Active and passive synergistic efficient heat insulation structure and forming method

Abstract

The invention belongs to the technical field related to thermal protection, and discloses an active and passive synergistic efficient thermal insulation structure and a forming method. The structure comprises a heat bearing panel, a heat insulation panel and a hollow dot matrix sandwich, the heat bearing panel and the heat insulation panel are oppositely arranged, the hollow dot matrix sandwich is arranged between the heat bearing panel and the heat insulation panel, the hollow dot matrix sandwich comprises polyhedrons which are distributed in an array mode, each edge of each polyhedron is a hollow rod, and each edge of each polyhedron is a hollow rod. And the center of the hollow rod is filled with a phase change material. According to the invention, the problem that thermal short circuit is easily generated due to high thermal conductivity of the lattice sandwich is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to thermal protection, and more specifically, relates to an active and passive coordinated efficient thermal insulation structure and a molding method. Background Art

[0002] Hypersonic vehicles are important strategic equipment for winning in the air and space. Due to the friction between the surface and the air during the hypersonic flight process (≥ 5 Mach), the outer surface will be heated to thousands of degrees Celsius during flight, and the heat flow will gradually be transferred to the internal structure of the aircraft. The fuel tanks, equipment bays and structural parts in the aircraft are all affected by the high temperature, which may lead to high temperature warnings, high temperature failure of major components and even the risk of explosion. In addition, the weight of fuel in hypersonic vehicles accounts for more than 50%. The aircraft skin and fuel tank need to have efficient heat insulation and lightweight effects. Therefore, it is urgent to develop lightweight, high-strength and efficient heat-insulating devices.

[0003] In order to prevent the high-temperature heat flow on the surface of the aircraft from being conducted inward, the existing sandwich composite structure uses a lattice structure as a skeleton and fills the insulation layer and the phase change material layer to obtain an integrated structure of heat insulation and load bearing. CN 112728297A discloses a device for improving the heat insulation effect based on additive manufacturing. The device uses an eight-fold truss unit cell structure with upper and lower solid plates and an array arrangement in the middle. By adopting an additive manufacturing method, it can produce three-dimensional lattice structure heat insulation parts with high precision and excellent surface quality. CN113562202A also discloses a multi-layer heat insulation and load bearing integrated lattice thermal protection system based on phase change material. The structure is mainly composed of a top panel, a core rod, an intermediate panel, a core rod and a bottom panel. There is a lattice sandwich structure between the panels. The heat insulation material and the phase change material are filled between the three layers of panels. The high phase change material and high heat capacity of the phase change material are used to store energy, which has a good heat insulation effect.

[0004] In these two types of thermal insulation structures, since there is a lattice sandwich structure between the layers, the lattice sandwich structure has a higher thermal conductivity than the surrounding insulation layer, which is prone to thermal short-circuit effect. Therefore, a key problem that needs to be solved urgently is to reduce the thermal conductivity of the lattice sandwich structure to reduce the thermal short-circuit effect. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides an active and passive coordinated efficient thermal insulation structure and a molding method to solve the problem that the high thermal conductivity of the lattice sandwich core is prone to thermal short circuit.

[0006] To achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided an active and passive coordinated efficient thermal insulation structure, which includes a heat-bearing panel, a thermal insulation panel and a hollow lattice sandwich, wherein the heat-bearing panel and the thermal insulation panel are arranged opposite to each other, and the hollow lattice sandwich is arranged between the heat-bearing panel and the thermal insulation panel, and the hollow lattice sandwich includes polyhedrons distributed in an array, each edge of each polyhedron is a hollow rod, and the center of the hollow rod is filled with phase change material.

[0007] Further preferably, the phase change material is alkane or aerogel.

[0008] Further preferably, the centers of all hollow rods in the hollow lattice core are connected.

[0009] Further preferably, the relative density of the hollow lattice sandwich between the heat-bearing panel and the heat-insulating panel is 15% to 30%.

[0010] Further preferably, the polyhedron is a regular octahedron or an octahedron.

[0011] Further preferably, the heat-bearing panel, the heat-insulating panel and the hollow rod are made of a high-temperature titanium alloy that can withstand temperatures above 500°C.

[0012] Further preferably, the titanium alloy is Ti60, Ti600 or Ti1100.

[0013] Further preferably, an active cooling medium is also provided in the hollow lattice core, and the Reynolds number of the cooling medium is greater than 4000.

