Hypersonic leading edge cooling design method based on combined heat transfer enhancement method of branch pipes and wall depressions

Abstract

The present invention provides a hypersonic leading edge cooling design method based on a combined tributary pipe and wall depression enhanced heat transfer method, which is suitable for leading edge areas with severe aerodynamic thermal problems in hypersonic aircraft, and relates to a hypersonic leading edge cooling technology based on a combined tributary pipe and wall depression enhanced heat transfer method, which realizes coolant diversion and increases the roughness of the pipe wall surface through a combination of adding tributary pipes and adding arc-shaped depressions on the pipe wall surface, thereby enhancing heat transfer. The present invention uses a hypersonic leading edge cooling technology based on a combined tributary pipe and wall depression enhanced heat transfer method to improve the heat transfer capacity of the cooling medium of the active convection cooling technology under limited cold source conditions, and enhance the heat reduction effect of the active cooling technology.

Description

Technical Field

[0001] The present invention relates to a hypersonic leading edge cooling design method based on a combined branch pipe and wall depression enhanced heat transfer method, which is suitable for improving the heat transfer capacity of a cooling medium of an active convection cooling technology under a limited cold source condition. Background Art

[0002] The rapid development of hypersonic vehicles has brought many challenges to designers. High pressures and heating occur in areas of the vehicle that are affected by shock waves during flight. Typical areas of concern are the wings, tail, control surface compression angles, and the axial angle area at the wing / fuselage surface junction. For air-breathing vehicles, aerodynamic heating of the leading edge of the engine cowling is of particular concern because of the need to maximize engine thrust by maximizing air capture. Shock waves can generate extremely high pressures and heat at the leading edge of the cowling, depending on where they intersect with the cowling bow shock. Peak pressure and heating also depend on Mach number, Reynolds number, gas composition, and shock wave strength.

[0003] There are many types of thermal protection technologies for hypersonic vehicles, and their applicable occasions and effects are also different. Among them, convection cooling technology is a typical active thermal protection solution. During the long-duration flight of a hypersonic vehicle, the coolant flows in the pipeline to absorb and take away the heat in the structure, thereby greatly reducing the temperature of the structure and achieving the role of thermal protection. Its cooling effect is significant and is suitable for long-duration, high heat flux, and reusable aircraft. In addition, convection cooling technology also uses the fuel carried by the aircraft itself as a cooling medium. Without increasing the mass of the aircraft, the fuel flows through the cooling pipeline and absorbs the heat in the structure to preheat itself. The preheated fuel enters the combustion chamber and is fully burned, and the heat is used again. This is usually also called regenerative cooling technology. This dual advantage gives convection cooling thermal protection technology huge development potential, and it has become a research hotspot in hypersonic thermal protection technology in various countries around the world.

[0004] The advantages of active convection cooling technology give it a broad development prospect, but this thermal protection technology is still facing many problems that need to be improved. For example, when convection cooling technology relies on the fuel carried by the aircraft itself to cool the high-temperature structure, the limited coolant seriously restricts its rapid development. Therefore, designers are eager to improve the heat transfer capacity of the cooling medium under the condition of limited cold source. By changing the various factors that affect the heat transfer process so that the same amount of coolant absorbs more heat, it is called heat transfer enhancement. At present, the most commonly used heat transfer enhancement technologies include increasing the roughness of the pipe wall (depression or protrusion), changing the aspect ratio of the pipe, adding ribs, pipe diversion and spoiler devices, etc.

[0005] Since it has attracted attention, enhanced heat transfer technology has also made outstanding research progress. Ulas pointed out that by increasing the aspect ratio of the cooling channel, the wall temperature of the structure can be further reduced without increasing the pressure drop of the channel. Li Haohan numerically analyzed the effects of different channel diameters on the coolant flow and heat transfer characteristics. The results show that when the coolant mass flow rate remains unchanged, reducing the channel size will lead to an enhanced coupling effect between the coolant flow, heat transfer and chemical reaction in the channel. Wang Pengen analyzed the effect of the spoiler on the heat transfer characteristics of the structure. The study found that the convex spherical structure can effectively improve the flow and heat transfer effect of the coolant, while the concave spherical structure can reduce the pressure drop in the cooling channel. Youn explored the sensitivity of the optimal coolant mass flow rate to the roughness of the wall of the rectangular cross-section cooling channel. The results show that under the same coolant mass flow rate, appropriately increasing the roughness of the wall can significantly improve the heat transfer efficiency of the structure. Sumanta numerically analyzed the effects of four different shapes of depressions, square, triangle, circle and teardrop, on the heat transfer characteristics of the structure.

