Phase change sweating cooling porous structure and application of phase change sweating cooling porous structure in aircraft return capsule

Abstract

The invention relates to a phase change sweating cooling porous structure and application thereof in an aircraft reentry capsule, the porous structure comprises a porous layer comprising a plurality of densely arranged porous units; the liquid separation cavity is connected with the porous layer; the liquid storage cavity is used for storing a cooling agent; the coolant conveying pipeline is connected with the liquid storage cavity and the liquid separation cavity; the regulating valve is arranged on the coolant conveying pipeline; each porous unit comprises a small-porosity porous part as well as a large-porosity porous part and a liquid channel which are respectively connected with the small-porosity porous part, and a gas channel is formed between the small-porosity porous part and the large-porosity porous part; and a coolant is introduced from the liquid channel, permeates into the small-porosity porous part, escapes from the large-porosity porous part along the gas channel after being gasified, and forms a gas film for heat insulation. Compared with the prior art, rapid gas-liquid separation and partitioned flow regulation and control of the coolant in the sweating cooling porous layer can be effectively achieved, and the phase change sweating cooling efficiency and reliability are effectively improved.

Description

Technical Field

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

[0002] Spacecraft face severe aerodynamic heating during flight, so efficient thermal protection must be implemented for key hot components. Take the spacecraft reentry capsule as an example. When entering the Earth's atmosphere, the friction with the atmosphere will cause its surface temperature to rise sharply. In order to maintain the normal operating temperature inside the reentry capsule and ensure the safety of equipment and personnel, the development of an efficient and stable thermal protection system is the core of solving this key problem. At the same time, the weight of the thermal protection structure accounts for 3%-50% of the total weight of the reentry capsule, and its structural efficiency is an important measure of the overall performance of the spacecraft.

[0003] Phase change sweating cooling uses the powerful convective heat transfer capacity of liquid coolant to exchange heat with porous skeletons to remove heat, and uses the rapid escape of gas coolant after phase change to form a gas film on the solid surface to block heat transfer. At the same time, the latent heat of coolant phase change can bring huge heat sink, thus achieving efficient thermal protection with low coolant consumption, which is considered to be one of the important development directions of efficient and lightweight thermal protection technology.

[0004] However, during the phase change sweating 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 limits the effective transport of the coolant on the one hand, and prevents the gas from being quickly discharged to form an air film on the other hand, which significantly reduces the efficiency and reliability of phase change sweating cooling. At the same time, when the spacecraft's return capsule enters the Earth's atmosphere, its surface exhibits a strong 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 deterioration.

[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 sweat cooling porous structure and its application in the aircraft return capsule, so as to achieve rapid gas-liquid separation of the coolant in the sweat cooling porous layer, so as to effectively improve the efficiency and reliability of the phase change sweat 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, the porous structure comprising:

[0009] a porous layer comprising a plurality of closely arranged porous units;

[0010] A liquid separation chamber connected to the porous layer, used to provide a coolant to the porous layer;

[0011] a liquid storage chamber for storing a coolant;

[0012] A coolant delivery pipeline connecting the liquid storage chamber and the liquid separation chamber;

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

[0014] The porous unit includes a small porosity porous part and a large porosity porous part and a liquid channel respectively connected to the small porosity porous part, and a gas channel is formed between the small porosity porous part and the large porosity porous part; the coolant enters and penetrates into the small porosity porous part through the liquid channel, and after being vaporized, it escapes from the large porosity porous part along the gas channel and forms an air film insulation.

[0015] Furthermore, the small-porosity porous portion is in a "J" shape.

[0016] Furthermore, the liquid channel is directly connected to the small-porosity porous portion, and the large-porosity porous portion is arranged in a groove formed between adjacent small-porosity porous portions.

[0017] Furthermore, the porosity of the small-porosity porous part is 0.25-0.35, and the porosity of the large-porosity porous part is 0.65-0.75.