[0014] Further preferably, the ratio of the diameter of the hollow part of the hollow rod to the wall thickness is 1-10.

[0015] According to another aspect of the present invention, a method for forming an active and passive coordinated high-efficiency thermal insulation structure is provided, the method comprising:

[0016] Constructing a three-dimensional geometric model of the efficient thermal insulation structure, and slicing the three-dimensional geometric model to obtain a plurality of slice layers;

[0017] Laser melting and forming metal powders to obtain a preform of a heat insulation structure layer by layer by slicing the slices;

[0018] The phase change material is filled in the hollow rods in the preform, so as to obtain the desired high-efficiency heat insulation structure.

[0019] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0020] 1. The active and passive coordinated efficient thermal insulation structure provided by the present invention designs the hollow lattice core as a hollow component. By filling the hollow part with phase change material and adjusting the ratio of the hollow part diameter to the lattice structure wall thickness as needed, the controllable change of the thermal conductivity of the lattice structure can be achieved, and then the appropriate thermal conductivity sandwich layer can be selected according to the actual service conditions to reduce the thermal short-circuit effect. The device can adapt to different service environments and can flexibly change the design according to the use conditions. It has both good mechanical properties and thermal insulation effects, low cost and excellent thermal insulation effects.

[0021] 2. The present invention arranges in the hollow lattice sandwich to enhance convective insulation by flowing cooling medium to strengthen the cooling effect. This cooling design can ensure the insulation effect and mechanical properties under extreme service conditions. At the same time, the cooling medium can be replaced with a low-cost insulation material such as aerogel in places where the insulation requirement of the device is relatively low. The device can select different designs according to the actual service conditions to match the insulation requirements, and has extremely high economy.

[0022] 3. The lattice structure of the present invention can adjust the mechanical properties by changing the unit cell size and the diameter and wall thickness of the hollow rod. According to the requirements of the service conditions for mechanical bearing performance, different relative density designs are selected. The high relative density design has stronger mechanical bearing performance, but increases the weight of the device. The low relative density design can make the device lightweight. The mechanical bearing performance requirements of the service conditions can be met and the device can be lightweight through reasonable relative density design.

[0023] 4. The structural dimensions of the high-efficiency heat insulation device of the present invention can range from millimeters to meters. Different sizes can be manufactured in different ways according to the assembly requirements of the components, and the device has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of an active and passive coordinated high-efficiency thermal insulation structure constructed according to a preferred embodiment of the present invention;

[0025] Figure 2 It is a flow chart of a method for forming an active and passive coordinated efficient thermal insulation structure according to a preferred embodiment of the present invention;

[0026] Figure 3 This is a performance diagram of Ti600 alloy, a raw material for the active-passive coordinated high-efficiency thermal insulation structure constructed in an embodiment of the present invention;

[0027] Figure 4 It is a diagram of the temperature change of the structure center of the active-passive coordinated high-efficiency thermal insulation structure of the present invention obtained by finite element analysis of the phase change material without filling and with filling.

[0028] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0029] 1-heat bearing panel, 2-hollow rod, 3-area where active cooling medium is set, 4-insulation panel, 5-phase change material filling area, 6-reserved holes. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] like Figure 1 As shown, an active-passive coordinated high-efficiency thermal insulation structure includes a heat-bearing panel 1, a thermal insulation panel 4, a hollow lattice core, the hollow lattice core is filled with low-density lightweight phase change material and a flowing cooling medium, and the inner and outer ends of the hollow lattice core are respectively connected to the heat-bearing panel and the thermal insulation panel.

[0032] By designing the lattice sandwich as a hollow structure and arranging it in a three-dimensional array, and taking advantage of the good connectivity of the hollow lattice sandwich, phase change materials can be injected with fewer openings. At the same time, by selecting different phase change materials, the thermal conductivity of the structure can be freely changed, which can well adapt to the insulation requirements under different service conditions. The thermal conductivity of this structure is significantly lower than that of the traditional solid structure, which can well reduce the thermal short-circuit effect without losing its load-bearing performance and increasing the weight of the device, and can achieve lightweight and high specific strength of the structure.

[0033] In one embodiment of the present invention, the lattice structure type is preferably a regular octahedron or an eight-fold truss lattice structure. These two structures can meet the mechanical bearing performance requirements of the device while maintaining light weight, and at the same time, due to the good connectivity of the internal phase change material filling area, it is easy to fill the phase change material.

