A combustion chamber regenerative cooling structure

Abstract

The application discloses a combustion chamber regenerative cooling structure, which comprises periodically and alternately arranged shunt cavities and cooling unit groups, and a turbulence column is arranged in the shunt cavity; each cooling unit comprises a shunt passage, a vortex backflow cavity and a gradually expanding outlet section; the vortex backflow cavity is a U-shaped cavity structure; the shunt cavity is connected to both sides of a small head region of the vortex backflow cavity through two shunt passages; the shunt passage comprises an inlet section and an outlet section; the outlet section is obliquely connected to the vortex backflow cavity; the gradually expanding outlet section is arranged at the tail of a large head region of the vortex backflow cavity; and the tail of the gradually expanding outlet section is connected to the next shunt cavity; when fuel enters the vortex backflow cavity from the shunt passage, two oblique jets collide, and a vortex is formed at the jet outlet of the oblique part; due to the jet collision and the vortex interaction, the fuel periodically oscillates in the vortex backflow cavity and is strengthened in the gradually expanding outlet section, the heat exchange performance of the fuel and the hot wall is improved, and the purposes of effectively utilizing the fuel cooling heat sink and improving the cooling performance of the combustion chamber are achieved.

Description

Technical Field

[0001] This invention relates to the field of efficient cooling for scramjet engines, and more particularly to a combustion chamber regenerative cooling structure. Background Technology

[0002] Extensive research has been conducted both domestically and internationally on engine thermal protection technology, mainly categorized into passive thermal protection, active thermal protection, and combined active-passive thermal protection. Passive cooling refers to the use of the physicochemical properties of the structural components or surface coatings, such as high heat capacity, high oxidation resistance, high melting point, low coefficient of thermal expansion, high emissivity, and low thermal conductivity, to ensure stable operation of components under certain conditions for extended periods. However, the increase in flight Mach numbers has far outpaced the improvement in material properties, making passive thermal protection technology ill-suited to the harsh thermal environment of scramjet engines at higher Mach numbers due to aerodynamic heating and combustion exothermics. Developing safe and reliable active cooling methods is the best way to address the shortcomings of passive cooling. Active cooling can be categorized into regenerative cooling, film cooling, evaporative cooling, and impact cooling, based on the cooling channel structure and the flow pattern of the cooling medium. Currently, combined active-passive cooling is still in its early stages of development, with most composite cooling schemes using a combination of cooling methods to suppress heat propagation and achieve thermal protection.

[0003] Scramjet engines, with their advantages of simple structure, small mass, low cost, and high specific impulse, are considered the most promising primary power source for hypersonic vehicles. However, with increasing Mach numbers, aerodynamic and combustion heat release levels rise sharply, and combustion chamber temperatures exceed the limits of conventional materials. Due to the excessively high total temperature of the incoming air, it loses its cooling capacity, and the limited propellant becomes the only available cold source on the engine. Therefore, regenerative cooling based on hydrocarbon fuels is considered an important cooling method for scramjet engines. Taking the cooling of the scramjet engine combustion chamber surface as an example, fuel is first injected into the regenerative cooling channels on the inner surface of the engine, absorbing the heat released during combustion and increasing its own temperature through convective heat transfer, before finally returning to the combustion chamber for further reaction. To reduce the risk of material ablation under the high-temperature environment of scramjet engines, optimizing the geometry of the regenerative cooling channels is an effective means to enhance heat transfer and make rational use of the fuel cooling heat sink. Summary of the Invention

[0004] Purpose of the invention: The present invention aims to provide a regenerative cooling structure that causes fuel to collide and vortex within the combustion chamber wall, forming periodic oscillations.

[0005] Technical Solution: The combustion chamber regenerative cooling structure of the present invention includes periodically alternating flow-dividing chambers and cooling unit groups. Several turbulence columns are provided within the flow-dividing chambers. Each cooling unit includes a flow-dividing channel, a vortex return chamber, and a gradually expanding outlet section. The vortex return chamber has a U-shaped cavity structure. The flow-dividing chambers are connected to both sides of the small-head region of the vortex return chamber through two flow-dividing channels. Each flow-dividing channel includes an inlet section and an outlet section. The outlet section is obliquely connected to the vortex return chamber. The gradually expanding outlet section is located at the tail of the large-head region of the vortex return chamber, and the tail of the gradually expanding outlet section connects to the next flow-dividing chamber. When fuel enters the vortex return chamber from the flow-dividing channel, the two oblique jets collide, forming a vortex at the jet outlet of the oblique section, generating periodic oscillations to achieve heat exchange.

