Pixelization function gradient sweating cooling structure and application method thereof

Abstract

The invention discloses a pixelated functional gradient sweating cooling structure and an application method thereof. The sweating cooling structure is composed of a plurality of sweating units arranged in a pixelated mode, and each sweating unit sequentially comprises a flow distribution layer, a pressure control layer, a buffer heat insulation layer and a phase change heat exchange layer from inside to outside. The pressure control layer comprises a plurality of sections of porous medium pressure control structures with small pore diameters and low porosity, and the pressure drop of the porous medium pressure control structures accounts for more than 90% of the total pressure drop of the sweating unit. The phase-change heat exchange layer is composed of a porous medium heat exchange structure with large aperture and high porosity, and the single-phase cooling working medium can perform sufficient phase-change heat exchange in the phase-change heat exchange layer. The buffering heat insulation layer plays a role in flow secondary distribution on one hand, and on the other hand, the pressure control layer is always kept in a single-phase state through the heat insulation effect of a working medium. The device has the characteristics of high use efficiency of a cooling medium, good sweating and cooling stability, arbitrary design of sweating flow distribution and the like.

Description

Technical Field

[0001] The present invention relates to the field of aerospace high-speed aircraft structure design and thermal protection technology, and in particular to a pixelated functional gradient transpiring cooling structure and an application method thereof. Background Art

[0002] As high-Mach number aircraft evolve toward higher airspace, faster Mach numbers, and greater lift-to-drag ratios, the aerodynamic-thermal coupling loads they face exhibit a significant nonlinear growth characteristic, with surface heat flux densities reaching megawatts. Achieving long-term, repeatable, and efficient thermal protection is a key issue in the development of high-Mach number aircraft.

[0003] Traditional thermal protection solutions, such as heat sinks and ablatives, suffer from drawbacks such as altered aerodynamic shape due to ablation, redundant structural mass, and non-reusability, making them difficult to meet the thermal protection requirements of high-Mach number aircraft. Against this backdrop, the use of active flow control technology to create a flow environment conducive to cross-domain, variable-speed flight has become a key research focus and hot topic in the field of thermal protection for reusable high-Mach number aircraft.

[0004] Among active thermal protection technologies, transpiration cooling is considered a key solution for active thermal protection systems in hypersonic vehicles due to its advantages, including high heat sink utilization efficiency, aerodynamic shape stability, and reusability. However, under complex flight conditions, the strong heat flux-pressure gradient distribution on the vehicle surface leads to a significant heat flux-flow mismatch in traditional transpiration cooling systems. The physical mechanism behind this mismatch can be attributed to the asymmetry between the flow resistance distribution of the homogeneous porous medium and the heat flux gradient on the vehicle surface. This leads to a premature, large-scale phase change within the homogeneous porous medium corresponding to high heat flux regions, resulting in steam blockage. The coolant preferentially penetrates into low heat flux regions, while high heat flux regions face insufficient coolant supply due to the flow resistance imbalance. This mismatch not only significantly reduces the overall coolant utilization rate but also easily induces localized thermal failure in high-speed vehicles. Therefore, the development of novel phase-change transpiration cooling configurations is urgently needed to overcome the bottleneck of strong heat flux-phase-state-flow coupling. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the present invention provides a pixelated functional gradient transpiring cooling structure and its application method in response to the thermal protection performance requirements of high Mach number aircraft and the requirements for surface temperature uniformity of thin-walled thermal protection structures.

[0006] The technical solution for achieving the technical purpose of the present invention is as follows: The sweating cooling structure is composed of a number of sweating units arranged in a pixelated manner. Each sweating unit includes four parts from the inside to the outside, namely, a flow distribution layer, a pressure control layer, a buffer insulation layer and a phase change heat transfer layer. The flow distribution layer contains a sweating medium inlet and a main flow channel for distributing the flow. The sweating medium inlet and the main flow channel are shared by the sweating units arranged in a pixelated manner. The pressure control layer contains a branch flow channel for distributing the flow, a unit inlet flow channel and a multi-section porous medium pressure control structure. All branch flows are connected to the main flow channel, and each row of pixelated sweating units arranged along the span direction shares a The unit inlet flow channel is connected to the branch channel, and the multi-section porous medium pressure control structure is arranged along the span direction; the buffer insulation layer contains a liquid buffer zone and an insulation layer flow channel; the buffer insulation layer not only connects the pressure control layer and the phase change heat transfer layer, but also plays a role of heat insulation, and the insulation layer flow channel can perform secondary flow distribution on the sweating medium inside the pixelated unit; the phase change heat transfer layer is composed of a number of pixelated surface thin-layer porous medium heat exchange structures and a non-permeable solid wall surface, and the geometric parameters of the surface thin-layer porous medium heat exchange structure can be adjusted according to the flow control requirements.

