A divergent and film double cooling system applied to the nose cone surface of a reusable hypersonic vehicle

Abstract

The present invention provides a divergence and film double cooling system applied to the surface of the nose cone of a reusable hypersonic vehicle. The invention mainly includes the surface of the hypersonic vehicle nose cone, a divergence cooling system, and a film cooling system. The surface of the hypersonic vehicle nose cone is divided into two regions, a stagnation point region including the stagnation point and a non-stagnation point region not including the stagnation point. Divergence cooling is adopted for the stagnation point region of the nose cone surface, and the coolant is liquid water. Film cooling is adopted for the non-stagnation point region of the nose cone surface, and the coolant is nitrogen. The divergence cooling system and the film cooling system work independently. The present invention can not only meet the cooling requirements of both the stagnation point region and the non-stagnation point region at the same time, with the cooling efficiency of the stagnation point region not less than 90% and the cooling efficiency of the non-stagnation point region not less than 60%, but also effectively reduce the weight of the coolant required to be carried by the vehicle.

Description

Technical Field

[0001] The invention belongs to the field of aircraft thermal protection, and in particular relates to a divergence and air film dual cooling system for a hypersonic aircraft. Background Art

[0002] Since the 20th century, aerospace engineering has developed rapidly. The flight speeds and altitudes of various aircraft are constantly challenging the limits of human technology. However, reciprocating hypersonic aircraft with speeds between Mach 5 and Mach 10 are still blank, and are also the key direction for the development of future aircraft. All major aerospace powers have conducted research. Reciprocating hypersonic aircraft will produce an "aerodynamic heating" effect when flying in the atmosphere. The gas close to the surface of the aircraft will heat up significantly due to intense friction, thereby heating the surface structure of the aircraft body, causing the temperature of the aircraft surface, especially the nose cone and other parts, to rise significantly. Existing materials cannot withstand such high temperatures, and appropriate thermal protection measures must be adopted. Traditional ablative thermal protection, ablative coatings cannot be reused, and they must be re-sprayed after each flight, which is very costly. Reciprocating hypersonic aircraft have higher requirements for flight speed, reusability and reliability, as well as lower maintenance costs. Therefore, it is necessary to study more efficient and reliable thermal protection methods.

[0003] Active thermal protection can work for a long time without changing the aerodynamic shape of the aircraft. It is reusable and has higher cooling efficiency. It is an effective means to replace passive thermal protection such as ablation in the future. The most common active thermal protection technologies are divergent cooling and film cooling. Divergent cooling usually uses liquid as a coolant. The liquid is heated and vaporized in the porous wall. This process can take away a lot of heat due to the existence of latent heat of vaporization. The vaporized coolant is discharged through the porous wall, forming a protective gas film on the cooled surface. This gas film can effectively reduce the heat exchange between the wall and the mainstream gas. Film cooling uses gas as a coolant. The gas is discharged through multiple small hole structures (also called cooling holes or film holes) on the wall of the aircraft, forming a protective gas film on the cooled surface.

[0004] It can be seen that the cooling process of divergent cooling consists of two parts: internal heat transfer: the coolant vaporizes and takes away the heat, and external heat insulation: the air film reduces the heat exchange between the wall and the mainstream gas, while the cooling process of air film cooling only includes the latter. Therefore, divergent cooling has a stronger cooling capacity. For the stagnation area of ​​the nose cone, the heat flux density is very large, and divergent cooling can better meet the thermal protection needs. Although the cooling capacity of divergent cooling is higher than that of air film cooling, it needs to carry more coolant. For aircraft, weight reduction is also very important, so air film cooling can be used in non-stagnation areas with relatively low heat flux density.

[0005] This divergence and film cooling system can not only meet the thermal protection requirements of the nose cone surface of a reusable hypersonic vehicle, but also effectively reduce the weight of the coolant to be carried.

