Sharp-wedge-shaped small-channel thermally-driven gas-liquid phase change heat dredging device

Abstract

The invention discloses a sharp-wedge-shaped small-channel thermally-driven gas-liquid phase change heat dredging device which comprises two symmetrical half base bodies which are integrally formed into a sharp wedge shape through high-temperature-resistant alloy, the interiors of the two symmetrical half base bodies are each provided with a vacuumized ratchet wheel channel loop partially filled with high-temperature melting point alkali metal, and the two channel loops are independent of each other. The ratchet channel loop is formed by sequentially connecting a plurality of groups of ratchet channels which are alternated in size and parallel to one another end to end in series; every two adjacent channels of the ratchet wheel channel loop are based on two middle channels with different widths, and asymmetrical obtuse triangle grooves are periodically distributed in the two side wall faces to form an asymmetrical expansion and contraction structure; the bottom wall face and the top wall face of the ratchet wheel channel loop are each provided with a tiny groove. Compared with an existing heat dredging device, the high-temperature heat dredging device has higher high-temperature heat dredging efficiency, limit heat dredging capacity and load adaptability, is simple in structure and reliable in work, and can provide important support for progress of the dredging type heat protection technology of the hypersonic flight vehicle.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hypersonic vehicle thermal protection, and particularly relates to a sharp wedge type small channel thermal driven gas-liquid phase change heat dissipation device. BACKGROUND

[0002] A hypersonic vehicle is an aircraft flying at high speed in the atmosphere or near space, and its flight speed is usually above 5 Mach (Ma). The hypersonic vehicle has the characteristics of high-speed cruising, high penetration and high maneuverability. When flying at high speed in the air, the surface of the hypersonic vehicle (especially the nose cone and wing leading edge) will withstand severe aerodynamic heating, thereby causing a "thermal barrier" problem, resulting in deformation of the aircraft shape due to high temperature, and even ablation and damage. When the new generation of cruise vehicles fly at the highest flight speed (>25Ma), the maximum flight overload exceeds 15g0, and the flight time reaches the order of 104s, making the "thermal barrier" problem more prominent (the local stagnation heat flux of the nose cone, wing leading edge and the like can be above 10MW / m2).

[0003] At present, the thermal protection technology under extreme conditions mainly includes passive, active and semi-active thermal protection. The passive thermal protection technology is simple in structure and reliable in operation, but the thermal protection efficiency is low and the heat absorption threshold is small. The active thermal protection technology uses a working medium or cooling flow to carry away most of the heat, and has strong heat dissipation capacity and good controllability, but it often needs a complex pumping and control system to drive and control the transport of the cooling medium, and has a large self-weight and poor operation reliability. The semi-active thermal protection is between passive and active thermal protection technologies, and includes ablation thermal protection and dissipation type thermal protection. The ablation thermal protection absorbs and carries away a large amount of heat by ablation of the ablation material at high temperature, although the thermal protection efficiency is high, but the thermal protection performance is limited by the environment, and the aerodynamic performance is easily affected by the change of mass and shape; compared with the ablation thermal protection, the dissipation type thermal protection is a kind of semi-active thermal protection technology with great potential, which introduces a heat dissipation layer between the surface layer and the heat insulation layer of the traditional multilayer composite passive thermal protection structure, and efficiently dissipates the heat of the severely heated region (such as the nose cone and wing leading edge of the hypersonic vehicle) to the low heat flux area for dissipation, thereby effectively reducing the heat accumulation and temperature level of the high heat flux density area, significantly increasing the effective heat exchange area, and having the characteristics of compact structure, small self-weight and high reliability.

[0004] The heat dissipation layer can efficiently dissipate heat and is the core of the heat dissipation type heat protection technology. Compared with high-temperature-resistant materials with high thermal conductivity (such as diamond and graphite-based composite materials), the high-temperature self-driven phase change heat transfer device relying on the internal gas-liquid phase change circulation heat transfer has more excellent heat dissipation performance, and becomes the preferred technical scheme of the heat dissipation layer structure of the heat dissipation type heat protection technology. However, the existing high-temperature self-driven phase change heat transfer device generally relies on the liquid absorption core structure to maintain the self-circulation phase change heat transfer process of the internal working medium (such as high-temperature capillary core heat pipe and high-temperature capillary vapor cavity), which significantly affects the additional mass force generated by the overloading / variable loading operation of the aircraft, and then causes the heat transfer performance of the heat dissipation device to fluctuate significantly, and even causes functional failure, which seriously weakens the reliability of the heat protection system. SUMMARY

[0005] The application provides a sharp wedge type small channel heat-driven gas-liquid phase change heat dissipation device, which is suitable for working in an extremely high temperature range of 500-1500 DEG C and provides a self-driven high-temperature heat dissipation means with high heat dissipation efficiency, strong load adaptability, simple structure and reliable operation for high-speed aircraft heat protection.

