Micro-channel device for phase change sweating and application method

Abstract

The invention discloses a micro-channel device for phase change sweating and an application method, and belongs to the technical field of thermal protection of aircrafts. The structure sequentially comprises a solid inner wall, a transportation phase change layer and a sweating outer wall surface from inside to outside, and is mainly composed of a bottom plate, a porous rib wall, a solid rib wall, a solid outer wall, an inlet flow channel, a main flow channel, a branch flow channel and the like. The bottom plate is a solid inner wall and is used for supporting and conveying; the flow channel can be divided into an inlet flow channel, a main flow channel and a branch flow channel, and a cooling medium sequentially passes through the inlet flow channel, the main flow channel and the branch flow channel; a cooling medium is injected into an external flow field through the porous rib walls which are periodically arranged; the solid rib walls isolate the adjacent main runners, so that a cooling medium flows out through the porous rib walls; the outer surfaces of the porous rib walls of the solid outer wall are flush to form a sweating outer wall surface; the device has the advantages of being integrated in structure, small in thickness, uniform in sweating and efficient, and a new way can be provided for long-time cross-domain sailing thermal protection of high-speed aircrafts.

Description

Technical Field

[0001] The present invention relates to the technical field of high-speed aircraft thermal protection, and in particular to a microchannel device for phase change sweating and an application method thereof. Background Art

[0002] When an aircraft flies for a long time at a high Mach number in a dense atmosphere, the temperature of the aircraft's outer surface can reach nearly 3000 degrees Celsius due to aerodynamic heating. In order to ensure that the aircraft fuselage and its internal environment work normally within the allowable temperature range, effective structural thermal protection design is required. Transpiration cooling has the advantages of reducing surface aerodynamic drag, reducing surface infrared target characteristics, and resisting oxidation and ablation. It has now become a key technology for active thermal protection of various high-speed aircraft in aerospace.

[0003] Aircraft design usually pursues extreme lightness to achieve the goal of higher, faster and farther. When applying sweating cooling technology to large areas of aircraft, it will face serious limitations in thickness and weight. Therefore, the thickness of large-area sweating structures should be reduced as much as possible. Thermal protection of large areas requires uniform sweating and uniform internal cooling, which places high demands on the uniform distribution of cooling media within the structure. At the same time, the reliability and completeness of thin-walled thermal protection structures must meet the requirements of engineering applications.

[0004] Patent CN117324638A discloses a laminated thin plate sweating cooling structure, which realizes sweating cooling by transporting to the porous surface layer through a solid substrate with a four-level liquid collection cavity transport channel. This scheme realizes the uniform distribution of cooling medium under the conditions of limited thickness and area size. However, this structure has some problems. First, in this dendritic multi-level distribution flow channel structure, the blockage of the upper flow channel will cause insufficient supply or even drying of the cooling medium in the lower flow channel, resulting in the inability to achieve sweating cooling in the corresponding local area of ​​the surface. Secondly, the liquid cooling medium has flow instability caused by phase change during transportation, and the dryness increases along the way, resulting in the phenomenon that the local flow channel is blocked by bubbles and difficult to wet. Therefore, the problem of uneven distribution of cooling medium will occur in the liquid collection cavity at each level. Finally, the expansion of the extensional area of ​​the structure is limited, that is, under the given thickness limit, the extensional area is difficult to expand further. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, in view of the requirements for thermal protection performance of high-speed aircraft and the size constraints of thin-walled thermal protection structures, the purpose of the present invention is to provide a microchannel device for phase change sweating and an application method. While meeting the thickness size constraints, this device can achieve uniform transportation of cooling medium, reduce the risk of local surface difficulty in sweating caused by local flow channel blockage or insufficient medium transportation capacity, achieve a more uniform sweating cooling effect, and have a better ability to expand the size of the extension area.