[0006] Current research on film cooling and transpiration cooling mostly focuses on the premise of low-speed mainstream applications. There is less research on the characteristics of film cooling and transpiration cooling under hypersonic mainstream conditions, and there is no dual-cooling active thermal protection system that combines transpiration cooling and film cooling, nor research on its performance. Summary of the Invention

[0007] The purpose of the present invention is to provide a divergence and film dual-cooling system applied to the nose cone surface of a reusable hypersonic vehicle.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention provides a divergence and film dual-cooling system applied to the nose cone surface of a reusable hypersonic vehicle, which is characterized in that it includes a nose cone (17) of a reusable hypersonic vehicle, a transpiration cooling system, and a film cooling system;

[0010] Among them, the transpiration cooling system includes a water storage tank (1), a cooling water delivery pipeline, a cold liquid cavity (5), a porous wall surface (6), and corresponding accessory systems;

[0011] Among them, the film cooling system includes a liquid nitrogen tank (7), a vaporization device (11), an acceleration device (13), a liquid nitrogen delivery pipeline, a cold gas cavity (15), a film hole array (16), and corresponding accessory systems;

[0012] The cooling water delivery pipeline includes a pump (2), a first flowmeter (3), and corresponding pipelines connected in sequence;

[0013] The cooling water delivery pipeline further includes a first pressure sensor (4) arranged after the first flowmeter (3);

[0014] The liquid nitrogen tank (7) is a self-pressurizing liquid nitrogen tank;

[0015] The liquid nitrogen delivery pipeline includes a valve (8), a vaporization device (11), an acceleration device (13), a second flowmeter (14), and corresponding pipelines connected in sequence;

[0016] The liquid nitrogen delivery pipeline further includes a second pressure sensor (10) and a first temperature sensor (9) arranged between the valve and the vaporization device;

[0017] The liquid nitrogen delivery pipeline further includes a third pressure sensor (12) arranged between the vaporization device and the acceleration device;

[0018] The hypersonic vehicle nose cone (17) has its surface divided into two regions, namely a stagnation region (18) containing the stagnation point and a non-stagnation region (19) not containing the stagnation point; the porous wall surface (6) is arranged in the stagnation region (18) of the nose cone surface and is connected to the cold liquid cavity (5) arranged inside the stagnation region of the nose cone; the film hole array (16) is arranged in the non-stagnation region (19) of the nose cone surface and is connected to the cold gas cavity (15) arranged inside the non-stagnation region of the nose cone;

[0019] The included angle between the boundary line of the stagnation region on the nose cone surface and the central axis (20) of the vehicle nose cone is 25°;

[0020] For the divergence and film double cooling system, the stagnation region (18) of the nose cone surface adopts divergence cooling with the coolant being liquid water, and the non-stagnation region (19) of the nose cone surface adopts film cooling with the coolant being nitrogen; the divergence cooling system and the film cooling system work independently.

[0021] The method for the divergence cooling system to achieve divergence cooling of the stagnation region on the nose cone surface includes the following steps:

[0022] 1) After ensuring that the water storage tank (1) stores a sufficient amount of liquid cooling water, start the pump (2) to extract the cooling water, which reaches the cold liquid cavity (5) through the delivery pipeline;

[0023] 2) The cooling water stored in the cold liquid cavity (5) is discharged after being depressurized and vaporized through the porous wall surface (6), forming a protective gas film in the stagnation region (18) of the nose cone surface. At the same time, the vaporization of the cooling water absorbs heat to cool the stagnation region (18) of the nose cone surface.

[0024] Among them, when the pressure signal returned by the first pressure sensor (4) is too low, that is, when the pressure of the cooling water entering the cold liquid cavity (5) is insufficient, increase the power of the pump (2) to ensure that the pressure of the cooling water entering the cold liquid cavity (5) is high enough.

[0025] The method for the film cooling system to achieve divergence cooling of the non-stagnation region on the nose cone surface includes the following steps:

[0026] 1) After ensuring that the liquid nitrogen tank (7) stores a sufficient amount of high-pressure liquid nitrogen, open the valve (8), and the liquid nitrogen becomes gas through the vaporization device (11);

[0027] 2) The nitrogen gas is accelerated through the acceleration device (13) and enters the cold gas cavity (15). The nitrogen gas stored in the cold gas cavity is discharged through the film hole array (16) to form a protective gas film in the non-stagnation region on the nose cone surface.

[0028] Among them, when the pressure signal returned by the second pressure sensor (10) is too low, that is, the nitrogen pressure before gasification is insufficient, the opening degree of the valve (8) is increased to ensure that the nitrogen pressure after gasification is high enough.

[0029] Among them, the included angle between the central axis of the first film hole in the film hole array close to the stagnation region and the central axis of the aircraft nose cone is 5° to 10°.

