A phase-change sweat-cooling porous structure and its application in spacecraft reentry capsule

Abstract

The present invention relates to a phase-change transudation cooling porous structure and its application in an aircraft reentry capsule. The porous structure comprises: a porous layer comprising a plurality of closely arranged porous units; a liquid separation chamber connected to the porous layer; a liquid storage chamber for storing coolant; a coolant delivery pipeline connecting the liquid storage chamber and the liquid separation chamber; and a regulating valve disposed on the coolant delivery pipeline. The porous units comprise a small-porosity porous portion, a large-porosity porous portion connected to each of the small-porosity porous portions, and a liquid channel, with a gas channel formed between the small-porosity porous portion and the large-porosity porous portion. Coolant enters through the liquid channel and permeates the small-porosity porous portion. After vaporization, it escapes from the large-porosity porous portion along the gas channel to form an air film for thermal insulation. Compared with existing technologies, the present invention can effectively achieve rapid gas-liquid separation and zoned flow control of the coolant in the transudation cooling porous layer, effectively improving the efficiency and reliability of phase-change transudation cooling.

Description

Technical Field

[0001] The present invention belongs to the technical field of phase change transpiration cooling and thermal protection, and in particular relates to a phase change transpiration cooling porous structure and its application in an aircraft reentry capsule. Background Art

[0002] Spacecraft face severe aerodynamic heating during flight, necessitating efficient thermal protection for critical hot components. For example, a spacecraft's re-entry capsule experiences a dramatic rise in surface temperature due to friction with the Earth's atmosphere upon entry. To maintain the capsule's internal operating temperature and ensure the safety of equipment and personnel, developing an efficient and stable thermal protection system is crucial to addressing this critical issue. Furthermore, the thermal protection structure accounts for 3% to 50% of the capsule's total weight, making its structural efficiency a crucial indicator of overall spacecraft performance.

[0003] Phase-change transpiration cooling utilizes the powerful convective heat transfer capability of liquid coolant to intensively exchange heat with the porous framework, removing heat. It also utilizes the rapid escape of gaseous coolant after phase change, forming a film on the solid surface to block heat transfer. Simultaneously, the latent heat of the coolant phase change creates a significant heat sink, enabling efficient thermal protection with low coolant consumption. This is considered a key development direction for efficient, lightweight thermal protection technologies.

[0004] However, during the phase change transpiration cooling process, when the liquid coolant vaporizes inside the porous medium, the pressure in the vaporization area increases significantly due to the significant density difference between the gas and liquid phases, resulting in a significant increase in flow resistance. This phenomenon not only limits the effective transport of the coolant, but also prevents the gas from being quickly discharged to form an air film, significantly reducing the efficiency and reliability of phase change transpiration cooling. At the same time, during the process of entering the Earth's atmosphere, the surface of the spacecraft's return capsule exhibits a highly non-uniform heat flux distribution, which causes the coolant to vaporize non-uniformly in the porous layer on the surface of the return capsule. The flow resistance of the high heat flux position that vaporizes first increases, further aggravating the non-uniform vaporization and easily causing heat transfer to deteriorate.

[0005] Therefore, it is urgent to propose a porous sweating cooling structure that can achieve faster gas-liquid separation. At the same time, it is also necessary to regulate the coolant distribution to effectively avoid non-uniform vaporization of the coolant and achieve efficient and reliable phase change sweating thermal protection. Summary of the Invention

[0006] The purpose of the present invention is to provide a phase change transpiration cooling porous structure and its application in an aircraft return capsule, so as to achieve rapid gas-liquid separation of the coolant in the transpiration cooling porous layer, thereby effectively improving the efficiency and reliability of phase change transpiration cooling.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] The present invention provides a phase change sweating cooling porous structure, and the porous structure includes:

[0009] A porous layer, which includes a plurality of closely arranged porous units;

[0010] A liquid distribution cavity connected to the porous layer, which is used to supply coolant to the porous layer;

[0011] A liquid storage cavity for storing coolant;

[0012] A coolant delivery pipeline connecting the liquid storage cavity and the liquid distribution cavity;

[0013] A regulating valve provided on the coolant delivery pipeline;

[0014] The porous unit includes a low porosity porous part, a high porosity porous part and a liquid channel respectively connected to the low porosity porous part. A gas channel is formed between the low porosity porous part and the high porosity porous part; the coolant enters through the liquid channel and infiltrates into the low porosity porous part, and after gasification, it escapes from the high porosity porous part along the gas channel and forms a gas film for heat insulation.