[0034] In one embodiment of the present invention, the ratio of the diameter of the hollow part of the hollow rod 2 of the hollow lattice sandwich to the wall thickness is 1 to 10. In one embodiment of the present invention, the diameter of the hollow part of the hollow rod 2 is preferably greater than 0.5 mm, and the wall thickness of the hollow rod is greater than 0.2 mm. Considering the molding accuracy of the additive manufacturing technology, the diameter and wall thickness of the hollow part of the hollow rod should not be too small, so as to facilitate the removal of residual raw materials and filling of phase change materials after manufacturing, while ensuring that the phase change material does not leak.

[0035] In one embodiment of the present invention, the edge length of the hollow rod 2 of the hollow lattice sandwich is preferably 3 to 10 mm, and the interiors of all hollow rods are connected. If the edge length is too long, support needs to be added during the manufacturing process, and it is not easy to remove the support in post-processing, and the rod is prone to deformation during the manufacturing process.

[0036] In one embodiment of the present invention, the relative density of the lattice can be adjusted by adjusting the diameter of the hollow rod 2. Considering the minimum precision of additive manufacturing and the requirement for lightweight, the relative density is preferably 15% to 30%.

[0037] In one embodiment of the present invention, the materials of the heat bearing panel 1, the heat insulating panel 4 and the hollow rod 2 are preferably high temperature titanium alloys resistant to above 500°C, such as Ti60, Ti600, Ti1100, etc.

[0038] In one embodiment of the present invention, Figure 1 As shown, the area 3 where the active cooling medium is set is in the middle of the hollow lattice core. The active cooling medium is preferably a high-speed airflow or a circulating liquid according to needs, and the flow is turbulent with a Reynolds number greater than 4000.

[0039] In one embodiment of the present invention, the hollow rod 2 is filled with a phase change material. Considering the lightweight structure and thermal effect, the phase change material is preferably an alkane, an aerogel, etc. The region 5 filled with the phase change material is as follows: Figure 1 as shown in .

[0040] In one embodiment of the present invention, reserved holes 6 are designed on the heat bearing panel 1 to facilitate the subsequent cleaning of the powder inside the hollow lattice sandwich and the filling of the phase change material.

[0041] In one embodiment of the present invention, the diameter of the reserved hole 6 should preferably be no less than the diameter of the hollow part of the hollow rod 2, and the number of holes should preferably be no less than 2, so as to facilitate cleaning of the internal raw materials and filling of the phase change material.

[0042] like Figure 2 As shown, the manufacturing method of the above-mentioned high-efficiency thermal insulation structure comprises the following steps:

[0043] Component device parts model and slice processing;

[0044] Using high temperature resistant metal powder as raw material, metal powder bed molten deposition technology is used to print layer by layer to finally produce formed parts;

[0045] The residual powder inside and outside the obtained formed parts is removed, and the phase change material is filled, and then the reserved holes are sealed, thereby obtaining the high-efficiency heat insulation device component.

[0046] Specifically, the steps for cleaning powder and filling phase change material are as follows:

[0047] The obtained parts are taken out from the additive manufacturing equipment and separated from the substrate using the wire EDM technology. The external powder of the lattice structure rod is cleaned by vibration and high-pressure air gun. The internal powder of the lattice structure is poured out from the holes reserved in advance and put into the ultrasonic cleaning machine for thorough cleaning;

[0048] Use a syringe to inject the liquid phase change material into the lattice structure through the reserved holes, and shake the device sufficiently to completely remove the air blocked inside;

[0049] The reserved holes are filled with welding or laser additive manufacturing technology according to the shape and size of the reserved holes to completely seal the phase change material inside the lattice structure.

[0050] The technical solution of the present invention is further described below in conjunction with embodiments.

[0051] The method for constructing a regular octahedron hollow lattice sandwich is as follows: a cube unit cell is constructed using CAD software, and the unit cell size is designed to be 5mm. The unit cell size can be changed according to the specific usage. The cube unit cell can be divided into eight equal cube blocks through the middle parallel planes of the two opposite faces of the cube. The center point of the upper top surface of the cube unit cell is connected to the midpoint of the side edge and a certain extension is made on both sides. Two concentric cylinders are constructed with this as the center line, and the diameters of the cylinders are 1mm and 0.5mm respectively. The two concentric cylinders are subjected to Boolean operation difference processing to obtain a hollow cylindrical rod, and the cylindrical rod is subjected to Boolean operation intersection processing with the small cube in which it is located. The rod is symmetrically operated through the three central symmetry planes of the cube to obtain a complete regular octahedron hollow lattice structure. The obtained lattice structure unit cell is arrayed to obtain the entire sandwich layer lattice structure.