[0006] The technical scheme for achieving the purpose of the present invention is as follows: A microchannel device for phase change sweating, with three layers of interlocking structures on the top and bottom, which are a bottom plate, a rib wall, and a solid outer wall in sequence; and periodically arranged multi-link structures on the left and right; the multi-link structure is expandable; The rib walls include porous rib walls and solid rib walls; the porous rib walls and the solid rib walls are arranged in parallel and spaced apart, and the solid rib walls are located on one side or the other side of one of the multiple-linked structures, and are arranged in a staggered manner to play a barrier role; The solid outer wall is a rib plate distributed at intervals in the vertical and horizontal directions, the transverse rib plates are staggered, and the gaps between the rib plates are filled with porous rib walls; The bottom plate, the porous rib wall, the solid rib wall, and the transverse ribs of the solid outer wall together form a branch channel; The bottom plate, the end surface of the solid rib wall, the end surface of the porous rib wall, and the longitudinal ribs of the solid outer wall together constitute the main flow channel; the main flow channel and the branch flow channel are located in the same plane and are perpendicular to each other; The main channel and branch channel are used to transport cooling medium; the thermal protection structure is cooled through convection heat transfer and medium phase change; The bottom plate is provided with a cooling medium inlet, an inlet flow channel, and a main flow channel inlet; The outer surfaces of the porous rib wall and the solid outer wall are flush with each other to form a sweating outer wall surface.

[0007] The inner side of the bottom plate is provided with a cooling medium inlet connected to the liquid supply pipeline, and the parallel distributed internal inlet flow channels distribute the liquid cooling medium input from the cooling medium inlet to each main flow channel through each main flow channel inlet.

[0008] The cooling medium enters the microchannel device from the cooling medium inlet of the bottom plate and finally flows out of the porous rib wall, undergoing a series of transition states from liquid to two-phase mixed state and finally becoming gaseous. The cooling medium is mainly in liquid state when transported in the inlet channel of the bottom plate, and then undergoes phase change when entering the main channel and branch channel of the transport phase change layer, and realizes cooling of the structure through convection heat transfer and phase change heat absorption; The cooling medium in the branch channel can only flow out through the porous rib walls on both sides, and further changes into gas during the flow of the porous structure, enters the external flow field, and forms a continuous gas film near the wall.

[0009] The overall structure of the device is formed by laser selective melting additive manufacturing technology, in which the porosity and pore size of the porous rib wall are regulated by the additive manufacturing process.

[0010] The device is expanded in size according to the wall thermal protection requirements and the characteristics of the aircraft wall structure, that is, the flow channel structures at all levels are distributed in a periodic structure, and the area size is changed by changing the number of periods.

[0011] The microchannel device for phase change sweating adjusts the thermal protection performance of the structure by designing the dimensions of each flow channel and structure and adjusting the flow rate of the cooling medium.

[0012] In the microchannel device for phase change sweating, the cross-sectional areas of the branch channel, the main channel, and the inlet channel should increase in sequence.

[0013] The application method of the microchannel device for phase change sweating, The liquid cooling medium enters the microchannel structure from the cooling medium inlet on the bottom plate, is transported through the stepped flow channel network of the inlet flow channel, the main flow channel, and the branch flow channel, and is evenly distributed in the transport phase change layer. The structural cooling is achieved through convective heat transfer and phase change. Finally, the gaseous working medium diverges from the porous rib wall into the external flow field to form an air film, change the near-wall flow field structure, and reduce the input aerodynamic heat. Each main channel is connected to the inlet channel on one side only through the main channel inlet, and the distribution is staggered, that is, the cooling medium of adjacent main channels comes from different inlet channels, which makes the cooling medium flow direction in every two adjacent main channels opposite; the cooling medium in every two adjacent branch channels comes from the adjacent main channel, that is, the cooling medium on both sides of each porous rib wall comes from the adjacent main channel, and the flow direction in the branch channels on both sides is also opposite; each main channel supplies cooling medium to the branch channels on both sides, and the inlets of the corresponding branch channels on both sides are staggered; the medium of the staggered and discretely distributed sweating areas on the sweating outer wall surface comes from each porous rib wall; the non-sweating solid outer wall structure is cooled by air film insulation, structural heat conduction, and heat transfer in the internal flow channel; Beneficial effects of the present invention: The medium transport channel network of this structure can be divided into three levels: inlet channel, main channel and branch channel. In space, each level of channel is staggered, for example, the inlet channels are staggered in parallel, and each has an independent cooling medium inlet. In the intermediate transport phase change layer, the main channels connected to different inlet channels are staggered, and the branch channels connected to different main channels are also staggered. This allows the adjacent channels to still provide cooling medium when there is local blockage or damage somewhere in a certain level of channel. For example, if a branch channel is blocked, the adjacent branch channels on both sides can still provide cooling medium for the porous rib walls on both sides of the blocked branch channel because their cooling medium comes from another channel network. If a main channel is blocked, the porous rib walls in the multi-connected structure on both sides can still avoid drying up through the adjacent main channel supply. If an inlet channel is blocked, the adjacent inlet channel can still provide cooling medium to the porous rib walls in the transport phase change layer. This staggered arrangement of multi-level channels can not only achieve relatively uniform thermal protection performance, but also improve the safety and reliability of operation.