[0006] The sharp wedge type small channel heat-driven gas-liquid phase change heat dissipation device comprises a substrate, a plurality of ratchet channel loops are arranged in the substrate, and a working medium is filled in the ratchet channel loops.

[0007] Preferably, each sawtooth-shaped groove of the middle channel is connected in sequence by a plurality of triangular grooves, two triangular grooves symmetrically arranged on the two sides and a part of the middle channel between the two triangular grooves jointly form an expansion and contraction unit, each triangular groove forms a long side and a short side of the recess, and the connecting line between the two end points of the long side and the short side away from each other forms two side lines of the middle channel, and the two side lines are parallel.

[0008] Preferably, the convergence angle a of the triangular groove is 15-20 DEG, the divergence angle β is 35-45 DEG, the convergence angle a is the included angle between the long side and the side line, the divergence angle β is the included angle between the short side and the side line, each ratchet channel unit is an asymmetric expansion and contraction unit, the asymmetric expansion and contraction unit comprises an expansion section and a contraction section, the total length of the asymmetric expansion and contraction unit is 15-20 mm, and the length of the contraction section is 3-6 mm.

[0009] Preferably, the substrate is a sharp wedge type, and the sharp wedge turning angle θ is 5-10°.

[0010] Preferably, the ratchet channel loop in each of the two sub-boards is independent and mirror-symmetrical, and the ratchet channel height is 4-8 mm.

[0011] Preferably, the ratchet channel loop front edge is a whole curvature R i Matching the sharp wedge turning angle θ.

[0012] Preferably, the groove width is 0.5-0.8 mm, the depth is 0.6-1 mm, and the distance between adjacent grooves is greater than 0.5 mm.

[0013] Preferably, the working medium is sodium, potassium, sodium-potassium alloy and rubidium, and the internal vacuum degree of the ratchet channel loop is ≤10 - 4 Pa, and the liquid filling rate is 45-65%.

[0014] Preferably, the substrate material is 42.75Ir-4.5Nb-42.75Ni-10Al, Ir 85 Nb 15 Alloy.

[0015] Preferably, the substrate includes an evaporation section, an adiabatic section and a condensation section, the evaporation section is arranged at the bottom end of the substrate, the adiabatic section is located in the middle of the substrate, and the condensation section is located at the top end of the substrate; the length of the evaporation section accounts for 30%-40% of the sub-plate, the length of the adiabatic section accounts for 5%-10% of the sub-plate, and the working medium in the groove flows along the condensation section→adiabatic section→evaporation section.

[0016] Beneficial effects: the sharp wedge type small channel heat driven gas-liquid phase change heat dissipation device provided by the application sets the ratchet channel loop filled with high temperature working medium on the substrate, sets the triangular groove on the ratchet channel to form the asymmetric expansion and contraction unit, the gas bubble / gas plug head-tail gas-liquid interface curvature radius in the asymmetric expansion and contraction unit is different, so that a single direction interface tension driving pressure difference is induced on the gas bubble / gas plug, and the single direction interface tension driving pressure difference can be superimposed on the gas bubble / gas plug in multiple asymmetric expansion and contraction units, and then the directional movement of the working medium is self-driven; in addition, the alternating arrangement of the large resistance channel and the small resistance channel is formed in the whole closed ratchet channel loop by the parallel channels of alternating sizes, so that the working medium preferentially flows into the large channel with small resistance, thereby cooperating with the interface tension driving pressure difference, greatly enhancing the directional movement driving force of the gas-liquid two-phase working medium in the ratchet channel loop, and generating stable and efficient directional circulation operation; in addition, the periodic asymmetric expansion and contraction structure can enhance the internal disturbance of the flowing working medium and form local vortex at the triangular groove, so as to disturb or even destroy the near-wall boundary layer, and then reduce the convective heat transfer thermal resistance between the working medium and the wall, which significantly enhances the heat dissipation capacity and load adaptability of the heat dissipation device. On the other hand, the bottom and top walls of the ratchet channel are each arranged with a small groove, which not only provides more sites for bubble nucleation on the evaporation section wall to strengthen nucleate boiling, but also in the small groove, the gas-liquid interface curvature radius which decreases in the direction of condensation section→adiabatic section→evaporation section will generate a capillary suction force pointing to the evaporation section, which can automatically suction the working medium in the condensation section back to the evaporation section, thereby enhancing the evaporation section backflow liquid supply capacity and the maximum heat dissipation capacity of the device. The above beneficial effects are mutually coordinated, which will greatly improve the heat protection efficiency, maximum heat protection capacity and load adaptability of the sharp wedge type small channel heat driven gas-liquid phase change heat dissipation device. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a partial sectional view of the heat dissipation device in the embodiment of the application;

