Thin-wall sweating cooling structure and application method thereof

Abstract

The invention discloses a thin-wall sweating cooling structure and an application method thereof. The sweating cooling structure is composed of a plurality of sweating units arranged in an array mode. Each sweating unit sequentially comprises a flow distribution layer, a pressure control layer and a porous sweating surface from bottom to top. The flow distribution layer internally comprises a sweating working medium inlet and a main flow channel for distributing flow; the sweating working medium inlet and the main runner are shared by the sweating units which are arranged in an array manner; the pressure control layer internally comprises a branch flow channel for distributing flow, a porous medium pressure control structure and a buffer area, the branch flow channel is connected with the main flow channel, and the porous medium pressure control structure is arranged parallel to the sweating wall surface; the porous sweating surface is composed of a plurality of sweating micropores and a non-permeable solid wall surface, and the number, the size and the angle of the sweating micropores can be adjusted according to flow regulation and control requirements. The structure has the remarkable characteristics that the structure thickness is small, the sweating flow distribution can be adjusted at will, the porous array structure on the sweating surface can be adjusted at will, and the use efficiency of the sweating working medium is high.

Description

Technical Field

[0001] The present invention relates to the technical field of active flow control for heat reduction and drag reduction of aerospace high-speed aircraft. Specifically, it relates to a thin-walled transpiration cooling structure and an application method thereof. Background Art

[0002] Higher Mach number, lower cost, and reusability are important development directions for future high-Mach aircraft. Since the aerodynamic heating on the aircraft surface is approximately proportional to the cube of the flight speed, with the increase in Mach number, the thermal protection design of high-Mach aircraft faces huge challenges. Most of the thermal protection scheme designs for traditional high-Mach aircraft are to arrange an ablative thermal protection layer on the outer layer of the aircraft structure and then arrange heat insulation materials inside. However, with the increase in heat flux density, the thicknesses of the thermal protection layer and the heat insulation layer required for thermal protection and insulation increase synchronously, and the proportion of the thermal protection and insulation system in the total weight of the aircraft will gradually increase, which will undoubtedly seriously affect the flight performance and carrying capacity of high-Mach aircraft. In this context, achieving efficient heat reduction on the aircraft surface through active flow control means has currently become an important research direction in the field of thermal protection of high-Mach aircraft.

[0003] In the field of active flow control technology, transpiration cooling technology has significant advantages such as outstanding heat reduction ability and good engineering feasibility, and is one of the key research directions in the field of high-Mach active flow control in recent years. However, for near-space high-Mach aircraft, their flight states are complex and changeable, and the heat flux and pressure on the aircraft surface show highly non-uniform distribution characteristics. At this time, if a uniform transpiration cooling scheme is simply adopted, not only the heat reduction effect in the high-heat area cannot be guaranteed, but also the utilization efficiency of the transpiration cooling working medium will be significantly reduced, the installation volume and weight of the transpiration cooling system will be increased, and the engineering feasibility of the transpiration cooling technology will be seriously affected. Therefore, developing a new concept of transpiration cooling structure to solve the flow matching problem faced by transpiration cooling is of great significance for the development of new low-cost and reusable high-Mach aircraft.

[0004] Patent application CN119637069A discloses a microchannel device for phase change transpiration and its application. Although this technical solution has advantages such as integrated structure and thin thickness, the transpiration amount of the entire phase change transpiration structure is uniformly distributed on the wall surface and is difficult to adapt to the variable heat flux gradient environment. Although this technical solution also adopts a unitized design, since the porous medium is still arranged along the normal thickness direction, when this phase change transpiration structure faces the atmospheric environment with variable heat flux gradient, phenomena such as steam blockage and subsequent heat transfer deterioration will occur. At the same time, the thin and light thickness design will result in a very limited pressure control range for the entire phase change transpiration structure, which greatly limits the application range of this phase change transpiration structure. Summary of the Invention