[0014] The present invention has the characteristics of integrated structure, thin thickness, uniform and efficient sweating, and can provide a new approach for thermal protection of high-speed aircraft during long-term cross-domain navigation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the microchannel structure used for phase change sweating of the present invention, and the arrow indicates the sweating direction.

[0016] Figure 2 It is a schematic diagram of the microchannel structure bottom plate 1 and part of the flow channel, and the arrow indicates the flow direction of the cooling medium.

[0017] Figure 3 It is a top view of the bottom plate structure of the microchannel structure, and the arrow indicates the flow direction of the cooling medium.

[0018] Figure 4 It is a bottom view of the bottom plate structure of the microchannel structure, and the arrow indicates the flow direction of the cooling medium.

[0019] Figure 5 It is a schematic diagram of the phase change sweating layer structure, and the arrows indicate the cooling medium flow direction and sweating direction.

[0020] Figure 6 Schematic diagram of cooling medium transport in the phase change sweating layer, and the arrow indicates the flow direction of the cooling medium.

[0021] Figure 7 Schematic diagram of the area expansion of the microchannel structure for phase change sweating.

[0022] In the figure, there is a bottom plate 1, a cooling medium inlet 1.1, a main channel inlet 1.2, a porous rib wall 2, a solid rib wall 3, a solid outer wall 4, an inlet channel 5, a main channel 6, and a branch channel 7. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below in conjunction with the specific implementation methods and the drawings of the specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection claimed by the present invention.

[0024] A microchannel structure for phase change sweating, such as Figure 1As shown, from the inside to the outside, they are the solid inner wall, the transport phase change layer, and the sweating outer wall. The bottom plate 1 is a solid inner wall, which plays a structural support role, and the inlet flow channel 5 inside it can transport the cooling medium. The porous rib wall 2 and the solid rib wall 3 are connected on the bottom plate 1 to form a transport phase change layer. The cooling medium is distributed to the main channel 6 and the branch channel 7 formed by the structural connection through the inlet flow channel 5 for transportation, and the cooling of the thermal protection structure is achieved through convective heat transfer and medium phase change. The porous rib wall 2 and the solid outer wall 4 are connected, and the outer surface is kept flush to form a sweating outer wall with a staggered discrete distribution of sweating areas. The cooling medium in a gas-liquid mixed state enters the porous structure of the porous rib wall 2 through the branch channels 7 on both sides of the porous rib wall 2 to further fully phase change and absorb heat. As shown by the arrows in the figure, it becomes gaseous and then dissipates into the external flow field to form an air film.

[0025] like Figure 2 The figure shows an axonometric cross-sectional view of the structure of the base plate 1. Figure 3 and Figure 4 They are respectively a top view and a bottom view of the base plate 1, and a cooling medium inlet 1.1 is arranged on the bottom surface thereof, which can be connected to the liquid supply pipeline of the cooling system through different interface connection forms. Parallel inlet channels 5 are arranged in the structure, and each inlet channel 5 has a corresponding cooling medium inlet 1.1. The cooling medium flows in the inlet channel 5, and is distributed into the main channel 6 of the upper layer through the main channel inlets 1.2 arranged at intervals, so that the cooling medium flows in opposite directions between adjacent main channels 6, i.e., reverse channels. The main channel 6 can be partially embedded in the base plate 1, so as to increase the channel cross-sectional area within a limited width and enhance the medium transport capacity. The inlet channel 5 is a plurality of main channels for transporting cooling medium, and its cross-sectional area is larger than the cross-sectional area of ​​the main channel 6 to a certain extent.

