A transpiration cooling leading edge thermal protection structure coupled with steam reverse injection

Abstract

The present invention discloses a sweat-cooled leading edge thermal protection structure coupled with reverse steam injection, which belongs to the field of aircraft thermal protection technology, and includes a nose cone leading edge body, wherein the nose cone leading edge body includes a porous end cap, a cooling cavity, a front connecting pipe, a rear connecting pipe, an impermeable solid wall, a water injection pipeline, an internal cooling flow channel, a vapor-liquid separator, a front cooling pipe, a one-way throttle valve, a steam ejector and a reverse steam nozzle. The present invention uses liquid water to sweat-cool the leading edge non-stagnation area, and performs thermal protection on the stagnation area in the form of reverse steam injection. Under the protection of a double air film, uniform and efficient cooling of the stagnation and non-stagnation areas is achieved, effectively avoiding steam blockage and heat transfer deterioration in the stagnation area when the two areas sweat uniformly, as well as cooling transition in the non-stagnation area. The reverse steam injection can further push the bow shock wave of the leading edge away from the surface of the structure, reduce the aerodynamic pressure on the outer surface of the structure, and reduce the flow resistance of the liquid sweat-cooling medium.

Description

Technical Field

[0001] The present invention relates to the technical field of hypersonic vehicle thermal protection, and in particular to a transpiring cooling leading edge thermal protection structure coupled with reverse steam injection. Background Art

[0002] Hypersonic vehicle design needs to alleviate the high heat flux problem caused by gas viscosity. Figure 4 As shown in Figure 1, during the reentry of the aircraft, the aerodynamic force and aerodynamic heat in the stagnation area of ​​the sharp leading edge structures such as the nose cone and the wing leading edge are the strongest, and may need to withstand extremely high heat flux density exceeding 10MW / m2. In order to ensure the integrity of the aircraft's aerodynamic shape, advanced active thermal protection technology must be used. One of the candidate technologies that can be locally applied to these areas is sweat cooling.

[0003] The sweating cooling thermal protection structure uses an active supply system to spray the working fluid stored in the aircraft through the porous structure into the heated area under pressure, thereby reducing the surface temperature of the structure and forming a boundary layer thermal blocking effect. Liquid cooling working fluid has a larger specific heat capacity and can absorb a large amount of latent heat of phase change during the cooling process, so it has a stronger cooling capacity. However, when sweating cooling using liquid cooling working fluid as the cooling working fluid encounters local overheating, the proportion of steam in the porous structure of the corresponding area is higher than that of other low-heat areas. Since the flow resistance of the same working fluid in the gas state is much greater than that in the liquid state, the cooling working fluid in the porous structure tends to flow to the low-heat area with smaller flow resistance, and the sweating flow in the local overheating area will be reduced, which will cause excessive accumulation of steam inside the porous structure, resulting in the expansion and deterioration of the local overheating area. Therefore, the use of traditional single sweating cooling system at sharp leading edges such as nose cones and wing leading edges has the following problems:

[0004] (i) The spatial distribution of aerodynamic heat / force on the leading edge structure surface is extremely uneven. The aerodynamic heat / force borne by the stagnation area is much greater than that of the downstream structure. Single sweating cooling cannot "sweat" at the stagnation point position and "over-cools" downstream. The cooling effect is extremely uneven and the structural thermal stress is significant. At the same time, due to the large amount of waste of cooling medium heat sink, the aircraft needs to carry more cooling medium, resulting in a reduction in the effective load that can be carried;

[0005] (ii) Liquid coolant needs to be driven by a high-pressure injection system such as a pump to flow out of the leading edge porous structure. Limited by the internal space and weight requirements of the aircraft, a single sweat cooling system has limitations in adjusting the injection parameters to cope with the changing heat load. It is difficult to achieve precise control of the cooling medium flow rate and the external heat load in different regions, and it is difficult to achieve uniform cooling effect over a large area.