[50] Based on the comparative analysis of the calculation results and the experimental results, he believes that among the four depression shapes studied, the teardrop-shaped depression has the best heat transfer performance.

[0006] However, the existing heat transfer enhancement technologies also have some technical problems. For example, although the heat transfer enhancement method of adding branch pipes can improve the overall heat transfer performance, the temperature of the local position at the front edge of the structure will rise, which will also lead to the increase of the maximum temperature of the outer edge of the structure and the inner wall of the pipe. In addition, the existing heat transfer enhancement methods mostly use a single heat transfer enhancement technology. For example, although methods such as reducing the diameter of the coolant flow channel or increasing the surface roughness of the flow channel can enhance the heat transfer efficiency, the improvement effect is not very obvious. Summary of the invention

[0007] The present invention is based on hypersonic leading edge cooling technology. Aiming at the leading edge area with severe aerodynamic thermal problems in hypersonic aircraft, the present invention adopts a method of enhancing heat transfer by adding branch pipes and combining arc-shaped wall depressions to achieve coolant diversion and increase the wall surface roughness, thereby improving the heat transfer capacity of the cooling medium of the active convection cooling technology under the condition of limited cold source.

[0008] The technical solution of the present invention:

[0009] A hypersonic leading edge cooling design method based on a combined enhanced heat transfer method of branch pipes and wall depressions, which uses two enhanced heat transfer methods: adding branch pipes to achieve coolant diversion and adding curved wall depressions to increase the roughness of the pipe wall. The two enhanced heat transfer methods are combined to enhance the heat transfer performance of the active convection cooling leading edge structure model, further improving the thermal protection effect of the active cooling scheme under the condition of limited cold source.

[0010] The active convection cooling leading edge structure model without enhanced heat transfer scheme as a benchmark is shown in Figure 1 A symmetrical cooling pipe is arranged in the middle of the structure, wherein the pipe size is d=2mm, the inlet size is 2d=4mm, the outer side of the annular pipe is 4.6mm away from the outer side of the leading edge structure, and a chamfer with a radius of d / 2 is arranged at the split. Structural material 1Crl8Ni9Ti stainless steel material.

[0011] The active convection cooling leading edge structure model with branch pipes and wall depressions to enhance heat transfer is shown in the figure. Figure 2 The coolant diversion scheme diverts the hydrogen in the mainstream straight pipe by arranging branch pipes. Under the premise of ensuring that the total flow rate and inlet velocity of hydrogen remain unchanged, the hydrogen in the pipe undergoes jet heat exchange with the structure at different positions to enhance the heat transfer performance of the structure at different positions. Figure 2 It can be seen that the angle between the branch pipe and the mainstream pipe is ±30°, and the sum of the mainstream pipe diameter dimension d1 and the branch pipe diameter dimension d2 is consistent with the original mainstream pipe inlet diameter dimension 2d, d1 = 2mm, d2 = 1mm. In this way, when the hydrogen inlet velocity remains unchanged, the total mass flow rate of hydrogen can be guaranteed not to change. Among them, the scheme of increasing the roughness of the pipeline wall is achieved by arranging arc-shaped depressions on the arc-shaped cooling pipe wall. The maximum width of the arc-shaped depression is L = 2mm, the aspect ratio is 0.2, and the arrangement spacing is 14°. The heat transfer performance of the active convection cooling leading edge structure model is enhanced by combining the branch pipe and the arc-shaped depression.

