Heat preservation and insulation double-layer different-height composite microstructure imitating fargesia qinlingensis leaves

Abstract

The invention discloses a Qinlingling fargesia leaf imitated heat preservation and heat insulation double-layer different-height composite microstructure, and belongs to the field of microstructure surface heat transfer. Comprising fusiform and mastoid double-layer different-height microstructures which are periodically and regularly arranged on the surface of a substrate, fusiform microstructure layers and mastoid microstructure layers are arranged in a staggered mode in the spanwise direction, a height difference is formed in the vertical direction perpendicular to the substrate, the vorticity strength is weakened through the fusiform microstructure layers, the fluid speed is reduced through the mastoid microstructure layers, and the vorticity strength is improved through the fusiform microstructure layers. And the temperature boundary layer is thickened in a combined mode, and heat transfer paths are reduced. The invention provides a low-energy-consumption solution aiming at special requirements of an electric heating anti-icing and deicing system of a high-speed aircraft, and solves the problem that the prior art bureau is limited to a single scene of cold protection or ice and snow protection.

Description

Technical Field

[0001] The invention belongs to the field of microstructure surface heat transfer, and in particular relates to a Qinling Arrow Bamboo Leaf-like thermal insulation double-layer composite microstructure with different heights. Background Art

[0003] In recent years, most of the research on thermal insulation at home and abroad has focused on the development and application of materials, while there are relatively few studies on thermal insulation based on surface microstructure design. At present, a variety of thermal insulation materials such as aerogel, rock wool, and foam glass have been developed on the market. Although they have good thermal insulation performance, they still have significant disadvantages such as high cost, easy cracking, and environmental pollution, which limits their widespread application. In addition, these materials mainly achieve thermal insulation by reducing thermal conductivity, and the heat transfer methods include heat conduction, heat convection, and radiation heat transfer. At present, research on thermal insulation by reducing convective heat transfer is relatively rare. In the heat exchange process on the surface of high-speed aircraft, convective heat transfer occupies a major position. The high-speed airflow on the surface will take away a lot of heat through convective heat transfer, which significantly reduces the temperature of the electric heating film icing protection system on the surface of the aircraft and increases the risk of icing accidents.

[0004] The interfacial phenomenon caused by the difference in surface microstructure is a frontier issue in the study and exploration of microscale heat transfer. The micro-nanostructure surface can change the motion state of the fluid through interaction with fluid media such as air and water, reduce the rate at which heat is taken away from the solid surface, and thus weaken the convective heat transfer. Therefore, weakening convective heat transfer by designing and preparing microstructures on the surface is expected to become a new method of thermal insulation.

[0005] However, current research on the heat transfer characteristics of microstructured surfaces mainly focuses on microchannel surfaces for the purpose of enhancing heat transfer and heat dissipation cooling, and the surface structures are mostly single structures, with scales usually at the level of hundreds of micrometers or even millimeters. There are few reports on the convective heat transfer characteristics of microstructured surfaces with multi-layer complex and smaller structures. This not only limits the in-depth understanding of microscale heat transfer mechanisms, but also hinders the development of new thermal insulation technologies. The biological surface structure in nature provides important inspiration for microstructure design. For example, the leaves of Qinling alpine arrow bamboo growing in an ice and snow environment have multi-layer micro-nano structures of unequal heights. Studies have shown that this structure can effectively inhibit convective heat transfer, thereby enhancing ice and snow resistance. Summary of the invention

[0006] Technical issues to be solved:

[0007] In order to avoid the shortcomings of the prior art, the present invention provides a thermal insulation double-layer composite microstructure imitating the Qinling arrow bamboo leaf, which adopts a composite design of shuttle-shaped and mastoid double-layer with different heights, combines geometric shape differences (triangular prism + semi-cylinder; close to lotus leaf mastoid) and size optimization to achieve coordinated control of convective field vorticity and temperature boundary layer. The present invention provides a low-energy solution for the special needs of the electric heating anti-icing system of high-speed aircraft, solving the problem that the prior art is limited to a single scenario of cold protection or ice and snow protection.

[0008] The technical solution of the present invention is: a double-layer composite microstructure with different heights that imitates the Qinling arrow bamboo leaves for thermal insulation, including a fusiform and mastoid double-layer microstructure with different heights that is periodically arranged on the surface of a base, wherein the fusiform microstructure layer and the mastoid microstructure layer are staggered along the span direction and form a height difference in the vertical direction perpendicular to the base, the vortex intensity is weakened by the fusiform microstructure layer, the mastoid microstructure layer reduces the fluid velocity, and the temperature boundary layer is thickened together to reduce the heat transfer path.