[0005] In order to break through the existing technical bottlenecks, the purpose of the present invention is to provide a thin-walled transpiration cooling structure and its application method. Based on the traditional active thermal protection structure of transpiration cooling, firstly, independent control of the transpiration flow rate of each unit is achieved through the design of discrete array units. Then, by arranging the porous medium pressure control structure horizontally parallel to the wall surface, the dependence of the traditional transpiration cooling pressure drop regulation on the structure thickness is solved, significantly reducing the installation volume and weight of the transpiration cooling structure. Finally, by optimizing the micropore size and its layout form of the porous transpiration surface, the heat reduction effect of the thin-walled transpiration cooling structure and the utilization efficiency of the transpiration working fluid are further improved, significantly enhancing the engineering feasibility and cost-effectiveness ratio of the transpiration cooling technology.

[0006] A thin-walled transpiration cooling structure, which is composed of a number of transpiration units arranged in an array. Each transpiration unit sequentially includes a flow distribution layer, a pressure control layer, and a porous transpiration surface from bottom to top; the flow distribution layer internally contains a transpiration working fluid inlet and a main flow channel for distributing the flow rate; the transpiration working fluid inlet and the main flow channel are shared by the transpiration units arranged in an array; the pressure control layer internally contains a branch flow channel for distributing the flow rate, a porous medium pressure control structure, and a buffer zone. The branch flow channel is connected to the main flow channel, and the porous medium pressure control structure is arranged parallel to the transpiration wall surface; the porous transpiration surface is composed of a number of transpiration micropores and a non-permeable solid wall surface, and the number, size, and angle of the transpiration micropores can be adjusted according to the requirements of flow regulation.

[0007] The porous medium material is made of sintered metal, sintered ceramic, or photocurable resin, with a porosity not exceeding 0.20 and a permeability range of 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.

[0008] The porous medium pressure control structure is arranged parallel to the wall surface, so that the pressure drop characteristics of the transpiration structure do not depend on the thickness dimension of the porous medium pressure control structure in the vertical direction of the wall surface. By adjusting the length of the porous medium pressure control structure, the pressure drop-flow rate relationship of the transpiration unit can be adjusted, so that the flow pressure drop in the porous medium area accounts for more than 95% of the pressure difference between the working fluid inlet and the ambient pressure.

[0009] Application method of the thin-wall transpiration cooling structure. The thin-wall transpiration cooling structure is applied to the high-heat areas of an aircraft, including the leading edge and the windward surface of the aircraft. A continuous gas film formed by a surface microhole array isolates the high-heat oncoming flow, inhibits aerodynamic heating, and realizes active thermal protection. In the design stage of the transpiration cooling structure, after obtaining the aerodynamic heat distribution on the aircraft surface through numerical simulation, the preset configuration of the transpiration cooling structure is designed: ① By adjusting the length of the porous media pressure control structure of each transpiration unit, the transpiration flow rate in the high-heat area is increased, and the transpiration flow rate in the low-heat area is reduced, so as to improve the cost-effectiveness of the transpiration working fluid on the premise of achieving reliable thermal protection; ② By changing the flow direction length dimension, span width dimension of the transpiration unit and the geometric parameters of the transpiration microholes, the geometric parameters and layout scheme of the surface microhole array of the transpiration cooling structure are optimized, and the heat reduction and drag reduction benefits of the transpiration working fluid per unit mass are improved.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: First, the independent control of the transpiration flow rate of each unit is realized through discrete unit design; second, by arranging the porous media pressure control structure transversely along the direction of the high-temperature and high-speed oncoming flow, the dependence of the traditional transpiration cooling pressure drop adjustment on the structure thickness is solved, and the installation volume and weight of the transpiration cooling structure are greatly reduced; third, by changing the length of the porous media pressure control structure of the pressure control layer, the pressure drop characteristics of each transpiration unit can be arbitrarily regulated, so that a transpiration cooling structure with an arbitrarily preset transpiration flow rate distribution can be designed according to the aerodynamic heat distribution of the aircraft under the condition of a certain total transpiration flow rate; fourth, by changing the flow direction length dimension, span width dimension of the transpiration unit and the geometric parameters of the transpiration microholes, the geometric parameters and layout scheme of the surface microhole array of the transpiration cooling structure can be optimized, the heat reduction efficiency of the transpiration working fluid per unit mass is improved, and the engineering feasibility of the transpiration cooling technology is further improved. Description of the drawings

[0011] Figure 1 It is a schematic diagram of the transpiration working fluid seepage path of the whole thin-wall transpiration cooling structure.