[0006] (III) When the liquid coolant undergoes a drastic phase change inside a porous structure that is heated non-uniformly, the steam blocking effect causes the phase change position and the structural temperature to fluctuate continuously. The coolant pressure simultaneously shows sharp peaks. The structural temperature oscillation can easily cause thermal fatigue failure inside the material. The sudden rise and fall in pressure makes it difficult for the control module to adjust the coolant flow rate in time to cope with the rapidly changing heat load. Based on this, a sweat cooling leading edge thermal protection structure coupled with steam reverse injection is proposed. Summary of the invention

[0007] The purpose of the present invention is to solve the problems in the prior art, and a sweat cooling leading edge thermal protection structure coupled with steam reverse injection is proposed. The proposed sweat cooling structure coupled with steam reverse injection realizes the directional utilization of the cooling medium heat sink and the zoning control of the stagnation area and non-stagnation area, and has high stability, good uniformity, flexible control and high reliability.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A sweat-cooling leading edge thermal protection structure coupled with steam reverse injection, comprising a nose cone leading edge body, wherein the nose cone leading edge body comprises a porous end cap, a cooling cavity, a front connecting pipe, a rear connecting pipe, an impermeable solid wall, a water injection pipeline, an inner cooling flow channel, a vapor-liquid separator, a front cooling pipe, a one-way throttle valve, a steam ejector and a reverse steam nozzle;

[0010] The porous end cap is located at the end of the impermeable solid wall and is sealedly connected to the impermeable solid wall to form a nose cone leading edge body shell;

[0011] A water injection pipeline, an internal cooling channel and a vapor-liquid separator are sequentially installed inside the nose cone leading edge body;

[0012] The inner cooling channel and the inlet of the vapor-liquid separator are connected by a closed straight plate and a rear connecting pipe;

[0013] The steam outlet of the steam-liquid separator and the reverse steam nozzle of the porous end cap are connected to the steam ejector via a front connecting pipe;

[0014] The liquid working medium outlet of the vapor-liquid separator is connected to the cooling chamber by a closed straight plate and a front cooling pipe, and is located radially inside the impermeable solid wall.

[0015] Preferably, the water injection pipeline adopts a split-flow design to evenly transport the liquid cooling medium to the inner cooling channel through a bypass branch pipe.

[0016] Preferably, the inner cooling channel is connected to the water injection pipeline via three bypass branches.

[0017] Preferably, a one-way throttle valve for controlling the outflow speed of steam is installed in the front connecting pipe, so that steam is only allowed to pass in a directional manner.

[0018] Preferably, one end of the inner cooling channel is connected to the water injection pipeline, and the other end is connected to the rear connecting pipe, and the other end of the rear connecting pipe is connected to the vapor-liquid separator.

[0019] Preferably, the one-way throttle valve is installed on the front connecting pipe to control the steam outflow speed and only allow the steam to penetrate in a directional manner.

[0020] Preferably, the wall thickness of the inner cooling channel and the water injection pipe is mm, the wall thickness of the connecting pipe is mm, and the water injection pipe, front connecting pipe, steam ejector, rear connecting pipe and reverse steam nozzle are coaxially distributed with the entire leading edge structure.

[0021] Preferably, the material of the porous end cap is a lightweight ceramic-based composite material.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. For the extremely uneven heat load faced by the sharp leading edge of the aircraft, the present invention uses liquid water to perform sweat cooling on the non-stagnation area of ​​the leading edge, and at the same time performs thermal protection on the stagnation area by reverse steam injection. Under the protection of the double air film, uniform and efficient cooling of the stagnation and non-stagnation areas is achieved, effectively avoiding steam blockage and heat transfer deterioration in the stagnation area when the two areas sweat uniformly, and excessive cooling of the non-stagnation area.

