WO2023082528A1 - 一种热防护结构及其制备方法 - Google Patents

一种热防护结构及其制备方法 Download PDF

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WO2023082528A1
WO2023082528A1 PCT/CN2022/083265 CN2022083265W WO2023082528A1 WO 2023082528 A1 WO2023082528 A1 WO 2023082528A1 CN 2022083265 W CN2022083265 W CN 2022083265W WO 2023082528 A1 WO2023082528 A1 WO 2023082528A1
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heat
temperature
thermal protection
protection structure
thermal
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PCT/CN2022/083265
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English (en)
French (fr)
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金华
张劭捷
周印佳
吴亚东
尤延铖
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厦门大学
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Priority to JP2022522852A priority Critical patent/JP7483873B2/ja
Publication of WO2023082528A1 publication Critical patent/WO2023082528A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
    • B32B3/26—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer
    • B32B3/266—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer characterised by an apertured layer, the apertures going through the whole thickness of the layer, e.g. expanded metal, perforated layer, slit layer regular cells B32B3/12
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/20—Layered products comprising a layer of metal comprising aluminium or copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
    • B32B3/02—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by features of form at particular places, e.g. in edge regions
    • B32B3/08—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by features of form at particular places, e.g. in edge regions characterised by added members at particular parts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B33/00—Layered products characterised by particular properties or particular surface features, e.g. particular surface coatings; Layered products designed for particular purposes not covered by another single class
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/08—Interconnection of layers by mechanical means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
    • B32B9/005—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising one layer of ceramic material, e.g. porcelain, ceramic tile
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
    • B32B9/04—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising such particular substance as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B9/041—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising such particular substance as the main or only constituent of a layer, which is next to another layer of the same or of a different material of metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
    • B64G1/00—Cosmonautic vehicles
    • B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
    • B64G1/52—Protection, safety or emergency devices; Survival aids
    • B64G1/58—Thermal protection, e.g. heat shields
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/304—Insulating

Definitions

  • the invention relates to the technical field of heat protection, in particular to a heat protection structure and a preparation method thereof.
  • the thermal protection mechanism is a special mechanism specially used for aircraft thermal protection. It is a kind of mechanism that includes the thermal protection mechanism (for example, based on material properties, physical and chemical effects, or structural principles, etc.), system structure and working principle.
  • the thermal protection mechanisms adopted by active or tested hypersonic vehicles can be divided into passive types (such as heat sinks, heat insulation structure), semi-passive (such as ablation, heat pipes) and active (such as working fluid, cooling flow).
  • passive types such as heat sinks, heat insulation structure
  • semi-passive such as ablation, heat pipes
  • active such as working fluid, cooling flow.
  • Embodiments of the present invention provide a thermal protection structure and a preparation method thereof, which can provide a thermal protection structure to meet the thermal protection requirements of future hypersonic aircraft.
  • the present invention provides a heat protection structure, the heat protection structure comprises a heat insulation layer, a cavity layer and a skin arranged in sequence, and the heat insulation layer is arranged on the outer surface of the aircraft inner cabin;
  • the heat insulation layer includes a porous heat insulation structure, a temperature-sensitive hydrogel arranged in the porous heat insulation structure, and a cooling working fluid adsorbed in the temperature-sensitive hydrogel;
  • the temperature-sensitive hydrogel When the thermal protection structure is not thermally protected, the temperature-sensitive hydrogel is in a swollen state, which is used to adsorb the cooling working medium in the temperature-sensitive hydrogel in the form of a solid phase;
  • the temperature-sensitive hydrogel absorbs the heat radiated inwards from the skin and the cavity layer, making it in a deswelled state for cooling the
  • the existence form of the working fluid is changed from solid phase to liquid phase and gas phase in turn, and the cooling working fluid in the gas phase is released into the cavity layer and then discharged.
  • the purpose of the present invention is to provide an active and passive synergistic thermal protection mechanism for the long-term and repeatable thermal protection structure required by the next generation of hypersonic aircraft, specifically by increasing inward radiation heat dissipation (passive) and solid
  • the thermal protection mechanism of phase water phase change heat dissipation (active) synergy realizes thermal protection.
  • the traditional heat protection structure mainly realizes heat dissipation through the outer skin (outer side) radiating outwards.
  • the present invention adds a cavity layer between the skin and the heat insulation material on the basis of the external radiation, so that the inner side of the skin can also radiate outwards.
  • Water is the best cooling medium for phase change cooling because of its highest latent heat of phase change.
  • the fluidity and storage of water require a series of complex auxiliary structures such as sealing, storage, and anti-corrosion in the thermal protection structure.
  • the present invention adopts solid-phase water to replace traditional liquid-phase water, and transforms liquid-phase water into solid-phase water into small particles of solid-phase water through temperature-sensitive hydrogel and inorganic-organic assembly technology and fills them in the lower inorganic heat-insulating material.
  • Alumina porous insulation material is selected for comparison. Solid-phase water particles are fixed in the micropores of porous media through chemical branching.
  • the solid phase hydrogel After the solid phase hydrogel is filled, it can be tightly connected with the porous heat insulating material.
  • the radiation causes the temperature in the cavity to rise, the solid-phase water will form liquid-phase water through slow release, and the liquid-phase water will evaporate into water vapor immediately after being heated, and then take away heat through this liquid-gas phase transition.
  • the thermal protection capability of the thermal protection structure can be greatly improved.
  • the thickness of the cavity between the skin and the porous medium, the distribution and pore size of the micropores inside the porous medium, and the content of solid-phase water can be designed and adjusted according to the needs of thermal protection.
  • the thermal protection mechanism of the present invention is an active-passive cooperative thermal protection mechanism. On the basis of giving full play to the radiation heat dissipation of the outer surface, not only the internal radiation heat dissipation phase is increased, but more importantly, the phase change heat dissipation of solid-phase water is increased.
  • the heat dissipation The amount is 30 to 50 times that of radiation heat dissipation, and its thermal protection effect is better than other single active or passive thermal protection machines and structures such as ceramic-based adiabatic heat protection, sweat cooling, and film cooling.
  • the thermal protection structure based on the active/passive cooperative thermal protection mechanism of the present invention can be applied to thermal protection structures such as wing leading edges and nose cones of hypersonic aircraft, and can also be applied to large-area areas on the windward side, and can withstand thermal loads of 100-10MW/m 2 , and not less than 30 minutes;
  • the thickness of the heat protection structure provided by the invention is 10 ⁇ 100mm; the back wall temperature of the heat protection structure provided by the invention is lower than 100 °C; Carrying the characteristics of integration.
  • the heat protection structure further includes screws and nuts, and the heat insulation layer and the skin are fixed on the outer surface of the inner cabin of the aircraft through the cooperation of the screws and the nuts.
  • both the screw and the nut are made of alumina ceramics.
  • the porous heat insulation structure is made of alumina ceramics.
  • the cooling working medium includes water.
