Thermal protection capillary filament screen composite shell structure and preparation method thereof

Abstract

The present application relates to a kind of heat protection capillary filament screen composite shell structure and its preparation method, it is characterized in that including heat protection capillary filament screen and shell, the heat protection capillary filament screen is compounded on shell, heat protection capillary filament screen only includes single direction arrangement warp fiber, and fiber arrangement direction is identical with the flow direction of liquid phase working medium in heat protection mechanism, and it is constituted dumbbell type unidirectional ordered microchannel between warp fiber.The present application uses the method of different material warp, weft fiber differentiation weaving, in combination with the preparation method of the targeted removal of weft fiber, significantly reduces the liquid flow resistance in warp direction under the premise of not affecting the size of capillary driving force, improves the transport capacity of capillary structure as a whole, can effectively improve the heat transfer capacity of heat pipe or heat dissipation type heat protection structure.

Description

Technical Field

[0001] This invention belongs to the technical field of aerospace engineering thermophysics, integrated thermal management or high-speed aircraft guided aerodynamic thermal protection system, and proposes a heat pipe or guided thermal protection wire mesh structure. Background Technology

[0002] In the aerospace industry, woven mesh structures are commonly used as capillary adsorption structures for liquid working fluids in heat pipes or conductive thermal protection structures. Traditional woven meshes, made of the same material in both warp and weft directions, exhibit good capillary forces due to the presence of fibers in both directions. However, the liquid's flow in both directions is inconsistent with the fiber orientation, leading to increased flow resistance and hindering the full realization of the mesh's capillary performance. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a thermal protection capillary mesh composite shell structure and its preparation method, which improves the overall transport capacity of the capillary structure and can effectively enhance the heat transfer capacity of heat pipes or conductive thermal protection structures.

[0004] The solution of this invention is: a thermal protection capillary mesh composite shell structure, which includes a thermal protection capillary mesh and a shell. The thermal protection capillary mesh is composited on the shell. The thermal protection capillary mesh contains only warp fibers arranged in a single direction, and the fiber arrangement direction is the same as the flow direction of the liquid working fluid in the thermal protection mechanism. The warp fibers form a... Dumbbell-shaped unidirectional ordered microchannels.

[0005] Preferably, the wire mesh is composed of fibers in two directions, warp and weft, during the weaving process. The warp and weft fibers are made of different materials. The warp fibers are the fiber structures that need to be retained in the wire mesh forming structure, while the weft fibers are the fiber structures that need to be removed in the wire mesh forming structure.

[0006] Another technical solution of the present invention is: a method for preparing a heat-protective capillary mesh composite shell structure, the method comprising the following steps:

[0007] Weave the fiber mesh according to the preset warp and weft fiber ratio;

[0008] Clean and dry the surface of the fiber mesh;

[0009] Composite wire mesh with fiber mesh onto a solid wall shell;

[0010] Weft fibers are removed using physical or chemical methods, while warp fibers are retained;

[0011] After removing the weft fibers, the fiber mesh composite solid wall structure is cleaned and dried to obtain a unidirectional fiber mesh composite solid wall shell structure.

[0012] Preferably, the fiber mesh is woven using plain weave, twill weave, or satin weave methods in both warp and weft directions.

[0013] Preferably, the composite processing method is one of mechanical fixing or laser, electron beam, or resistance spot welding processes.

[0014] Preferably, the physical removal method is melting, evaporation, sublimation or solvent dissolution, and the chemical removal method is pyrolysis, carbonization or oxidation.

[0015] Preferably, the required warp fiber diameter d and the spacing l between the warp fibers in the wire mesh structure satisfy the following formula:

[0016]

[0017]

[0018] In the formula, p cap,max The maximum capillary driving force of the wire mesh structure is given by σ, where σ is the surface tension coefficient of the liquid working fluid, and r is the surface tension coefficient of the liquid working fluid. eff The effective capillary radius of the micropores.

[0019] Preferably, the warp fiber material meets the following requirements:

[0020] The selection principle for warp fiber materials is that the melting point of the fiber material must be higher than the highest structural temperature of the wire mesh during the heat protection process. At the same time, the liquid working fluid and the fiber material must maintain physical and chemical stability at high temperatures during the heat protection process.

[0021] Preferably, the weft fibers meet the following material requirements:

[0022] The principle for selecting materials for weft fibers is that the weft fiber material should meet the requirements of feasible physical and chemical removal processes, and the removal process should not have any additional impact on the structure, material, physical and chemical properties of the warp fibers.

[0023] Preferably, the woven fiber mesh is produced using a plain weave, twill weave, or satin weave method in both warp and weft directions.