[0009] A further technical solution of the present invention is: the first layer of the fusiform and mastoid double-layer microstructure with different heights is a fusiform microstructure layer formed by an array of several fusiform structures, and the second layer is a mastoid microstructure layer formed by an array of several mastoid structures, wherein the vertical height of the fusiform structure is greater than the vertical height of the mastoid structure, and the vertical height is the axial height of the fusiform structure or the mastoid structure.

[0010] A further technical solution of the present invention is that the shuttle-shaped structure is composed of an isosceles triangular prism end, a semi-cylindrical end and a cuboid connecting the two; the radial cross-sectional width w of the shuttle-shaped structure is 150-200 μm, the length is 400-500 μm, and the axial height h is 梭形 Meet the aspect ratio: h 梭形 / w=0.3~1, the spacing between adjacent shuttle-shaped structures along the span direction is 300~1200μm, and the spacing along the direction perpendicular to the span direction is 500~600μm; and the isosceles triangular prism top angles of each shuttle-shaped structure are in the same direction, and the symmetry plane is located in the direction perpendicular to the span direction.

[0011] A further technical solution of the present invention is that the top angle of the isosceles triangular prism of the shuttle-shaped structure is an acute angle, and the angle range is 30° to 60°.

[0012] A further technical solution of the present invention is that the diameter of the semi-cylindrical end of the shuttle-shaped structure is 100-150 μm, and the length of the cuboid connected to the isosceles triangular prism end is 200-300 μm.

[0013] A further technical solution of the present invention is that the mastoid structure is a cylinder with a diameter d of 50 to 80 μm and an axial height h 乳突 Meet the aspect ratio: h 乳突 / d=0.8-2, the spacing between adjacent mastoid structures along the span direction is 70-160 μm, and the spacing along the direction perpendicular to the span direction is 70-160 μm.

[0014] A further technical solution of the present invention is that the spacing of the mastoid structures in the span direction and perpendicular to the span direction are equal.

[0015] A further technical solution of the present invention is: the materials of the shuttle microstructure layer and the papillary microstructure layer are selected from one of metal, inorganic non-metallic material or polymer material; the metal is aluminum, copper or alloy, and the inorganic non-metallic material is ceramic, polydimethylsiloxane PDMS or photoresist.

[0016] A further technical solution of the present invention is that the base is a plane or a curved surface with curvature.

[0017] A design method for a thermal insulation double-layer composite microstructure imitating the leaves of Qinling arrow bamboo, wherein the shuttle-shaped structure and the mastoid structure are optimized in structural size by using a mathematical model of the Nusselt number;

[0018] The mathematical model of the shuttle structure is:

[0019]

[0020] The mathematical model of the mastoid structure is:

[0021]

[0022] In the formula, h 梭形 is the height of the shuttle-shaped structure, w is the cross-sectional width of the shuttle-shaped structure, l 2 is the spanwise spacing between adjacent shuttle-shaped structures, h 乳突 is the height of the mastoid structure, d is the diameter of the mastoid structure, l 1 is the spanwise spacing between adjacent mastoid structures.

[0023] Beneficial Effects

[0024] The beneficial effect of the present invention is that the Qinling Arrow Bamboo Leaf-like thermal insulation double-layer composite microstructure proposed in the present invention can effectively reduce the surface convective heat transfer efficiency, thereby reducing the energy required to resist convective heat transfer in the anti-icing system, thereby effectively reducing the energy consumption of the Qinling Arrow Bamboo Leaf-like ice-repellent skin anti-icing system.

[0025] The main function of the present invention is to reduce the convective heat transfer effect of the solid surface, reduce the heat transfer rate of the surface, and achieve the purpose of thermal insulation. According to the established mathematical model of the Nusselt number and structural parameters of the fusiform and papillary microstructures, it can be seen that the Nusselt number of the surface is affected by the aspect ratio of the structure (i.e. ) has a great influence. Within a certain range (0.8-2 for the mastoid structure and 0.3-1 for the shuttle structure), the surface Nusselt number decreases with the increase of the aspect ratio of the two structures. Since the Nusselt number is a dimensionless parameter that characterizes the strength of convective heat transfer, as the Nusselt number decreases, it indicates that the convective heat transfer intensity of the surface decreases, the heat transfer rate slows down, and the purpose of thermal insulation can be achieved. The specific effect analysis is as follows:

[0026] 1. Significantly reduce the efficiency of convective heat transfer. The double-layer composite microstructure design (fusiform + papillae) imitating the Qinling arrow bamboo leaves can effectively suppress the surface fluid vortex intensity and reduce the momentum exchange inside the flow field. Experiments show that this structure reduces the surface convective heat transfer Nusselt number (Nu) by about 55% on average compared to smooth surfaces, significantly reducing heat loss and achieving efficient thermal insulation.