  • the present invention provides a method for preparing a thermal protection structure, comprising:
  • the temperature-sensitive hydrogel and the porous heat-insulating structure in a container containing a cooling working fluid, so that the temperature-sensitive hydrogel enters the porous heat-insulating structure; wherein, the temperature of the cooling working medium is a first preset temperature, and at the first preset temperature, the thermosensitive hydrogel is in a deswelling state;
  • thermosensitive hydrogel in the form of a solid phase to obtain a thermal insulation layer; wherein, in the At the second preset temperature, the thermosensitive hydrogel is in a swollen state;
  • the heat insulation layer and the skin are fixed, and a cavity layer is arranged between the heat insulation layer and the skin to form a heat protection structure; wherein, the heat insulation layer is arranged outside the inner cabin of the aircraft On the surface.
  • the purpose of the present invention is to provide an active and passive synergistic thermal protection mechanism for the long-term and repeatable thermal protection structure required by the next generation of hypersonic aircraft, specifically by increasing inward radiation heat dissipation (passive) and solid
  • the thermal protection mechanism of phase water phase change heat dissipation (active) synergy realizes thermal protection.
  • the traditional heat protection structure mainly realizes heat dissipation through the outer skin (outer side) radiating outwards.
  • the present invention adds a cavity layer between the skin and the heat insulation material on the basis of the external radiation, so that the inner side of the skin can also radiate outwards.
  • Water is the best cooling medium for phase change cooling because of its highest latent heat of phase change.
  • the fluidity and storage of water require a series of complex auxiliary structures such as sealing, storage, and anti-corrosion in the thermal protection structure.
  • the present invention adopts solid-phase water to replace traditional liquid-phase water, and transforms liquid-phase water into solid-phase water into small particles of solid-phase water through temperature-sensitive hydrogel and inorganic-organic assembly technology and fills them in the lower inorganic heat-insulating material.
  • Alumina porous insulation material is selected for comparison. Solid-phase water particles are fixed in the micropores of porous media through chemical branching.
  • the solid phase hydrogel After the solid phase hydrogel is filled, it can be tightly connected with the porous heat insulating material.
  • the radiation causes the temperature in the cavity to rise, the solid-phase water will form liquid-phase water through slow release, and the liquid-phase water will evaporate into water vapor immediately after being heated, and then take away heat through this liquid-gas phase transition.
  • the thermal protection capability of the thermal protection structure can be greatly improved.
  • the thickness of the cavity between the skin and the porous medium, the distribution and pore size of the micropores inside the porous medium, and the content of solid-phase water can be designed and adjusted according to the needs of thermal protection.
  • the thermal protection mechanism of the present invention is an active-passive cooperative thermal protection mechanism. On the basis of giving full play to the radiation heat dissipation of the outer surface, not only the internal radiation heat dissipation phase is increased, but more importantly, the phase change heat dissipation of solid-phase water is increased.
  • the heat dissipation The amount is 30 to 50 times that of radiation heat dissipation, and its thermal protection effect is better than other single active or passive thermal protection machines and structures such as ceramic-based adiabatic heat protection, sweat cooling, and film cooling.
  • the thermal protection structure based on the active/passive cooperative thermal protection mechanism of the present invention can be applied to thermal protection structures such as wing leading edges and nose cones of hypersonic aircraft, and can also be applied to large-area areas on the windward side, and can withstand thermal loads of 100-10MW/m 2 , and not less than 30 minutes;
  • the thickness of the heat protection structure provided by the invention is 10 ⁇ 100mm; the back wall temperature of the heat protection structure provided by the invention is lower than 100 °C; Carrying the characteristics of integration.
  • said fixing the heat insulation layer and the skin includes:
  • the heat insulation layer and the skin are fixed by cooperation of screws and nuts.
  • both the screw and the nut are made of alumina ceramics.
  • the porous heat insulation structure is made of alumina ceramics.
  • the cooling working medium includes water.
  • the present invention has at least the following beneficial effects:
  • a heat protection structure including a heat insulation layer, a cavity layer and a skin on the outer surface of the aircraft inner cabin, it has excellent heat protection performance.
  • the skin and cavity in the thermal protection structure enable it to have a passive thermal protection function.
  • the passive thermal protection mechanism is that the skin absorbs external heat and heats up, and then partially releases the absorbed heat through thermal radiation.
  • there are two ways of skin heat radiation one is to release external radiation from the skin to the external environment, and the other is to release internal radiation to the cavity.
  • the skin can radiate heat to the inside as well as the cavity layer while radiating heat outward, thereby adding a way of inward radiation on the basis of traditional heat protection, thereby improving the Thermal protection efficiency for passive thermal protection.
  • the heat insulation layer in the thermal protection structure includes a porous heat insulation structure, a temperature-sensitive hydrogel arranged in the porous heat insulation structure, and a cooling working medium adsorbed in the temperature-sensitive hydrogel.
  • the pores in the porous thermal insulation structure can accommodate the temperature-sensitive hydrogel, which can absorb the liquid-phase cooling medium and convert it into a solid phase.
  • Thermal insulation and cavities in the thermal protection structure allow for active thermal protection.
  • the temperature-sensitive hydrogel absorbs the heat radiated inward from the skin and the cavity layer, making it in a state of deswelling, which is used to sequentially change the existence form of the cooling medium from the solid phase It is in liquid phase and gas phase, and the cooling working fluid in gas phase is released into the cavity layer and then discharged.
  • the heat-insulating layer contains thermosensitive hydrogel. When the temperature of the heat-insulating layer is lower than the lower critical solution temperature (LCST) of the thermo-sensitive hydrogel, the thermo-sensitive hydrogel is in a swollen state and absorbs cooling work.
  • LCST critical solution temperature
  • thermosensitive hydrogel absorbs heat and presents a deswelling state, transforming the cooling medium from a solid phase to a liquid phase and releasing it, and then, the liquid phase cooling medium continues to absorb heat and further transforms into a gas phase and is released to the cavity for discharge, thereby achieving excellent thermal protection Function.
  • LCST lower critical solution temperature
  • the heat protection structure provided by the present invention is reusable. Through the reversible swelling-de-swelling characteristics of the temperature-sensitive hydrogel in the heat-insulating layer as the ambient temperature changes, the reuse of the thermal protection structure can be realized.
  • the thermal protection structure after use can make the temperature-sensitive hydrogel swell and absorb the cooling fluid by cooling down and replenishing the cooling fluid, thereby restoring the excellent thermal protection performance.
  • Fig. 1 is a schematic diagram of the principle of a thermal protection structure provided by an embodiment of the present invention
  • Fig. 2 is a flowchart of a method for preparing a thermal protection structure provided by an embodiment of the present invention
  • Fig. 3 (a) is the perspective view of the thermal protection structure that the embodiment of the present invention provides
  • Fig. 3 (b) is a partial sectional view of the thermal protection structure provided by the embodiment of the present invention.
  • FIG. 4 is a comparison diagram of the heat protection effect of the heat protection structure provided by Example 1 of the present invention and the heat protection structure provided by Comparative Example 1.
  • FIG. 4 is a comparison diagram of the heat protection effect of the heat protection structure provided by Example 1 of the present invention and the heat protection structure provided by Comparative Example 1.
