A porous material transpiration cooling leading edge structure and an aircraft

Abstract

The present invention discloses a porous material transpiration cooling leading edge structure, which includes multiple layers of porous material layers and a cooling cavity provided on one side of the multiple layers of porous material layers. A coolant supply channel is provided in the cooling cavity, and the coolant supply channel is used to supply coolant to the cooling cavity. The multiple layers of porous material layers include an outer layer, an intermediate layer, and an inner layer, and the material of the inner layer is a shape memory alloy porous material. The present invention can adaptively adjust the porosity of the porous material, automatically adjust the usage amount of the coolant, effectively improve the usage efficiency of the coolant, and further enhance the thermal protection effect in the high-temperature tip region. Moreover, the shape memory alloy material can be reused. The porous material transpiration cooling leading edge structure can be used for structures such as the nose cone of an aircraft, the leading edge of a rudder, and the leading edge of a wing that are subjected to more high-temperature heat fluxes.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft thermal protection, and specifically to a porous material transpiration cooling leading edge structure and an aircraft. Background Art

[0002] With the significant increase in the flight speed and cruise time of hypersonic aircraft, one of the most important challenges faced is extremely high thermal loads. In particular, parts such as the nose cone, rudder leading edge, and wing leading edge of the aircraft are subjected to strong compression and severe friction of the surrounding air, and are impacted and damaged by high-temperature hot airflows. The maximum heat flux can reach 20 - 30 MW / m 2 , and the surface temperature can reach over 3000°C at the highest. Therefore, developing an efficient and stable active thermal protection system is one of the key technologies to solve the problems in this field. The existing active thermal protection technologies mainly include: convective cooling, film cooling, transpiration cooling, and spray cooling. Among them, transpiration cooling has received extensive attention from researchers due to its excellent cooling effect.

[0003] For traditional transpiration cooling technology, due to shock wave interference and surface curvature effects, the surfaces in the tip regions such as the nose cone, rudder leading edge, and wing leading edge of the aircraft will be subjected to more high-temperature heat fluxes compared to other surfaces. Therefore, uneven distribution of thermal and mechanical loads occurs, resulting in insufficient coolant supply to the tip regions, and heat transfer deterioration phenomenon occurs, which greatly reduces the reliability of this technology.

[0004] Currently, the improvement method for this problem is to targetedly regulate the flow rate of the coolant in different regions by changing the transpiration cooling structure itself or filling pyrolyzable carbonized materials in the pores of the porous material. When improving by changing the transpiration cooling structure, corresponding structures need to be designed artificially, which not only has a complex structure design and high cost, but also when using filling materials for improvement, the filled pyrolyzable carbonized materials cannot be regenerated after preheating consumption, so they cannot be reused repeatedly, nor can the precise regulation of the coolant usage amount be achieved. Summary of the Invention

[0005] The purpose of the present invention is to provide a porous material transpiration cooling leading edge structure, which can adaptively adjust the porosity of the porous material according to the degree of exposure to high-temperature heat fluxes, and automatically adjust the usage amount of the coolant flowing into different regions, thereby effectively improving the efficiency of the coolant used, and further enhancing the thermal protection effect of the high-temperature tip region. Moreover, the shape memory alloy material can be reused.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0007] A porous material transpiration cooling leading edge structure, comprising multiple layers of porous material layers and a cooling cavity provided on one side of the multiple layers of porous material layers. A coolant supply channel is provided in the cooling cavity, and the coolant supply channel is used to supply coolant to the cooling cavity. The multiple layers of porous material layers include an outer layer, an intermediate layer, and an inner layer, and the material of the inner layer is a shape memory alloy porous material. For example, a nickel-titanium shape memory alloy porous material.

[0008] Preferably, the outer layer and the intermediate layer are made of the same material, and the materials of the outer layer and the intermediate layer are ceramics or stainless steel. The porosity of the porous material of the outer layer is greater than the porosity of the porous material of the intermediate layer, and the porosity of the porous material of the intermediate layer is greater than the porosity of the porous material of the inner layer. For example, in the initial state, the porosity of the porous material of the outer layer is 0.3, the porosity of the porous material of the intermediate layer is 0.2, and the porosity of the shape memory alloy porous material of the inner layer is 0.01.

