Thermal protection structure based on gradient crystal lattice and preparation method thereof

Abstract

The invention provides a gradient lattice-based thermal protection structure, which comprises an inner layer plate, an outer layer plate and a lattice filling structure, the lattice filling structure is filled and connected between the inner layer plate and the outer layer plate, the lattice filling structure comprises a plurality of spliced unit cells, the unit cells are body-centered cubic unit lattices, a liquid cooling flow channel is arranged in the lattice filling structure, and the liquid cooling flow channel is communicated with the liquid cooling flow channel. A liquid inlet of the liquid cooling flow channel is exposed between the inner-layer plate and the outer-layer plate, the closer to the liquid cooling flow channel, the larger the size of the unit cell is, and the sparser the arrangement density of the unit cell is; the farther the unit cells are away from the liquid cooling flow channel, the smaller the size of the unit cells is, the denser the arrangement density of the unit cells is, turbulent flow columns of water-drop-shaped structures are arranged on the wall face of the side, close to the outer layer plate, of the liquid cooling flow channel, and the tip ends of the water-drop-shaped structures face the liquid inlet. The thermal protection structure has the advantages of high heat dissipation performance, high mechanical bearing capacity and light weight. The thermal protection structure is prepared by using a selective laser melting method.

Description

Technical Field

[0001] This invention relates to the technical field of thermal protection structure design and manufacturing, specifically to a thermal protection structure based on a gradient lattice and its preparation method. Background Technology

[0002] Spacecraft, particularly their hot-end components such as the nose cone leading edge, tail fins, and skin, face severe thermal barrier challenges under high-temperature aerodynamic environments. Achieving efficient cooling and thermal protection has become a crucial aspect of modern spacecraft development. High-speed aircraft not only need to minimize the overall structural weight but also overcome the high temperatures generated by aerodynamic heating during high-speed flight, and withstand the enormous loads and vibrations from the propulsion system and aerodynamic forces. Therefore, high-strength, high-thermal-protection structural materials are essential for further development in the aerospace field.

[0003] Currently, traditional thermal protection structure designs have revealed numerous limitations in addressing the complex flight requirements of these high-speed aircraft. While some thermal protection structures possess a certain degree of thermal insulation, they still fall short in terms of mechanical load-bearing capacity and lightweight design. Structures with better mechanical properties often have a large mass, making it difficult to achieve lightweight goals, and their thermal protection technologies mostly focus on a single thermal protection method, lacking integrated and innovative designs. Traditional active thermal protection structures inevitably struggle to meet the ever-increasing demands for lightweight, high strength, and thermal insulation. How to achieve more efficient heat dissipation and lightweight yet high strength in active thermal protection structures through structural design and optimization has become a key aspect in promoting the development of new thermal protection technologies and high-speed aerospace equipment. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a thermal protection structure with the advantages of high heat dissipation performance, high mechanical load-bearing capacity and light weight.

[0005] This application also provides a method for preparing a thermal protection structure based on a gradient lattice. The method of preparing the thermal protection structure by 3D printing has the advantages of simple operation and precise structural control.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows: A thermal protection structure based on a gradient lattice includes: Inner layer; An outer layer plate, spaced apart on one side of the inner layer plate; and A lattice-filled structure is provided, which fills and connects the inner and outer layers. The lattice-filled structure comprises multiple interconnected unit cells, each unit cell being a body-centered cubic lattice. A liquid-cooling channel is provided within the lattice-filled structure, with its inlet exposed between the inner and outer layers. The inlet is used to introduce coolant for heat dissipation. The closer to the liquid-cooling channel, the larger the size of the unit cell, and the sparser the density of the unit cells. The further away from the inner and outer layers, the larger the size of the unit cell. The smaller the size of the unit cell and the denser the arrangement of the unit cells in the liquid cooling channel, the more the lattice filling structure forms a gradient hollow structure with a denser outer layer and a sparser inner layer. The hollow area of ​​the lattice filling structure is used as a natural air convection flow area. The wall surface of the liquid cooling channel near the outer plate is arranged with a teardrop-shaped turbulence column. The structure is specifically presented as a splicing of a semi-cone and a semi-sphere, with the generatrix of the cone tangent to the surface of the sphere. The tip of the teardrop-shaped structure is set towards the liquid inlet.

[0007] In some possible implementations, when viewed along the direction of the variation trend of the unit cell, the side length of the larger unit cell is 1.5-2 times the side length of the adjacent smaller unit cell.