  • thermal protection structure comprises heat insulation layer 3, cavity layer 2 and skin 1 that are arranged in sequence, insulation
  • the heat layer 3 is arranged on the bottom plate 4;
  • the thermal insulation layer 3 includes a porous thermal insulation structure, a temperature-sensitive hydrogel arranged in the porous thermal insulation structure, and a cooling medium adsorbed in the thermosensitive hydrogel;
  • the temperature-sensitive hydrogel When the thermal protection structure is not thermally protected, the temperature-sensitive hydrogel is in a swollen state, which is used to adsorb the cooling working medium in the temperature-sensitive hydrogel in the form of solid phase;
  • the temperature-sensitive hydrogel absorbs the heat radiated inward by the skin 1 and the cavity layer 2, making it in a deswelling state, which is used to change the existing form of the cooling working medium from the solid phase It is transformed into liquid phase and gas phase in turn, and the cooling working fluid in the gas phase is released to the cavity layer 2 and then discharged.
  • bottom plate 4 is a part of the outer surface of the interior cabin of the aircraft, and the commonly used material is aluminum alloy.
  • the heat protection structure including the heat insulation layer 3 , the cavity layer 2 and the skin 1 on the bottom plate 4 , it has excellent heat protection performance.
  • the skin 1 and the cavity in the thermal protection structure enable it to have a passive thermal protection function.
  • the passive thermal protection mechanism is that the skin 1 absorbs external heat and heats up, and then releases part of the absorbed heat through thermal radiation.
  • the skin 1 there are two ways for the skin 1 to radiate heat, one is that the skin 1 releases external radiation to the external environment, and the other is that the skin 1 releases internal radiation to the cavity.
  • the skin 1 can radiate heat to the cavity layer 2 while radiating heat outward, thereby adding an inward radiation path on the basis of traditional heat protection, This in turn increases the thermal protection efficiency of the passive thermal protection.
  • the thermal insulation layer 3 in the thermal protection structure includes a porous thermal insulation structure, a temperature-sensitive hydrogel arranged in the porous thermal insulation structure, and a cooling working fluid adsorbed in the thermal-sensitive hydrogel.
  • the pores in the porous thermal insulation structure can accommodate the temperature-sensitive hydrogel, which can absorb the liquid-phase cooling medium and convert it into a solid phase.
  • the heat insulation layer 3 and the cavity in the heat protection structure enable it to have an active heat protection function.
  • the temperature-sensitive hydrogel absorbs the heat radiated inward by the skin 1 and the cavity layer 2, making it in a deswelling state, which is used to change the existing form of the cooling working medium from the solid phase It is transformed into liquid phase and gas phase in turn, and the cooling working fluid in the gas phase is released into the cavity layer 2 and then discharged.
  • the heat-insulating layer 3 contains thermosensitive hydrogel, and when the temperature of the heat-insulating layer 3 is lower than the lower critical solution temperature (LCST) of the thermo-sensitive hydrogel, the thermo-sensitive hydrogel therein is in a swollen state, absorbing Cool the working fluid and convert it into a solid phase to obtain a thermal insulation layer 3; during the use of the thermal protection structure, its operating environment temperature is higher than the lower critical solution temperature (LCST) of the temperature-sensitive hydrogel.
  • the sensitive hydrogel absorbs heat and presents a deswelling state, which changes the cooling medium from a solid phase to a liquid phase and releases it. Then, the liquid phase cooling medium continues to absorb heat and is further transformed into a gas phase and released to the cavity, thereby achieving excellent thermal protection function.
  • the heat protection structure provided by the present invention is reusable. Through the reversible swelling-de-swelling characteristics of the temperature-sensitive hydrogel in the thermal insulation layer 3 as the ambient temperature changes, the reuse of the thermal protection structure can be realized.
  • the thermal protection structure after use can make the temperature-sensitive hydrogel swell and absorb the cooling fluid by cooling down and replenishing the cooling fluid, thereby restoring the excellent thermal protection performance.
  • the thermal protection structure achieves excellent thermal protection performance through an active-passive coordinated thermal protection mechanism.
  • the internal radiation heat dissipation (passive thermal protection) is added; in addition, the phase change heat dissipation of solid-phase water (active thermal protection) is added.
  • the thermal protection structure provided by the present invention can ensure that the temperature of the interior and exterior surfaces of the hypersonic aircraft is less than 100°C under the aerodynamic heating environment, and the thermal protection effect is obviously better than ceramic-based adiabatic heat protection, sweat cooling and film cooling, etc. Other single active or passive thermal protection mechanisms.
  • the cooling medium continuously absorbs heat through the phase transition process of solid phase, liquid phase, and gas phase. -Liquid-gas phase balance, so that the temperature of the thermal insulation layer 3 is kept below the boiling point of the cooling medium until the solid-phase cooling medium is exhausted and the active thermal protection mechanism fails.
  • the active thermal protection mechanism time can be adjusted through the pore size and pore distribution of the porous thermal insulation structure, the controlled water release rate of the temperature-sensitive hydrogel, and the quality of the cooling working medium.
  • the cooling medium selected in the traditional active thermal protection structure is liquid phase. Since the liquid phase cooling medium has fluidity, placing it in the thermal protection structure requires a series of complex arrangements such as sealing, storage and anti-corrosion. Auxiliary structures make it difficult to apply in actual thermal protection structures.
  • the present invention adds temperature-sensitive hydrogel in the thermal insulation layer 3, and the temperature-sensitive hydrogel can absorb the cooling working fluid and convert it into a solid phase, thus avoiding the need to set Auxiliary structure required to store liquid-phase cooling fluid.
  • the active thermal protection mechanism in the thermal protection structure of the present invention is completely automatically triggered by temperature changes, and the thermal protection is realized by the phase change of the cooling fluid to absorb heat, and the whole process does not require any sensors and control devices.
  • the thermal protection structure provided by the present invention can be applied to hypersonic aircraft wing leading edge, nose cone, etc., and can also be applied to large areas on the windward side, and can withstand 100kW/m 2 ⁇ 10MW/m 2 thermal load, and the loading time Up to 30 minutes.
  • the loading time is the effective time of the active thermal protection mechanism.
  • the heat protection structure further includes screws 5 and nuts 6 , and the heat insulation layer 3 and the skin 1 are fixed on the bottom plate 4 through the cooperation of the screws 5 and the nuts 6 .
  • both the screw 5 and the nut 6 are made of alumina ceramics.
  • the porous heat insulation structure is made of alumina ceramics.
  • the heat protection structure can use the cooperation of screws 5 and nuts 6 to fix the skin 1, heat insulation layer 3 and bottom plate 4 in turn, wherein the nuts 6 It is fixed on both sides of the skin 1 to keep the cavity layer 2 between the heat insulation layer 3 and the skin 1 .
  • the skin 1 is made of a superalloy plate; the porous heat insulation structure and the screws 5 and nuts 6 are made of alumina ceramic material, which has excellent heat insulation. Compared with other porous insulation materials (such as zirconia ceramic materials), alumina ceramic materials have lower unit price and more uniform pore distribution.
  • the cooling working medium includes water.
  • water because water has the highest latent heat of phase change, water is selected as the best cooling medium for phase change cooling.
