynamic heating.

[0006] To achieve the objectives of this invention, the invention is implemented through the following technical solution: a fractal structure functional integrated thermal protection system containing composite phase change material, comprising an outer plate and an inner plate, wherein a fractal structure web is fixedly provided on the inner side of the outer plate, an inner plate is fixedly provided on the lower side of the fractal structure web, a middle partition is fixedly provided on the fractal structure web between the outer plate and the inner plate, the cavity between the middle partition and the outer plate is filled with thermal insulation material, and the cavity between the middle partition and the inner plate is filled with composite phase change material.

[0007] A further improvement is that the outer plate, the middle partition plate, and the inner plate are arranged in parallel to each other and are supported and fixed by a fractal structure web.

[0008] A further improvement is that the fractal structure web is distributed in a leaf vein pattern from the outside to the inside, and adjacent fractal structure webs are parallel to each other. The fractal structure web is a branched corrugated plate structure.

[0009] A further improvement is that the outer plate, inner plate, fractal structure web plate, and middle partition plate are all made of silicon carbide or high-temperature alloy and are integrally formed by 3D printing.

[0010] A further improvement is that the thermal insulation material is aerogel with a density of 220 kg / m³. 3 Its specific heat capacity is 500 J / kg·K, and its thermal conductivity is 0.02 W / m·K.

[0011] A further improvement is that the thermal conductivity of the composite phase change material is 2.31 W·m. -1 ·K -1 Latent heat 152.1-207.2 kJ / kg, leakage rate <7%.

[0012] A further improvement is that the composite phase change material is composed of 75-95 wt% paraffin wax, 5 wt% expanded graphite, and 0-20 wt% modified low-melting-point metal-based alloy.

[0013] Further improvements include: the phase transition temperature of the paraffin is 42°C, and the latent heat is 207.1 J / g; the purity of the expanded graphite is ≥99%; and the modified low-melting-point metal-based alloy is composed of 50 wt% bismuth, 25 wt% tin, 12.5 wt% cadmium, and 12.5 wt% chromium, with a melting point of 70°C.

[0014] The beneficial effects of this invention are as follows: This invention constructs a "alloy-graphite" dual-level thermal conductivity network by synergistically combining the nano-wetting effect of modified low-melting-point metal-based alloys with the micron-level skeleton of expanded graphite. The thermal conductivity is greatly improved, which can quickly transfer the heat of the fractal structure web to the composite phase change material for storage, so that the temperature in the system can be evenly distributed and there will be no thermal short circuit problem.

[0015] This invention utilizes the high specific strength and large surface area of ​​fractal structures to achieve large-area contact with composite phase change materials. This allows for the rapid absorption and storage of heat transferred from the web of the fractal structure, reducing the heat gradient transferred to the interior of the aircraft, improving thermal protection performance and temperature uniformity, and providing reliable protection for the safe flight of the aircraft in environments with severe aerodynamic heating. Attached Figure Description

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

[0017] The components include: 1. Outer panel; 2. Inner panel; 3. Middle partition; 4. Fractal structure web; 5. Thermal insulation material; 6. Composite phase change material. Detailed Implementation

[0018] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0019] When an aircraft flies at high speed, the temperature on and around the skin surface rises rapidly due to shock wave compression, boundary layer friction, and adiabatic stagnation effects. This rapid increase in aerodynamic heat can lead to material failure, structural deformation, electronic system malfunctions, and communication interruptions. Therefore, developing a highly efficient and reliable aerodynamic thermal protection system for high-speed aircraft is crucial to maintaining the overall or local aerodynamic stability of the aircraft and ensuring the normal operation of internal electronic equipment and personnel within permissible temperature ranges. The corrugated plate integrated thermal protection system combines load-bearing and heat protection functions, possessing high structural efficiency and aligning with the future design principles of lightweight, low-redundancy, and multi-functional aircraft. However, it suffers from a thermal short-circuit problem: heat is always transferred to the aircraft's interior through the web structure, which has high thermal conductivity, leading to increased internal ambient temperature and exacerbated temperature unevenness.

[0020] Phase change materials (PCMs) possess characteristics such as high latent heat, low density, and small volume change, making them suitable as heat-absorbing materials to alleviate thermal short-circuit problems in integrated thermal protection systems, thereby significantly improving the thermal insulation performance of these systems. However, while common PCMs can absorb heat through their latent heat of phase change, they suffer from low thermal conductivity, narrow phase change temperatures, and leakage at excessively high temperatures. Typically, the thermal conductivity of PCMs is improved by adding substrate or carrier materials, such as graphene, metal oxides, and metal foams, to regulate the phase change temperature and optimize the phase change process. Experimental studies have shown that the thermal conductivity of copper-based porous framework / paraffin composite materials prepared by vacuum impregnation is up to 15 times higher than that of the matrix PCM. Numerical simulations further confirm that topology optimization design of the porous metal framework can effectively enhance the heat transfer efficiency of the phase change process, improving the temperature field uniformity of the composite system by more than 76% and shortening the heat storage period by 42%-58%.