[0027] 2. Optimize the performance of the temperature boundary layer. The composite microstructure thickens the temperature boundary layer (1.5 to 2.5 times that of the smooth surface), prolongs the heat transfer path, reduces the temperature difference between the wall and the fluid, and further weakens the heat transfer rate. The simulation results show that under the same heat flow conditions, the temperature distribution on the surface of the composite structure is more uniform, and the temperature gradient is reduced by more than 30%.

[0028] 3. Outstanding energy-saving effect. For the electric heating anti-icing system of high-speed aircraft, this structure can reduce the energy consumption required to resist external convection heat exchange. In practical applications, the electric heating power demand is reduced by about 40% to 50%, which significantly improves the energy utilization efficiency of the system and meets the stringent requirements of energy conservation and emission reduction in the aerospace field.

[0029] 4. Dynamic flow field control capability. The shuttle-shaped structure of the present invention weakens the fluid wake vortex intensity and inhibits the development of turbulence through the special-shaped combination of isosceles triangular prisms and semi-cylinders. The densely arranged cylinders of the mastoid structure increase the surface resistance, reduce the mainstream velocity (reduced by 20% to 30% compared to the smooth surface velocity), and synergistically achieve laminar flow maintenance and vortex attenuation.

[0030] 5. Based on the mathematical model of Nusselt number and aspect ratio, the present invention clarifies the optimal range of fusiform aspect ratio of 0.3-1 and mastoid aspect ratio of 0.8-2, ensuring that the design is quantifiable and reproducible, breaking through the limitation of traditional microstructure relying on trial and error method.

[0031] 6. It has been verified that the composite microstructure of the present invention can maintain stable performance without cracking or deformation under conditions of high-speed airflow (Mach number > 0.5) and extreme temperature (50°C to 150°C), and is suitable for harsh environments such as aerospace, high-speed trains, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The relationship between Nu distribution along the flow direction on the surface of the mastoid microstructure and the aspect ratio of the structure in the embodiment of the present invention;

[0033] Figure 2 The relationship between Nu distribution along the flow direction and the aspect ratio of the shuttle-shaped microstructure surface in the embodiment of the present invention;

[0034] Figure 3 It is an axonometric view of a double-layer composite microstructure with different heights, imitating the thermal insulation of Qinling Arrow Bamboo Leaves in an embodiment of the present invention.

[0035] Figure 4 It is a top view of the thermal insulation double-layer composite microstructure imitating Qinling Arrow Bamboo Leaves in an embodiment of the present invention.

[0036] Figure 5 It is a front view of the thermal insulation double-layer composite microstructure imitating Qinling Arrow Bamboo Leaves in an embodiment of the present invention.

[0037] Figure 6 This is a cross-sectional dimension diagram of a double-layer composite microstructure imitating Qinling Arrow Bamboo Leaves for thermal insulation in an embodiment of the present invention.

[0038] Figure 7 Comparison of fluid temperature distribution between composite microstructure and smooth surface in the embodiment of the present invention

[0039] Figure 8 Comparison of fluid velocity distribution between composite microstructure and smooth surface in the embodiment of the present invention

[0040] Fig. 9 Comparison of convective heat transfer effects between smooth surface and composite microstructure surface in the embodiment of the present invention

[0041] Explanation of the accompanying drawings: 1. fusiform structure, 2. mastoid structure. DETAILED DESCRIPTION

[0042] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0043] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0044] Based on the problem that the existing technology is limited to a single scenario of cold protection or ice and snow protection, the present invention provides a thermal insulation double-layer composite microstructure imitating Qinling arrow bamboo leaves, which can significantly reduce the surface convective heat transfer efficiency to better maintain the electric heating temperature of the bionic electrothermal ice-repellent skin surface. The mechanism of reducing the convective heat transfer efficiency of the microstructure surface is:

[0045] Existing studies have shown that the convective heat transfer efficiency of solid surfaces is affected by the fluid, including factors such as the velocity of the fluid, the motion state of the fluid, and the temperature of the surface. Under turbulent conditions, compared with smooth and unstructured surfaces, the microstructure of the papillary layer in the Qinling Arrow Bamboo Leaf Thermal Insulation Double-layer Height Composite Microstructure can reduce the momentum exchange inside the flow field by reducing the vorticity intensity of the surface fluid, weaken the disturbance effect on the surface temperature boundary layer, and thus reduce the convective heat transfer efficiency of the surface. Moreover, along the flow direction, the vortex structure of the papillary and shuttle-shaped microstructure wakes gradually decreases, the vorticity intensity gradually decreases, and the convective heat transfer intensity weakens.

[0046] In addition, by comparing the fluid movement speed of a smooth unstructured surface and a surface containing a double-layer heterogeneous composite microstructure imitating the thermal insulation of the Qinling Arrow Bamboo Leaf, it was found that the surface velocity containing the microstructure was significantly lower. According to the conclusion that the convective heat transfer efficiency of a solid surface is positively correlated with the surface fluid movement speed, the double-layer heterogeneous composite microstructure imitating the thermal insulation of the Qinling Arrow Bamboo Leaf can significantly reduce the convective heat transfer efficiency of the surface.

[0047] The temperature boundary layer is a thin layer where the fluid temperature changes dramatically near the solid wall, which can directly reflect the speed of surface convective heat transfer efficiency. By comparing the temperature distribution of the smooth structureless surface and the surface with microstructures, it can be seen that the temperature boundary layer of the surface with microstructures is relatively thicker, and within the calculated structural aspect ratio range, as the structural aspect ratio of the microstructure surface increases (the mastoid microstructure is 0.8-2, and the shuttle microstructure is 0.3-1), the surface temperature boundary layer continues to thicken. According to the conclusion that the thickening of the temperature boundary layer will increase the heat diffusion path, resulting in the heat on the bottom wall to be transferred to the fluid through a longer distance, thereby limiting the heat transfer, it can be seen that the Qinling Arrow Bamboo Leaf Thermal Insulation Double-layer Height Composite Microstructure can effectively reduce the surface convective heat transfer efficiency.

[0048] The invention discloses a thermal insulation double-layer composite microstructure imitating Qinling Arrow Bamboo Leaves, comprising a fusiform and mastoid double-layer microstructures of different heights arranged on a substrate surface in a periodic pattern, wherein the fusiform microstructure layer and the mastoid microstructure layer are arranged alternately along the span direction and form a height difference in the vertical direction perpendicular to the substrate, the vorticity intensity is weakened by the fusiform microstructure layer, the fluid velocity is reduced by the mastoid microstructure layer, and the temperature boundary layer is thickened together to reduce the heat transfer path.

[0049] Specifically, the first layer of the mastoid double-layer microstructure with different heights is a fusiform microstructure layer formed by an array of several fusiform structures, and the second layer is a mastoid microstructure layer formed by an array of several mastoid structures, wherein the vertical height of the fusiform structure is greater than the vertical height of the mastoid structure, and the vertical height is the axial height of the fusiform structure or the mastoid structure.

[0050] The above technical solution is further described below in conjunction with the accompanying drawings:

[0051] In one embodiment, referring to Figure 3-6 As shown, in this embodiment, a thermal insulation double-layer composite microstructure imitating the leaves of Qinling Arrow Bamboo includes a fusiform and mastoid double-layer microstructures with different heights placed on a base, the fusiform structure 1 is longitudinally arranged in a single row and periodically on the base layer of the material, the mastoid structure 2 is also longitudinally arranged between the fusiform microstructures, and the two structures are arranged in an array in sequence to form the thermal insulation double-layer composite microstructure imitating the leaves of Qinling Arrow Bamboo.

[0052] Preferably, the shuttle-shaped structure is composed of an isosceles triangular prism end, a semi-cylindrical end and a cuboid connecting the two; the radial cross-sectional width w of the shuttle-shaped structure is 150-200 μm, the length is 400-500 μm, and the axial height h is 梭形 Meet the aspect ratio: h 梭形 / w=0.3~1, the spacing between adjacent shuttle-shaped structures along the span direction is 300~1200μm, and the spacing along the direction perpendicular to the span direction is 500~600μm; and the isosceles triangular prism top angles of each shuttle-shaped structure are in the same direction, and the symmetry plane is located in the direction perpendicular to the span direction.