  • the present invention also provides a method for preparing a thermal protection structure, comprising:
  • the temperature-sensitive hydrogel and the porous heat-insulating structure in a container containing a cooling working fluid, so that the temperature-sensitive hydrogel enters the porous heat-insulating structure; wherein, the temperature of the cooling working medium is a first preset temperature , at the first preset temperature, the thermosensitive hydrogel is in a deswelling state;
  • the temperature of the cooling working fluid is reduced to a second preset temperature, so that the cooling working fluid is adsorbed in the temperature-sensitive hydrogel in the form of a solid phase to obtain a thermal insulation layer; wherein, at the second preset temperature, The thermosensitive hydrogel is in a swollen state;
  • the heat insulation layer and the skin are fixed, and a cavity layer is arranged between the heat insulation layer and the skin to form a heat protection structure; wherein, the heat insulation layer is arranged on the bottom plate.
  • the first preset temperature is slightly higher than the LCST (lower critical solution temperature of the thermosensitive hydrogel in the thermal insulation layer), and the second preset temperature is lower than the LCST.
  • the temperature of the thermosensitive hydrogel is higher than the LCST, it is in a deswelling state, and there is no water inside; Solid phase water is formed inside.
  • the temperature-sensitive hydrogel in the container when the cooling working medium is at the first preset temperature, the temperature-sensitive hydrogel in the container is in a liquid-phase deswelling state.
  • the sensitive hydrogel macromolecules are combined with the inner wall of the pores of the porous thermal insulation structure by grafting.
  • the temperature-sensitive hydrogel in the pores of the porous heat-insulating structure is in a swollen state during the cooling process, and the polymer through the hydrophilic-based network structure It absorbs a large amount of distilled water and swells, and as the temperature decreases, the swelling speed increases.
  • the temperature in the container is lowered to the second preset temperature, the temperature-sensitive hydrogel reaches swelling balance, and a heat-insulating layer is obtained.
  • the temperature-sensitive hydrogel in the porous insulation structure absorbs water and swells, and the liquid-phase water in the container is converted into solid-phase water, and the solid-phase water exists in the form of bound water and free water at temperature. in sensitive hydrogels.
  • the heat protection structure provided by the invention has a thickness of 10-100mm (thickness including the bottom plate), and has the functions of heat protection, heat insulation and bearing integration.
  • the preparation method provided by the present invention has simple structure, low cost, convenient installation, and strong designability.
  • the thickness of the heat insulation layer, the path and distribution of the microfluidic channel can be designed according to the flight time and the thermal load of the flight corridor. , Cooling fluid quality to meet the needs of different missions.
  • fixing the insulation layer and the skin comprises:
  • the insulation layer and the skin are fixed by the cooperation of screws and nuts.
  • both the screw and the nut are made of alumina ceramics.
  • the porous heat insulation structure is made of alumina ceramics.
  • the heat protection structure can use screws and nuts to fix the skin, heat insulation layer and bottom plate together in turn, wherein the nuts are fixed on both sides of the skin to connect the heat insulation layer and the The cavity layer remains between the skin.
  • the superalloy plate is used for the skin; the porous heat insulation structure and the screws and nuts are made of alumina ceramic material, which has excellent heat insulation. Compared with other porous insulation materials (such as zirconia ceramic materials), alumina ceramic materials have lower unit price and more uniform pore distribution.
  • the cooling medium includes water.
  • water because water has the highest latent heat of phase change, water is selected as the best cooling medium for phase change cooling.
  • the temperature-sensitive hydrogel and the porous alumina ceramic plate of 100 mm ⁇ 100 mm ⁇ 8 mm are placed in a container containing distilled water, so that the temperature-sensitive hydrogel enters the porous alumina ceramic plate; wherein, the temperature of the distilled water is 36 °C, the temperature-sensitive hydrogel is in a deswelling state;
  • thermosensitive hydrogel is in a swollen state
  • the heat insulation layer, the skin and the bottom plate are fixed by the cooperation of screws and nuts to obtain the bottom plate of the heat protection structure.
  • the skin is made of 100mm ⁇ 100mm ⁇ 5mm high-temperature alloy plate
  • the bottom plate is made of 100mm ⁇ 100mm ⁇ 5mm aluminum alloy plate
  • the screws and nuts are made of M4 alumina ceramic screws and nuts.
  • nuts are fixed on both sides of the skin to reserve an 8mm cavity layer between the heat insulation layer and the skin.
  • thermocouples on the outer surface of the skin and the outer surface of the thermal insulation layer place them under a high-power quartz lamp, and adjust the heat flux density through the high-power quartz lamp to 0.9MW/m 2 , and conduct a thermal assessment test.
  • the measured outer surface temperature of the skin is 865°C, and the outer surface temperature of the heat insulation layer does not exceed 100°C, and lasts for 3 minutes (the effective time of the active thermal protection mechanism).
  • the heat flux is 0.1MW/m 2 , and the thickness of the porous alumina ceramic plate is 5mm.
  • the measured temperature of the outer surface of the skin is 420°C, and the effective time of the active thermal protection mechanism is 30 minutes.
  • the thermal protection structure is placed in a high-frequency plasma wind tunnel, the heat flux density is adjusted to 5MW/m 2 , and the thickness of the porous alumina ceramic plate is 15mm.
  • the measured temperature of the outer surface of the skin is 870°C, and the effective time of the active thermal protection mechanism is 15 minutes.
  • the thermal protection structure is placed in a high-frequency plasma wind tunnel, the heat flux density is adjusted to 10MW/m 2 , and the thickness of the porous alumina ceramic plate is 30mm.
  • the measured temperature of the outer surface of the skin is 910°C, and the effective time of the active thermal protection mechanism is 20 minutes.
  • the thermal protection structure provided by the present invention can carry a thermal load of up to 10W/m 2 , and the effective time of the active thermal protection mechanism can reach 30 minutes.
  • the active thermal protection mechanism in the thermal protection structure of the present invention has an excellent thermal protection effect, and can control the temperature of the inner and outer surfaces of the aircraft inside and outside the cabin below 100°C, and can pass through the porous thermal insulation structure.
  • the thickness and heat flux adjust the active thermal protection mechanism time.
  • Example 1 As can be seen from Example 1 and Comparative Example 1 (as shown in Figure 4), the skin outer surface temperature of Example 1 is 865°C, and the skin outer surface temperature of Comparative Example 1 is 1170°C, which proves that the thermal protection structure provided by the present invention
  • the thermal protection effect of materials can be improved by internal radiation in passive thermal protection mechanism.