[0018] Figure 2 is a sectional view and a partial enlarged view of the ratchet channel loop of the heat dissipation device in the embodiment of the application at A-A in Figure 1

[0019] Figure 3 is a triangular groove parameter diagram of the heat dissipation device in the embodiment of the application;

[0020] Figure 4 is a schematic diagram of the ratchet channel loop of the heat dissipation device in the embodiment of the application;

[0021] Figure 5 is a partial enlarged view of the ratchet channel loop of the heat dissipation device in the embodiment of the application at B-B; Figure 4

[0022] ​​Figure 6 The working principle diagram of the ratchet channel of the heat dissipation device in the embodiment of the application;

[0023] Figure 7 The working principle diagram of the groove of the heat dissipation device in the embodiment of the application;

[0024] Figure 8 The working principle diagram of the groove of the heat dissipation device in the embodiment of the application at E-E, F-F and G-G. Figure 7 The working principle diagram of the groove of the heat dissipation device in the embodiment of the application at E-E, F-F and G-G. DETAILED DESCRIPTION

[0025] Referring to Figures 1-8 , the wedge-shaped small-channel heat-driven gas-liquid phase change heat dissipation device provided by the application can be installed in the aerodynamic heating severe area of a hypersonic vehicle, such as a nose cone and a wing leading edge, is suitable for working in a high-temperature interval of 500-1500℃, and can realize efficient heat dissipation of the area under extreme conditions of high heat flux, large accumulated heating and variable load / overload.

[0026] As Figure 1 shown is a structural schematic diagram of a wedge-shaped small-channel gas-liquid phase change heat dissipation device, specifically including a substrate 1, a ratchet channel loop 2, a groove 3 and a liquid filling port 4. The substrate 1 is made of a high-temperature-resistant alloy resistant to corrosion of alkali metals with high melting points, specifically including 42.75Ir-4.5Nb-42.75Ni-10Al, Ir 85 Nb 15 alloy, and is integrally formed into a wedge shape. The substrate 1 is symmetric about a center plane after being bent and has a ratchet channel loop 2 inside a single side. The substrate 1 is provided with a liquid filling port 4 at both sides of a top end, the liquid filling port 4 is connected with the ratchet channel loop 2, and the ratchet channel loop 2 is filled with a working medium. The ratchet channel loop 2 includes a plurality of ratchet channels 21 connected in a head-tail manner. The ratchet channel 21 includes a plurality of intermediate channels 211 with alternating widths and parallel to each other and a plurality of triangular grooves 212 symmetrically arranged at both sides of the intermediate channels 211. The triangular grooves 212 are shaped as asymmetric obtuse-angle triangles. The widths of the intermediate channels 211 of adjacent ratchet channels 21 are inconsistent. The substrate 1 is provided with a plurality of grooves 3 at the bottom and the top of the intermediate channels 211.

[0027] In combination Figure 1 , Figure 2 and Figure 3 , the turning angle θ of the wedge shape formed by the bending of the substrate 1 is 5-10°. Because Figure 3 the angle changes after the bottom end of the substrate 1 is bent, but the overall zigzag channel remains consistent. The substrate 1 is symmetrically provided with independent and mirror-symmetric ratchet channel loops 2 inside both sides. The ratchet channel loop 2 has a meandering closed layout in a reverse fold, and the number of U-shaped bends is preferably greater than 16. The overall device has good load resistance. The overall curvature R iMatch with the sharp wedge corner θ; the working medium is selected from high-temperature melting point alkali metals such as sodium, potassium, sodium-potassium alloy and rubidium, and the inside of the ratchet channel loop 2 can be vacuumed through the liquid charging port 4 to ≤10 -4 Pa, and the liquid filling rate is controlled at 45-65%.