[0012] Figure 2 It is a schematic diagram of the transpiration working fluid seepage path in a single transpiration unit of the thin-wall transpiration cooling structure.

[0013] Figure 3 It is a schematic diagram of the discretized design of the thin-wall transpiration cooling structure.

[0014] Figure 4 It is a top view of various adjustment forms of the thin-wall transpiration cooling structure.

[0015] Figure 5 It is a comparison of the drag reduction effects of the forward uniform arrangement and the cross uniform arrangement structures of the thin-wall transpiration cooling structure under typical working conditions.

[0016] Figure 6 is the pressure distribution of the sweating working fluid under typical working conditions of a single sweating unit of the thin-walled transpiration cooling structure.

[0017] Figure 7 is the thin-walled transpiration cooling structure along X axial direction heat flux density distribution curve and flow rate distribution bar chart.

[0018] Explanation of reference numerals: 1, flow rate distribution layer; 2, pressure control layer; 3, porous transpiration surface; 4, sweating working fluid inlet; 5, main flow channel; 6, branch flow channel; 7, porous medium pressure control structure; 8, buffer zone; 9, transpiration micropores; 10, non-permeable solid wall surface. Specific implementation mode

[0019] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation modes.

[0020] As Figure 1 and Figure 2 shown, a thin-walled transpiration cooling structure is composed of a number of sweating units arranged in an array. Each sweating unit successively includes three parts: a flow rate distribution layer 1, a pressure control layer 2, and a porous transpiration surface 3 from bottom to top. The flow rate distribution layer 1 internally contains a sweating working fluid inlet 4 and a main flow channel 5 for distributing the flow rate. The pressure control layer 2 internally contains a branch flow channel 6 for distributing the flow rate, a porous medium pressure control structure 7, and a buffer zone 8. The porous transpiration surface 3 is composed of a number of transpiration micropores 9 and a non-permeable solid wall surface 10. The number, size, and angle of the transpiration micropores 9 can be adjusted according to the requirements of flow regulation.

[0021] As Figure 2 shown, the porous medium material can use sintered metal, sintered ceramic, or photocuring resin, with a porosity not exceeding 0.20 and a permeability range of 1.0×10 -13 m 2 to 5.0×10 -13 m 2 , which can meet the pressure control requirements of the pressure control layer 2 of the functionally gradient structure. The porous medium pressure control structure 7 is arranged parallel to the wall surface, so that the pressure drop characteristic of the transpiration structure does not depend on the thickness dimension of the porous medium pressure control structure 7 along the vertical direction of the wall surface. By adjusting the length of the porous medium pressure control structure 7, the pressure drop-flow rate relationship of the sweating unit can be adjusted within a large range, so that the flow pressure drop in the porous medium region accounts for more than 95% of the pressure difference between the working fluid inlet and the ambient pressure. This design method, on the one hand, greatly reduces the thickness of the transpiration cooling structure, reduces the installation volume and weight of the transpiration cooling structure, and on the other hand, makes the thickness of the transpiration cooling structures in different regions of the aircraft basically the same, reducing the installation difficulty of the transpiration cooling structure.

[0022] Application method of the thin-wall transpiration cooling structure: The thin-wall transpiration cooling structure can be applied to high-heat areas such as the leading edge and windward surface of an aircraft. A continuous gas film formed by the surface micro-hole array isolates the high-heat oncoming flow, inhibits aerodynamic heating, and realizes active thermal protection. In the design stage of the transpiration cooling structure, after obtaining the aerodynamic heat distribution on the aircraft surface through numerical simulation, the preset configuration of the transpiration cooling structure can be designed according to the following steps: ① By adjusting the length of the porous medium pressure control structure of each transpiration unit, increasing the transpiration flow rate in the high-heat area and decreasing the transpiration flow rate in the low-heat area, the cost-effectiveness of the transpiration working fluid can be improved on the premise of achieving reliable thermal protection; ② By changing the flowwise length dimension, spanwise width dimension of the transpiration unit and the geometric parameters of the transpiration micro-holes, optimizing the geometric parameters and layout scheme of the surface micro-hole array of the transpiration cooling structure, and enhancing the heat reduction and drag reduction benefits of the transpiration working fluid per unit mass.