[0053] Preferably, the apex angle of the isosceles triangular prism of the shuttle-shaped structure is an acute angle, and the angle ranges from 30° to 60°.

[0054] Preferably, the diameter of the semi-cylindrical end of the shuttle-shaped structure is 100-150 μm, and the length of the cuboid connected to the isosceles triangular prism end is 200-300 μm.

[0055] Preferably, the mastoid structure is a cylinder with a diameter d of 50 to 80 μm and an axial height h of the mastoid satisfying a height-to-width ratio: h 乳突 / d=0.8-2, the spacing between adjacent mastoid structures along the span direction is 70-160 μm, and the spacing along the direction perpendicular to the span direction is 70-160 μm.

[0056] Preferably, the spacing of the mastoid structures in the span direction and perpendicular to the span direction are equal.

[0057] Preferably, the materials of the shuttle microstructure layer and the papillary microstructure layer are selected from metal, inorganic non-metallic material or polymer material; the metal is aluminum, copper or alloy, and the inorganic non-metallic material is ceramic, polydimethylsiloxane PDMS or photoresist.

[0058] Preferably, the substrate is a plane or a curved surface with curvature.

[0059] In one embodiment, referring to Figure 1 and 2 As shown, in a design method for a thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaves, the shuttle-shaped structure and the mastoid structure are optimized in structural size through a mathematical model of the Nusselt number;

[0060] The mathematical model of the shuttle structure is:

[0061]

[0062] The mathematical model of the mastoid structure is:

[0063]

[0064] In the formula, h 梭形 is the height of the shuttle-shaped structure, w is the cross-sectional width of the shuttle-shaped structure, l 2 is the spanwise spacing between adjacent shuttle-shaped structures, h 乳突 is the height of the mastoid structure, d is the diameter of the mastoid structure, l 1 is the spanwise spacing between adjacent mastoid structures.

[0065] In one embodiment, the shuttle-shaped microstructure of the thermal insulation double-layer composite microstructure imitating the Qinling arrow bamboo leaf is 450 μm long, 200 μm wide, 100 μm high, with a lateral spacing of 900 μm and a longitudinal spacing of 500 μm, and the mastoid microstructure is 50 μm in diameter and 80 μm high, with both the lateral spacing and the longitudinal spacing being 100 μm. The thermal insulation double-layer composite microstructure imitating the Qinling arrow bamboo leaf and the base material layer are both made of aluminum material and processed by femtosecond laser, and the base material layer is a plane.

[0066] Reference Figure 7 As shown in the figure, the composite surface with nipple and shuttle microstructure in this embodiment has a significantly higher flow field mainstream temperature than the smooth surface, resulting in a smaller difference between the temperature of the wall surface heated by constant heat flux and the flow field mainstream temperature, that is, the temperature difference between the wall surface and the fluid is reduced, which leads to a decrease in heat transfer efficiency, so that the composite structure surface shows a weakened heat transfer effect. And from the velocity distribution cloud diagram of each section in the flow field corresponding to the two surfaces ( Figure 8) It can also be found that the mainstream velocity in the entire flow field of the composite structure surface is significantly smaller than that of the smooth surface. According to the general conclusion, under low-speed conditions, the Nusselt number increases with the increase of the Reynolds number. Since the mainstream velocity of the flow field on the composite structure surface is relatively small, the heat transfer capacity of the surface also decreases accordingly.

[0067] In order to further characterize the effect of the composite structure on the surface convective heat transfer behavior, the heat transfer of the composite structure surface and the smooth surface was quantitatively compared and analyzed. Fig. 9 By comparing the numerical simulation results of the two, it is found that under the same flow velocity and other working conditions, the composite structure has a smaller average Nusselt number than the ordinary smooth surface, and within the range of gas Reynolds numbers studied, the average Nusselt number of the composite structure surface is reduced by about 55%. Therefore, from the above analysis, it can be concluded that the composite structure can effectively weaken the convective heat transfer of the surface.

[0068] In one embodiment, the fusiform microstructure of the thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaf is 420 μm long, 160 μm wide, 120 μm high, with a lateral spacing of 880 μm and a longitudinal spacing of 520 μm. The diameter of the mastoid microstructure is 60 μm, the height is 90 μm, and the lateral and longitudinal spacings are both 120 μm. The thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaf and the base material layer are both made of silicon-based materials, and the upper surface of the base is a smooth plane.