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Abstract

本发明提供了一种热防护结构及其制备方法，该热防护结构包括依次设置的隔热层、空腔层和蒙皮，隔热层设置于飞行器内舱的外表面上；隔热层包括多孔隔热结构、设置于多孔隔热结构中的温敏性水凝胶和吸附于温敏性水凝胶中的冷却工质；在热防护结构未进行热防护时，温敏性水凝胶处于溶胀状态，用于将冷却工质以固相的存在形式吸附于温敏性水凝胶中；在热防护结构进行热防护时，温敏性水凝胶吸收由蒙皮和空腔层向内辐射的热量，使其处于退溶胀状态，用于将冷却工质的存在形式由固相依次转变为液相和气相，并使得气相的冷却工质释放到空腔层后排出。本发明提供的热防护结构具备优异的热防护性能。

Description

一种热防护结构及其制备方法 技术领域
本发明涉及热防护技术领域，特别涉及一种热防护结构及其制备方法。
背景技术
现今，飞行器高速飞行技术大幅度提高了人类探索空间、进入空间、控制空间和利用空间的能力，具有特殊的军事战略意义和重要的科学价值。然而，无论临近空间高超声速飞行器，还是星际探测进入或返回的航天器，在大气层中以高超声速(>5马赫)再入或飞行时，由于经历严酷的气动加热环境，飞行器或航天器会面临“新热障”这一关键技术难题，而发展热防护机制，指导飞行器热防护系统的设计与制备，是解决此难题的有效途径。
热防护机制是专门用于飞行器热防护的特殊机制，是一类包含防热机理(例如，基于材料属性、物理化学效应或结构原理等)和系统结构构造及其工作原理的机制。目前，现役或已经试飞的高超声速飞行器(如X-15、X-37B、Apollo返回舱、X-43A以及SHEFEX II)采用的热防护机制按照防热机理可分为被动式(如热沉、绝热结构)、半被动式(如烧蚀、热管)和主动(如工质、冷却流)。这些传统热防护机制具有共同的特点，都是依靠材料或结构自身的耗、散、阻、抗来实现热防护功能。
然而，未来临近空间高超声速飞行器向着高速域、宽空域、长航时和可重复的方向发展，同时随着未来针对月球、火星、木星、太阳等多项重点深空探测任务的开展，气动加热环境将变得更加严峻，飞行器面临的热障问题将更加突出，仅仅依靠传统热防护机制已难以满足未来高超声速飞行器对热防护的需求。
发明内容
本发明实施例提供了一种热防护结构及其制备方法，能够提供一种热防护结构，满足未来高超声速飞行器对热防护的需求。
第一方面，本发明提供了一种热防护结构，所述热防护结构包括依次设 置的隔热层、空腔层和蒙皮，所述隔热层设置于飞行器内舱的外表面上；
所述隔热层包括多孔隔热结构、设置于所述多孔隔热结构中的温敏性水凝胶和吸附于所述温敏性水凝胶中的冷却工质；
在所述热防护结构未进行热防护时，所述温敏性水凝胶处于溶胀状态，用于将所述冷却工质以固相的存在形式吸附于所述温敏性水凝胶中；
在所述热防护结构进行热防护时，所述温敏性水凝胶吸收由所述蒙皮和所述空腔层向内辐射的热量，使其处于退溶胀状态，用于将所述冷却工质的存在形式由固相依次转变为液相和气相，并使得气相的所述冷却工质释放到所述空腔层后排出。
本发明的目的是针对下一代高超声速飞行器所需要的长时间、可重复热防护结构的需求，提供了主动、被动协同作用的热防护机制，具体是通过增加向内辐射散热(被动)和固相水相变散热(主动)协同作用的热防护机制实现热防护。
被动：传统热防护结构主要通过外蒙皮(外侧)向外辐射实现散热，本发明在外辐射的基础之上通过在蒙皮与隔热材料之间增加空腔层，使得蒙皮内侧也可向内辐射热量，通过蒙皮内侧表层的改性可大幅度提升蒙皮内侧的辐射系数，最高可达0.9，从而增加了在传统热防护基础之上增加了一项内辐射散，实现提升热防护结构防热效率的目的；
主动:水因为其相变潜热最高，成为相变冷却最佳的冷却工质，但是水的流动性、储存性的需要在热防护结构中配置密封、存储、防腐等一系列复杂的辅助结构，导致其无法应用于实际工程热防护结构中。本发明为解决这一问题，采用固相水替代传统的液相水，通过温敏水凝胶、无机-有机组装技术将液相水变成固相水小颗粒装填到下层无机隔热材料中，通过对比选择氧化铝多孔隔热材料。固相水颗粒通过化学枝结固定在多孔介质的微孔洞中。固相水凝胶填装完毕后可与多孔隔热材料紧密连接。当辐射导致空腔内温度升高后，固相水会通过缓释形成液相水，液相水受热后马上蒸发成水蒸气，进而通过这种液-气相变带走热量。
通过内辐射散热(被动)和固相水相变散热(主动)相互协同作用，可大幅度提升热防护结构的热防护能力。其中蒙皮与多孔介质之间的空腔厚 度、多孔介质内部微孔的分布和孔径、固相水的含量可根据热防护的需求进行设计和调节。
本发明的热防护机制为主动-被动协同热防护机制，在充分发挥外表面辐射散热的基础之上，不仅增加内辐射散热相，更重要的是增加了固相水的相变散热，该散热量是辐射散热的30～50倍，其热防护效果优于陶瓷基绝热式防热、发汗冷却以及薄膜冷却等其他单一的主动或者被动热防护机与结构。
基于本发明主/被动协同热防护机制的热防护结构可适用于高超声速飞行器翼前缘、头锥等防热结构，也可适用于迎风面的大面积区域，承受热载荷100～10MW/m 2，且不少于30分钟；
根据不同热载荷的条件，本发明提供的热防护结构的厚度10～100mm；本发明提供的热防护结构的背壁温度低于100℃；本发明提供的热防护结构具有防热、隔热和承载一体化的特征。
优选地，所述热防护结构还包括螺钉和螺母，所述隔热层和所述蒙皮通过所述螺钉和所述螺母的配合固定于飞行器内舱的外表面上。
优选地，所述螺钉和所述螺母均采用氧化铝陶瓷制成。
优选地，所述多孔隔热结构采用氧化铝陶瓷制成。
优选地，上述第一方面任一所述的热防护结构，所述冷却工质包括水。
第二方面，本发明提供一种热防护结构的制备方法，包括：
将温敏性水凝胶和多孔隔热结构置于含有冷却工质的容器中，以使所述温敏性水凝胶进入所述多孔隔热结构中；其中，所述冷却工质的温度为第一预设温度，在所述第一预设温度下，所述温敏性水凝胶处于退溶胀状态；
将所述冷却工质的温度降低至第二预设温度，以使所述冷却工质以固相的存在形式吸附于所述温敏性水凝胶中，得到隔热层；其中，在所述第二预设温度下，所述温敏性水凝胶处于溶胀状态；
将所述隔热层和蒙皮固定，并在所述隔热层与所述蒙皮之间设置空腔层，以形成热防护结构；其中，所述隔热层设置于飞行器内舱的外表面上。