[0015] [[ID=2,2]]Further, the low porosity porous part is in a "ji" shape.

[0016] Furthermore, the liquid channel is directly connected to the low porosity porous part, and the high porosity porous part is arranged in a groove formed between adjacent low porosity porous parts.

[0017] Further, the porosity of the low porosity porous part is 0.25 - 0.35, and the porosity of the high porosity porous part is 0.65 - 0.75.

[0018] Further, the pore diameters of both the low porosity porous part and the high porosity porous part are 0.08 - 0.12 mm. [[ID=,3]]

[0019] Further, the porous layer is integrally manufactured by 3D printing microfabrication metal through selective laser sintering method to form a three-dimensional pore structure.

[0020] Further, the heat flux distribution regions on the outer surface of the porous layer are sequentially defined as a high heat flux region, a medium heat flux region and a low heat flux region.

[0021] Furthermore, the liquid distribution cavity includes a first liquid distribution cavity corresponding to the high heat flux region, a second liquid distribution cavity corresponding to the medium heat flux region and a third liquid distribution cavity corresponding to the low heat flux region, and the three liquid distribution cavities are independently arranged.

[0022] Further, the coolant delivery pipeline includes a first pipeline corresponding to the high heat flux region, a second pipeline corresponding to the medium heat flux region and a third pipeline corresponding to the low heat flux region.

[0023] Furthermore, the first pipeline, the second pipeline and the third pipeline are all provided with regulating valves.

[0024] Furthermore, the regulating valve is selected from a manual valve or an electric valve.

[0025] The present invention also provides an application of a phase-change sweat cooling porous structure in a return capsule of a spacecraft.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The porous unit structure of the present invention can achieve relatively rapid gas-liquid separation through the arrangement of liquid channels, small-porosity porous parts, and large-porosity porous parts. It can promote the rapid escape of gas after phase change while enhancing heat exchange to form an air film insulation, thereby avoiding gas blockage in the porous structure and affecting the efficiency and reliability of phase change sweating cooling.

[0028] (2) The porous unit structure of the present invention has a better heat dissipation effect than a uniform porous structure by alternating the porous parts with different porosities, and can effectively increase the escape rate of the gas after the phase change, and promote the formation of an air film on the surface of the porous layer for thermal insulation.

[0029] (3) The present invention divides the return capsule into three heat flow areas of high, medium and low according to the non-uniform distribution of heat flow on the surface, and separates the liquid separation chambers accordingly, so as to realize flow control of different liquid separation chambers, and thus distribute the coolant according to the coolant flow requirements corresponding to each heat flow area, thereby promoting uniform vaporization of the coolant in the porous layer, avoiding the deterioration of heat transfer caused by the deepening of non-uniform vaporization, and realizing efficient and reliable phase change sweating cooling thermal protection under non-uniform heat flow distribution.

[0030] (4) The phase change sweat cooling under the porous unit structure of the present invention is more reliable and has stronger cooling efficiency, and the surface temperature uniformity of the return capsule is also better. It has broad application prospects in the design of thermal protection structures related to spacecraft such as return capsules. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of the phase change sweat cooling porous structure of the present invention.

[0032] Figure 2 Schematic diagram of the structure of the porous unit in the porous layer of the present invention.

[0033] Figure 3 This is a schematic structural diagram of the phase change sweat cooling porous structure of Example 3 of the present invention.

[0034] Figure 4 This is a diagram of the numerical simulation results of Example 4 of the present invention.

[0035] Description of the marks in the figure:

[0036] 1-porous layer, 11-small porosity porous portion, 12-large porosity porous portion, 13-liquid channel;

[0037] 2-liquid separation chamber, 21-first liquid separation chamber, 22-second liquid separation chamber, 23-third liquid separation chamber;

[0038] 3-liquid storage chamber;

[0039] 4-coolant delivery pipeline, 41-first pipeline, 42-second pipeline, 43-third pipeline;

[0040] 5- regulating valve;

[0041] 6-high heat flow area;

[0042] 7-medium heat flow region;

[0043] 8- Low heat flow area. DETAILED DESCRIPTION

[0044] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0045] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0046] Example 1:

[0047] A phase change sweat cooling porous structure, such as Figure 1-2 As shown, the porous structure includes a porous layer 1, a liquid separation cavity 2, a liquid storage cavity 3, a coolant delivery pipeline 4 and a regulating valve 5.