[0024] The advantages of this invention compared to the prior art are:

[0025] (1) The heat-protective capillary mesh of the present invention contains only warp fibers arranged in a single direction, and the fiber arrangement direction is the same as the liquid working fluid flow direction in the heat protection mechanism. The warp fibers form a... Dumbbell-shaped unidirectional ordered microchannels significantly reduce the resistance to liquid flow in the meridional direction, improve the overall transport capacity of the capillary structure, and can effectively enhance the heat transfer capacity of heat pipes or conductive thermal protection structures.

[0026] (2) The present invention adopts a method of differentiated weaving of warp and weft fibers of different materials, combined with a preparation method of targeted removal of weft fibers, which can significantly improve the overall porosity of the wire mesh structure without affecting the magnitude of capillary driving force. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the design and fabrication process of a high-porosity, low-flow-resistance capillary mesh structure according to an embodiment of the present invention.

[0028] Figure 2(a) is a top view of the warp and weft dissimilar fiber woven capillary mesh structure of an embodiment of the present invention;

[0029] Figure 2(b) is a cross-sectional view of the warp and weft dissimilar fiber woven capillary mesh structure according to an embodiment of the present invention;

[0030] Figure 3 This invention relates to a high-porosity, low-flow-resistance capillary mesh composite shell structure.

[0031] Figure 4 This invention provides a high-porosity, low-flow-resistance wire mesh composite shell structure with the weft fibers removed.

[0032] Figure 5(a) is a cross-sectional view of a representative structural unit of the mesh before the weft fibers are removed in an embodiment of the present invention, and its characteristic dimensions are shown below.

[0033] Figure 5(b) is a top view of a representative structural unit of the mesh before the weft fibers are removed in an embodiment of the present invention, and its characteristic dimensions.

[0034] Figure 6(a) is a cross-sectional view of a representative structural unit of the wire mesh after the weft fibers have been removed, and its characteristic dimensions are shown in Figure 6(a) of the present invention.

[0035] Figure 6(b) is a top view of a representative structural unit of the wire mesh after the weft fibers have been removed, and its characteristic dimensions are shown in the figure. Detailed Implementation

[0036] The present invention will be further described below with reference to the embodiments.

[0037] This invention provides a thermally protective capillary mesh composite shell structure, comprising a thermally protective capillary mesh and a shell. The thermally protective capillary mesh is composited onto the shell. The thermally protective capillary mesh contains only warp fibers arranged in a single direction, and the fiber arrangement direction is the same as the flow direction of the liquid working fluid in the thermal protection mechanism. The warp fibers form a... Dumbbell-shaped unidirectional ordered microchannels.

[0038] The wire mesh is composed of fibers in both the warp and weft directions during the weaving process. Different materials are used for the warp and weft fibers. The warp fibers are the fiber structure that needs to be retained in the wire mesh formation, while the weft fibers are the fiber structure that needs to be removed. Because this capillary wire mesh retains the warp fiber structure and removes the weft fiber structure, it can significantly reduce the liquid flow resistance in the warp direction without affecting the magnitude of the capillary driving force. Simultaneously, it significantly increases the overall porosity of the wire mesh structure, thus improving the overall transport capacity of the capillary structure and effectively enhancing the heat transfer capacity of heat pipes or conductive thermal protection structures.

[0039] Figure 1 A flowchart illustrating the design and fabrication process of a high-porosity, low-flow-resistance capillary mesh structure is provided, as shown in the figure. The aforementioned thermally protective capillary mesh composite shell structure is fabricated using the following steps:

[0040] S1. Weave the fiber mesh according to the preset weaving ratio of warp and weft fibers;

[0041] Based on the maximum capillary driving force and porosity of the wire mesh determined by the heat protection requirements, and using the formulas for capillary driving force and effective capillary radius of the pore microstructure, combined with the porosity formula, the fiber diameter d and the spacing I between fibers can be finally determined.

[0042] Maximum capillary driving force p cap,max Satisfy the following formula:

[0043]

[0044]

[0045] In the formula, σ is the surface tension coefficient of the liquid working fluid, and r eff The effective capillary radius of the micropores.

[0046] The present invention selects the wire mesh structure material based on the working temperature of the wire mesh and the compatibility of the wetting medium.

[0047] The warp fiber is the fiber that is ultimately retained. The selection of the wire mesh fiber material is based on the working temperature of the heat pipe or duct structure and the chemical compatibility between the wire mesh structure and the heat pipe working fluid. The material melting point and chemical stability of the fiber are also considered. The selection principle for the warp fiber material is that its melting point must be higher than the highest structural temperature of the wire mesh during the heat protection process. At the same time, during the heat protection process, the liquid working fluid and the fiber material maintain physical and chemical stability at high temperatures.