[0009] Preferably, the leading edge structure is further provided with a diverter plate. The diverter plate is located in the cooling cavity, and the four peripheral edges of the diverter plate are hermetically connected to the inner wall of the cooling cavity. The diverter plate divides the cooling cavity into a front cavity of the cooling cavity and a rear cavity of the cooling cavity, and the diverter plate is densely provided with a plurality of impact holes.

[0010] Preferably, the plurality of impact holes are arranged in a circular pattern, and the aperture of the impact holes is on the order of millimeters.

[0011] Preferably, the coolant supply channel is tubular, and injection holes are provided on the tube wall of the coolant supply channel, and the aperture of the injection holes is on the order of millimeters.

[0012] Preferably, the injection holes are inclined from the inside to the outside along the traveling direction of the coolant in the supply channel.

[0013] An aircraft, comprising the porous material transpiration cooling leading edge structure described above.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The inner layer of the porous material layer of the leading edge structure of the present invention adopts a two-way nickel-titanium shape memory alloy porous structure material that shrinks when heated and expands when cooled. When subjected to an external high-temperature heat flux, it can adjust the coolant flow rate flowing into the porous material layer by adaptively changing the porosity of the material, effectively and accurately controlling the usage amount of the coolant, and solving the problems of uneven cooling in different parts of the leading edge structure, low cooling efficiency, and poor thermal protection effect existing in the prior art. It can further achieve uniform heat dissipation, making the thermal protection effect better and the cost lower. It also eliminates the trouble of artificially designing to change the transpiration cooling structure to adjust the coolant flow rate. Moreover, this shape memory alloy material can be reused.

[0016] 2. The inner layer, middle layer, and outer layer included in the porous material layer of the present invention have a porosity of the porous material in the outer layer greater than that in the middle layer, and a porosity of the porous material in the middle layer greater than that in the inner layer. Moreover, the porosity of the inner layer in the initial state is very small, which can effectively prevent unnecessary waste of the coolant.

[0017] 3. By providing a splitter plate in the leading-edge structure of the present invention, not only the strength of structures such as the nose cone, leading edge of the rudder, and leading edge of the wing is increased, but also the strength reduction caused by using a loose and porous medium is compensated. Moreover, the coolant ejected from the multiple impact holes densely distributed on the splitter plate cools the inner surface of the front cavity of the cooling chamber, further enhancing the thermal protection effect in the high-temperature tip region.

[0018] 4. In the leading-edge structure of the present invention, the coolant supply channel is provided with injection holes at a certain inclination angle. Before the coolant fills the cooling chamber, the coolant ejected from the injection holes jets to the inner surface of the rear cavity of the cooling chamber, achieving a certain temperature reduction effect. Description of the Drawings

[0019] Figure 1 It is a schematic structural diagram of a porous material transpiration cooling leading-edge structure described in the present invention;

[0020] Figure 2 It is a radial sectional view of the splitter plate in the present invention;

[0021] Figure 3 is Figure 1 an enlarged view of the splitter plate part in

[0022] Figure 4 It is a sectional view taken along the A-A section of the structure of the present invention;

[0023] Figure 5 is Figure 1 an enlarged view of the coolant supply channel part in

[0024] Figure 6 It is a schematic diagram of the self-adaptive activation state of the inner layer material of the present invention when subjected to a high-temperature oncoming flow;

[0025] Figure 7 It is a schematic diagram of the change process of the present invention from the initial state to the self-adaptive activation state.