[0007] The pressure control layer contains multiple sections of small-pore, low-porosity porous media pressure control structures, and its pressure drop accounts for more than 90% of the total pressure drop of the sweating unit; the phase change heat exchange layer is composed of a large-pore, high-porosity porous media heat exchange structure. The single-phase cooling medium can undergo sufficient phase change heat exchange in the phase change heat exchange layer, thereby increasing the dryness of the cooling medium on the unit surface, improving the efficiency of the cooling medium use, and reducing the difficulty of predicting the phase change sweating cooling performance. The pressure control layer, buffer insulation layer and phase change heat transfer layer are pixelated and discretely designed along the in-plane flow direction and the span direction, and the entire surface is divided into small units that do not affect each other in a two-dimensional grid arrangement, cutting off the lateral flow path of the sweating cooling medium in the pressure control layer, buffer insulation layer and phase change heat transfer layer. The phase change sweating process is constrained within the pixelated unit structure, so that the flow rate of the sweating medium in different areas can be arbitrarily designed, suppressing the influence of the strong surface thermal gradient on the flow transport inside the entire functional gradient sweating cooling structure; the size of the pixelated unit is determined by the gradient of the surface heat flux density. The larger the surface heat flux density gradient, the smaller the size of the pixelated unit and the finer the flow control, so that the distribution of the cooling medium matches the distribution of the heat flux density.

[0008] The porosity of the multi-stage porous medium pressure control structure does not exceed 0.2, and the permeability range is 1.0×10 -13 m 2 to 5.0×10 -13 m 2 , which can meet the pressure control requirements of the functional gradient structure pressure control layer.

[0009] The porosity of the surface thin layer porous medium heat exchange structure is not less than 0.5, and the pore size is not less than 100 μm, so that the cooling medium can fully change phase when flowing through the phase change heat exchange layer, thereby improving the dryness of the cooling medium at the outer surface of the sweat unit.

[0010] The porous medium pressure control structure and the thin layer porous medium heat exchange structure are made of metal, ceramic, resin and the like.

[0011] The pressure control layer and the phase change heat transfer layer are designed separately based on the idea of ​​normal functional gradient decoupling. The buffer insulation layer plays the role of secondary flow distribution on the one hand, and on the other hand, the pressure control layer is always maintained in a single-phase state through the thermal insulation effect of the working fluid. The system pressure drop is concentrated in the pressure control layer, and the heat exchange is concentrated in the phase change heat transfer layer. The pressure drop fluctuation caused by the phase change of the cooling working fluid in the phase change heat transfer layer has a negligible effect on the overall flow pressure drop of the sweating unit, so that the pressure drop of the sweating unit does not increase with the increase of the dryness of the phase change heat transfer layer, realizing the decoupling of pressure drop and heat transfer, solving the problem of heat transfer deterioration caused by the positive feedback of heat flow-flow, and establishing a negative feedback mechanism of heat flow-flow by utilizing the characteristic that the viscosity of the liquid working fluid decreases with increasing temperature, realizing adaptive control of phase change sweating.

[0012] The application method of the pixelated functional gradient transpiring cooling structure is as follows: for high-temperature areas such as the leading edge and windward surface of high-speed aircraft, the aerodynamic thermal distribution of the structure surface is first obtained through numerical simulation or ground testing. Then, the surface aerodynamic thermal distribution is discretized into pixels according to the size of the surface aerodynamic thermal distribution, and the transpiring flow rate of each pixel transpiring unit is determined. Finally, the length of the multi-section porous medium pressure-controlled structure inside the unit is designed according to the expected transpiring flow rate of each pixel transpiring unit. Under the premise of maintaining a high dryness at the outlet of each transpiring unit, the phase change position of the cooling medium is always controlled within the phase change transpiring layer, thereby achieving efficient and reliable active thermal protection.