[0028] The two adjacent ratchet channels are based on the intermediate channels 211 with two different widths W1 and W2, and the triangular grooves 212 are periodically arranged on the two side walls of the intermediate channels 211. The channel width W1 and W2 are both controlled in the range of 3-6 mm, and the channel height h1 is 4-8 mm. The convergence angle α of the triangular groove is small, being 15-20°, and the divergence angle β is large, reaching 35-45°. The intermediate channel 211 between the two symmetrically arranged triangular grooves 212 forms a single asymmetric expansion and contraction unit, and the asymmetric expansion and contraction unit includes a contraction section and an expansion section. The total length l2 of the asymmetric expansion and contraction unit is 15-20 mm, and the length l1 of the contraction section is 3-6 mm.

[0029] In combination with Figure 4 , Figure 5 and Figure 6 , the curvature radius of the gas-liquid interface at the head and tail of the bubble / gas plug in each asymmetric expansion and contraction unit of the ratchet channel of the application is different. According to the Young-Laplace interface pressure difference, the capillary force can be expressed as , is the surface tension of the liquid working medium. The smaller the curvature radius R is, the greater the capillary force is. In the asymmetric expansion and contraction unit, R b is the gas-liquid interface curvature radius on one side of the convergence angle α of the triangular groove, and R f is the gas-liquid interface curvature radius on one side of the divergence angle β of the triangular groove. When the gas-liquid interface curvature radius R b < R f , it can be known that the capillary forces at the two ends are in opposite directions and different in size, which are = b and = f , is the capillary force on one side of the convergence angle α of the triangular groove, is the capillary force on one side of the divergence angle β of the triangular groove, and it can be known that P b > P f , thereby inducing a single-direction interface tension driving pressure difference P cAnd the driving pressure difference can be superimposed on the bubbles / gas plugs of multiple asymmetric expansion units, and then the directional motion of the working fluid is generated. At the same time, the parallel channels with alternating sizes form an alternating arrangement of large and small resistance channels in the entire ratchet channel loop 2, and the working fluid will preferentially flow to the large channel with small resistance, and the interface tension driving pressure difference is coordinated with each other, which greatly enhances the driving force of the directional motion of the gas-liquid two-phase working fluid in the ratchet channel loop 2, and tends to produce stable and efficient directional circulation operation. In addition, the periodic asymmetric expansion structure can increase the internal disturbance of the flowing working fluid, and vortexes can be formed at the triangular grooves 212, and the disturbance even destroys the boundary layer near the wall, thereby enhancing the convective heat transfer between the working fluid and the wall. These significantly enhance the heat dissipation capacity and load adaptability of the heat dissipation device.

[0030] In combination Figure 2 , Figure 7 and Figure 8 , the present application is divided into three sections in whole, which are evaporation section, adiabatic section and condensation section, wherein the length of the evaporation section accounts for 30%-40% of the total length, and the length of the adiabatic section accounts for 5%-10% of the total length. The grooves 3 are arranged at the bottom and top of the ratchet channel wall surface with a specific groove spacing, the groove width b1 is 0.5-0.8 mm, the groove depth h2 is 0.6-1 mm, and the spacing b2 between adjacent grooves 3 is greater than 0.5 mm. The grooves are adjusted as needed under the constraints of these parameters. On the one hand, the grooves 3 make the channel have more micro pits and gaps, providing more sites for bubble nucleation on the evaporation section wall surface, thereby strengthening the nucleate boiling. On the other hand, during the operation of the device, the liquid working fluid in the evaporation section is less, and the gas-liquid curvature radius R e is smaller than that in the adiabatic section R a and the condensation section R c , while the liquid working fluid in the condensation section is more, and the gas-liquid curvature radius R c is the largest. On the other hand, in the grooves 3, along the direction of the condensation section→the adiabatic section→the evaporation section, the gas-liquid curvature radius with decreasing gradient generates a capillary suction force pointing to the evaporation section, so that the working fluid in the condensation section is sucked back to the evaporation section, thereby strengthening the ability of the evaporation section to return and supplement the liquid, and improving the maximum heat dissipation capacity of the device.

