A microchannel device for phase change sweating and its application method

Abstract

The present invention discloses a microchannel device for phase change sweating and an application method, which belongs to the field of aircraft thermal protection technology. The structure is composed of a solid inner wall, a transport phase change layer, and a sweating outer wall from the inside to the 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, which plays a supporting and transporting role; the flow channel can be divided into an inlet flow channel, a main flow channel and a branch flow channel, and the cooling medium passes through the inlet flow channel, the main flow channel and the branch flow channel in turn; the cooling medium is injected into the external flow field through the periodically arranged porous rib walls; the solid rib walls isolate adjacent main flow channels, so that the cooling medium flows out through the porous rib walls; the outer surface of the porous rib wall of the solid outer wall is flush, forming a sweating outer wall; the present invention has the characteristics of structural integration, thin thickness, uniform sweating and high efficiency, and can provide a new way for long-term cross-domain navigation thermal protection of high-speed aircraft.

Description

Technical Field

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

[0002] When an aircraft flies for extended periods at high Mach numbers in a dense atmosphere, its outer surface temperature can reach nearly 3000°C due to aerodynamic heating. To ensure the aircraft's fuselage and internal environment remain within the permitted temperature range, effective structural thermal protection design is essential. Transpiration cooling, with its advantages of reducing surface aerodynamic drag, lowering surface infrared target characteristics, and combating oxidation and ablation, has become a key technology for active thermal protection in various high-speed aerospace vehicles.

[0003] Aircraft design typically pursues extreme lightweighting to achieve higher, faster, and farther goals. Applying transpiration cooling technology to large areas of an aircraft presents significant limitations in thickness and weight. Therefore, the thickness of large-area transpiration structures should be minimized. Thermal protection over large areas requires uniform transpiration and internal cooling, placing high demands on uniform distribution of the cooling medium within the structure. Furthermore, the reliability and integrity of thin-walled thermal protection structures must meet the requirements of engineering applications.

[0004] Patent CN117324638A discloses a laminated thin-plate transpiration cooling structure, which realizes transpiration cooling by transporting the cooling medium to the porous surface layer through a solid substrate having a four-level liquid collection cavity transport channel. This solution realizes the uniform distribution of the cooling medium under the conditions of limited thickness and area size. However, this structure has some problems. First, in this tree-like multi-level distributed flow channel structure, the blockage of the upper flow channel will cause insufficient supply of cooling medium in the lower flow channel or even dryness, resulting in the inability to achieve transpiration 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 process, 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 spanwise area of ​​the structure is limited, that is, under the given thickness limit, the spanwise area is difficult to expand further. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies and address the thermal protection performance requirements of high-speed aircraft and the dimensional constraints of thin-walled thermal protection structures, the present invention provides a microchannel device for phase change transpiration and its application method. While meeting thickness dimensional constraints, this device achieves uniform transport of the cooling medium, reducing the risk of localized surface transpiration difficulties caused by localized flow channel blockage or insufficient medium transport capacity, achieving a more uniform transpiration cooling effect while also offering good scalability across the entire surface area.

[0006] The technical solution for achieving the purpose of the present invention is as follows:

[0007] A microchannel device for phase change sweating, comprising a three-layer interlocking structure, which comprises a bottom plate, a rib wall, and a solid outer wall in that order; and a periodically arranged multi-link structure on the left and right; the multi-link structure is expandable;

[0008] 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 staggered to play a barrier role;

[0009] 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;

[0010] The bottom plate, porous rib wall, solid rib wall, and transverse ribs of the solid outer wall together form a branch channel;

[0011] 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 channel; the main channel and the branch channel are located in the same plane and are perpendicular to each other;

[0012] The main channel and branch channel are used to transport the cooling medium; the thermal protection structure is cooled through convection heat transfer and medium phase change;

[0013] The bottom plate is provided with a cooling medium inlet, an inlet flow channel, and a main flow channel inlet;

[0014] 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.

[0015] The inner side of the bottom plate is provided with a cooling medium inlet, which is connected to the liquid supply pipeline. The parallel internal inlet flow channels distribute the liquid cooling medium input from the cooling medium inlet to each main channel through each main channel inlet.

[0016] 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.

[0017] The cooling medium is mainly in liquid state when transported in the inlet channel of the base plate, and then undergoes phase change when entering the main channel and branch channel of the transport phase change layer, cooling the structure through convection heat transfer and phase change heat absorption;

[0018] The cooling medium in the branch channel can only flow out through the porous rib walls on both sides. During the flow of the porous structure, it further changes into a gaseous state and enters the external flow field, forming a continuous gas film near the wall.