[0048] Weft fibers are used to temporarily maintain the woven mesh structure and are ultimately removed through physical or chemical methods. The selection of fiber materials is based on the removal process, taking into account the physical and chemical removal characteristics of the fibers. The selection principle for weft fiber materials is that the weft fiber material should meet the requirements of feasible physical and chemical removal processes, and the removal process should not have any additional impact on the structure, material, physical, and chemical properties of the warp fibers.

[0049] Commonly selected fiber materials include: cotton fiber, nylon fiber, Kevlar fiber, stainless steel fiber, nickel alloy fiber, chromium alloy fiber, niobium alloy fiber, molybdenum alloy fiber, glass fiber, quartz fiber, carbon fiber, silicon carbide fiber, silicon nitride fiber, boron nitride fiber, etc.

[0050] The weaving density of the warp fibers is determined by the maximum capillary driving force and porosity of the mesh required for the thermal protection objective; the weft fibers are weaving density determined by comprehensively considering the differences in size, material stiffness, and material strength between the warp and weft fibers, with the principle of ensuring the stability of the mesh forming structure, and finally forming the weaving ratio of warp and weft fibers.

[0051] Based on the differences in size, material strength, and material stiffness between warp and weft fibers, and taking into account the overall structural strength, stiffness, and structural stability requirements of the formed mesh, the weaving ratio of warp and weft fibers can be flexibly determined. Any ratio that meets the requirements for structural stability can be 2:1, 1:1, 1:2, etc.

[0052] The weaving structure of a fiber mesh can be determined based on the characteristics of the fibers themselves and the applicability of the actual process. Weaving methods such as plain weave, twill weave, and satin weave can be used. Figures 2(a) and 2(b) show an example of a high-porosity, low-flow-resistance capillary fiber mesh structure, in which the ratio of warp to weft fibers is 1:1, and a plain weave is used. The warp fibers 1 and weft fibers 2 are interlaced in plain weave to form the entire mesh structure. The representative repeating unit 3 of the mesh is the smallest warp and weft translation unit of the mesh.

[0053] S2. Clean and dry the surface of the fiber mesh;

[0054] Before integrating the wire mesh structure into the application structure, the wire mesh surface needs to be cleaned. Common cleaning methods include solvent cleaning, acid washing, and ultrasonic cleaning. When choosing a solvent, it is important to consider the compatibility between the wire mesh fibers and the solvent. For example, strong organic solvents such as acetone should not be used to clean cotton or nylon fibers, nor should acids that react with metal fibers be used.

[0055] S3. Composite the wire mesh fiber to the solid wall shell;

[0056] After the wire mesh is cleaned and dried, it can be laminated with the solid wall surface. The appropriate process method needs to be selected according to the material of the fiber wire mesh and the characteristics of the solid wall material. Common lamination methods include mechanical fixing or laser, electron beam, and resistance spot welding processes. Figure 3 The composite shell structure formed by bonding a wire mesh to a solid wall shell is given, which consists of warp fibers 1, weft fibers 2 and shell 4.

[0057] S4. Remove the weft fibers using physical or chemical methods, while retaining the warp fibers;

[0058] Once the wire mesh structure is laminated to a solid wall shell, the weft direction can be removed, typically using physical or chemical methods. Physical removal methods include melting, evaporation, sublimation, and solvent dissolution, while chemical removal methods include pyrolysis, carbonization, and oxidation.

[0059] This step employs a differentiated weaving method using dissimilar materials in the warp and weft directions, combined with the targeted removal of the weft fibers, to create a structure that consists only of warp fibers and inter-fiber components. A novel capillary mesh structure with dumbbell-shaped unidirectional ordered microchannels.

[0060] S5. Clean and dry the fiber mesh composite solid wall structure after removing the weft fibers to obtain a unidirectional fiber mesh composite solid wall shell structure.

[0061] The unidirectional fiber mesh composite solid wall structure after the weft fibers are removed needs to be cleaned again. The cleaning steps and process requirements are the same as in step S2.

[0062] After cleaning and drying, a unidirectional fiber-arranged, high-porosity, low-flow-resistance wire mesh composite solid wall structure is obtained.