[0024] 2. The cooling medium fully absorbs heat in the inner cold flow channel until a partial phase change occurs. After the vapor-liquid separation, the liquid part further absorbs heat in the porous structure of the leading edge non-stagnation point area until a full phase change occurs. The saturated steam part is transported to the stagnation point reverse nozzle. The steam flowing out of the stagnation point area and the non-stagnation point area forms a double air film, which continues to absorb the aerodynamic heat of the boundary layer to insulate the structure. Therefore, compared with the direct outflow and overcooling of the liquid medium in the non-stagnation point area when the two areas sweat uniformly, the entire latent heat and sensible heat of the cooling medium in the present invention are fully and efficiently utilized, greatly saving the amount of cooling medium.

[0025] 3. Independent thermal control is performed on the stagnation point area on the leading edge structure that bears the highest aerodynamic heat / force load and the non-stagnation point area where the aerodynamic heat / force load is low and changes smoothly. This avoids the structural temperature oscillation and sudden rise and fall of the cooling fluid pressure caused by uneven heat load when the two areas sweat at the same time, enhances the stability of the entire thermal protection system, and avoids thermal fatigue failure inside the material.

[0026] 4. The reverse injection of steam can push the bow shock wave at the leading edge further away from the surface of the structure, reduce the aerodynamic pressure on the outer surface of the sweating structure, reduce the flow resistance of the liquid sweating cooling medium, and thus reduce the injection pressure of the system, saving system energy consumption, and making the injection system design more flexible.

[0027] 5. The design of the cooling medium injection pipeline adopts branched injection to ensure the uniform delivery of the cooling medium. At the same time, efficient impact cooling is formed in the local area of ​​each branch pipe, which improves the turbulence of the fluid in the inner cold channel, thereby maximizing the heat sink utilization of the cooling medium and increasing steam production. The two-phase mixed cooling medium in the tube has a stronger convective heat transfer capacity than the single-phase fluid, which can effectively cool the large area of ​​non-permeable wall downstream of the non-stagnation area, and evenly maintain the temperature of the cold channel near the boiling point of the cooling medium to protect the internal equipment.

[0028] 6. Since the entire leading edge structure of the aircraft is divided into three areas: the stagnation area for reverse steam injection, the non-stagnation area for liquid working fluid sweating, and the downstream large area for internal impact convection, the division of the three areas greatly reduces the difficulty of processing and the flexibility of material selection, avoiding the difficulty of integrated processing of micropores and complex flow channels. Each partition can also flexibly select the most suitable lightweight material, effectively reducing the weight of the entire thermal protection system and achieving the goal of lightweighting.

[0029] 7. Steam can achieve two-stage physical pressurization through the steam ejector and conical nozzle design, effectively increasing the pressure energy of the fluid, thereby saving the energy consumption of the injection system and achieving higher energy utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the three-dimensional structure of a sweat-cooling leading edge heat protection structure coupled with reverse steam injection proposed by the present invention;

[0031] Figure 2 A front view of a transpiring cooling leading edge thermal protection structure coupled with reverse steam injection proposed by the present invention;

[0032] Figure 3 A cross-sectional view of a transpiring cooling leading edge heat protection structure coupled with reverse steam injection proposed by the present invention;

[0033] Figure 4 It is a schematic diagram of the sweat-generating cooling thermal protection structure of the prior art.

[0034] In the figure: 1. porous end cap; 2. cooling chamber; 3. front connecting pipe; 4. rear connecting pipe; 5. impermeable solid wall; 6. water injection pipe; 7. internal cooling channel; 8. vapor-liquid separator; 9. front cooling pipe; 10. one-way throttle valve; 11. steam ejector; 12. reverse steam nozzle. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] Example, see Figures 1 to 3 , a sweat-cooling leading edge thermal protection structure coupled with steam reverse injection, comprising a nose cone leading edge body, the nose cone leading edge body comprising a porous end cap 1, a cooling cavity 2, a front connecting pipe 3, a rear connecting pipe 4, an impermeable solid wall 5, a water injection pipeline 6, an inner cooling flow channel 7, a vapor-liquid separator 8, a front cooling pipe 9, a one-way throttle valve 10, a steam ejector 11 and a reverse steam nozzle 12;

[0039] The porous end cap 1 is located at the end of the impermeable solid wall 5 and is sealed and connected to the impermeable solid wall 5 in the form of welding to form a rotating body head cone structure. A water injection pipe 6 is fixedly connected to the rear of the front edge of the head cone. The liquid cooling medium is injected into the inner cooling channel 7 through the three internal bypass branches through the water injection pipe 6; the length of the inner cooling channel 7 is 75 mm.