[0019] 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 controlled by the additive manufacturing process.

[0020] The device is expanded in size according to the wall thermal protection requirements and the structural characteristics of the aircraft wall. 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.

[0021] The microchannel device for phase change sweating adjusts the thermal protection performance of the structure by designing the flow channels and structural dimensions and adjusting the flow rate of the cooling medium.

[0022] In the microchannel device for phase change perspiration, the cross-sectional areas of the branch channel, the main channel, and the inlet channel should increase in sequence.

[0023] The application method of the microchannel device for phase change sweating,

[0024] Liquid cooling medium enters the microchannel structure from the cooling medium inlet on the bottom plate, is transported through a cascade flow channel network consisting of an inlet channel, a main channel, and a branch channel, and is evenly distributed in the transport phase change layer. 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, forming an air film, changing the near-wall flow field structure, and reducing the input aerodynamic heat.

[0025] 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 of 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 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;

[0026] Beneficial effects of the present invention:

[0027] The structure's medium transport channel network can be divided into three levels: inlet channels, main channels, and branch channels. Spatially, each level of channels is staggered, for example, the inlet channels are arranged in a parallel and staggered pattern, each with its own independent cooling medium inlet. Within 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 ensures that even if a channel level is locally blocked or damaged, the adjacent channels can still provide cooling medium. For example, if a branch channel is blocked, the adjacent branch channels, whose cooling medium comes from another channel network, can still provide cooling medium to the porous ribs on both sides of the blocked branch channel. If a main channel is blocked, the porous ribs in the multi-connected structure on both sides can still avoid drying up by receiving liquid from the adjacent main channels. If an inlet channel is blocked, the adjacent inlet channels can still provide cooling medium to the porous ribs in the transport phase change layer. This staggered arrangement of multi-level channels achieves relatively uniform thermal protection performance while improving operational safety and reliability.

[0028] The present invention has the characteristics of structural integration, thin thickness, uniform and efficient sweating, and can provide a new way for thermal protection of high-speed aircraft during long-term cross-domain navigation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the microchannel structure for phase change sweating of the present invention, with arrows indicating the direction of sweating.

[0030] Figure 2 Schematic diagram of the microchannel structure base plate 1 and part of the flow channel, with arrows indicating the flow direction of the cooling medium.

[0031] Figure 3 It is a top view of the bottom plate structure of the microchannel structure, and the arrows indicate the flow direction of the cooling medium.

[0032] Figure 4 It is a bottom view of the microchannel structure base plate structure, and the arrow indicates the flow direction of the cooling medium.

[0033] Figure 5 Schematic diagram of the phase change sweating layer structure, and the arrows indicate the flow direction of the cooling medium and the sweating direction.

[0034] 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.

[0035] Figure 7 Schematic diagram of the area expansion of the microchannel structure for phase change sweating.

[0036] 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

[0037] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the specific implementation methods and the accompanying drawings. 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 making any creative efforts are within the scope of protection claimed by the present invention.

[0038] A microchannel structure for phase change sweating, such as Figure 1 As shown, from the inside out, there are the solid inner wall, the transport phase change layer, and the sweating outer wall. The bottom plate 1 is the solid inner wall, which plays a structural support role. 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 transport, and the heat protection structure is cooled by convection heat transfer and medium phase change. The porous rib wall 2 and the solid outer wall 4 are connected and keep the outer surface flush, forming 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 and further fully changes phase to absorb heat. As shown by the arrows in the figure, it becomes gaseous and then disperses into the external flow field to form an air film.

[0039] like Figure 2 Shown is an axonometric cross-sectional view of the base plate 1 structure. Figure 3 and Figure 4 They are respectively a top view and a bottom view of the base plate 1, with a cooling medium inlet 1.1 arranged on its bottom surface, 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 flow directions between adjacent main channels 6 are opposite, that is, reverse flow channels. The main channel 6 can be partially embedded in the base plate 1, thereby increasing the channel cross-sectional area within a limited width and enhancing 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.