[0013] Compared with the prior art, the present invention is beneficial in that: First, based on the thin-walled transpiring cooling structure, a buffer insulation layer and a phase-change heat transfer layer are added. This not only achieves phase-change transpiring cooling, significantly improving the efficiency of the transpiring medium, but also decouples the heat flow from the flow rate, fundamentally suppressing the deterioration of heat transfer caused by the heat flow-flow mismatch and shifting the flow control of the transpiring structure from a phase-dominated mode to a viscosity-dominated mode. The thin layer of porous medium on the surface of this structure overcomes the localized overcooling or cooling blind spots that are prone to occur in traditional discrete pore structures. A dense air film is formed on the surface of the transpiring structure, enabling precise control of the transpiring medium and improving temperature uniformity across the surface. This provides a new, engineering-viable structure for dynamic thermal management under complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1A two-dimensional schematic diagram of a pixelated functionally graded transpiration cooling structure.

[0015] Figure 2 Schematic diagram of the global percolation path of a pixelated functionally graded transpiration cooling structure.

[0016] Figure 3 It is a schematic diagram of the percolation path of a single sweat unit in a pixelated functional gradient sweat cooling structure.

[0017] Figure 4 It is a directional schematic diagram of a pixelated functional gradient transpiration cooling structure.

[0018] Figure 5 It is a typical working pressure distribution diagram of a single transpiration unit of a pixelated functional gradient transpiration cooling structure.

[0019] Figure 6 This is a process diagram of pixelated discretization of heat flux density on the surface of a pixelated functional gradient transpiration cooling structure under high temperature and high speed flow conditions.

[0020] Figure 7 is Figure 6 The preset layout diagram of the porous medium pressure control structure in the internal pressure control layer of the pixelated functional gradient transpiring cooling structure under the incoming flow condition shown.

[0021] Explanation of the accompanying symbols: 1. Flow distribution layer; 2. Pressure control layer; 3. Buffer insulation layer; 4. Phase change heat exchange layer; 5. Sweating medium inlet; 6. Main channel; 7. Branch channel; 8. Unit inlet channel; 9. Multi-section porous medium pressure control structure; 10. Liquid buffer zone; 11. Insulation layer channel; 12. Thin layer porous medium heat exchange structure; 13. Non-permeable solid wall. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1 、 Figure 2 and Figure 3As shown, a pixelated functional gradient sweating cooling structure is composed of a number of sweating units arranged in a pixelated manner. Each sweating unit includes four parts from the inside to the outside, namely, a flow distribution layer 1, a pressure control layer 2, a buffer insulation layer 3 and a phase change heat transfer layer 4. The flow distribution layer 1 contains a sweating medium inlet 5 and a main flow channel 6 for distributing the flow. The sweating medium inlet 5 and the main flow channel 6 are shared by the sweating units arranged in a pixelated manner. The pressure control layer 2 contains a branch flow channel 7 for distributing the flow, a unit inlet flow channel 8 and a multi-section porous medium pressure control structure 9. All the branch flow channels 7 are connected to the main flow channel 6. Each row of pixelated sweating units arranged along the span direction Sharing a branch channel 7, the unit inlet channel 8 is connected to the branch channel 7, and a multi-section porous medium pressure control structure 9 is arranged along the span direction; the buffer insulation layer 3 contains a liquid buffer zone 10 and an insulation layer channel 11; the buffer insulation layer 3 not only connects the pressure control layer 2 and the phase change heat exchange layer 4, but also plays a role of heat insulation. The insulation layer channel 11 can perform secondary flow distribution on the sweating medium inside the pixelated unit; the phase change heat exchange layer 4 is composed of a number of pixelated surface thin-layer porous medium heat exchange structures 12 and a non-permeable solid wall 13. The geometric parameters of the surface thin-layer porous medium heat exchange structure 12 can be adjusted according to the flow control requirements.

[0024] like Figure 2 、 Figure 3 and Figure 4 As shown, the pressure control layer 2, the buffer insulation layer 3 and the phase change heat transfer layer 4 are pixelated and discretely designed along the in-plane flow direction and the extension direction, and the entire surface is divided into small units that do not affect each other in a two-dimensional grid arrangement, cutting off the lateral flow path of the sweating cooling medium in the pressure control layer 2, the buffer insulation layer 3 and the phase change heat transfer layer 4. The phase change sweating process is constrained within the pixelated unit structure, so that the flow rate of the sweating medium in different areas can be arbitrarily designed, suppressing the influence of the strong surface thermal gradient on the flow transport inside the entire functional gradient sweating cooling structure; the size of the pixelated unit is determined by the surface heat flux density. The larger the surface heat flux density gradient, the smaller the size of the pixelated unit and the finer the flow control, so that the distribution of the cooling medium matches the distribution of the heat flux density.