[0026] like Figure 5 and Figure 6The figures are respectively the axonometric view and the top view of the intermediate transport phase change layer structure after the bottom plate 1 and the solid outer wall 4 are removed. Each main channel 6 transports the cooling medium to the branch channels 7 connected to it on both sides. The branch channels on the same side are arranged at intervals, and the branch channels 7 connected to the adjacent main channels 6 are in the middle. The opposite branch channels of the main channel 6 are arranged in a staggered manner to avoid the channel openings facing each other, and reduce the mutual influence of the unstable characteristics of the flow phase change process in the opposite branch channels 7, such as pressure fluctuations and flow fluctuations. The flow directions of the branch channels 7 on both sides of the porous rib wall 2 are opposite, and the cooling medium comes from the adjacent counter-flowing main channel 6. The cooling medium mixed with gas and liquid on both sides can enter the porous rib wall 2 structure for further phase change, and then diverge into the external high-speed flow field. This countercurrent setting of the multi-stage flow channel makes the temperature of the main channel axially along the structure more uniform, and the flow of the cooling medium transported to each porous rib wall 2 along the way is complementary through the branch channels 7 on both sides, which is more uniform. At the same time, the axial distribution of the cooling medium input flow of a single porous rib wall 2 structure is also relatively uniform. To a certain extent, the uniform distribution and transportation of cooling medium in the plane structure is achieved, and uniform cooling medium is provided for each porous rib wall 2 structure, and the medium flow rate of the air film formed in each sweating area of ​​the outer wall is relatively uniform. Therefore, the thermal protection effect in the plane of this compact and interwoven multi-stage countercurrent flow channel structure is uniform. At the same time, structural heat conduction can, to a certain extent, weaken the local temperature fluctuation caused by the instability of the two-phase flow caused by phase change.

[0027] like Figure 7 The figure shows the area expansion schematic diagram of the phase change sweating microchannel structure. The thin-walled microfluidic structure can be expanded in size according to the wall thermal protection requirements and the characteristics of the aircraft wall structure, that is, the multi-link structure is periodically distributed, and the area size can be changed by changing the number of periods. The figure shows that it can be expanded in both the horizontal and vertical directions, and the number of multi-link structures after actual expansion does not need to be a multiple of three. The structure can be assembled as modular components, which is convenient for universal design and batch assembly according to the actual shape and area, and finally spliced ​​and combined into a large-area sweating cooling structure, which has strong practical value.

[0028] The overall structure can be formed by laser selective melting additive manufacturing technology, and the size of each structure can be adjusted according to different thermal protection requirements and actual performance, such as flow channel size, wall thickness of porous rib wall 2, etc. The porosity and pore size of porous rib wall 2 can be adjusted by additive manufacturing process to meet different thermal protection requirements. The capillary transport capacity of the porous rib wall 2 structure can be improved through design and manufacturing, and the medium transport performance in the structure can be further improved.

[0029] The cooling medium of each porous rib wall 2 structure comes from the flow channel network to which different main channels 6 belong, which reduces to a certain extent the risk of structural damage caused by local heat transfer deterioration due to local flow channel blockage, increased flow resistance or local dry liquid. If a branch flow channel 7 is blocked, the adjacent branch flow channel 7 can still provide cooling medium. If a main flow channel 6 is blocked, the flow channel network where the adjacent main flow channel 6 is located can still provide cooling medium. If the pipeline where a certain inlet flow channel 5 is located is damaged and cannot provide enough cooling medium, the adjacent inlet flow channel 5 can increase the flow rate to continuously provide cooling medium for all porous rib walls 2. This flow channel network structure design can not only achieve relatively uniform thermal protection performance, but also improve the safety and reliability of operation.

[0030] In actual engineering applications, the thermal protection performance can be regulated by adjusting the cooling medium flow rate of different inlet flow channels 5 .

[0031] The technical features of the above-described embodiments can be further combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A microchannel device for phase change sweating, characterized in that: The top and bottom are three-layer interlocking structures, which are the bottom plate (1), the rib wall, and the solid outer wall (4) in sequence; the left and right are periodically arranged multi-linked structures; the multi-linked structure is expandable; The rib wall comprises a porous rib wall (2) and a solid rib wall (3); the porous rib wall (2) and the solid rib wall (3) are arranged in parallel and spaced apart, and the solid rib wall (3) is located on one side or the other side of one of the multiple-linked structures, and is arranged in a staggered manner to play a barrier role; The solid outer wall (4) is a rib plate distributed at intervals in the vertical and horizontal directions, the transverse rib plates are distributed in a staggered manner, and the gaps between the rib plates are filled with porous rib walls (2); The bottom plate (1), the porous rib wall (2), the solid rib wall (3), and the transverse ribs of the solid outer wall (4) together form a branch channel (7); The bottom plate (1), the end surface of the solid rib wall (3), the end surface of the porous rib wall (2), and the longitudinal ribs of the solid outer wall (4) together form a main flow channel (6); the main flow channel (6) and the branch flow channel (7) are located in the same plane and are perpendicular to each other; The main flow channel (6) and the branch flow channel (7) are used to transport the cooling medium; the cooling of the thermal protection structure is achieved through convection heat transfer and medium phase change; The bottom plate (1) is provided with a cooling medium inlet (1.1), an inlet flow channel (5), and a main flow channel inlet (1.2); The outer surfaces of the porous rib wall (2) and the solid outer wall (4) are flush with each other, forming a sweat-generating outer wall surface.