[0040] like Figure 5 and Figure 6The figures show the isometric and top views of the intermediate transport phase change layer structure after removing the base plate 1 and the solid outer wall 4. Each main channel 6 transports cooling medium to the adjacent branch channels 7 on either side. Branch channels on the same side are spaced apart, with branch channels 7 connecting to adjacent main channels 6 located in between. Opposing branch channels of the main channel 6 are staggered to avoid direct alignment of the channel openings, minimizing the mutual influence of unstable characteristics of the flow phase change process in the opposing branch channels 7, such as pressure and flow fluctuations. The branch channels 7 on either side of the porous rib 2 flow in opposite directions, and the cooling medium originates from the adjacent countercurrent main channel 6. The mixed gas-liquid cooling medium on both sides can enter the porous rib 2 structure for further phase transformation, and then dissipate into the external high-speed flow field. This multi-stage countercurrent flow arrangement ensures a relatively uniform temperature along the axial direction of the main channel. The cooling medium flow rate delivered to each porous rib 2 along the main channel is complemented by the branch channels 7 on both sides, making it more uniform. Furthermore, the axial distribution of the cooling medium input flow rate within a single porous rib 2 structure is also relatively uniform. This achieves a certain degree of uniform distribution and transport of the cooling medium within the planar structure, providing uniform cooling medium to each porous rib wall 2 structure. The flow rate of the medium forming the air film in each sweating zone on the outer wall is relatively uniform. Therefore, this compact and interwoven multi-stage countercurrent flow channel structure provides uniform thermal protection within the plane. Furthermore, structural heat conduction can, to a certain extent, mitigate local temperature fluctuations caused by two-phase flow instabilities due to phase change.

[0041] like Figure 7 Shown is a schematic diagram of the area expansion of a phase-change transpiration microchannel structure. This thin-walled microfluidic structure can be expanded in size based on the wall thermal protection requirements and the structural characteristics of the aircraft wall. Specifically, the multi-link structure is periodically distributed, and the area size can be adjusted by varying the number of periods. The diagram illustrates that expansion is possible in both the horizontal and vertical directions, and the actual number of links in the expanded multi-link structure does not need to be a multiple of three. This structure can be assembled as modular components, facilitating universal design and mass assembly based on actual shape and area. Ultimately, these components can be assembled to form a large-area transpiration cooling structure, demonstrating strong practical value.

[0042] The entire structure is formed using additive manufacturing technology using selective laser melting. The dimensions of each structure, such as the flow channel dimensions and the thickness of the porous ribs 2, can be adjusted to meet varying thermal protection requirements and actual performance. The porosity and pore size of the porous ribs 2 can be controlled through additive manufacturing to accommodate varying thermal protection requirements. This design and manufacturing process can enhance the capillary transport capacity of the porous ribs 2, further improving the transport performance of the medium within the structure.

[0043] 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 channel 6 is blocked, the flow channel network where the adjacent main 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 more uniform thermal protection performance, but also improve the safety and reliability of operation.

[0044] In actual engineering applications, the thermal protection performance can be regulated by adjusting the cooling medium flow rate of different inlet flow channels 5.

[0045] The various technical features of the above-described embodiments can be further combined. To make the description concise, not all possible combinations of the various 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 by: The upper and lower parts 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 parts are periodically arranged multi-linked structures; the multi-linked structures are 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 staggered, and the gaps between the rib plates are filled with the porous rib wall (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 channel (6) and the branch 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 sweating outer wall surface; The inner side of the bottom plate (1) is provided with a cooling medium inlet (1.1) connected to a liquid supply pipeline, and parallel 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); The cooling medium undergoes a series of transition states from a liquid state to a two-phase mixed state and finally to 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, and realizes cooling of the structure through convection heat transfer and phase change heat absorption; The cooling medium in the branch 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.

2. The microchannel device for phase change perspiration 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 controlled by the additive manufacturing process.

3. 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 structural characteristics of the aircraft wall. 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.

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

5. The application method of the microchannel device for phase change perspiration 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 cascade flow channel network of the inlet flow channel (5), the main flow channel (6), and the branch flow channel (7), and is evenly distributed in the transport phase change layer. The structure is cooled by convection heat transfer and phase change. Finally, the gaseous working medium diverges from the porous rib wall (2) into the external flow field, forming an air film, changing the near-wall flow field structure, and reducing the input aerodynamic heat. Each main channel (6) is connected to the inlet channel (5) on one side only through the main channel inlet (1.2), and the cooling media are staggered, that is, the cooling media of adjacent main channels (6) are derived from different inlet channels (5), so that the cooling media in each two adjacent main channels (6) flow in opposite directions; The cooling medium in each of two adjacent branch channels (7) originates from the adjacent main channel (6), that is, the cooling medium on both sides of each porous rib wall (2) originates from the adjacent main channel (6), and the flow directions in the branch channels (7) on both sides are also opposite; Each main channel (6) supplies cooling medium to the branch channels (7) on both sides thereof, and the inlets of the branch channels (7) on both sides are staggered; The medium of the sweating zones staggered and discretely distributed on the sweating outer wall is derived 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 through the internal flow channel.

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