[0030] Among them, the porosity of the porous wall surface is between 0.5 and 0.9, and the average pore diameter is between 40μm and 60μm.

[0031] Among them, the shape of the film holes in the film hole array is circular, the diameter of the film holes is 2mm, and the outflow angle of the film holes, that is, the included angle between the center line of the film holes and the local wall tangent plane, is 90°.

[0032] Among them, the film hole array is arranged in the following form: evenly distributed circumferentially, the number of film holes in each row is between 10 and 100, and a total of 10 rows are arranged. The closer to the downstream, the more the number of film holes in each row, so as to ensure that the distance between two adjacent film holes in the same row will not be too large; axially, the axial intervals of the film holes in adjacent rows are the same and are arranged staggeredly.

[0033] In the present invention, divergent cooling is adopted in the stagnation region with high surface heat flux density on the nose cone of the reusable hypersonic aircraft. Water is heated and vaporized in the porous wall surface from the liquid state, taking away a large amount of latent heat of vaporization, which can fully meet the cooling requirements of the stagnation region. Film cooling is adopted in the non-stagnation region with low heat flux density. The cooling capacity is weaker than that of divergent cooling, but it can meet the cooling requirements of the non-stagnation region. At the same time, the coolant flow required for film cooling is much smaller than that of divergent cooling. Therefore, the present invention can not only meet the cooling requirements of both the stagnation region and the non-stagnation region, but also effectively reduce the weight of the coolant carried by the aircraft. Brief Description of the Drawings

[0034] Figure 1 is a schematic diagram of the divergent and film double cooling system for the reusable hypersonic aircraft of the present invention;

[0035] Figure 2 is a schematic diagram of the stagnation region and the non-stagnation region;

[0036] Figure 3 is a schematic diagram of the film hole arrangement. Detailed Embodiments

[0037] The following further describes the present invention in detail with reference to the drawings, but this is only exemplary and is not intended to limit the protection scope of the present invention in any way.

[0038] See Figure 1 , Figure 1Schematic diagram of the transpiration and film cooling dual-cooling system for a reusable hypersonic vehicle of the present invention. It includes a reusable hypersonic vehicle nose cone, a transpiration cooling system, and a film cooling system. The transpiration cooling system and the film cooling system operate independently.

[0039] See Figure 1 , the transpiration cooling system includes a water storage tank (1), a cooling water delivery pipeline, a cold liquid cavity (5), a porous wall surface (6), and corresponding accessory systems.

[0040] See Figure 1 , the film cooling system includes a liquid nitrogen tank (7), a vaporization device (11), an acceleration device (13), a liquid nitrogen delivery pipeline, a cold gas cavity (15), a film hole array (16), and corresponding accessory systems.

[0041] See Figure 1 , the cooling water delivery pipeline includes a pump (2), a first flowmeter (3), and corresponding pipelines connected in sequence;

[0042] See Figure 1 , the cooling water delivery pipeline further includes a first pressure sensor (4) arranged after the first flowmeter (3).

[0043] See Figure 1 , the liquid nitrogen delivery pipeline includes a valve (8), a vaporization device (11), an acceleration device (13), a second flowmeter (14), and corresponding pipelines connected in sequence.

[0044] See Figure 1 , the liquid nitrogen delivery pipeline further includes a second pressure sensor (10) and a first temperature sensor (9) arranged between the valve and the vaporization device.

[0045] See Figure 1 , the liquid nitrogen delivery pipeline further includes a third pressure sensor (12) arranged between the vaporization device and the acceleration device.

[0046] See Figure 2 , the surface of the reusable hypersonic vehicle nose cone (17) is divided into two regions: a stagnation point region (18) including the stagnation point and a non-stagnation point region (19) not including the stagnation point; the porous wall surface (6) is arranged on the stagnation point region (18) of the nose cone surface and is connected to the cold liquid cavity (5) arranged inside the stagnation point region of the nose cone; the film hole array (16) is arranged on the non-stagnation point region (19) of the nose cone surface and is connected to the cold gas cavity (15) arranged inside the non-stagnation point region of the nose cone;

[0047] In a specific embodiment, the included angle between the boundary line of the stagnation point region on the nose cone surface and the central axis of the vehicle nose cone is 25° ( Figure 2 ).