2. The microchannel device for phase change sweating according to claim 1, characterized in that: The inner side of the bottom plate (1) is provided with a cooling medium inlet (1.1) connected to a liquid supply pipeline, and the parallel distributed internal inlet flow channels (5) distribute the liquid cooling medium input from the cooling medium inlet (1.1) to each main flow channel (6) through each main flow channel inlet (1.2).

3. The microchannel device for phase change sweating according to claim 1, characterized in that: The cooling medium undergoes a series of transition states from a liquid state to a two-phase mixed state and finally becomes a gaseous state during the process of entering the microchannel device from the cooling medium inlet (1.1) of the bottom plate (1) to finally flowing out of the porous rib wall (2); The cooling medium is mainly in liquid state when transported in the inlet flow channel (5) in the bottom plate (1), and then undergoes phase change when entering the main flow channel (6) and the branch flow channel (7) of the transport phase change layer, thereby cooling the structure through convection heat transfer and phase change heat absorption; The cooling medium in the branch flow channel (7) can only flow out through the porous rib walls (2) on both sides, and further changes into a gaseous state during the flow of the porous structure, enters the external flow field, and forms a continuous gas film near the wall surface.

4. The microchannel device for phase change sweating according to claim 1, characterized in that: The overall structure of the device is formed by laser selective melting additive manufacturing technology, wherein the porosity and pore size of the porous rib wall (2) are regulated by the additive manufacturing process.

5. The microchannel device for phase change perspiration according to claim 1, characterized in that: The device is expanded in size according to the wall thermal protection requirements and the characteristics of the aircraft wall structure, that is, the flow channel structures at all levels are distributed in a periodic structure, and the area size is changed by changing the number of periods.

6. The microchannel device for phase change sweating according to claim 1, characterized in that: The thermal protection performance of the structure can be adjusted by designing the flow channels and structural dimensions and adjusting the flow rate of the cooling medium.

7. The microchannel device for phase change perspiration according to claim 1, characterized in that: The cross-sectional areas of the branch channel (7), the main channel (6), and the inlet channel (5) should increase in sequence.

8. The application method of the microchannel device for phase change sweating according to claim 1, characterized in that: The liquid cooling medium enters the microchannel structure from the cooling medium inlet (1.1) on the bottom plate (1), is transported through the stepped flow channel network of the inlet flow channel (5), the main flow channel (6), and the branch flow channel (7), is evenly distributed in the transport phase change layer, and achieves structural cooling through convective heat transfer and phase change. Finally, the gaseous working medium diverges from the porous rib wall (2) into the external flow field, forms an air film, changes the near-wall flow field structure, and reduces the input aerodynamic heat. Each main flow channel (6) is connected to the inlet flow channel (5) on one side only through the main flow channel inlet (1.2), and the cooling media are staggered, that is, the cooling media of adjacent main flow channels (6) are derived from different inlet flow channels (5), so that the cooling media in every two adjacent main flow channels (6) flow in opposite directions; The cooling medium in each of two adjacent branch flow channels (7) originates from the adjacent main flow channel (6), that is, the cooling medium on both sides of each porous rib wall (2) originates from the adjacent main flow channel (6), and the flow directions in the branch flow channels (7) on both sides are also opposite; Each main flow channel (6) supplies cooling medium to the branch flow channels (7) on both sides thereof, and the inlets of the branch flow channels (7) on both sides are staggered; The medium of the sweating zones staggered and discretely distributed on the sweating outer wall is sourced from each porous rib wall (2); The non-sweating solid outer wall (4) structure achieves cooling through air film insulation, structural heat conduction, and heat transfer in the internal flow channel.

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