[0025] like Figure 3 and Figure 5 As shown, the pressure control layer 2 contains multiple sections of porous medium pressure control structures with small pore size and low porosity, and its pressure drop accounts for more than 90% of the total pressure drop of the sweating unit; the phase change heat exchange layer 4 is composed of a porous medium heat exchange structure with large pore size and high porosity. The single-phase cooling medium can undergo sufficient phase change heat exchange in the phase change heat exchange layer 4, thereby improving the dryness of the cooling medium on the surface of the unit, improving the utilization efficiency of the cooling medium, and reducing the difficulty of predicting the phase change sweating cooling performance.

[0026] like Figure 3As shown, the porosity of the multi-stage porous medium pressure-controlled structure does not exceed 0.2, and the permeability range is 1.0×10 -13 m 2 to 5.0×10 -13 m 2 , capable of meeting the pressure control requirements of the functionally graded pressure control layer. The surface thin-layer porous medium heat exchange structure has a porosity of no less than 0.5 and a pore size of no less than 100 μm, enabling sufficient phase change of the cooling medium as it flows through the phase change heat exchange layer, thereby increasing the dryness of the cooling medium at the outer surface of the sweat unit. The porous medium pressure control structure and thin-layer porous medium heat exchange structure are made of metal, ceramic, resin, etc.

[0027] like Figure 1 and Figure 3 As shown, the pressure control layer 2 and the phase change heat exchange layer 4 are designed separately based on the idea of ​​normal functional gradient decoupling. The buffer insulation layer 3 plays the role of secondary flow distribution on the one hand, and on the other hand, the pressure control layer 2 is always maintained in a single-phase state through the insulation effect of the working fluid. The system pressure drop is concentrated in the pressure control layer 2, and the heat exchange is concentrated in the phase change heat exchange layer 4. The pressure drop fluctuation caused by the phase change of the cooling working fluid in the phase change heat exchange layer 4 has a negligible effect on the overall flow pressure drop of the sweating unit, so that the pressure drop of the sweating unit does not increase with the increase of the dryness of the phase change heat exchange layer 4, realizing the decoupling of pressure drop and heat exchange, solving the problem of heat transfer deterioration caused by the positive feedback of heat flow-flow, and establishing a negative feedback mechanism of heat flow-flow by utilizing the characteristic that the viscosity of the liquid working fluid decreases with increasing temperature, thereby realizing adaptive control of phase change sweating.

[0028] like Figure 6 and Figure 7 As shown, even if local hot spots or extreme working conditions appear on the surface of the structure, causing the phase change position in the corresponding regional unit to penetrate through the buffer insulation layer 3 and invade into the pressure control layer 2, or even cause heat transfer deterioration such as steam blockage, it will not cause the re-coupling of pressure drop and heat exchange in the entire pixelated functional gradient sweating cooling structure, will not induce the flow control to return from viscosity-dominated to phase-dominated, and the overall structure has good reliability.

[0029] like Figure 1 、 Figure 6 and Figure 7As shown, the application method of the pixelated functional gradient transpiring cooling structure is as follows: for high-temperature areas such as the leading edge and windward surface of a high-speed aircraft, the aerodynamic thermal distribution of the structure surface is first obtained through numerical simulation or ground testing, and then pixelated discretization is performed according to the size of the surface aerodynamic thermal distribution, and the transpiring flow rate of each pixel transpiring unit is determined. Finally, the length of the multi-section porous medium pressure control structure 9 inside the unit is designed according to the expected transpiring flow rate of each pixel transpiring unit. Under the premise of maintaining a high dryness at the outlet of each transpiring unit, the phase change position of the cooling medium is always controlled within the phase change transpiring layer 4, thereby achieving efficient and reliable active thermal protection.

[0030] The foregoing description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the foregoing embodiment but includes all technical solutions within the scope and spirit of the present invention. Those skilled in the art may improve or modify the foregoing embodiment without departing from the principles of the present invention. Such improvements or modifications should also be considered within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims and any equivalents thereof.