[0021] Example

[0022] Based on the above, this embodiment provides a fractal structure functional integrated thermal protection system containing composite phase change materials, as per the appendix of the specification. Figure 1 As shown, it comprises an outer plate 1, an inner plate 2, a fractal structure web 4, a middle partition 3, thermal insulation material 5, and a composite phase change material 6. The outer plate 1, the middle partition 3, and the inner plate 2 are parallel to each other. The middle partition 3 is located between the outer plate 1 and the inner plate 2, dividing the area enclosed by the outer plate 1 and the inner plate 2 into two parts. The first part is close to the outer plate 1 and is used to accommodate the thermal insulation material 5, while the second part is close to the inner plate 2 and is used to accommodate the composite phase change material 6. The fractal structure web 4 is shaped like fractal veins and runs through the entire cavity. It serves as a supporting structure for the outer plate 1, the inner plate 2, and the middle partition 3, and connects the outer plate 1, the middle partition 3, and the inner plate 2 into a whole.

[0023] In this embodiment, the outer plate 1, the fractal structure web plate 4, the intermediate partition plate 3, and the inner plate 2 are made of silicon carbide ceramic or high-temperature alloy and are manufactured in one piece by 3D printing; the spatial distribution of each component and its function are as follows:

[0024] Outer Plate 1: Located at the outermost layer of the entire thermal protection system, it is in direct contact with the external environment and mainly bears the aerodynamic and thermal loads generated by high-speed airflow. When the aircraft flies at high speed, the thermal load generated by the high-speed airflow acts directly on the outer plate 1. Then, some of the heat on the outer plate 1 returns to the outside environment by radiation, and the remaining heat is transferred into the aircraft through the fractal structure web plate 4.

[0025] Fractal structure web 4: Located between outer plate 1 and inner plate 2, its shape resembles a leaf vein and runs through the entire cavity, connecting outer plate 1, inner plate 2, and intermediate partition 3 into a whole. Its main function is to transfer the aerodynamic uniformly distributed load borne by outer plate 1 to inner plate 2. Furthermore, the thermal conductivity of fractal structure web 4 is much higher than that of the insulation material 5; therefore, the heat transmitted from outer plate 1 is mainly transferred into the aircraft interior through fractal structure web 4.

[0026] Intermediate partition 3: Located between outer panel 1 and inner panel 2, it mainly separates the heat insulation material 5 and composite phase change material 6. Secondly, intermediate partition 3 connects multiple fractal structure webs 4 into a whole. Part of the heat from the upper part of the fractal structure web 4 is transferred to the composite phase change material and inner panel 1 through the branch structure, and the other part is transferred to intermediate partition 3, which then transfers the heat to the composite phase change material 6.

[0027] Inner Panel 2: Located at the innermost layer of the entire thermal protection system, it is in direct contact with the internal environment of the aircraft and mainly separates the composite phase change material from the internal environment.

[0028] Thermal insulation material 5: Located between the outer panel 1 and the middle partition 3, its main function is to block the heat on the outer panel 1 from being transferred to the interior of the aircraft.

[0029] Composite phase change material 6: Located near the inner plate 2, between the middle partition 3 and the inner plate 2, with a thermal conductivity of 2.31 W·m. -1 ·K -1 The latent heat is 152.1-207.2 kJ / kg, and the leakage rate is <7%. Its main function is to rapidly absorb the heat transmitted from the fractal structure web 4 and the intermediate partition 3. The composite phase change material 6 is composed of 75-95 wt% paraffin wax, 5 wt% expanded graphite, and 0-20 wt% modified low-melting-point metal-based alloy. The paraffin wax phase change temperature is 42℃, the latent heat is 207.1 J / g, the expanded graphite purity is ≥99%, and the modified low-melting-point metal-based alloy is composed of 50 wt% bismuth (Bi), 25 wt% tin (Sn), 12.5 wt% cadmium (Cd), and 12.5 wt% chromium (Cr), with a melting point of 70℃.

[0030] The three-dimensional thermally conductive grid constructed from expanded graphite and low-melting-point metal-based alloys can quickly transfer local heat to the phase change material, while the paraffin and low-melting-point metal-based alloys will absorb and store the incoming heat using their own latent heat.