[0048] The steps for the transpiration cooling system to achieve thermal protection of the stagnation region on the nose cone surface are as follows:

[0049] 1) After ensuring that the water storage tank stores a sufficient amount of liquid cooling water, start the pump to extract the cooling water, and reach the cold liquid cavity through the delivery pipeline;

[0050] 2) The cooling water stored in the cold liquid cavity is discharged after depressurization and vaporization through the porous wall surface, forming a protective gas film in the stagnation region on the nose cone surface. At the same time, the cooling water vaporizes and absorbs heat to cool the stagnation region on the nose cone surface.

[0051] Among them, when the pressure signal returned by the first pressure sensor is too low, that is, when the pressure of the cooling water entering the cold liquid cavity is insufficient, increase the power of the pump to ensure that the pressure of the cooling water entering the cold liquid cavity is high enough.

[0052] The steps for film cooling to achieve thermal protection of the non-stagnation region on the nose cone surface are as follows:

[0053] 1) After ensuring that the liquid nitrogen tank stores a sufficient amount of high-pressure liquid nitrogen, open the valve, and the liquid nitrogen becomes gas through the vaporization device;

[0054] 2) The nitrogen gas is accelerated through the acceleration device and enters the cold gas cavity. The nitrogen gas stored in the cold gas cavity is discharged through the film hole array, forming a protective gas film in the non-stagnation region on the nose cone surface.

[0055] Among them, when the pressure signal returned by the second pressure sensor is too low, that is, when the pressure of the nitrogen gas before vaporization is insufficient, increase the opening degree of the valve to ensure that the pressure of the nitrogen gas after vaporization is high enough.

[0056] In a specific embodiment, the included angle between the central axis of the first film hole near the stagnation region in the film hole array and the central axis of the nose cone of the aircraft is 5° to 10°.

[0057] In a specific embodiment, the porosity of the porous wall surface is between 0.5 and 0.9, and the average pore diameter is between 40 μm and 60 μm.

[0058] In a specific embodiment, the shape of the film holes in the film hole array is circular, the diameter of the film holes is 2 mm, and the outflow angle of the film holes, that is, the included angle between the center line of the film holes and the local wall tangent plane, is 90°.

[0059] In a specific embodiment, the film hole array is arranged in the following form: circumferentially evenly distributed, the number of film holes in each row is between 10 and 100, and a total of 10 rows are arranged. The closer to the downstream, the more the number of film holes in each row, so as to ensure that the distance between two adjacent film holes in the same row is not too large; axially, the axial interval between adjacent rows of film holes is the same and staggered ( Figure 3 ).

Claims

1. A diverging and film double cooling system applied to the nose cone surface of a reusable hypersonic vehicle, characterized in that, It includes a reusable hypersonic vehicle nose cone (17), a transpiration cooling system, and a film cooling system; The transpiration cooling system includes a water storage tank (1), a cooling water delivery pipeline, a cold liquid cavity (5), a porous wall surface (6), and corresponding accessory systems; The film cooling system includes a liquid nitrogen tank (7), a vaporization device (11), an acceleration device (13), a liquid nitrogen delivery pipeline, a cold gas cavity (15), a film hole array (16), and corresponding accessory systems; The cooling water delivery pipeline includes a pump (2), a first flowmeter (3), and corresponding pipelines connected in sequence; The cooling water delivery pipeline further includes a first pressure sensor (4) arranged after the first flowmeter (3); The liquid nitrogen tank (7) is a self-pressurizing liquid nitrogen tank; The liquid nitrogen delivery pipeline includes a valve (8), the vaporization device (11), the acceleration device (13), a second flowmeter (14), and corresponding pipelines connected in sequence; The liquid nitrogen delivery pipeline further includes a second pressure sensor (10) and a first temperature sensor (9) arranged between the valve (8) and the vaporization device (11); The liquid nitrogen delivery pipeline further includes a third pressure sensor (12) arranged between the vaporization device (11) and the acceleration device (13); The surface of the reusable hypersonic vehicle nose cone (17) is divided into two regions: a stagnation point region (18) containing the stagnation point and a non-stagnation point region (19) not containing the stagnation point; the porous wall surface (6) is arranged in the stagnation point region (18) containing the stagnation point and is connected to the cold liquid cavity (5) arranged inside the stagnation point region (18) containing the stagnation point; the film hole array (16) is arranged in the non-stagnation point region (19) not containing the stagnation point and is connected to the cold gas cavity (15) arranged inside the non-stagnation point region (19) not containing the stagnation point; The included angle between the boundary line of the stagnation point region (18) containing the stagnation point and the central axis (20) of the vehicle nose cone is 25°; The stagnation point region (18) containing the stagnation point adopts transpiration cooling, and the coolant is liquid water. The non-stagnation point region (19) not containing the stagnation point adopts film cooling, and the coolant is nitrogen. The transpiration cooling system and the film cooling system work independently.