[0008] In some possible implementations, the smallest unit cell has a side length of 8-10 mm.

[0009] In some possible implementations, the number of the baffle columns is multiple, and the baffle columns are arranged at intervals between adjacent pairs.

[0010] In some possible implementations, the characteristic radius of the spherical portion of the teardrop-shaped structure is 2-3 mm, and the characteristic angle of the tip of the teardrop-shaped structure is 30-60°.

[0011] In some possible implementations, the plurality of the spoiler columns are arranged in multiple rows and columns. When viewed along the orientation of the tips, the adjacent two spoiler columns in different columns are staggered. The spoiler columns in even-numbered columns are arranged symmetrically, and the spoiler columns in odd-numbered columns are arranged symmetrically.

[0012] In some possible implementations, when viewed along the orientation of the tip, the spacing between two adjacent columns of the same type of spoiler is 4-6 of the characteristic radius, and the spacing between two adjacent spoiler columns in different columns is 10-15 mm.

[0013] In some possible implementations, both the inner and outer layers are arc-shaped structures, with the inner and outer layers bending in the same direction, and the arc-shaped structures protruding outwards.

[0014] This application also provides a method for preparing a thermal protection structure based on a gradient lattice, the method comprising the following steps: Step 1: Use modeling software to construct a three-dimensional solid geometric model of the thermal protection structure; Step 2: Use 3D printing model processing software to perform layer-by-layer slicing of the model; Step 3: Fill the material cylinder cavity of the laser selective melting equipment with powder and fill the material cylinder cavity with inert gas; Step 4: Using a laser selective melting device, powder is laid layer by layer for printing. The heat protection structure is printed according to the three-dimensional solid geometric model. The powder laying thickness is the same as the slice layer thickness. Step 5: Remove the printed heat protection structure and perform ultrasonic cleaning.

[0015] In some possible implementations, the powder in step 3 includes at least one of copper alloy, titanium alloy, and aluminum alloy.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) This thermal protection structure is not limited to a single thermal protection method, but adopts a combination of active thermal protection (liquid cooling channels can be used to introduce coolant to achieve forced convection) and passive thermal protection (natural air convection), which effectively enhances the overall thermal protection performance of the structure and achieves efficient heat dissipation and cooling.

[0017] 2) The lattice-filling structure utilizes a body-centered cubic lattice with excellent mechanical properties. Topology optimization yields a cell structure characterized by decreasing cell size and increasing density from the inside out. This effectively withstands and decomposes external loads, significantly enhancing the overall structural load-bearing capacity. Furthermore, the aforementioned cell structure design significantly reduces component mass, achieving lightweight construction.

[0018] 3) By introducing textured microchannels within the gradient structure, the streamlined turbulent microstructures within the microchannels increase the heat transfer area, disrupt the normal development of the thermal boundary layer, and enhance the disturbance effect of the working fluid, thereby significantly strengthening convective heat transfer and achieving efficient cooling.

[0019] This application utilizes 3D printing to fabricate thermal protection structures, which offers advantages such as ease of operation and precise structural control.

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0021] Figure 1 This is a partial structural schematic diagram of a thermal protection structure provided in an embodiment of this application; Figure 2 for Figure 1 A schematic diagram of the local thermal protection structure from another angle; Figure 3 Schematic diagrams of the unit cell structure at different angles; Figure 4 for Figure 2 A cross-sectional view of the thermal protection structure along AA; Figure 5 for Figure 4 Another structural diagram from a different perspective; Figure 6 for Figure 2 The diagram shown illustrates the working principle of the thermal protection structure in specific applications, including the stress on the outer plate, and the airflow and coolant flow along the cross sections AA and BB.

[0022] Figure 7 The arrangement of the baffle columns in different columns; Figure 8 This is a schematic diagram of the structure of the turbulence column.