[0052] As needed, add panels with a thickness of 0.6 mm and the same area as the outer contour of the hollow lattice sandwich to the upper and lower end surfaces of the hollow lattice sandwich, and use the stretching and cutting function to set reserved holes in the diagonal part where the hollow lattice sandwich and the outer panel are connected. The obtained model is repaired and sliced ​​in Magics software.

[0053] It is manufactured using fused deposition modeling technology, using Ti600 titanium alloy powder, and the additive manufacturing equipment melts and deposits layer by layer according to the three-dimensional slicing data.

[0054] The powder outside the structure is removed, and the powder inside the hollow lattice structure is poured out through the pre-reserved holes. The hollow structure is filled with liquid paraffin using a pinhole syringe, and the injection channel is a pre-designed hole. After the injection is completed, the reserved holes are closed using welding or laser additive manufacturing repair technology, and air is used as the flowing cooling medium to obtain a device with efficient heat insulation effect.

[0055] like Figure 3 As shown in the figure, the yield strength of Ti600 alloy at room temperature is nearly 1150Mpa, and at a high temperature of 600℃, Ti600 alloy still has excellent mechanical properties, with a yield strength of more than 600Mpa. In addition, the thermal conductivity of Ti600 alloy changes little with temperature, and the thermal conductivity is within 20W / (m·K) below 800℃, so Ti600 alloy has excellent mechanical properties and good thermal insulation effect.

[0056] like Figure 4 As shown in the figure, under a given heat flux input, the temperature of the hollow part of the regular octahedral hollow lattice sandwich after filling with phase change material is greatly reduced compared with no filling. This design can effectively reduce the thermal conductivity of the structure and weaken the thermal short-circuit effect.

[0057] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An active and passive coordinated high-efficiency thermal insulation structure, characterized in that: The structure comprises a heat-bearing panel (1), a heat-insulating panel (4) and a hollow lattice sandwich, wherein the heat-bearing panel (1) and the heat-insulating panel (4) are arranged relative to each other, and the hollow lattice sandwich is arranged between the heat-bearing panel and the heat-insulating panel (4), and the hollow lattice sandwich comprises polyhedrons distributed in an array, each side of each polyhedron is a hollow rod (2), and the center of the hollow rod (2) is filled with a phase change material.

2. The active and passive coordinated high-efficiency thermal insulation structure according to claim 1, characterized in that: The phase change material is alkane or aerogel.

3. An active and passive coordinated high-efficiency thermal insulation structure as claimed in claim 1 or 2, characterized in that: The centers of all the hollow rods (2) in the hollow lattice sandwich are connected.

4. The active and passive coordinated high-efficiency thermal insulation structure according to claim 3, characterized in that: The relative density of the hollow lattice sandwich between the heat-bearing panel and the heat-insulating panel (4) is 15% to 30%.

5. The active and passive coordinated high-efficiency thermal insulation structure according to claim 1 or 4, characterized in that: The polyhedron is a regular octahedron or an eight-fold truss.

6. The active and passive coordinated high-efficiency thermal insulation structure according to claim 1, characterized in that: The heat-bearing panel (1), the heat-insulating panel (4) and the hollow rod (2) are made of a titanium alloy that is resistant to high temperatures above 500°C.

7. The active and passive coordinated high-efficiency thermal insulation structure according to claim 6, characterized in that: The titanium alloy is Ti60, Ti600 or Ti1100.

8. The active and passive coordinated high-efficiency thermal insulation structure according to claim 1 or 4, characterized in that: An active cooling medium is also arranged in the hollow lattice core, and the Reynolds number of the cooling medium is greater than 4000.

9. The active and passive coordinated high-efficiency thermal insulation structure according to claim 1 or 4, characterized in that: The ratio of the diameter of the hollow part of the hollow rod (2) to the wall thickness is 1-10.

10. A molding method of an active and passive coordinated efficient thermal insulation structure, characterized in that: The method includes: Constructing a three-dimensional geometric model of the efficient thermal insulation structure, and slicing the three-dimensional geometric model to obtain a plurality of slice layers; Laser melting and forming metal powders to obtain a preform of a heat insulation structure layer by layer by slicing the slices; The phase change material is filled in the hollow rods in the preform, so as to obtain the desired high-efficiency heat insulation structure.

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