[0069] In one embodiment, the shuttle-shaped microstructure of the thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaf is 460 μm long, 180 μm wide, 140 μm high, with a lateral spacing of 920 μm and a longitudinal spacing of 530 μm. The diameter of the mastoid microstructure is 55 μm, the height is 100 μm, and the lateral spacing and the longitudinal spacing are both 110 μm. The thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaf and the base material layer are both made of UV glue (ultraviolet light curing) material, and the upper surface of the base is a smooth plane.

[0070] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A thermal insulation double-layer composite microstructure imitating the leaves of Qinling arrow bamboo, characterized by: It includes a double-layer microstructure of fusiform and mastoid arranged on the surface of the substrate in a periodic pattern, wherein the fusiform microstructure layer and the mastoid microstructure layer are staggered along the span direction and form a height difference in the vertical direction perpendicular to the substrate, the vorticity intensity is weakened by the fusiform microstructure layer, the fluid velocity is reduced by the mastoid microstructure layer, and the temperature boundary layer is thickened together to reduce the heat transfer path.

2. According to claim 1, a thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaf, characterized in that: The first layer of the fusiform and mastoid double-layer microstructure with different heights is a fusiform microstructure layer formed by an array of several fusiform structures, and the second layer is a mastoid microstructure layer formed by an array of several mastoid structures, wherein the vertical height of the fusiform structure is greater than the vertical height of the mastoid structure, and the vertical height is the axial height of the fusiform structure or the mastoid structure.

3. According to claim 2, a thermal insulation double-layer composite microstructure imitating Qinling Arrow Bamboo Leaves, characterized in that: The shuttle-shaped structure is composed of an isosceles triangular prism end, a semi-cylindrical end and a cuboid connecting the two; the radial cross-sectional width w of the shuttle-shaped structure is 150-200 μm, the length is 400-500 μm, and the axial height h is 梭形 Meet the aspect ratio: h 梭形 / w=0.3~1, the spacing between adjacent shuttle-shaped structures along the span direction is 300~1200μm, and the spacing along the direction perpendicular to the span direction is 500~600μm; and the isosceles triangular prism top angles of each shuttle-shaped structure are in the same direction, and the symmetry plane is located in the direction perpendicular to the span direction.

4. According to claim 3, a thermal insulation double-layer composite microstructure imitating Qinling Arrow Bamboo Leaves is characterized by: The apex angle of the isosceles triangular prism of the shuttle-shaped structure is an acute angle, and the angle ranges from 30° to 60°.

5. According to claim 4, the thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaf is characterized by: The diameter of the semi-cylindrical end of the shuttle-shaped structure is 100-150 μm, and the length of the cuboid connected to the isosceles triangular prism end is 200-300 μm.

6. According to claim 2, the thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaf is characterized by: The mastoid structure is a cylinder with a diameter d of 50 to 80 μm and an axial height h 乳突 Meet the aspect ratio: h 乳突 / d=0.8-2, the spacing between adjacent mastoid structures along the span direction is 70-160 μm, and the spacing along the direction perpendicular to the span direction is 70-160 μm.

7. According to claim 6, a thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaf, characterized in that: The spacings of the mastoid structures in the span direction and perpendicular to the span direction are equal.

8. According to claim 1, the thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaf is characterized by: The materials of the shuttle microstructure layer and the mastoid microstructure layer are selected from metal, inorganic non-metallic material or polymer material; the metal is aluminum, copper or alloy, and the inorganic non-metallic material is ceramic, polydimethylsiloxane PDMS or photoresist.

9. According to claim 1, the thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaf is characterized by: The substrate is a plane or a curved surface with curvature.

10. A design method for the thermal insulation double-layer composite microstructure imitating the Qinling Arrow Bamboo Leaf according to any one of claims 1 to 9, characterized in that: The fusiform structure and the mastoid structure are optimized in structure size by using a mathematical model of Nusselt number; The mathematical model of the shuttle structure is: The mathematical model of the mastoid structure is: In the formula, h 梭形 is the height of the shuttle-shaped structure, w is the cross-sectional width of the shuttle-shaped structure, l2 is the spanwise spacing between adjacent shuttle-shaped structures, and h 乳突 is the height of the mastoid structure, d is the diameter of the mastoid structure, and l1 is the spanwise spacing between adjacent mastoid structures.

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