[0026] Explanation of the reference numerals in the drawings:

[0027] 1. Inner layer; 2. Middle layer; 3. Outer layer; 4. Multilayer porous material layer; 5. Splitter plate; 6. Impact holes of the splitter plate; 7. Coolant supply channel; 8. Injection holes of the coolant supply channel; 9. Front cavity of the cooling chamber; 10. Rear cavity of the cooling chamber. Detailed Embodiments

[0028] The following further describes the invention in conjunction with the accompanying drawings:

[0029] In the description of the present invention, it should be noted that all directional indications (such as front, back, left, right, inside, outside, etc.) are based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0030] As Figure 1 shown, a porous material transpiration cooling leading edge structure includes a multi-layer porous material layer 4 with a layered gradient and a cooling cavity provided on one side of the multi-layer porous material layer 4. A diverter plate 5 is provided in the cooling cavity. The diverter plate 5 is provided at the arc end of the leading edge structure. The four peripheral edges of the diverter plate 5 are hermetically connected to the inner wall of the cooling cavity and are vertically arranged. Taking the vertical direction of the diverter plate 5 as the boundary, the multi-layer porous material layer 4 in the leading edge structure can be divided into a tip region and a gentle region. The multi-layer porous material layer 4 on the left side of the diverter plate 5 is the tip region, and the multi-layer porous material layer 4 on the right side of the diverter plate 5 is the gentle region. When a high-temperature heat flux hits, the tip region in the leading edge structure suffers more high-temperature heat flux than the gentle region. The diverter plate 5 divides the cooling cavity into a front cooling cavity 9 and a rear cooling cavity 10. The shape of the diverter plate 5 can adopt various plate-like shapes, for example, a circular plate-like shape or an elliptical plate-like shape. The setting of the position of the diverter plate 5 can ensure that the coolant can directly spray onto the inner wall surface of the front cooling cavity 9 through the impact holes 6, producing an impact cooling effect on the high-temperature wall surface. For example, when the diverter plate 5 is in a circular plate-like shape, the diverter plate 5 can be set such that the vertical distance from the inner wall surface at the top of the leading edge structure is 4 / 5 of the radius of the diverter plate. Setting the diverter plate 5 in the cooling cavity can also play a certain supporting role for the leading edge structure, not only increasing the strength of the leading edge structure, but also compensating for the weakening of strength caused by using a porous material medium.

[0031] A coolant supply channel 7 is also provided in the rear cooling cavity 10, and the coolant supply channel 7 is tubular. The coolant supply channel 7 is used to supply coolant to the cooling cavity. During the working process of the present invention, it can ensure that the coolant is continuously supplied under sufficient pressure conditions. The coolant can not only perform sufficient convective heat transfer with the solid skeleton in the dense pores, but also play a heat insulation role on the structure surface. The coolant can adopt a liquid that can absorb a large amount of heat and has good fluidity. For example, liquid water.

[0032] The porous material layer 4, starting from one side of the cooling cavity and extending outward, comprises an inner layer 1, an intermediate layer 2, and an outer layer 3. The intermediate layer 2 connects the inner layer 1 and the outer layer 3, and the intermediate layer can be a single layer or multiple layers. The outer layer 3, located at the outermost layer of the leading edge structure, becomes the directly heated layer, while the inner layer 1 forms the inner wall of the cooling cavity. The thickness of the inner layer 1 gradually increases from the tip of the leading edge structure to the flat area. This layered arrangement effectively improves cooling efficiency while saving costs.

[0033] The materials of the intermediate layer 2 and the outer layer 3 are both conventional porous materials of the same material. For example, high-temperature resistant ceramic or stainless steel. The material of the inner layer 1 is a porous material made of a memory alloy that has been trained to exhibit a full-range memory effect. For example, a nickel-titanium memory alloy porous material is manufactured by stacking two-way nickel-titanium memory alloy particles with negative thermal expansion properties. The nickel-titanium memory alloy has adaptive characteristics. The adaptive characteristics of this nickel-titanium memory alloy porous material are as follows: when the ambient temperature increases, the nickel-titanium memory alloy particles shrink, forming microchannels between the particles that can be used for coolant flow and heat exchange. Moreover, the higher the temperature, the more severe the particle contraction. However, when the temperature reaches a certain level, the nickel-titanium memory alloy stops contracting. When the temperature drops again and gradually approaches the initial state, the nickel-titanium memory alloy particles continue to expand as the temperature drops until the particles are completely fitted together without any gaps. Therefore, the particles of the nickel-titanium memory alloy porous material have the properties of shrinking at high temperatures and expanding at low temperatures.