Claims

1. A pixelated functional gradient transpiration cooling structure, characterized by: The sweating cooling structure is composed of a plurality of sweating units arranged in a pixelated manner, and each sweating unit includes, from the inside to the outside, a flow distribution layer (1), a pressure control layer (2), a buffer insulation layer (3), and a phase change heat transfer layer (4); the flow distribution layer (1) contains a sweating medium inlet (5) and a main flow channel (6) for distributing the flow; the sweating medium inlet (5) and the main flow channel (6) are shared by the sweating units arranged in a pixelated manner; the pressure control layer (2) contains a branch flow channel (7) for distributing the flow, a unit inlet flow channel (8), and a multi-section porous medium pressure control structure (9); all the branch flow channels (7) are connected to the main flow channel (6), and each row of pixelated sweating units arranged along the span direction share a branch flow channel (7). The flow channel (7) is connected to the unit inlet flow channel (8) and the branch flow channel (7), and the multi-section porous medium pressure control structure (9) is arranged along the span direction; the buffer insulation layer (3) contains a liquid buffer zone (10) and an insulation layer flow channel (11); the buffer insulation layer (3) is connected to the pressure control layer (2) and the phase change heat transfer layer (4), and is also used for heat insulation. The insulation layer flow channel (11) can perform secondary flow distribution on the sweating medium inside the pixelated unit; the phase change heat transfer layer (4) is composed of a plurality of pixelated thin-layer porous medium heat exchange structures (12) and a non-permeable solid wall surface (13), and the geometric parameters of the surface thin-layer porous medium heat exchange structure (12) can be adjusted according to the flow control requirements.

2. The pixelated functional gradient transpiration cooling structure according to claim 1, wherein: The pressure control layer (2) comprises multiple sections of porous medium pressure control structures (9) with small pore diameter and low porosity, with a porosity of no more than 0.2 and a permeability range of 1.0×10 -13 m 2 to 5.0×10 -13 m 2 The pressure drop of the porous medium pressure control structure (9) accounts for more than 90% of the total pressure drop of the sweating unit; the phase change heat exchange layer (4) is composed of a thin layer of porous medium heat exchange structure with large pore size and high porosity, the porosity is not less than 0.5, and the pore size is not less than 100μm. The single-phase cooling medium can undergo sufficient phase change heat exchange in the phase change heat exchange layer (4), thereby improving the phase change degree of the medium flowing through the sweating cooling unit.

3. The pixelated functional gradient transpiration cooling structure according to claim 1, wherein: The porous medium pressure control structure (9) and the thin-layer porous medium heat exchange structure (12) are made of metal, ceramic, or resin.

4. The pixelated functional gradient transpiration cooling structure according to claim 1, wherein: The pressure control layer (2), the buffer thermal insulation layer (3) and the phase change thermal layer (4) are pixelated and discretely designed along the in-plane flow direction and the span direction, and the entire surface is divided into small units that do not affect each other in a two-dimensional grid arrangement, cutting off the lateral flow path of the sweating cooling medium in the pressure control layer (2), the buffer thermal insulation layer (3) and the phase change thermal layer (4). The phase change sweating process is constrained within the pixelated unit structure, so that the flow of the sweating medium in different areas can be arbitrarily designed, thereby suppressing the influence of the strong surface thermal gradient on the flow transport inside the entire functional gradient sweating cooling structure; the size of the pixelated unit is determined by the gradient of the heat flux density on the aircraft surface. The larger the surface heat flux density gradient, the smaller the size of the pixelated unit and the finer the flow control, so that the distribution of the cooling medium matches the heat flux density distribution.

5. A method for applying the pixelated functional gradient transpiring cooling structure according to any one of claims 1 to 4, characterized in that: For high-temperature areas such as the leading edge and windward surface of high-speed aircraft, the aerodynamic thermal distribution of the structure surface is first obtained through numerical simulation or ground testing. Then, the surface aerodynamic thermal distribution is discretized into pixels according to the size of the surface aerodynamic thermal distribution and the sweating flow rate of each pixel sweating unit is determined. Finally, the length of the multi-section porous medium pressure control structure (9) inside the unit is designed according to the expected sweating flow rate of each pixel sweating unit. Under the premise of maintaining a high dryness at the outlet of each sweating unit, the phase change position of the cooling medium is always controlled within the phase change heat transfer layer (4), thereby achieving efficient and reliable active thermal protection.

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