本发明的目的是针对下一代高超声速飞行器所需要的长时间、可重复热防护结构的需求，提供了主动、被动协同作用的热防护机制，具体是通过增加向内辐射散热(被动)和固相水相变散热(主动)协同作用的热防护机制 实现热防护。
被动：传统热防护结构主要通过外蒙皮(外侧)向外辐射实现散热，本发明在外辐射的基础之上通过在蒙皮与隔热材料之间增加空腔层，使得蒙皮内侧也可向内辐射热量，通过蒙皮内侧表层的改性可大幅度提升蒙皮内侧的辐射系数，最高可达0.9，从而增加了在传统热防护基础之上增加了一项内辐射散，实现提升热防护结构防热效率的目的；
主动:水因为其相变潜热最高，成为相变冷却最佳的冷却工质，但是水的流动性、储存性的需要在热防护结构中配置密封、存储、防腐等一系列复杂的辅助结构，导致其无法应用于实际工程热防护结构中。本发明为解决这一问题，采用固相水替代传统的液相水，通过温敏水凝胶、无机-有机组装技术将液相水变成固相水小颗粒装填到下层无机隔热材料中，通过对比选择氧化铝多孔隔热材料。固相水颗粒通过化学枝结固定在多孔介质的微孔洞中。固相水凝胶填装完毕后可与多孔隔热材料紧密连接。当辐射导致空腔内温度升高后，固相水会通过缓释形成液相水，液相水受热后马上蒸发成水蒸气，进而通过这种液-气相变带走热量。
通过内辐射散热(被动)和固相水相变散热(主动)相互协同作用，可大幅度提升热防护结构的热防护能力。其中蒙皮与多孔介质之间的空腔厚度、多孔介质内部微孔的分布和孔径、固相水的含量可根据热防护的需求进行设计和调节。
本发明的热防护机制为主动-被动协同热防护机制，在充分发挥外表面辐射散热的基础之上，不仅增加内辐射散热相，更重要的是增加了固相水的相变散热，该散热量是辐射散热的30～50倍，其热防护效果优于陶瓷基绝热式防热、发汗冷却以及薄膜冷却等其他单一的主动或者被动热防护机与结构。
基于本发明主/被动协同热防护机制的热防护结构可适用于高超声速飞行器翼前缘、头锥等防热结构，也可适用于迎风面的大面积区域，承受热载荷100～10MW/m 2，且不少于30分钟；
根据不同热载荷的条件，本发明提供的热防护结构的厚度10～100mm；本发明提供的热防护结构的背壁温度低于100℃；本发明提供的热防护结构具有防热、隔热和承载一体化的特征。
优选地，所述将所述隔热层和蒙皮固定，包括：
利用螺钉和螺母的配合将所述隔热层和蒙皮固定。
优选地，所述螺钉和所述螺母均采用氧化铝陶瓷制成。
优选地，所述多孔隔热结构采用氧化铝陶瓷制成。
优选地，上述第二方面任一所述的热防护结构的制备方法，所述冷却工质包括水。
本发明与现有技术相比至少具有如下有益效果：
通过在飞行器内舱的外表面上设置包括隔热层、空腔层和蒙皮的热防护结构，使其具备优异的热防护性能。
热防护结构中的蒙皮和空腔，使其具备被动热防护功能，该被动热防护机制为蒙皮吸收外界热量升温后通过热辐射的方式将所吸收的热量部分释放。其中，蒙皮热辐射的途径有两种，一是蒙皮向外界环境释放外辐射，二是向空腔释放内辐射。本发明通过设置空腔层，使蒙皮在向外辐射热量的同时，也可以向内部辐射热量至空腔层，从而在传统热防护基础之上增加了一个向内辐射的途径，进而提升了被动热防护的热防护效率。
热防护结构中的隔热层包括多孔隔热结构、设置于多孔隔热结构中的温敏性水凝胶和吸附于温敏性水凝胶中的冷却工质。多孔隔热结构中的孔隙可收纳温敏性水凝胶，温敏性水凝胶可吸收液相冷却工质并将其转变为固相。
热防护结构中的隔热层和空腔，使其具备主动热防护功能。在热防护结构进行热防护时，温敏性水凝胶吸收由蒙皮和空腔层向内辐射的热量，使其处于退溶胀状态，用于将冷却工质的存在形式由固相依次转变为液相和气相，并使得气相的所述冷却工质释放到所述空腔层后排出。隔热层中含有温敏性水凝胶，当隔热层温度低于温敏性水凝胶的低临界溶解温度(LCST)时，其中的温敏性水凝胶呈溶胀状态，吸收冷却工质并将其转化为固相，得到隔热层；在该热防护结构使用过程中，其使用环境温度高于温敏性水凝胶的低临界溶解温度(LCST)，此时温敏性水凝胶吸收热量呈现退溶胀状态，将冷却工质由固相转变为液相并释出，然后，液相冷却工质继续吸热进一步转变为气相释放到空腔排出，从而实现优异的热防护功能。
此外，本发明提供的热防护结构可重复使用。通过隔热层中温敏性水凝 胶随环境温度变化发生可逆性溶胀-退溶胀的特性，可实现热防护结构的重复使用。使用后的热防护结构可通过降温、补充冷却工质的方式使其中的温敏性水凝胶溶胀吸收冷却工质，从而恢复优异的热防护性能。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是本发明实施例提供的热防护结构的原理示意图；
图2是本发明实施例提供的热防护结构制备方法的流程图；
图3(a)是本发明实施例提供的热防护结构的立体图；
图3(b)是本发明实施例提供的热防护结构的局部剖面图；
图4是本发明实施例1提供的热防护结构与对比例1提供的热防护结构的防热效果对比图。
图中：
1、蒙皮；2、空腔层；3、隔热层；4、底板；5、螺钉；6、螺母。
具体实施方式
为使本发明实施例的目的、技术方案和优点更加清楚，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例，基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动的前提下所获得的所有其他实施例，都属于本发明保护的范围。
如图1、图3(a)和图3(b)所示，本发明提供了一种热防护结构，热防护结构包括依次设置的隔热层3、空腔层2和蒙皮1，隔热层3设置于底板4上；
隔热层3包括多孔隔热结构、设置于多孔隔热结构中的温敏性水凝胶和吸附于温敏性水凝胶中的冷却工质；
在热防护结构未进行热防护时，温敏性水凝胶处于溶胀状态，用于将冷 却工质以固相的存在形式吸附于温敏性水凝胶中；
在热防护结构进行热防护时，温敏性水凝胶吸收由蒙皮1和空腔层2向内辐射的热量，使其处于退溶胀状态，用于将冷却工质的存在形式由固相依次转变为液相和气相，并使得气相的冷却工质释放到空腔层2后排出。
需要说明的是，底板4是飞行器内舱外表面的一部分，常用材料选取铝合金。
在本发明中，通过在底板4上设置包括隔热层3、空腔层2和蒙皮1的热防护结构，使其具备优异的热防护性能。