[0034] Furthermore, the porosity of the porous material of the outer layer 3 is greater than that of the porous material of the middle layer 2, and the porosity of the porous material of the middle layer 2 is greater than that of the porous material of the inner layer 1. Taking into account both cooling efficiency and the total flow resistance encountered by the coolant flowing from the cooling cavity to the outermost layer 3, it can be determined that the porosity of the porous material of the outer layer 3 is 0.3, and the porosity of the porous material of the middle layer 2 is 0.2. Because the inner layer 1 utilizes a porous nickel-titanium shape memory alloy, its porosity is determined and adjusted by the external heat flow. Therefore, the porosity of the inner layer 1 varies under different external heat flow conditions.

[0035] During the convective heat exchange between the multi-layer porous material layer 4 and the coolant in the cooling cavity, in the initial state, that is, when the high temperature of the external heat flow has not reached the value that causes the nickel-titanium memory alloy porous material particles to shrink, the porosity of the memory alloy porous material structure of the inner layer 1 is 0.01. It can be seen that the porosity of the porous material of the inner layer 1 is very small compared to the porosity of the porous materials of the outer layer 3 and the middle layer 2. Therefore, the coolant can be prevented from leaking out in the external environment state where the coolant is not needed (that is, in the initial state), causing unnecessary waste.

[0036] In contrast, as Figure 6 shown, when the high temperature degree of the external heat flux exceeds the particle shrinkage value of the NiTi shape memory alloy porous material, the NiTi shape memory alloy material particles in the high heat region (i.e., the tip region) that receive more heat flux highly shrink (this state is the self - adaptive activation state), forming a larger porosity. However, the porosity of the inner layer 1, that is, the NiTi shape memory alloy porous material, will not exceed the porosity of the porous material of the middle layer 2 at this time. Therefore, the high heat region can obtain more coolant supply from the cooling cavity, and thus the coolant can convectively exchange heat by passing through the inner layer 1, the middle layer 2, and the outer layer 3 in sequence. Finally, the coolant overflowing from the outer layer 3 wraps the directly heated surface of the leading edge structure to form a film (for example, a liquid film), which plays a heat insulation role. Thereby, it can further make the heated surface exchange heat evenly, which is beneficial to maintaining the constant temperature of the leading edge structure. Compared with this high heat region (i.e., the tip region), the shrinkage degree of the NiTi shape memory alloy porous material particles in the low heat region (i.e., the gentle region) that receive less external high - temperature heat flux is slower. Therefore, the porosity of the NiTi shape memory alloy material in the low heat region is smaller than that of the NiTi shape memory alloy material in the high heat region, and correspondingly less coolant flows into this low heat region. However, the overflowing coolant can also form a film.

[0037] When the external environmental temperature where the leading edge structure is located decreases again and gradually approaches the initial state, the NiTi shape memory alloy particles continue to expand as the temperature drops until there is no gap between the particles. The porosity of the porous material of the inner layer 1 also returns to 0.01 in the initial state. At this time, it can prevent the leakage of the coolant, thereby being able to automatically adjust the usage content of the coolant. Figure 7 It precisely shows the process in which the particles of the NiTi shape memory alloy porous material in the inner layer 1 change from the initial state to the self - adaptive activation state when the tip region of the leading edge structure of the present invention is heated.

[0038] Therefore, such a transpiration cooling structure adaptively adjusts the porosity for the external high - temperature heat flux, thereby dynamically adjusting the flow rate of the coolant entering different regions (the high heat region and the low heat region), ensuring that the high - temperature region receiving more heat flux can obtain more coolant and thus achieving a better thermal protection effect and improving the cooling efficiency. Moreover, such a hierarchical stepped porosity setting can, to a certain extent, control and optimize the usage amount of the coolant in the transpiration cooling system, avoid unnecessary waste, and improve the usage efficiency of the coolant. And when the next high - temperature heat flux comes, the NiTi shape memory alloy material in the inner layer 1 can play the same role again. Therefore, compared with filling the pores of the porous material with a thermally decomposable carbonized material that can only be used once to adjust the coolant flow rate, the shape memory alloy material can be reused, which also reduces the cost.