Claims

1. A wedge-shaped small-channel thermally driven gas-liquid phase change heat conduction device, characterized in that, The system includes a substrate (1), which has several ratchet channel circuits (2) inside. The ratchet channel circuits (2) are filled with working fluid. After the substrate (1) is bent, it forms two sub-substrates (11) symmetrical about the center plane. Each sub-substrate (11) has a ratchet channel circuit (2) inside. Each ratchet channel circuit (2) includes several ratchet channels (21) connected end to end. The two side walls of the middle channel of each ratchet channel (21) form a sawtooth groove, and the grooves on both sides are axially symmetrical. The width of the middle channel of two adjacent ratchet channels (21) is not consistent. The top and bottom walls of each ratchet channel (21) in the middle channel are provided with grooves (3), and the grooves (3) extend along the axial direction of the ratchet channel (21).

2. The wedge-shaped small-channel thermally driven gas-liquid phase change heat conduction device according to claim 1, characterized in that, Each sawtooth groove in the middle channel is formed by connecting several triangular grooves (212) end to end. Two symmetrical triangular grooves (212) on both sides and a part of the middle channel (211) between the two triangular grooves (212) together form an expansion and contraction unit. Each triangular groove (212) forms a long side and a short side of the recess. The line connecting the two ends of the long side and the short side that are far apart from each other forms the two side lines of the middle channel, and the two side lines are parallel.

3. The wedge-shaped small-channel thermally driven gas-liquid phase change heat conduction device according to claim 2, characterized in that, The convergence angle α of the triangular groove (212) is 15-20°, and the divergence angle β is 35-45°. The convergence angle α is the angle between the long side and the edge line, and the divergence angle β is the angle between the short side and the edge line. Each ratchet channel unit is an asymmetric expansion and contraction unit. The asymmetric expansion and contraction unit includes an expansion section and a contraction section. The total length of the asymmetric expansion and contraction unit is 15-20mm, and the length of the contraction section is 3-6mm.

4. The wedge-shaped small-channel thermally driven gas-liquid phase change heat conduction device according to claim 1, characterized in that, The substrate (1) has an overall cross-sectional shape of a wedge, and the wedge turning angle θ is 5-10°.

5. The wedge-shaped small-channel thermally driven gas-liquid phase change heat conduction device according to claim 1, characterized in that, The ratchet channel circuits (2) in the two sub-sub ...

6. The wedge-shaped small-channel thermally driven gas-liquid phase change heat conduction device according to claim 4, characterized in that, The overall curvature R of the leading edge of the ratchet channel circuit (2) i It matches the pointed wedge-shaped turning angle θ.

7. The wedge-shaped small-channel thermally driven gas-liquid phase change heat conduction device according to claim 1, characterized in that, The groove (3) has a width of 0.5-0.8 mm and a depth of 0.6-1 mm, and the spacing between adjacent grooves (3) is greater than 0.5 mm.

8. The wedge-shaped small-channel thermally driven gas-liquid phase change heat conduction device according to claim 1, characterized in that, The working fluid is sodium, potassium, sodium-potassium alloy and rubidium, and the internal vacuum degree of the ratchet channel circuit (2) is ≤10. -4 Pa, filling rate 45~65%.

9. The wedge-shaped small-channel thermally driven gas-liquid phase change heat conduction device according to claim 1, characterized in that, The substrate (1) is made of 42.75Ir–4.5Nb–42.75Ni–10Al, Ir 85 Nb 15 alloy.

10. The wedge-shaped small-channel thermally driven gas-liquid phase change heat conduction device according to claim 1, characterized in that, The substrate (1) includes an evaporation section, an insulation section and a condensation section. The evaporation section is located at the lower end of the substrate (1), the insulation section is located in the middle of the substrate (1), and the condensation section is located at the top of the substrate (1). The length of the evaporation section accounts for 30%-40% of the length of the sub-substrate (11), and the length of the insulation section accounts for 5%-10% of the length of the sub-substrate (11). The working fluid in the trench (3) flows back along the condensation section → insulation section → evaporation section.

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