2. The diverging and film double cooling system applied to the nose cone surface of a reusable hypersonic vehicle according to claim 1, characterized in that, The included angle between the central axis of the first film hole of the film hole array (16) of the film cooling system close to the stagnation point region and the central axis (20) of the vehicle nose cone is between 5° and 10°.

3. The diverging and film double cooling system applied to the nose cone surface of a reusable hypersonic vehicle according to claim 1, characterized in that, The porosity of the porous wall surface (6) of the transpiration cooling system is between 0.5 and 0.9, and the average pore diameter is between 40μm and 60μm.

4. The diverging and film double cooling system applied to the nose cone surface of a reusable hypersonic vehicle according to claim 1, characterized in that, The shape of the film holes in the film hole array (16) of the film cooling system is circular, the diameter of the film holes is 2mm, and the outflow angle of the film holes, that is, the included angle between the central line of the film holes and the local wall tangent plane, is 90°.

5. The diverging and film double cooling system applied to the nose cone surface of a reusable hypersonic vehicle according to claim 1, characterized in that, The film hole array (16) of the film cooling system is arranged in the following form: evenly distributed circumferentially, the number of film holes in each row is between 10 and 100, and a total of 10 rows are arranged. The closer to the downstream, the more the number of film holes in each row, so as to ensure that the distance between two adjacent film holes in the same row is not too large. Axially, the axial intervals of the film holes in adjacent rows are the same and are arranged staggeredly.

6. A method for diverging cooling of the stagnation point area on the nose cone surface, the method for diverging cooling of the stagnation point area on the nose cone surface being based on the diverging and film double cooling system applied to the nose cone surface of a reusable hypersonic vehicle according to claim 1, characterized in that, The steps are as follows: 1) After ensuring that the storage tank (1) stores a sufficient amount of liquid cooling water, start the pump (2) to extract the cooling water and reach the cold liquid cavity (5) through the conveying pipeline; 2) The cooling water stored in the cold liquid cavity (5) is discharged after being depressurized and vaporized by the porous wall surface (6), forming a protective gas film in the stagnation region (18) containing the stagnation point. At the same time, the cooling water vaporizes and absorbs heat to cool the stagnation region (18) containing the stagnation point.

7. The method for diverging cooling of the stagnation point area on the nose cone surface according to claim 6, characterized in that, It also includes: When the pressure signal returned by the first pressure sensor (4) is too low, that is, the pressure of the cooling water entering the cold liquid cavity (5) is insufficient, increase the power of the pump (2) to ensure that the pressure of the cooling water entering the cold liquid cavity (5) is high enough.

8. A method for film cooling of the non-stagnation point area on the nose cone surface, the method for film cooling of the non-stagnation point area on the nose cone surface being based on the diverging and film double cooling system applied to the nose cone surface of a reusable hypersonic vehicle according to claim 1, characterized in that, The steps are as follows: 1) After ensuring that the liquid nitrogen tank (7) stores a sufficient amount of high-pressure liquid nitrogen, open the valve (8), and the liquid nitrogen becomes gas through the gasification device (11); 2) The nitrogen gas is accelerated by the acceleration device (13) and enters the cold gas cavity (15). The nitrogen gas stored in the cold gas cavity (15) is discharged through the film hole array (16) to form a protective gas film in the non-stagnation region (19) without the stagnation point.

9. A method for film cooling in the non-stagnation region of the nose cone surface according to claim 8, characterized in that, It also includes: When the pressure signal returned by the second pressure sensor (10) is too low, that is, the pressure of the nitrogen gas before gasification is insufficient, increase the opening degree of the valve (8) to ensure that the pressure of the nitrogen gas after gasification is high enough.

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