[0039] As Figure 2 and3 As shown, the flow splitter 5 is densely provided with a plurality of impact holes 6, and the impact holes 6 penetrate through the plate surface of the flow splitter 5. Moreover, the apertures of the plurality of impact holes 6 are the same. The impact holes 6 can be arranged in a ring shape, that is, formed into annular impact holes 6. The impact holes 6 arranged in a ring shape are evenly distributed on circumferences with different radii centered on the center of the flow splitter 5. Moreover, a hole is also provided at the center of the flow splitter 5. The apertures of the plurality of impact holes 6 are of millimeter order. This design enables the coolant to be ejected from the rear cavity 10 of the cooling cavity through the impact holes 6 on the flow splitter 5 under the action of pressure, and sprayed on the inner surface of the front cavity 9 of the cooling cavity, achieving a certain temperature reduction effect. This can further enhance the thermal protection effect of the leading edge body tip region before the front cavity 9 of the cooling cavity is filled.

[0040] As Figure 4 shown, on the tube wall of the coolant supply channel 7, there are oriented injection holes 8, and the aperture of the injection holes 8 is of millimeter order. The injection holes 8 are arranged on the tube wall of the coolant supply channel 7, and the injection holes 8 are arranged in a ring shape on the tube wall. For example, on the tube wall surface, there are multiple groups of injection holes 8 distributed along the axial direction of the tube, each group having a plurality of injection holes 8, and the plurality of injection holes 8 in each group are circumferentially arranged in a ring shape on the tube. When the coolant with a certain pressure flows through the coolant supply channel 7, due to the very fine aperture of the injection holes 8, the coolant is sprayed onto the inner surface of the rear cavity 10 of the cooling cavity through the injection holes 8. Before the coolant flowing through the coolant supply channel 7 fills the rear cavity 10 of the cooling cavity, the coolant jets from the injection holes 8 onto the shape memory alloy porous material of the inner layer 1, making the gentle area reach a certain temperature reduction effect. This design can uniformly spray the coolant onto the inner surface of the rear cavity 10 of the cooling cavity in all directions at the initial stage of coolant supply, forming an impact cooling effect in a short time.

[0041] As Figure 5 shown, the injection holes 8 arranged on the tube wall of the coolant supply channel 7 are inclined from the inside to the outside along the advancing direction of the coolant in the supply channel 7. This inclined setting can ensure that the coolant is ejected from the impact holes 8 and vertically sprayed onto the inner surface of the rear cavity 10 of the cooling cavity. Moreover, one end of the coolant supply channel 7 in the cooling cavity is close to the flow splitter and has a certain distance from the flow splitter, so as to ensure that the coolant ejected through the injection holes 8 on the coolant supply channel 7 can evenly reach the inner surface of the rear cavity 10 of the cooling cavity close to the flow splitter 5. Moreover, it can also ensure that the coolant ejected through the coolant supply channel 7 can reach and pass through the impact holes 6 of the flow splitter 5 and be sprayed on the inner wall surface of the front cavity 9 of the cooling cavity.

[0042] The working principle of the coolant is as follows:

[0043] After the coolant is sprayed through the coolant supply channel 7, under the pressure of the coolant incoming flow, part of the coolant can directly spray onto the inner wall surface of the front wall 9 of the cooling cavity through the impact holes 6 of the splitter plate 5, enhancing the cooling capacity of the leading edge tip region. The remaining part of the coolant that fails to pass through the impact holes 6 continuously flows into the rear cavity 10 of the cooling cavity, gradually filling the rear cavity 10 of the cooling cavity, causing the pressure in the rear cavity 10 of the cooling cavity to gradually increase, resulting in the pressure in the rear cavity 10 of the cooling cavity being greater than the pressure in the front cavity 9 of the cooling cavity. Under the pressure generated thereby, the coolant in the rear cavity 10 of the cooling cavity sprays out through the impact holes 6 on the splitter plate 5. Part of the coolant sprays onto the inner wall surface of the front cavity 9 of the cooling cavity, and the remaining part of the coolant will finally flow into the front cavity 9 of the cooling cavity.