[0048] The porous layer 1 of this embodiment includes a plurality of closely arranged porous units, each of which includes a small-porosity porous portion 11 and a large-porosity porous portion 12 and a liquid channel 13 connected to the small-porosity porous portion 11. A gas channel is formed between the small-porosity porous portion 11 and the large-porosity porous portion 12.

[0049] In this embodiment, the liquid separation chamber 2 is connected to the porous layer 1 and is used to supply coolant to the liquid channel 13 of the porous layer 1. The liquid storage chamber 3 is used to store coolant, and the ends of the coolant delivery pipe 4 are respectively connected to the liquid storage chamber 3 and the liquid separation chamber 2. The coolant delivery pipe 4 is provided with a regulating valve 5.

[0050] This embodiment achieves relatively rapid gas-liquid separation through the arrangement of liquid channel 13, small-porosity porous portion 11, and large-porosity porous portion 12. Coolant enters through liquid channel 13 and permeates into small-porosity porous portion 11. Under the influence of external heat flow, the coolant efficiently exchanges heat and vaporizes in small-porosity porous portion 11. The vaporized coolant quickly escapes from large-porosity porous portion 12, promoting the formation of an air film on the surface of porous layer 1 for thermal insulation.

[0051] Example 2:

[0052] A phase-change sweat cooling porous structure comprises a porous layer 1, a liquid separation cavity 2, a liquid storage cavity 3, a coolant delivery pipeline 4 and a regulating valve 5.

[0053] The difference from Example 1 is that the porous layer 1 of this embodiment is manufactured by 3D printing micro-machining metal integrated additive manufacturing, and a three-dimensional porous structure is formed by a selective laser sintering method. Among them, the small porosity porous portion 12 is in the shape of a "J", the liquid channel 11 is directly connected to the small porosity porous portion 12, and the large porosity porous portion 13 is arranged in a groove formed between adjacent small porosity porous portions 12. In addition, the porosity of the small porosity porous portion 12 of this embodiment is 0.3, the porosity of the large porosity porous portion 13 is 0.7, and the pore diameters of the small porosity porous portion 12 and the large porosity porous portion 13 are both 0.1 mm.

[0054] The smaller the porosity of the porous medium, the stronger its heat exchange capacity. The small-porosity porous portion 12 can effectively ensure that the porous structure as a whole has a strong heat dissipation capacity. The greater the porosity of the porous medium, the smaller its flow resistance. The large-porosity porous portion 13 can effectively increase the escape rate of the gas after the phase change, and promote the formation of an air film on the surface of the porous layer for heat insulation. The large-porosity porous portion 13 of this embodiment adopts porous gas channels rather than empty channels, which can ensure the mechanical strength of the entire structure and enhance heat dissipation. When arranging the porous unit structure with gas-liquid separation channels in the porous layer 1, the liquid channel 11 is arranged for the position with higher heat flow, so that the coolant is ejected from the liquid channel 11 and the thinner porous part at a higher flow rate, thereby achieving efficient thermal protection at the high heat flow position.

[0055] Example 3:

[0056] A phase-change sweat cooling porous structure comprises a porous layer 1, a liquid separation cavity 2, a liquid storage cavity 3, a coolant delivery pipeline 4 and a regulating valve 5.

[0057] The difference from Example 1 is that, due to the strong non-uniform heat flux distribution on the outer surface of the return capsule, the heat flux distribution areas on the outer surface of the porous layer 1 of this embodiment are sequentially defined as a high heat flux area 6, a medium heat flux area 7 and a low heat flux area 8 (e.g. Figure 3As shown). Accordingly, the liquid separation chamber 2 includes a first liquid separation chamber 21 corresponding to the high heat flow region 6, a second liquid separation chamber 22 corresponding to the medium heat flow region 7, and a third liquid separation chamber 23 corresponding to the low heat flow region 8. The three liquid separation chambers 2 are independently arranged. The coolant delivery pipeline 4 includes a first pipeline 41 corresponding to the high heat flow region 6, a second pipeline 42 corresponding to the medium heat flow region 7, and a third pipeline 43 corresponding to the low heat flow region 8. The first pipeline 41, the second pipeline 42, and the third pipeline 43 are all provided with a regulating valve 5. The regulating valve 5 of this embodiment can be selected from a manual valve or an electric valve according to actual usage.