[0023] Explanation of icon numbers: 1-Inner layer plate; 2-Outer layer plate; 21-Connecting plate; 3-Lattice filling structure; 31-Liquid cooling channel; 310-Liquid inlet; 311-Liquid outlet; 4-Breakthrough column. Detailed Implementation

[0024] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0025] The following describes some embodiments of the present invention in detail. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] One embodiment of this application provides a heat protection structure, referring to... Figure 1 and Figure 2 The thermal protection structure includes an inner layer plate 1, an outer layer plate 2, and a lattice-filled structure 3. The outer layer plate 2 is spaced apart on one side of the inner layer plate 1. The outer layer plate 2 is the outer surface of the thermal protection structure, directly in contact with the external environment and directly bearing the thermal load from aerodynamic heating. The lattice-filled structure 3 fills and connects the inner layer plate 1 and the outer layer plate 2, thus making the lattice-filled structure 3 the main mechanical load-bearing structure. The lattice-filled structure 3 includes multiple interconnected unit cells, where each unit cell is a body-centered cubic lattice (refer to reference). Figure 3The lattice-filled structure 3 contains a liquid-cooled flow channel 31, with the inlet 310 of the liquid-cooled flow channel 31 exposed between the inner layer plate 1 and the outer layer plate 2. The inlet 310 is used to introduce coolant for heat dissipation. For example, the coolant can be one of glycerol-based coolant, ethylene glycol-based coolant, or propylene glycol-based coolant. In actual use, the coolant is introduced into the liquid-cooled flow channel 31 through the inlet 310. For example, the liquid-cooled flow channel 31 also has an outlet 311, which is arranged opposite to the inlet 310, allowing the coolant to flow out from the outlet 311. The closer to the liquid cooling channel 31, the larger the unit cell size and the sparser the unit cell density; the farther away from the liquid cooling channel 31, the smaller the unit cell size and the denser the unit cell density. This results in a gradient, denser outer and sparser inner hollow structure in the lattice-filled structure 3, with the hollow region of the lattice-filled structure 3 serving as a natural air convection domain. The wall of the liquid cooling channel 31 near the outer plate 2 is equipped with teardrop-shaped turbulence columns 4. These columns are specifically constructed from a semi-cone and a semi-sphere, with the generatrix of the cone tangent to the surface of the sphere. The tips of the teardrop-shaped structures face the liquid inlet 310, thus ensuring that the direction of the tips is opposite to the flow direction of the coolant. This further enhances the turbulence, disrupts the flow boundary layer, and increases the heat transfer area, thereby improving heat dissipation performance. Furthermore, compared to other structures, the teardrop-shaped structure exhibits superior quality through 3D printing, with a smoother overall curve and a smaller increase in pressure drop.

[0027] In practical application, the thermal protection structure, as part of the aircraft's outer surface, is affected by aerodynamic heating when the aircraft is flying at high speed. This heat is conducted through the outer plate 2, causing the temperature of the entire structure to rise. The active cooling system then activates, pumping coolant to the inlet 310. The coolant then carries away heat through forced convection within the liquid cooling channel 31, achieving active thermal protection. Simultaneously, air flows through the hollow region of the lattice-filled structure 3 in the opposite direction to the coolant flow, carrying away heat through natural convection. This combination of forced coolant convection and natural air convection creates a combined active and passive heat dissipation method, significantly improving thermal protection efficiency.

[0028] Specifically, such as Figure 6As shown in cross-sectional views A and B, the thermal protection structure employs a combination of active thermal protection (forced coolant convection) and passive thermal protection (natural air convection). The coolant is pumped to the tip of the teardrop-shaped turbulence column 4, flowing in the opposite direction. As the coolant flows along the liquid-cooled channel 3, it carries away a significant amount of heat transferred to the liquid-cooled channel 31 via heat conduction, thus lowering the overall structure temperature. Air flows in the hollow region of the lattice-filled structure 3 in the opposite direction to the coolant flow, and natural convection provides thermal protection by reducing the overall structural temperature. Once air enters its flow region, the lattice structure not only turbulents the air and disrupts the flow boundary layer, but also effectively increases the heat exchange area with the air, significantly improving the heat transfer performance of natural air convection. Furthermore, since this heat dissipation process is natural convection, no pumping is required throughout, effectively reducing the energy consumption of the thermal protection structure.

[0029] The beneficial effects of this structure are as follows: (1) This thermal protection structure is not limited to a single thermal protection method, but adopts a combination of active thermal protection (the liquid cooling channel 31 can be used to pass in coolant to achieve forced convection) and passive thermal protection (natural air convection), which effectively enhances the overall thermal protection performance of the structure and achieves efficient heat dissipation and cooling.

[0030] (2) The lattice-filling structure 3 uses a body-centered cubic lattice with excellent mechanical properties. The topology optimization produces a cell structure with the characteristics of decreasing size and increasing density from the inside to the outside of the unit cell. This can effectively bear and decompose the received external loads, and greatly improve the load-bearing capacity of the overall structure. In addition, the above cell structure design can significantly reduce the mass of the components and achieve lightweighting.