热防护结构中的蒙皮1和空腔，使其具备被动热防护功能，该被动热防护机制为蒙皮1吸收外界热量升温后通过热辐射的方式将所吸收的热量部分释放。其中，蒙皮1热辐射的途径有两种，一是蒙皮1向外界环境释放外辐射，二是向空腔释放内辐射。本发明通过设置空腔层2，使蒙皮1在向外辐射热量的同时，也可以向内部辐射热量至空腔层2，从而在传统热防护基础之上增加了一个向内辐射的途径，进而提升了被动热防护的热防护效率。
热防护结构中的隔热层3包括多孔隔热结构、设置于多孔隔热结构中的温敏性水凝胶和吸附于温敏性水凝胶中的冷却工质。多孔隔热结构中的孔隙可收纳温敏性水凝胶，温敏性水凝胶可吸收液相冷却工质并将其转变为固相。
热防护结构中的隔热层3和空腔，使其具备主动热防护功能。在热防护结构进行热防护时，温敏性水凝胶吸收由蒙皮1和空腔层2向内辐射的热量，使其处于退溶胀状态，用于将冷却工质的存在形式由固相依次转变为液相和气相，并使得气相的所述冷却工质释放到所述空腔层2后排出。隔热层3中含有温敏性水凝胶，当隔热层3温度低于温敏性水凝胶的低临界溶解温度(LCST)时，其中的温敏性水凝胶呈溶胀状态，吸收冷却工质并将其转化为固相，得到隔热层3；在该热防护结构使用过程中，其使用环境温度高于温敏性水凝胶的低临界溶解温度(LCST)，此时温敏性水凝胶吸收热量呈现退溶胀状态，将冷却工质由固相转变为液相并释出，然后，液相冷却工质继续吸热进一步转变为气相释放到空腔排出，从而实现优异的热防护功能。
此外，本发明提供的热防护结构可重复使用。通过隔热层3中温敏性水 凝胶随环境温度变化发生可逆性溶胀-退溶胀的特性，可实现热防护结构的重复使用。使用后的热防护结构可通过降温、补充冷却工质的方式使其中的温敏性水凝胶溶胀吸收冷却工质，从而恢复优异的热防护性能。在本发明中，热防护结构通过主动-被动协同的热防护机制来实现优异的热防护性能。在充分发挥外表面辐射散热的基础之上，增加了内辐射散热(被动热防护)；除此之外，还增加了固相水的相变散热(主动热防护)，该散热量是外表面辐射散热的30～50倍。本发明提供的热防护结构可确保高超声速飞行器在气动加热环境下，其飞行器内舱外表面的温度小于100℃，该热防护效果明显优于陶瓷基绝热式防热、发汗冷却以及薄膜冷却等其他单一的主动或者被动热防护机制。
需要说明的是，在隔热层3中温敏性水凝胶退溶胀的过程中，冷却工质通过固相、液相、气相的相变过程不断吸收热量，此时隔热层3中存在固-液-气相平衡，从而使隔热层3温度保持在冷却工质的沸点温度以下，直到固相冷却工质耗尽，主动热防护机制失效。
在本发明中，可通过多孔隔热结构的孔径、孔分布、温敏性水凝胶的水控释速率以及冷却工质的质量调节主动热防护机制时间。
需要说明的是，传统的主动热防护结构选取的冷却工质为液相，由于液相冷却工质具有流动性，将其置于热防护结构中需要配置密封、储存和防腐等一系列复杂的辅助结构，导致其难以在实际热防护结构中应用。为解决这一问题，本发明在隔热层3中加入温敏性水凝胶，温敏性水凝胶可吸收冷却工质并将其转变为固相，从而避免了在热防护结构中设置贮存液相冷却工质所需的辅助结构。除此之外，本发明的热防护结构中主动热防护机制完全由温度变化自动触发，由冷却工质的相变吸热实现热防护，全部过程无需任何传感器和控制装置。
本发明提供的热防护结构可适用于高超声速飞行器翼前缘、头锥等部位，也可适用于迎风面的大面积区域，可承受100kW/m 2～10MW/m 2热载荷，且加载时间最长可达30min。其中，加载时间即为主动热防护机制有效时间。
根据一些优选的实施方式，热防护结构还包括螺钉5和螺母6，隔热层3 和蒙皮1通过螺钉5和螺母6的配合固定于底板4上。
根据一些优选的实施方式，螺钉5和螺母6均采用氧化铝陶瓷制成。
根据一些优选的实施方式，多孔隔热结构采用氧化铝陶瓷制成。
如图3(a)和图3(b)所示，热防护结构可采用螺钉5和螺母6配合的方式，依次将蒙皮1、隔热层3和底板4固定在一起，其中，螺母6固定在蒙皮1两侧，用以在隔热层3和蒙皮1间保留空腔层2。
在本发明中，蒙皮1采用高温合金板；多孔隔热结构和螺钉5螺母6采用氧化铝陶瓷材料，氧化铝陶瓷材料具备优异的隔热性。氧化铝陶瓷材料相较于其他多孔隔热材料(如氧化锆陶瓷材料)，单价更低，孔隙分布更均匀。
根据一些优选的实施方式，上述第一方面任一的热防护结构，冷却工质包括水。
需要说明的是，因为水相变潜热最高，所以选取水作为相变冷却的最佳冷却工质。
如图2所示，本发明还提供一种热防护结构的制备方法，包括：
将温敏性水凝胶和多孔隔热结构置于含有冷却工质的容器中，以使温敏性水凝胶进入多孔隔热结构中；其中，冷却工质的温度为第一预设温度，在第一预设温度下，温敏性水凝胶处于退溶胀状态；
将冷却工质的温度降低至第二预设温度，以使冷却工质以固相的存在形式吸附于温敏性水凝胶中，得到隔热层；其中，在第二预设温度下，温敏性水凝胶处于溶胀状态；
将隔热层和蒙皮固定，并在隔热层与蒙皮之间设置空腔层，以形成热防护结构；其中，隔热层设置于底板上。需要说明的是，第一预设温度略高于LCST(隔热层中温敏性水凝胶低临界溶解温度)，第二预设温度低于LCST。当温敏性水凝胶温度高于LCST时，呈退溶胀状态，此时其内部无水；当温敏性水凝胶温度低于LCST时，呈溶胀状态，可吸收液相水并在其内部形成固相水。
在本发明中，冷却工质为第一预设温度时，容器内的温敏性水凝胶为液相退溶胀状态，此时温敏性水凝胶进入到多孔隔热结构内部孔隙，温敏性水 凝胶大分子通过接枝的方式与多孔隔热结构孔隙内壁结合。
在本发明中，冷却工质的温度降至第二预设温度时，降温过程中多孔隔热结构孔隙中的温敏性水凝胶呈溶胀状态，通过亲水基网状结构的高聚物吸收大量的蒸馏水而溶胀，且随着温度的降低，溶胀速度增加，当容器内进行降温至第二预设温度时，温敏性水凝胶达到溶胀平衡，得到隔热层。通过降低容器内的温度，使多孔隔热结构中的温敏性水凝胶吸水溶胀，将容器内的液相水转变为固相水，固相水以结合水和自由水的形式存在于温敏性水凝胶中。
本发明提供的热防护结构厚度为10～100mm(厚度包括底板)，具有防热、隔热和承载一体化的功能。
需要说明的是，本发明提供的制备方法结构简单、成本低、安装方便，且可设计性强，可根据飞行时间和飞行走廊的热载荷，设计隔热层的厚度、微流道路径与分布、冷却工质质量，以满足不同飞行任务的需求。
根据一些优选的实施方式，将隔热层和蒙皮固定，包括：
利用螺钉和螺母的配合将隔热层和蒙皮固定。
根据一些优选的实施方式，螺钉和螺母均采用氧化铝陶瓷制成。
根据一些优选的实施方式，多孔隔热结构采用氧化铝陶瓷制成。