[0023] As Figure 3 and Figure 4 shown, this thin-wall transpiration cooling structure realizes independent control of the transpiration flow rate of each unit through the discrete array unit design. Then, by arranging the porous medium pressure control structure parallel to the aircraft wall surface transversely, it solves the dependence of the traditional transpiration cooling pressure drop adjustment on the structure thickness, and greatly reduces the installation volume and weight of the transpiration cooling structure.

[0024] As Figure 1 , Figure 2 and Figure 4 shown, according to Darcy's law, in the laminar flow state, the flow rate Q is negatively correlated with the length L of the porous medium pressure control structure 7. Given the cross-sectional area A and permeability K of the porous medium pressure control structure 7, the flow pressure drop Δ P of the transpiration unit increases with the increase of the length L of the porous medium pressure control structure 7, that is, when the total transpiration flow rate Q is constant, by finely designing the length L of the porous medium pressure control structure 7 in the pressure control layer 2 of each transpiration unit, any form of transpiration flow rate distribution can be realized. The aerodynamic heat distribution on the surface of a high Mach number aircraft structure is highly uneven. In order to improve the matching degree between the transpiration flow rate distribution and the aerodynamic heat distribution, the length L of the porous medium pressure control structure 7 of the transpiration unit in the high-heat area of the aircraft can be shortened., increasing the sweating flow rate of the sweating unit in this area, enhancing the local sweating mass flow ratio, and achieving a stronger heat reduction effect. In addition, high-temperature areas are often accompanied by more intense air compression phenomena. Under the same mass flow ratio, the sweating heat reduction effect is relatively poor, and the heat reduction range that each sweating unit can cover is relatively small. Therefore, for high-temperature areas with strong air compression effects, the sweating flow control effect can be enhanced and the heat reduction effect under a given sweating flow rate can be strengthened by increasing the size of the microholes at the outlet of the local sweating unit in the spanwise direction, reducing the distance between adjacent sweating units, and optimizing the microhole combination parameters and shapes. For the medium- and low-temperature areas of the aircraft, the length of the porous medium pressure control structure (7) in the pressure control layer (2) of the local sweating unit can be appropriately increased to reduce the sweating flow rate in this area and prevent the waste of sweating working fluid. In addition, the air compression effect in the medium- and low-temperature areas is relatively weak. Under the same mass flow ratio, the sweating heat reduction effect is relatively good, and the heat reduction range that can be covered is large. Therefore, the size of the sweating unit array in the flow direction can be appropriately increased to reduce the consumption of sweating working fluid, improve the surface temperature uniformity of the aircraft, and enhance the heat reduction efficiency of the sweating working fluid per unit mass while ensuring the heat reduction effect in the medium- and low-temperature areas.

[0025] As Figure 4 shown in parts (a) and (b) of Figure 5 and Figure 4 as St shown, where C f represents the dimensionless heat flux and Figure 4 represents the friction drag coefficient. It can be seen from

[0026] that Figure 6 the heat reduction and drag reduction effect of the cross-uniform arrangement scheme is slightly better than that of the sequential-uniform arrangement scheme, and the uniform blowing scheme with a high porosity is significantly better than the cross-arrangement and sequential-arrangement schemes with a low porosity. The above phenomena indicate that by changing the microhole spacing, size, and layout form of the microhole array of the sweating unit and optimizing the geometric parameters and layout scheme of the microhole array on the surface of the sweating cooling structure, the heat reduction and drag reduction benefits of the sweating working fluid per unit mass can be effectively improved.