[0063] Figure 4 A schematic diagram of a high-porosity, low-flow-resistance wire mesh composite shell structure is presented. Figure 5(a) shows a cross-sectional view and characteristic dimensions of a representative structural unit of the wire mesh before weft fiber removal, and Figure 5(b) shows a top view and characteristic dimensions of a representative structural unit of the wire mesh before weft fiber removal. The unit cell volume V of the wire mesh before weft fiber removal is shown. 单胞1 Unit cell pore volume V 孔隙1 and porosity η 孔隙1 They are respectively:

[0064] V 单胞1 =l 2 ×d(1+(l 2 +d 2 ) 1 / 2 / l)

[0065] V 孔隙1 =l 2×d(1+(l 2 +d 2 ) 1 / 2 / l-2π(d / 2) 2 ×(l 2 +d 2 ) 1 / 2 )

[0066] η 孔隙1 =V 孔隙1 / V 单胞1 ×100%

[0067] Figure 6(a) shows a cross-sectional view and a schematic diagram of the characteristic dimensions of a representative structural unit of the mesh after the weft fibers have been removed. Figure 6(b) shows a top view and a schematic diagram of the characteristic dimensions of a representative structural unit of the mesh after the weft fibers have been removed. The unit cell volume V of the mesh after the weft fibers have been removed is shown. 单胞2 Unit cell pore volume V 孔隙2 and porosity η 孔隙2 They are respectively:

[0068] V 单胞2 =l 2 ×d(1+(l 2 +d 2 ) 1 / 2 / l)

[0069] V 孔隙2 =l 2 ×d(1+(l 2 +d 2 ) 1 / 2 / l-π(d / 2) 2 ×(l 2 +d 2 ) 1 / 2 )

[0070] η 孔隙2 =V 孔隙2 / V 单胞2 ×100%

[0071] After removing the weft fibers, the capillary mesh retains only the warp structure, forming Dumbbell-shaped unidirectional ordered microchannels. Unit cell volume remains constant (V). 单胞1 =V 单胞2 That is, V 孔隙2 >V 孔隙1 The increased porosity of the capillary structure reduces the flow resistance of the liquid in the warp direction due to the absence of obstruction from the weft fibers, thus improving the liquid transport performance of the wire mesh structure.

[0072] Example:

[0073] according to Figure 1The flowchart shown is for the design and fabrication of a high-porosity, low-flow-resistance capillary mesh structure. A fiber mesh structure with an equivalent capillary force of approximately 200 meshes was fabricated. The fiber diameter d required for weaving the mesh structure was determined to be 0.056 mm, and the fiber spacing l was determined to be 0.075 mm.

[0074] The warp fiber is selected as stainless steel fiber with a diameter of 0.056mm, and the weft fiber is selected as nylon fiber with a diameter of 0.056mm.

[0075] Based on the stability of the wire mesh's forming structure, the weaving ratio of warp and weft fibers is determined to be 1:1.

[0076] Based on the characteristics of the two types of fibers and their suitability for the process, a plain weave technique was selected, and the total size of the woven mesh was 500mm × 1000mm.

[0077] The mesh structure of the braided pattern was cleaned using anhydrous ethanol as the solvent, followed by ultrasonic cleaning for 1 hour. Then, it was removed and ultrasonically cleaned with distilled water for 15 minutes, repeated three times. Finally, it was placed in a cleanroom for drying.

[0078] After cleaning and drying, the stainless steel-nylon wire mesh undergoes solid wall composite treatment. The solid wall material is 316L stainless steel, with dimensions of 100mm (length) × 100mm (width) × 2.5mm (height). 100mm (length) × 100mm (width) stainless steel / nylon fiber filaments are cut and fixed to the 316L stainless steel and stainless steel / nylon fiber wire mesh using resistance spot welding. The required weld density is 1 weld point / cm². 2 Solder joints include those with a diameter of no more than 0.5 mm.

[0079] A physical dissolution method was used to remove the weft fibers from a 316L stainless steel / nylon fiber composite mesh. Phenol was selected as the solvent, and the composite mesh was immersed in phenol until all the weft fibers were dissolved. The unit cell volume V of the mesh before the removal of the weft nylon fibers was [not specified]. 单胞1 Unit cell pore volume V 孔隙1 and porosity η 孔隙1 They are respectively:

[0080] V 单胞1 =l 2 ×d(1+(l 2 +d 2 ) 1 / 2 / l)=7.08×10 -4 mm 3

[0081] V 孔隙1 =l 2 ×d(1+(l 2 +d 2 )1 / 2 / l-2π(d / 2) 2 ×(l 2 +d 2 ) 1 / 2 ) = 2.47 × 10 -4 mm 3

[0082] η 孔隙1 =V 孔隙1 / V 单胞1 ×100%=34.89%

[0083] The unit cell volume V of the web after removing the weft nylon fibers 单胞2 Unit cell pore volume V 孔隙2 and porosity η 孔隙2 They are respectively:

[0084] V 单胞2 =l 2 ×d(1+(l 2 +d 2 ) 1 / 2 / l)=7.08×10 -4 mm 3

[0085] V 孔隙2 =l 2 ×d(1+(l 2 +d 2 ) 1 / 2 / l-π(d / 2) 2 ×(l 2 +d 2 ) 1 / 2 ) = 4.76 × 10 -4 mm 3

[0086] η 孔隙2 =V 孔隙2 / V 单胞2 ×100%=67.44%

[0087] After removing the weft fibers, the capillary mesh retains only the warp structure, forming Dumbbell-shaped unidirectional ordered microchannels. Unit cell volume remains constant (V). 单胞1 =V 单胞2 That is, V 孔隙2 >V 孔隙1 The porosity of the capillary structure increased from 34.89% to 67.44%. Since there is no obstruction of the weft fibers in the warp direction of the liquid flow, the warp flow resistance is reduced, and the liquid working fluid transport performance of the wire mesh structure is improved.

[0088] The solid wall structure of unidirectional fiber mesh composite 316L stainless steel plate after the weft fibers are removed needs to be cleaned again, and the cleaning steps and process requirements are the same.

[0089] After cleaning and drying, a solid wall structure of 316L stainless steel plate composite material with high porosity and low flow resistance stainless steel wire mesh with unidirectional stainless steel fiber arrangement is obtained.

[0090] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A thermally protective capillary mesh composite shell structure, characterized in that... The system includes a heat-protective capillary mesh and a shell. The heat-protective capillary mesh is composited onto the shell. The heat-protective capillary mesh contains only warp fibers arranged in a single direction, and the direction of the warp fibers is the same as the direction of the liquid working fluid flow in the heat protection mechanism. The warp fibers form a " "Dumbbell-shaped unidirectional ordered microchannels;" During the weaving process, the wire mesh is composed of fibers in two directions: warp and weft. Different materials are selected for the warp and weft fibers. The warp fibers are the fiber structures that need to be retained in the wire mesh forming structure, while the weft fibers are the fiber structures that need to be removed in the wire mesh forming structure. The unit cell volume of the mesh remains unchanged after removing the weft nylon fibers, but the unit cell pore volume of the mesh increases after removing the weft nylon fibers.

2. The method for preparing a thermally protective capillary mesh composite shell structure according to claim 1, characterized in that... Includes the following steps: Weave the fiber mesh according to the preset warp and weft fiber ratio; Clean and dry the surface of the fiber mesh; Composite wire mesh with fiber mesh onto a solid wall shell; Weft fibers are removed using physical or chemical methods, while warp fibers are retained; After removing the weft fibers, the fiber mesh composite solid wall structure is cleaned and dried to obtain a unidirectional fiber mesh composite solid wall shell structure.

3. The method for preparing a thermally protective capillary mesh composite shell structure according to claim 2, characterized in that... The fiber mesh is woven using plain weave, twill weave, or satin weave methods in both warp and weft directions.

4. The method for preparing a thermally protective capillary mesh composite shell structure according to claim 2, characterized in that... The composite processing method is one of mechanical fixing or laser, electron beam, or resistance spot welding processes.

5. The method for preparing a thermally protective capillary mesh composite shell structure according to claim 2, characterized in that... Physical removal methods include sublimation or solvent dissolution, while chemical removal methods include pyrolysis, carbonization, or oxidation.

6. The method for preparing a thermally protective capillary mesh composite shell structure according to claim 2, characterized in that... The required warp fiber diameter d and the spacing l between warp fibers for the wire mesh structure satisfy the following formula: In the formula, The maximum capillary driving force for the wire mesh structure, The surface tension coefficient of the liquid working fluid. The effective capillary radius of the micropores.

7. The method for preparing a thermally protective capillary mesh composite shell structure according to claim 2, characterized in that... The warp fiber material meets the following requirements: The selection principle for warp fiber materials is that the melting point of the fiber material must be higher than the highest structural temperature of the wire mesh during the heat protection process. At the same time, the liquid working fluid and the fiber material must maintain physical and chemical stability at high temperatures during the heat protection process.

8. The method for preparing a thermally protective capillary mesh composite shell structure according to claim 2, characterized in that... The weft fiber material meets the following requirements: The principle for selecting materials for weft fibers is that the weft fiber material should meet the requirements of feasible physical and chemical removal processes, and the removal process should not have any additional impact on the structure, material, physical and chemical properties of the warp fibers.

9. The method for preparing a thermally protective capillary mesh composite shell structure according to claim 2, characterized in that... The woven fiber mesh is produced using plain weave, twill weave, or satin weave methods in both warp and weft directions.

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