[0012] Beneficial effects of the present invention: The hypersonic leading edge cooling design method based on the combined enhanced heat transfer method of the branch pipe and the wall depression proposed in the present invention combines two enhanced heat transfer methods, on the one hand, solving the problem of the maximum temperature rise at the local position caused by the single use of the branch pipe method; on the other hand, by Figure 4 It can be seen that compared with the enhanced heat transfer method of using branch pipes and wall depressions alone, the wall temperature reduction of the enhanced heat transfer method of the branch pipe and wall depression is the most obvious. Therefore, the use of the combined heat transfer method can maximize the heat transfer capacity of the cooling medium of the active convection cooling technology under the condition of limited cold source. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a model of the active convection cooling leading edge structure without enhanced heat transfer scheme.

[0014] Figure 2 Active convection cooling leading edge structure model for combined enhanced heat transfer scheme.

[0015] Figure 3 Schematic diagram of the concave shape of the wall.

[0016] Figure 4 The temperature distribution cloud diagram of the structure surface for different heat transfer enhancement schemes.

[0017] Figure 5 The pipe wall temperature variation curves for different heat transfer enhancement schemes. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution 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. It is obvious that the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without making creative work are all within the scope of protection of the present invention.

[0019] Based on hypersonic leading edge convection cooling technology, two heat transfer enhancement methods are adopted, namely, adding branch pipes to realize coolant diversion and increasing wall depressions to increase pipe wall roughness, to further improve the thermal protection effect of the active cooling scheme under the condition of limited cold source.

[0020] contrast Figure 1 and Figure 2 By comparison, it is found that the scheme for enhancing heat transfer is achieved by adding tributary pipes and adding arc-shaped depressions on the pipe wall. The angle between the branch pipe and the mainstream pipe is ±30°, and the sum of the mainstream pipe size d1 and the branch pipe size d2 is consistent with the original pipe inlet size 2d, d1 = 2mm, d2 = 1mm. In this way, when the hydrogen inlet velocity remains unchanged, the total mass flow rate of hydrogen can be guaranteed not to change. The scheme for increasing the roughness of the pipe wall is achieved by arranging arc-shaped depressions on the wall of the cooling pipe. The maximum width of the arc-shaped depression is L = 2mm, the aspect ratio is 0.2, the arrangement spacing is 14°, and its geometric shape is as follows: Figure 3 shown.

[0021] The effect of active convection cooling enhancement scheme was evaluated by numerical simulation method. Figure 4 It can be seen from the surface temperature distribution cloud diagram of the structure shown that, compared with the active convection cooling method of the smooth pipe (without branch flow), adding a branch pipe can make the leading edge structure of the branch pipe be impacted by the jet of hydrogen in the branch pipe, and the structural temperature at the corresponding position is significantly reduced; adding an arc-shaped depression can make the surface temperature of the corresponding structure significantly lower than the surface temperature of the structure under the smooth pipe. Figure 5 It can be seen from the pipe wall temperature change curve shown that the wall temperature drop of the enhanced heat transfer scheme with the addition of branch pipes and arc-shaped depressions is the most prominent, indicating that its thermal protection effect is the best.

[0022] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit its scope. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hypersonic leading edge cooling design method based on a combined branch pipe and wall depression enhanced heat transfer method, characterized in that: The heat transfer performance of the active convection cooling leading edge structure model is enhanced by adding branch pipes to realize coolant diversion and adding arc-shaped wall depressions to increase the roughness of the pipe wall. The details are as follows: Coolant diversion scheme: By arranging branch pipes, the hydrogen in the mainstream pipe is diverted. Under the premise of ensuring that the total flow rate and inlet velocity of hydrogen remain unchanged, the hydrogen in the pipe is allowed to exchange heat with the structure through impact jets at different positions, thereby enhancing the heat transfer performance of the structure at different positions. Solution to increase the roughness of the pipeline wall: This is achieved by arranging an arc-shaped depression on the arc-shaped cooling pipeline wall; the sum of the mainstream pipeline diameter size d1 and the branch pipeline diameter size d2 is kept consistent with the original mainstream pipeline inlet diameter size 2d; The angle between the branch pipe and the main pipe is ±30°, d1=2mm, d2=1mm; The maximum width of the arc-shaped depression is L=2 mm, the aspect ratio is 0.2, and the arrangement spacing is 14°.

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