[0044] After the coolant fills the cooling cavity, the coolant in the cooling cavity, under the action of the pressure in the cooling cavity, sequentially passes through the inner layer 1, the intermediate layer 2, and the outer layer 3 to perform sufficient fluid-solid heat exchange, and the jet disturbance enhances the heat exchange intensity between the coolant and the multi-layer porous material layer 4.

[0045] Moreover, the coolant continuously overflows from the pores of the heated porous material like sweat, forming a relatively uniform heat insulation film (for example, a liquid film) on the outer surface of the outer layer 3 (that is, on the surface of the aircraft) to wrap the heated surface of the leading edge body, which can increase the boundary layer thickness. Thus, it not only plays a heat insulation role but also reduces the wall friction resistance, further overcomes the defect that the local overheating of the porous material sweating cooling is prone to heat transfer deterioration, and further realizes the effects of uniform heat dissipation and good thermal protection effect.

[0046] Generally in an aircraft, the thermal environment at the top of the leading edge body such as the nose cone, the leading edge of the rudder, and the leading edge of the wing is more severe, and it bears more intense thermal and mechanical loads. Therefore, the above-mentioned porous material sweating cooling leading edge structure can be adopted.

[0047] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A porous material transpiration cooling leading edge structure, characterized in that: It includes a multi-layer porous material layer (4) and a cooling cavity provided on one side of the multi-layer porous material layer (4). A coolant supply channel (7) is provided in the cooling cavity. The coolant supply channel (7) is used to supply coolant to the cooling cavity. The multi-layer porous material layer (4) includes an outer layer (3), an intermediate layer (2), and an inner layer (1). The material of the inner layer (1) is a shape memory alloy porous material. The shape memory alloy porous material uses a nickel-titanium shape memory alloy porous material. The leading edge structure is further provided with a splitter plate (5). The splitter plate (5) is located in the cooling cavity. The four peripheral edges of the splitter plate (5) are hermetically connected to the inner wall of the cooling cavity. The splitter plate (5) divides the cooling cavity into a front cooling cavity (9) and a rear cooling cavity (10). The splitter plate (5) is densely provided with a plurality of impact holes (6).

2. The porous material transpiration cooling leading edge structure according to claim 1, characterized in that: The outer layer (3) and the intermediate layer (2) are made of the same material. The materials of the outer layer (3) and the intermediate layer (2) are ceramics or stainless steel. The porosity of the porous material of the outer layer (3) is greater than the porosity of the porous material of the intermediate layer (2). The porosity of the porous material of the intermediate layer (2) is greater than the porosity of the porous material of the inner layer (1).

3. A porous material transpiration cooling leading edge structure according to claim 2, characterized in that: The porosity of the porous material of the outer layer (3) is 0.3, and the porosity of the porous material of the intermediate layer (2) is 0.

2.

4. The porous material transpiration cooling leading edge structure according to claim 3, characterized in that: In the initial state, the porosity of the shape memory alloy porous material of the inner layer (1) is 0.

01.

5. A porous material sweating cooling leading edge structure according to claim 1, characterized in that: The plurality of impact holes (6) are arranged in a circular pattern, and the aperture of the impact holes (6) is on the order of millimeters.

6. A porous material sweating-cooling leading edge structure according to claim 1, characterized in that: The coolant supply channel (7) is tubular. Injection holes (8) are provided on the tube wall of the coolant supply channel (7), and the aperture of the injection holes (8) is on the order of millimeters.

7. A porous material sweating-cooling leading edge structure according to claim 6, characterized in that: The injection holes (8) are inclined from the inside to the outside along the direction of the coolant traveling in the supply channel (7).

8. An aircraft, characterized in that: It includes a porous material transpiration cooling leading edge structure according to any one of claims 1 to 7.

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