[0058] The above setting can realize flow control of different liquid separation chambers 2, so that the coolant can be distributed according to the coolant flow requirements corresponding to each heat flow area, thereby promoting uniform vaporization of the coolant in the porous layer 1 and avoiding the deterioration of heat transfer caused by deepening non-uniform vaporization.

[0059] Example 4:

[0060] This embodiment provides a phase-change transpiring cooling porous structure and its application in a spacecraft reentry capsule. The phase-change transpiring cooling porous structure of this embodiment comprises a porous layer 1, a liquid separation chamber 2, and a coolant delivery network (including a coolant delivery pipe 4, a regulating valve 5, and a liquid storage chamber 3).

[0061] In this embodiment, the thickness of the porous layer 1 is 2 mm, and the thickness of the liquid separation chamber 2 is 0.8 mm. Because the return capsule's outer surface exhibits a highly non-uniform heat flux distribution, the individual liquid separation chambers 2 are divided based on this distribution, corresponding to high heat flux regions 6, medium heat flux regions 7, and low heat flux regions 8. Each liquid separation chamber 2 (first liquid separation chamber 21, second liquid separation chamber 22, and third liquid separation chamber 23) is supplied with liquid via a coolant pipeline network. A regulating valve 5 is installed on the coolant delivery pipeline 4 to adjust the flow distribution between the liquid separation chambers 2.

[0062] The working process and principle of the phase change sweat cooling porous structure of this embodiment are as follows:

[0063] Before officially using the phase-change sweating cooling porous structure to carry out work, a solid plate test piece of the same shape and thickness of 2mm was placed in a 7Ma high-speed wind tunnel for preliminary experiments to obtain the corresponding heat flux distribution on the return capsule surface. Based on this heat flux distribution, the high heat flux area 6, the medium heat flux area 7, and the low heat flux area 8 were identified to divide the liquid separation cavity 2, and the corresponding coolant demand for each liquid separation cavity 2 was calculated accordingly. Subsequently, the coolant flow rate of each coolant delivery pipe 4 (first pipe 41, second pipe 42, and third pipe 43) delivered to the liquid separation cavity 2 was adjusted through the regulating valve 5. After the above adjustments, the phase-change sweating cooling porous structure can be used to carry out the corresponding work. The coolant is quantitatively delivered from the liquid storage chamber 3 to each liquid separation chamber 2 through the coolant delivery pipe 4 with a regulating valve 5, and then flows from the liquid separation chamber 2 to the porous layer 1, seeping in the porous layer 1 to carry out sufficient fluid-solid heat exchange. At this time, the liquid coolant absorbs heat in the porous layer 1 and vaporizes more evenly. The gaseous coolant continuously escapes from the porous layer 1, forming a layer of air film on the surface of the porous layer 1 that wraps the surface of the return capsule, playing a heat insulating role, thereby completing the phase change sweating heat protection of the return capsule surface.

[0064] The porous unit structure with gas-liquid separation channels constituting the porous layer 1 in this embodiment can achieve more efficient phase change sweating cooling thermal protection, which can be confirmed by carrying out relevant numerical simulations. The overall size of the porous unit structure with gas-liquid separation channels in this embodiment is 2mm×2mm (e.g. Figure 1 The structure (dashed line frame) specifically includes a liquid channel 13, a small-porosity porous portion 11, and a large-porosity porous portion 12. The liquid channel 13 is 0.6 mm wide and 1.6 mm deep; the large-porosity porous portion 12 is 0.6 mm wide and 1.7 mm thick. The porosities of the small-porosity porous portion 11 and the large-porosity porous portion 12 are 0.3 and 0.7, respectively, and both have a pore diameter of 0.1 mm.