[0031] Through the above design, when the aircraft flies at high speed, the heat load generated by the intense friction between the skin surface and the air is concentrated on the outer plate 1. At this time, part of the heat returns to the outside through thermal radiation, while the other part is transferred to the fractal structure web 4 and the thermal insulation material 5. The fractal structure web 4 adopts a branched corrugated plate structure, connecting the outer plate 1, the intermediate partition 3, and the inner plate 2, and mainly serves a load-bearing function. The thermal insulation material is aerogel with a density of 220 kg / m³. 3 With a specific heat capacity of 500 J / kg·K and a thermal conductivity of 0.02 W / m·K, it is in direct contact with the outer plate 1 and has extremely low thermal conductivity, effectively preventing further heat transfer inward. Since the thermal conductivity of the fractal structure web 4 is much higher than that of the insulation material 5, the heat transferred from the outer plate 1 is mainly transferred to the interior through the fractal structure web 4. Part of the heat transferred inward continues to be transferred downward along the branch structure of the fractal structure web and is then absorbed by the composite phase change material. Simultaneously, another part of the heat transferred inward is transferred to the intermediate partition 3 and then absorbed by the composite phase change material. The intermediate partition 3 is located between the insulation material 5 and the composite phase change material 6. Its main function is to isolate the insulation material 5 and the composite phase change material 6, and secondly, it can further transfer the heat transferred from the fractal structure web 4 to the composite phase change material 6.

[0032] During the heat transfer process, the three-dimensional thermally conductive mesh composed of expanded graphite and modified low-melting-point metal-based alloy in the composite phase change material 6 rapidly diffuses the heat near the fractal structure web 4 and the intermediate partition 3 to the surrounding area, while simultaneously transferring localized heat to the composite phase change material for absorption. The composite phase change material is composed of modified low-melting-point metal-based alloy (LMA), expanded graphite (EG), and paraffin wax (PA). In the low-temperature range, paraffin wax undergoes a phase change, utilizing its latent heat to store the transferred heat; in the medium-high temperature range, the low-melting-point metal-based alloy undergoes a phase change, absorbing a large amount of latent heat; thus, it greatly reduces the temperature of the inner plate 2 and maintains good temperature uniformity throughout the thermal protection system. Therefore, the temperature of the inner plate 2 can be maintained near the phase change temperature of the composite phase change material 6 for a long time, thereby ensuring that the internal environment temperature of the aircraft remains within a suitable temperature range.

[0033] In summary, this invention effectively solves the thermal short-circuit problem of traditional corrugated plate integrated thermal protection systems, improves thermal protection performance and temperature uniformity, and provides reliable protection for aircraft to fly safely in environments with severe aerodynamic heating.

[0034] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fractal structure functional integrated thermal protection system containing composite phase change material, characterized in that: The system includes an outer plate (1) and an inner plate (2). A fractal structure web (4) is fixedly provided on the inner side of the outer plate (1), and an inner plate (2) is fixedly provided on the lower side of the fractal structure web (4). A middle partition (3) is fixedly provided on the fractal structure web (4) between the outer plate (1) and the inner plate (2). The cavity between the middle partition (3) and the outer plate (1) is filled with a heat-insulating material (5). The heat-insulating material (5) is aerogel with a density of [insert density here]. Specific heat capacity is Thermal conductivity is The cavity between the intermediate partition (3) and the inner plate (2) is filled with a composite phase change material (6), and the composite phase change material (6) has a thermal conductivity of latent heat The leakage rate is less than 7%. The fractal structure web (4) is distributed in a leaf vein pattern from the outside to the inside and the adjacent fractal structure webs (4) are parallel to each other. The fractal structure web (4) is a branched corrugated plate structure. The composite phase change material (6) is composed of 75-95 wt% paraffin wax, 5 wt% expanded graphite and 0-20 wt% modified low-melting-point metal-based alloy. The phase change temperature of the paraffin wax is 42℃ and the latent heat is 207.1 J / g. The purity of the expanded graphite is ≥99%. The modified low-melting-point metal-based alloy is composed of 50 wt% bismuth, 25 wt% tin, 12.5 wt% cadmium and 12.5 wt% chromium, and the melting point is 70℃.

2. The fractal structure functional integrated thermal protection system containing composite phase change material according to claim 1, characterized in that: The outer plate (1), the middle partition plate (3) and the inner plate (2) are arranged in parallel to each other and are supported and fixed by the fractal structure web plate (4).

3. The fractal structure functional integrated thermal protection system containing composite phase change material according to claim 1, characterized in that: The outer plate (1), inner plate (2), fractal structure web plate (4) and middle partition plate (3) are all silicon carbide or high-temperature alloy and are integrally formed by 3D printing.

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