[0018] Furthermore, the pore diameters of the small-porosity porous portion and the large-porosity porous portion are both 0.08-0.12 mm.

[0019] Furthermore, the porous layer is manufactured by 3D printing micro-machining metal integrated additive manufacturing, and a three-dimensional pore structure is formed by a selective laser sintering method.

[0020] Furthermore, the heat flux distribution areas on the outer surface of the porous layer are defined as a high heat flux area, a medium heat flux area and a low heat flux area in sequence.

[0021] Furthermore, the liquid separation chamber includes a first liquid separation chamber corresponding to a high heat flow area, a second liquid separation chamber corresponding to a medium heat flow area, and a third liquid separation chamber corresponding to a low heat flow area, and the three liquid separation chambers are independently arranged.

[0022] Furthermore, the coolant delivery pipeline includes a first pipeline corresponding to a high heat flow area, a second pipeline corresponding to a medium heat flow area, and a third pipeline corresponding to a low heat flow area.

[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 fast 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 to form air film insulation while enhancing heat exchange, 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 alternately arranging porous parts with different porosities, and can effectively increase the escape rate of gas after 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 non-uniform distribution of heat flux on the surface of the return capsule into three heat flux areas of high, medium and low, and divides the liquid separation chambers accordingly, so as to realize flow control of different liquid separation chambers, thereby allocating coolant according to the coolant flow requirements corresponding to each heat flux area, thereby promoting uniform vaporization of the coolant in the porous layer, avoiding the deterioration of heat transfer caused by deepening of non-uniform vaporization, and realizing efficient and reliable phase change sweating cooling thermal protection under non-uniform heat flux 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 It is a schematic structural diagram of the phase change sweat cooling porous structure of the present invention.

[0032] Figure 2 It is a 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 markings in the figure:

[0036] 1-porous layer, 11-small porosity porous part, 12-large porosity porous part, 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- Area of ​​low heat flow. DETAILED DESCRIPTION

[0044] The present invention is described in detail below in conjunction with 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] Embodiment 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 chamber 2, a liquid storage chamber 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 respectively 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] The liquid separation chamber 2 of this embodiment is connected to the porous layer 1 and is used to provide coolant to the liquid channel 13 of the porous layer 1. The liquid storage chamber 3 is used to store coolant, and the two ends of the coolant delivery pipeline 4 are respectively connected to the liquid storage chamber 3 and the liquid separation chamber 2. The coolant delivery pipeline 4 is provided with a regulating valve 5.

[0050] This embodiment can achieve relatively fast gas-liquid separation through the arrangement of the liquid channel 13, the small porosity porous part 11, and the large porosity porous part 12. The coolant is introduced through the liquid channel 13 and penetrates into the small porosity porous part 11. Under the action of the external heat flow, the coolant efficiently exchanges heat and vaporizes in the small porosity porous part 11. The vaporized coolant quickly escapes from the large porosity porous part 12, promoting the formation of an air film on the surface of the porous layer 1 for heat insulation.

[0051] Embodiment 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-processing 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 larger 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 thermal insulation. The large porosity porous portion 13 of this embodiment adopts porous gas channels instead of 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] Embodiment 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 defined as high heat flux area 6, medium heat flux area 7 and low heat flux area 8 (such as Figure 3As shown). Accordingly, the liquid separation chamber 2 includes a first liquid separation chamber 21 corresponding to the high heat flow area 6, a second liquid separation chamber 22 corresponding to the medium heat flow area 7, and a third liquid separation chamber 23 corresponding to the low heat flow area 8, and 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 area 6, a second pipeline 42 corresponding to the medium heat flow area 7, and a third pipeline 43 corresponding to the low heat flow area 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 use.