[0065] This embodiment uses pure water as the coolant, and the inlet flow rate is 1.4 kg / (m 2 ·s), the outlet pressure is 1 atm, and the heat flux density at the hot end boundary is 1 MW / m 2 , the initial temperature is 300K, and the initial pressure is 1atm. Figure 4 As shown, when the simulation calculation reaches stability, the maximum temperature of the porous unit structure of the gas-liquid separation channel reaches 373.80K, which is more than 10K lower than the maximum temperature of 384.72K of the ordinary uniform porous structure (without distinguishing between the small porosity porous part and the large porosity porous part, and the porosity is 0.3) under the same working conditions. It can be considered that the porous unit structure with a gas-liquid separation channel in the present application has stronger thermal protection capabilities.

[0066] In summary, the phase-change transpiration cooling porous structure of the present invention effectively avoids uneven vaporization of the coolant in the porous layer by supplying coolant to the liquid chamber, preventing the resulting deterioration in heat transfer. Furthermore, the porous unit structure with gas-liquid separation channels achieves more efficient thermal protection within each unit structure. Therefore, the phase-change transpiration cooling in the phase-change transpiration cooling porous structure of the present invention is more reliable and has a higher cooling efficiency, while also achieving better surface temperature uniformity in the return capsule. This has broad application prospects in the design of thermal protection structures for return capsules and other aerospace vehicles.

[0067] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A phase change sweat cooling porous structure, characterized in that: The porous structure includes: A porous layer (1) comprising a plurality of closely arranged porous units; A liquid distribution cavity (2) connected to the porous layer (1) for supplying a coolant to the porous layer (1); A liquid storage cavity (3) for storing the coolant; A coolant delivery pipe (4) connecting the liquid storage cavity (3) and the liquid distribution cavity (2); A regulating valve (5) provided on the coolant delivery pipe (4); The porous unit includes a low porosity porous part (11), a high porosity porous part (12) and a liquid channel (13) respectively connected to the low porosity porous part (11). A gas channel is formed between the low porosity porous part (11) and the high porosity porous part (12). The coolant enters through the liquid channel (13) and infiltrates into the low porosity porous part (11), vaporizes and then escapes from the high porosity porous part (12) along the gas channel to form a gas film for heat insulation; The low porosity porous part (11) is in a "ji" shape; the liquid channel (13) is directly connected to the low porosity porous part (11), and the high porosity porous part (12) is provided in a groove formed between adjacent low porosity porous parts (11).

2. The phase change sweat cooling porous structure according to claim 1, characterized in that: The porosity of the low porosity porous part (11) is 0.25 - 0.35, and the porosity of the high porosity porous part (12) is 0.65 - 0.

75.

3. The phase change sweat cooling porous structure according to claim 1, characterized in that: The pore diameters of both the low porosity porous part (11) and the high porosity porous part (12) are 0.08 - 0.12 mm.

4. The phase change sweat cooling porous structure according to claim 1, characterized in that: The porous layer (1) is integrally manufactured by 3D printing microfabrication metal through a selective laser sintering method to form a three-dimensional pore structure.

5. The phase change sweat cooling porous structure according to claim 1, characterized in that: The heat flux distribution regions on the outer surface of the porous layer (1) are sequentially defined as a high heat flux region (6), a medium heat flux region (7) and a low heat flux region (8).

6. The phase change sweat cooling porous structure according to claim 5, characterized in that: The liquid distribution cavity (2) includes a first liquid distribution cavity (21) corresponding to the high heat flux region (6), a second liquid distribution cavity (22) corresponding to the medium heat flux region (7) and a third liquid distribution cavity (23) corresponding to the low heat flux region (8). The three liquid distribution cavities (2) are independently provided.

7. The phase change sweat cooling porous structure according to claim 5, characterized in that: The coolant delivery pipe (4) includes a first pipe (41) corresponding to the high heat flux region (6), a second pipe (42) corresponding to the medium heat flux region (7) and a third pipe (43) corresponding to the low heat flux region (8); Regulating valves (5) are provided on all of the first pipe (41), the second pipe (42) and the third pipe (43).

8. The phase change sweat cooling porous structure according to claim 1, characterized in that: The regulating valve (5) is selected from a manual valve or an electric valve.

9. Application of the phase change sweating cooling porous structure according to any one of claims 1 - 8 in the return capsule of a spacecraft.

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