[0040] The porous end cap 1 is tangentially connected to the impermeable solid wall 5, and the central angle of the corresponding cross-section circle of the porous end cap 1 is 164°. The material of the sweat-cooled porous end cap 1 is a lightweight ceramic-based composite material, and the radius of the inner arc surface and the radius of the outer arc surface are 20 mm and 30 mm respectively;

[0041] The material of the impermeable solid wall 5 is 7055 aluminum alloy, the semi-cone angle of the entire leading edge structure is 8°, and the water injection pipeline 6 adopts a split-flow design to evenly transport the liquid cooling medium to the inner cooling channel 7 through five bypass branches.

[0042] The inner cooling channel 7 is connected to the inlet of the vapor-liquid separator 8 by a closed straight plate and the rear connecting pipe 4, and the steam outlet of the vapor-liquid separator 8 is connected to the stagnation point reverse steam nozzle 12 of the porous end cap 1 by the front connecting pipe 3 and the steam ejector 11. A one-way throttle valve 10 for controlling the steam outflow speed is installed in the front connecting pipe 3, and only directional steam permeation is allowed. The one-way throttle valve 10 is a straight-through throttle valve; the vapor-liquid separator 8 is a cyclonic vapor-liquid separator, and the liquid working medium outlet of the vapor-liquid separator 8 is connected to the cooling chamber 2 by a closed straight plate and a front cooling pipe 9; the height of the inner cooling channel is 10mm, and it is located on the radial inner side of the impermeable solid wall 5; the wall thickness of the inner cooling channel and the water injection pipe is 2mm, and the wall thickness of the connecting pipe is 1mm. The water injection pipe 6, the front connecting pipe 3, the steam ejector 11, the rear connecting pipe 4, and the reverse steam nozzle 12 are coaxially distributed with the entire leading edge structure;

[0043] When the liquid water is heated to the boiling point in the inner cooling channel 7, the water-vapor mixture moves forward into the vapor-liquid separator 8. The separated dry saturated steam is accelerated by the one-way throttle valve 10, the steam ejector 11 and the reverse steam nozzle 12 and ejected from the stagnation point, forming an air film covering the surface of the structure. The liquid water is transported to the cooling cavity 2, flows through the porous material for heat exchange, and forms a secondary air film on the surface of the structure.

[0044] While the cooling medium water flows out, the water injection pipeline continuously replenishes the inner cooling channel 6 to ensure that the cooling medium water in the inner cooling channel 7 is sufficient.

[0045] The cooling medium is a liquid cooling medium, preferably water; the reverse steam nozzle 12 is a conical nozzle;

[0046] Among them, it is worth noting that the porous material of the porous end cap 1 can be obtained by using different existing processing techniques, such as traditional powder sintering and molding, or new centrifugal deposition technology, wet spraying and brushing, 3D printing technology, selective laser sintering and powder injection molding technology, etc.

[0047] This solution can adjust the length of the sweating surface, the downstream impermeable solid wall and the internal cooling channel according to the reserved space of the reentry vehicle and the specific cooling requirements of the actual working conditions.

[0048] Working principle: During the flight of a hypersonic vehicle, driven by pressure, the liquid cooling medium is injected into the inner cooling channel 7 through the water injection pipeline 6 for forced convection heat exchange. Part of the liquid cooling medium is heated to the boiling point, and the resulting two-phase mixed medium moves to the vapor-liquid separator 8. The separated dry saturated steam is further pressurized by the steam ejector 11 and then ejected from the stagnation point at high speed by the reverse steam nozzle 12. At the same time, the liquid medium flows into the porous end cap 1 through the cooling chamber 2 for sweat cooling.