如图3所示，热防护结构可采用螺钉和螺母配合的方式，依次将蒙皮、隔热层和底板固定在一起，其中，螺母固定在蒙皮两侧，用以在隔热层和蒙皮间保留空腔层。
在本发明中，蒙皮采用高温合金板；多孔隔热结构和螺钉螺母采用氧化铝陶瓷材料，氧化铝陶瓷材料具备优异的隔热性。氧化铝陶瓷材料相较于其他多孔隔热材料(如氧化锆陶瓷材料)，单价更低，孔隙分布更均匀。
根据一些优选的实施方式，上述任一的热防护结构的制备方法，冷却工质包括水。
需要说明的是，因为水相变潜热最高，所以选取水作为相变冷却的最佳冷却工质。
为了更加清楚地说明本发明的技术方案及优点，下面通过几个实施例对一种热防护结构及其制备方法进行详细说明。
实施例1
将温敏性水凝胶和100mm×100mm×8mm的多孔氧化铝陶瓷板置于含有蒸馏水的容器中，以使温敏性水凝胶进入多孔氧化铝陶瓷板中；其中，蒸馏水的温度为36℃，温敏性水凝胶处于退溶胀状态；
将蒸馏水的温度降低至25℃，以使蒸馏水以固相的存在形式吸附于温敏性水凝胶中，得到隔热层；其中，所述温敏性水凝胶处于溶胀状态；
将隔热层、蒙皮和底板利用螺钉螺母配合的方式固定，得到热防护结构底板。其中，蒙皮选用100mm×100mm×5mm的高温合金板，底板材料选用100mm×100mm×5mm的铝合金板，螺钉螺母采用M4氧化铝陶瓷螺钉螺母。其中，螺母固定在蒙皮两侧，用以在隔热层和蒙皮间保留8mm空腔层。
将制备的热防护结构底板置于隔热毡上，在蒙皮外表面和隔热层外表面分别粘接热电偶，将其置于高功率石英灯下，通过高功率石英灯将热流密度调整至0.9MW/m 2，并进行热考核测试，测得蒙皮外表面温度为865℃，隔热层外表面温度不超过100℃，并持续3min(主动热防护机制有效时间)。
实施例2
实施例2与实施例1的制备方法基本相同，不同之处在于：
热流密度为0.1MW/m 2，多孔氧化铝陶瓷板厚度为5mm。
测得蒙皮外表面温度为420℃，主动热防护机制有效时间为30min。
实施例3
实施例3与实施例1的制备方法基本相同，不同之处在于：
将热防护结构置于高频等离子风洞中，热流密度调整至5MW/m 2，多孔氧化铝陶瓷板厚度为15mm。
测得蒙皮外表面温度为870℃，主动热防护机制有效时间为15min。
实施例4
实施例4与实施例1的制备方法基本相同，不同之处在于：
将热防护结构置于高频等离子风洞中，热流密度调整至10MW/m 2，多孔氧化铝陶瓷板厚度为30mm。
测得蒙皮外表面温度为910℃，主动热防护机制有效时间为20min。
对比例1
选取100mm×100mm×5mm高温合金板作为蒙皮，在蒙皮外表面粘接热电偶，将其置于高功率石英灯下，通过高功率石英灯将热流密度调整至0.9MW/m 2，并进行热考核测试，测得蒙皮外表面温度为1170℃。
将实施例1～4，对比例1的热考核测试数据汇总如表1：
表1
Figure PCTCN2022083265-appb-000001
由实施例1～4可知，本发明提供的热防护结构最高可承载10W/m 2的热载荷，主动热防护机制有效时间可达30min。
由实施例1～4还可知，本发明热防护结构中的主动热防护机制具有优异的热防护效果，可将内部的飞行器内舱外表面温度控制在100℃以下，且可通过多孔隔热结构的厚度、热流密度调节主动热防护机制时间。
由实施例1和对比例1可知(如图4)，实施例1的蒙皮外表面温度为865℃，对比例1的蒙皮外表面温度为1170℃，证明了本发明提供的热防护结构可通过被动热防护机制中的内辐射来提高材料的热防护效果。
最后应说明的是：以上实施例仅用以说明本发明的技术方案，而非对其限制；尽管参照前述实施例对本发明进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本发明各实施例技术方案的精神和范围。

Claims (10)

  1. 一种热防护结构，其特征在于，所述热防护结构包括依次设置的隔热层、空腔层和蒙皮，所述隔热层设置于飞行器内舱的外表面上；
    所述隔热层包括多孔隔热结构、设置于所述多孔隔热结构中的温敏性水凝胶和吸附于所述温敏性水凝胶中的冷却工质；
    在所述热防护结构未进行热防护时，所述温敏性水凝胶处于溶胀状态，用于将所述冷却工质以固相的存在形式吸附于所述温敏性水凝胶中；
    在所述热防护结构进行热防护时，所述温敏性水凝胶吸收由所述蒙皮和所述空腔层向内辐射的热量，使其处于退溶胀状态，用于将所述冷却工质的存在形式由固相依次转变为液相和气相，并使得气相的所述冷却工质释放到所述空腔层后排出。
  2. 根据权利要求1所述的热防护结构，其特征在于，所述热防护结构还包括螺钉和螺母，所述隔热层和所述蒙皮通过所述螺钉和所述螺母的配合固定于飞行器内舱的外表面上。
  3. 根据权利要求2所述的热防护结构，其特征在于，所述螺钉和所述螺母均采用氧化铝陶瓷制成。
  4. 根据权利要求1-3中任一项所述的热防护结构，其特征在于，所述多孔隔热结构采用氧化铝陶瓷制成。
  5. 根据权利要求1-4中任一项所述的热防护结构，其特征在于，所述冷却工质包括水。
  6. 一种热防护结构的制备方法，其特征在于，包括：
    将温敏性水凝胶和多孔隔热结构置于含有冷却工质的容器中，以使所述温敏性水凝胶进入所述多孔隔热结构中；其中，所述冷却工质的温度为第一预设温度，在所述第一预设温度下，所述温敏性水凝胶处于退溶胀状态；
    将所述冷却工质的温度降低至第二预设温度，以使所述冷却工质以固相的存在形式吸附于所述温敏性水凝胶中，得到隔热层；其中，在所述第二预设温度下，所述温敏性水凝胶处于溶胀状态；
    将所述隔热层和蒙皮固定，并在所述隔热层与所述蒙皮之间设置空腔 层，以形成热防护结构；其中，所述隔热层设置于飞行器内舱的外表面上。
  7. 根据权利要求6所述的热防护结构的制备方法，其特征在于，所述将所述隔热层和蒙皮固定，包括：
    利用螺钉和螺母的配合将所述隔热层和蒙皮固定。
  8. 根据权利要求7所述的热防护结构的制备方法，其特征在于，所述螺钉和所述螺母均采用氧化铝陶瓷制成。
  9. 根据权利要求6-8中任一项所述的热防护结构的制备方法，其特征在于，所述多孔隔热结构采用氧化铝陶瓷制成。
  10. 根据权利要求6-9中任一项所述的热防护结构的制备方法，其特征在于，所述冷却工质包括水。
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