[0031] (3) By introducing textured microchannels into the gradient structure, the streamlined turbulent microstructures in the microchannels increase the heat transfer area, disrupt the normal development of the thermal boundary layer, and enhance the effect of working fluid disturbance, thereby significantly strengthening convective heat transfer and achieving efficient cooling.

[0032] In some embodiments, the materials of the inner layer plate 1, the outer layer plate 2, and the lattice filling structure 3 can all be metal alloy materials, such as copper alloys (e.g., CuCrZr), titanium alloys (e.g., TC4), and aluminum alloys, thereby improving the thermal conductivity and mechanical properties of the thermal protection structure.

[0033] In some embodiments, when viewed along the direction of the unit cell variation trend, the side length of the larger unit cell is 1.5-2 times the side length of the adjacent smaller unit cell.

[0034] In some embodiments, the smallest unit cell has a side length of 8-10 mm.

[0035] In some embodiments, the number of turbulence columns 4 is multiple (exemplarily, there may be two or more), and adjacent turbulence columns 4 are spaced apart. The turbulence columns 4 have the functions of turbulence, disrupting the flow boundary layer, and increasing the heat transfer area, thereby facilitating further improvement of heat dissipation performance.

[0036] In some embodiments, the characteristic radius R of the spherical portion of the teardrop structure is 2-3 mm, and the characteristic angle α of the tip of the teardrop structure is 30-60°.

[0037] In some embodiments, multiple spoiler columns 4 are arranged in multiple rows and columns. When viewed along the direction of the tip, adjacent spoiler columns 4 in different columns are staggered. Spoiler columns 4 in even-numbered columns are arranged symmetrically, and spoiler columns 4 in odd-numbered columns are arranged symmetrically.

[0038] In some embodiments, when viewed along the direction of the tip, the arrangement spacing D between two adjacent columns of the same type of spoiler column 4 is 4-6 characteristic radii R, and in adjacent columns, the arrangement spacing L between two adjacent spoiler columns 4 in different columns is 10-15 mm.

[0039] In some embodiments, in conjunction with reference Figure 1 and Figure 2 Both the inner layer 1 and the outer layer 2 are arc-shaped structures, and the bending directions of the inner layer 1 and the outer layer 2 are the same, with the arc-shaped structures protruding and bending outwards.

[0040] For example, the radius of curvature of the outer layer 2 can be greater than the radius of curvature of the inner layer 1.

[0041] In some embodiments, the thermal protection structure further includes two connecting plates 21. When viewed relative to the liquid inlet 310, one connecting plate 21 is connected to one end of the lattice-filled structure 3, and the other connecting plate 21 is connected to the opposite end of the lattice-filled structure 3. The connecting plates 21 are also connected between the outer layer plate 2 and the inner layer plate 1.

[0042] This application also provides a method for preparing a thermal protection structure, the method being used to prepare any of the thermal protection structures described above, the method comprising the following steps.

[0043] Step 1: Use modeling software to construct a 3D solid geometric model of the thermal protection structure. After the model is created, save it in STL format. For example, the modeling software can be one of Blender, Fusion 360, FreeCAD, SketchUp, or AutoCAD.

[0044] Step 2: Perform layer-by-layer slicing on the model using 3D printing model processing software. For example, the slice thickness can be 20-100 μm. For instance, import the STL format 3D solid geometry model into the laser melting and slicing software Magics, and perform layer-by-layer slicing on the structure.

[0045] Step 3: Fill the material cylinder cavity of the laser selective melting equipment with powder and purify the cavity with inert gas. The powder particle size ranges from 20-50 μm, and the powder includes at least one of copper alloy (e.g., CuCrZr), titanium alloy (e.g., Ti6Al4V), and aluminum alloy. For example, in one embodiment of this application, spherical metal powder is used as the printing powder; exemplarily, it can be Ti6Al4V spherical powder. The purpose of purging with inert gas is to remove oxygen from the material cylinder cavity. For example, the inert gas can be either helium or argon.

[0046] Step 4: Using a laser selective melting device, powder is laid layer by layer for printing. The heat protection structure is printed according to the three-dimensional solid geometric model. The powder thickness is the same as the slice layer thickness. For example, the parameters of the laser selective melting device are set as follows: laser power is 200-300 W, scanning speed is 500-1000 mm / s, spot diameter is 50-100 μm, and scanning spacing is 100-150 μm.