[0049] When the cooling medium flows through the porous structure, it uses the dense micropores inside to carry out sufficient convective heat exchange, thereby reducing the temperature of the porous end cap. After flowing out of the porous structure, the cooling medium enters the high-temperature mainstream and converges with the air film layer formed by the steam ejected from the stagnation area, forming a double air film covering layer on the outer surface of the leading edge structure, thereby isolating the entire leading edge structure from the high-temperature heat flow.

[0050] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A sweat-cooling leading edge thermal protection structure coupled with reverse steam injection, characterized in that: The invention comprises a nose cone leading edge body, wherein the nose cone leading edge body comprises a porous end cap (1), a cooling cavity (2), a front connecting pipe (3), a rear connecting pipe (4), an impermeable solid wall (5), a water injection pipe (6), an internal cooling channel (7), a vapor-liquid separator (8), a front cooling pipe (9), a one-way throttle valve (10), a steam ejector (11) and a reverse steam nozzle (12); The porous end cap (1) is located at the end of the impermeable solid wall (5) and is sealedly connected to the impermeable solid wall (5) to form a nose cone front edge body shell; A water injection pipeline (6), an internal cooling channel (7) and a vapor-liquid separator (8) are sequentially installed inside the nose cone leading edge body; The inner cooling channel (7) and the inlet of the vapor-liquid separator (8) are connected to the rear connecting pipe (4) via a closed straight plate; The steam outlet of the steam-liquid separator (8) and the reverse steam nozzle (12) of the porous end cap (1) are connected to the steam ejector (11) via a front connecting pipe (3); The liquid working medium outlet of the vapor-liquid separator (8) is connected to the cooling chamber (2) by a closed straight plate and a front cooling pipe (9), and is located radially inside the impermeable solid wall (5).

2. The sweat-cooling leading edge thermal protection structure coupled with steam reverse injection according to claim 1 is characterized in that: The water injection pipeline (6) adopts a split-flow design and evenly transports the liquid cooling medium to the inner cooling channel (7) through five bypass branches.

3. The sweat-cooling leading edge thermal protection structure coupled with steam reverse injection according to claim 1 is characterized in that: The inner cooling channel (7) is connected to the water injection pipeline (6) via three bypass branches.

4. The sweat-cooling leading edge thermal protection structure coupled with steam reverse injection according to claim 1 is characterized in that: A one-way throttle valve (10) for controlling the outflow speed of steam is installed in the front connecting pipe (3), allowing steam to pass only in a directional manner.

5. The sweat-cooling leading edge thermal protection structure coupled with steam reverse injection according to claim 1 is characterized in that: One end of the inner cooling channel (7) is connected to the water injection pipeline (6), and the other end is connected to the rear connecting pipe (4), and the other end of the rear connecting pipe (4) is connected to the vapor-liquid separator (8).

6. The sweat-cooling leading edge thermal protection structure coupled with steam reverse injection according to claim 1 is characterized in that: The one-way throttle valve (10) is installed on the front connecting pipe (3) and is used to control the steam outflow speed and only allow the steam to flow out in a directional manner.

7. The sweat-cooling leading edge thermal protection structure coupled with steam reverse injection according to claim 1 is characterized in that: The wall thickness of the inner cooling channel (7) and the water injection pipe (6) is 2 mm, and the wall thickness of the connecting pipe is 1 mm. The water injection pipe (6), the front connecting pipe (3), the steam ejector (11), the rear connecting pipe (4) and the reverse steam nozzle (12) are coaxially distributed with the entire leading edge structure.

8. The sweat-cooling leading edge thermal protection structure coupled with steam reverse injection according to claim 1 is characterized in that: The material of the porous end cap (1) is specifically a lightweight ceramic-based composite material.

Images