[0058] The above arrangement 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] Embodiment 4:

[0060] The present embodiment provides a phase change sweat cooling porous structure and its application in a spacecraft return capsule. The phase change sweat cooling porous structure of the present embodiment comprises a porous layer 1, a liquid separation cavity 2 and a coolant delivery network (including a coolant delivery pipeline 4, a regulating valve 5 and a liquid storage cavity 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. Since the outer surface of the return capsule presents a strong non-uniform heat flux distribution, the division of each liquid separation chamber 2 is determined according to the heat flux distribution of the outer surface of the return capsule, corresponding to the high heat flux area 6, the medium heat flux area 7 and the low heat flux area 8 respectively. Liquid is supplied to each liquid separation chamber 2 (the first liquid separation chamber 21, the second liquid separation chamber 22, and the third liquid separation chamber 23) through the coolant pipeline network, and a regulating valve 5 is installed on the coolant delivery pipeline 4 to adjust the flow distribution of each liquid separation chamber 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 the same 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. According to 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 demand for coolant corresponding to each liquid separation cavity 2 was calculated accordingly, and then the coolant flow rate of each coolant delivery pipeline 4 (first pipeline 41, second pipeline 42 and third pipeline 43) delivered to the liquid separation cavity 2 was adjusted through the regulating valve 5. After the above adjustment, the phase-change sweating cooling porous structure can be used to carry out the corresponding work. The coolant is quantitatively transported 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, and seeps 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, and 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 on the surface of the return capsule.

[0064] In this embodiment, the porous unit structure with gas-liquid separation channels constituting the porous layer 1 can achieve more efficient phase change sweating cooling thermal protection, which can be confirmed by carrying out relevant numerical simulation. The overall size of the porous unit structure with gas-liquid separation channels in this embodiment is 2mm×2mm (such as Figure 1 The liquid channel 13 is a porous part with a small porosity and a porous part with a large porosity, and the ...

[0065] In this embodiment, pure water is used as the coolant, and the inlet flow rate is 1.4 kg / (m 2 ·s), the outlet pressure is 1atm, and the heat flux density at the hot end boundary is 1MW / 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 an ordinary uniform porous structure (without distinguishing between a small porosity porous part and a 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 a stronger thermal protection capability.

[0066] In summary, the phase change sweating cooling porous structure of the present invention, on the one hand, effectively avoids the non-uniform gasification of the coolant in the porous layer by supplying the coolant in the liquid chamber, thereby preventing the deterioration of heat transfer that may be caused by this; on the other hand, through the design of the porous unit structure with a gas-liquid separation channel, a more efficient thermal protection efficiency is achieved on each unit structure. Therefore, the phase change sweating cooling under the phase change sweating cooling porous structure of the present invention is more reliable and has a stronger cooling efficiency, and the surface temperature uniformity of the return capsule is also better, which has broad application prospects in the design of thermal protection structures related to return capsules and other aerospace vehicles.

[0067] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 coolant to the porous layer (1); a liquid storage cavity (3) for storing 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), and after gasification, escapes from the high-porosity porous part (12) along the gas channel to form a gas film for heat insulation.

2. A phase change sweat cooling porous structure according to claim 1, characterized in that: The low-porosity porous part (12) is in a "ji" shape; The liquid channel (11) is directly connected to the low-porosity porous part (12), and the high-porosity porous part (13) is arranged in a groove formed between adjacent low-porosity porous parts (12).

3. The phase change sweat cooling porous structure according to claim 1, characterized in that: The porosity of the low-porosity porous part (12) is 0.25 - 0.35, and the porosity of the high-porosity porous part (13) is 0.65 - 0.

75.

4. The phase change sweat cooling porous structure according to claim 1, characterized in that: The pore diameters of the low-porosity porous part (12) and the high-porosity porous part (13) are both 0.08 - 0.12 mm.

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

6. 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).

7. The phase change sweat cooling porous structure according to claim 6, 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 arranged.

8. The phase change sweat cooling porous structure according to claim 6, 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 the first pipe (41), the second pipe (42) and the third pipe (43).

9. 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.

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

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