[0047] Step 5: Remove the printed thermal protection structure and perform ultrasonic cleaning to obtain the finished thermal protection structure.

[0048] This application utilizes 3D printing to fabricate thermal protection structures, which offers advantages such as ease of operation and precise structural control.

[0049] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0051] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are constructed to distinguish different objects, not to describe a particular order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. It should be noted that when an element is referred to as "fixed to" or "connected to" another element, it may be directly on the other element or there may be an intervening element. When an element is referred to as "connected to" another element, it may be directly connected to the other element or there may be an intervening element. The accompanying drawings only depict the stacking relationship between different layers and do not limit their thickness relationships.

Claims

1. A thermal protection structure based on a gradient lattice, characterized in that, include: Inner layer; An outer layer plate, which is spaced apart on one side of the inner layer plate; as well as A lattice-filled structure is provided, which fills and connects the inner and outer layers. The lattice-filled structure comprises multiple interconnected unit cells, each unit cell being a body-centered cubic lattice. A liquid-cooling channel is provided within the lattice-filled structure, with its inlet exposed between the inner and outer layers. The inlet is used to introduce coolant for heat dissipation. The closer to the liquid-cooling channel, the larger the size of the unit cell, and the sparser the density of the unit cells. The further away from the inner and outer layers, the larger the size of the unit cell. The smaller the size of the unit cell and the denser the arrangement of the unit cells in the liquid cooling channel, the more the lattice filling structure forms a gradient hollow structure with a denser outer layer and a sparser inner layer. The hollow area of ​​the lattice filling structure is used as a natural air convection flow area. The wall surface of the liquid cooling channel near the outer plate is arranged with a teardrop-shaped turbulence column. The structure is specifically presented as a splicing of a semi-cone and a semi-sphere, with the generatrix of the cone tangent to the surface of the sphere. The tip of the teardrop-shaped structure is set towards the liquid inlet.

2. The thermal protection structure as described in claim 1, characterized in that, Observing along the direction of the variation trend of the unit cell, the side length of the larger unit cell is 1.5-2 times the side length of the adjacent smaller unit cell.

3. The thermal protection structure as described in claim 2, characterized in that, The smallest unit cell has a side length of 8-10 mm.

4. The thermal protection structure as described in claim 1, characterized in that, The number of the turbulence-disrupting columns is multiple, and the turbulence-disrupting columns are arranged at intervals between adjacent pairs.

5. The thermal protection structure as described in claim 1, characterized in that, The characteristic radius of the spherical portion of the teardrop-shaped structure is 2-3 mm, and the characteristic angle of the tip of the teardrop-shaped structure is 30-60°.

6. The thermal protection structure as described in claim 4, characterized in that, Multiple of the aforementioned spoiler columns are arranged in multiple rows and columns. When viewed along the orientation of the tips, in adjacent columns, the two adjacent spoiler columns in different columns are staggered. The spoiler columns in even-numbered columns are arranged axially symmetrically, and the spoiler columns in odd-numbered columns are arranged axially symmetrically.

7. The thermal protection structure as described in claim 6, characterized in that, When viewed along the direction of the tip, the spacing between two adjacent columns of the same type of spoiler is 4-6 of the characteristic radius, and the spacing between two adjacent spoiler columns in different columns is 10-15 mm.

8. The thermal protection structure as described in claim 1, characterized in that, Both the inner and outer layers are arc-shaped structures, and the inner and outer layers bend in the same direction, with the arc-shaped structures protruding outwards.

9. A method for fabricating a thermal protection structure based on a gradient lattice, characterized in that, The preparation method is used to prepare the thermal protection structure according to any one of claims 1 to 8, and the preparation method includes the following steps: Step 1: Use modeling software to construct a three-dimensional solid geometric model of the thermal protection structure; Step 2: Use 3D printing model processing software to perform layer-by-layer slicing of the model; Step 3: Fill the material cylinder cavity of the laser selective melting equipment with powder and fill the material cylinder cavity with inert gas; Step 4: Using a laser selective melting device, powder is laid layer by layer for printing. The heat protection structure is printed according to the three-dimensional solid geometric model. The powder laying thickness is the same as the slice layer thickness. Step 5: Remove the printed heat protection structure and perform ultrasonic cleaning.

10. The preparation method according to claim 9, characterized in that, The powder in step 3 includes at least one of copper alloy, titanium alloy, and aluminum alloy.

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