[0026] As Figure 6 shown, for the thin-walled sweating cooling structure, when the heat flux density on the hot side wall surface of the sweating cooling structure is 100 kW / m 2 and the mass flow rate of the sweating working fluid at the inlet is 6.0×10 -3 kg / s, the flow pressure drop in the porous medium region accounts for more than 99% of the pressure difference between the working fluid inlet and the environment.

[0027] As Figure 7 shown, for the thin-walled sweating cooling structure, by designing the sweating units arranged in an array and finely adjusting the length of the porous medium pressure control structure (7) in the pressure control layer (2) of each sweating unit, the sweating flow rate through each sweating unit can be made to match the heat flux density distribution on the surface of the aircraft.

[0028] The above are only the preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments, but also includes all technical solutions within the concept and scope of the present invention. For those of ordinary skill in the art, without departing from the principle of the present invention, improvements and refinements made to the above embodiments should also be regarded as within the protection scope of the present invention. The protection scope of the present invention is given by the appended claims and any equivalents thereof.

Claims

1. A thin-walled transpiration cooling structure, characterized in that: The transpiration cooling structure consists of a number of transpiration units arranged in an array. Each transpiration unit successively includes three parts from bottom to top: a flow distribution layer (1), a pressure control layer (2), and a porous transpiration surface (3). The flow distribution layer (1) internally contains a transpiration working fluid inlet (4) and a main flow channel (5) for distributing the flow rate. The transpiration working fluid inlet (4) and the main flow channel (5) are shared by the transpiration units arranged in an array. The pressure control layer (2) internally contains a branch flow channel (6) for distributing the flow rate, a porous medium pressure control structure (7), and a buffer zone (8). The branch flow channel (6) is connected to the main flow channel (5), and the porous medium pressure control structure (7) is arranged parallel to the transpiration wall surface. The porous transpiration surface (3) consists of a number of transpiration microholes (9) and a non-permeable solid wall surface (10). The number, size, and angle of the transpiration microholes (9) can be adjusted according to the requirements of flow regulation.

2. The thin-wall transpiration cooling structure according to claim 1, characterized in that: The porous medium material described above is made of sintered metal, sintered ceramic or photocuring resin, with a porosity not exceeding 0.20 and a permeability ranging from 1.0×10 -13 m 2 to 5.0×10 - 13 m 2 , which can meet the pressure control requirements of the pressure control layer with a functionally gradient structure.

3. The thin-wall transpiration cooling structure according to claim 1, wherein: The porous medium pressure control structure (7) is arranged parallel to the wall surface, so that the pressure drop characteristic of the transpiration structure does not depend on the thickness dimension of the porous medium pressure control structure (7) in the direction perpendicular to the wall surface. By adjusting the length of the porous medium pressure control structure (7), the pressure drop-flow rate relationship of the transpiration unit can be adjusted, so that the flow pressure drop in the porous medium region accounts for more than 95% of the pressure difference between the working fluid inlet and the ambient pressure.

4. A method for applying the thin-walled transpiration cooling structure according to claim 1, characterized in that: The thin-walled transpiration cooling structure is applied to the high-temperature regions of the aircraft, including the leading edge and the windward surface of the aircraft. A continuous gas film formed by the surface microhole array isolates the high-temperature oncoming flow, inhibits aerodynamic heating, and realizes active thermal protection. At the design stage of the transpiration cooling structure, after obtaining the aerodynamic heat distribution on the aircraft surface through numerical simulation, the preset configuration of the transpiration cooling structure is designed: ① By adjusting the length of the porous medium pressure control structure (7) of each transpiration unit, increasing the transpiration flow rate in the high-temperature region and decreasing the transpiration flow rate in the low-temperature region, the cost-effectiveness of the transpiration working fluid is improved on the premise of achieving reliable thermal protection; ② By changing the flow direction length dimension, span width dimension of the transpiration unit, and the geometric parameters of the transpiration microholes, the geometric parameters and layout scheme of the surface microhole array of the transpiration cooling structure are optimized, and the heat reduction and drag reduction benefits of the transpiration working fluid per unit mass are enhanced.

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