[0006] Preferably, the cooling units are arranged in a staggered pattern, meaning that the outlet of each cooling unit is located between two adjacent downstream cooling units.

[0007] Preferably, the diversion channel is a circular cross-section channel with a diameter of 0.15δ to 0.25δ. The inlet section of the diversion channel is perpendicular to the rectangular diversion cavity. The turning angle α between the outlet section and the inlet section of the diversion channel is 50° to 70°. The angle β between the outlet section and the wall of the vortex return cavity is 60° to 80°. The length of a single diversion channel is 2δ to 3δ.

[0008] Preferably, the length l of the vortex reflux cavity c The width is 2δ~3δ, and the width is w. c The value is 1.5δ~2.5δ, and the height is h. c The height is the same as that of the gradually widening exit section, which is 0.2δ~0.4δ.

[0009] Preferably, the outlet throat of the vortex reflux chamber is square, and the width of the outlet throat is w. t The flow direction length l of the gradually expanding outlet section is 0.2δ~0.4δ. t The value is 0.5δ~1.0δ, and the expansion angle γ is 50°~80°.

[0010] Preferably, the flow divider cavity is a circumferential channel with a square cross-section and a channel height h. f The value is 0.5δ to 0.7δ, and the height of the shunt cavity is higher than the height of the gradually expanding outlet section and the diameter of the shunt channel.

[0011] Preferably, the turbulence column is a circular or elliptical cross-section column, the turbulence column is at the same height as the flow divider cavity, and is arranged at equal intervals in the flow divider cavity, with a spacing P of 1.0δ~1.5δ.

[0012] Optionally, the number of cooling units in the cooling unit group may be the same, increase, decrease, or be distributed in a regular or random manner within each cycle.

[0013] Optionally, the sum of the areas of all vortex recirculation cavities in each cycle may be the same, increasing, decreasing, or distributed in a regular or random manner.

[0014] The combustion chamber regenerative cooling structure of the present invention is applied to the combustion chamber wall with a thickness δ of 3 to 10 mm.

[0015] Beneficial effects: Compared with the prior art, the significant advantages of this invention are: 1. By combining an inclined jet channel and a U-shaped return cavity, this invention causes the fuel to oscillate periodically in the vortex return cavity due to collision and vortex interaction, transforming steady flow into unsteady flow, increasing the complexity of the flow field, and significantly enhancing internal heat transfer; 2. This invention overcomes the limitations of commonly used simple rectangular cross-section channels in regenerative cooling, and optimizes the geometry of the regenerative cooling channel, thereby improving the cooling efficiency of the combustion chamber; 3. This invention utilizes equally spaced turbulence columns in the flow divider cavity to disturb the fuel flow field, achieving the purpose of effectively utilizing fuel to cool the heat sink and improving the cooling performance of the combustion chamber. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the invention installed on the combustion chamber wall.

[0017] Figure 2 This is a partial structural schematic diagram of the present invention;

[0018] Figure 3 This is a schematic diagram of the cooling unit. Detailed Implementation

[0019] The invention will now be further described with reference to the accompanying drawings.

[0020] The combustion chamber regenerative cooling structure of this invention includes periodically alternating flow dividers 1 and cooling unit groups. Each flow divider 1 contains several turbulence columns 2. Each cooling unit includes a flow divider channel 3, a vortex return chamber 4, and a gradually expanding outlet section 5. The vortex return chamber 4 has a U-shaped cavity structure. The flow dividers 1 are connected to both sides of the small-head region of the vortex return chamber 4 via two flow divider channels 3. Each flow divider channel 3 includes an inlet section and an outlet section. The outlet section is obliquely connected to the vortex return chamber 4. The gradually expanding outlet section 5 is located at the tail of the large-head region of the vortex return chamber 4, and its tail connects to the next flow divider. Fuel enters the square flow divider and flows circumferentially, then flows into pairs of circular flow divider channels. Due to the oblique outlet section of the flow divider channel, the two fuel streams in the same group form obliquely opposing jets that collide after entering the U-shaped return chamber. Due to the special configuration of the U-shaped return chamber, the fuel forms a periodically changing vortex characteristic within the return chamber. Two inclined jets collide and interact with vortices in the vortex return chamber, creating periodic oscillations that transform steady flow into unsteady flow. After passing through a narrow square throat, they form a swept flow in the outlet expansion section before entering the next split chamber. Cooling units in different rows are arranged in a staggered pattern, meaning the outlet of each cooling unit is located between two adjacent downstream cooling units. Optionally, the number of cooling units in each cooling unit group may be the same, increasing, decreasing, or distributed systematically or randomly within each cycle. Optionally, the sum of the areas of all vortex return chambers may be the same, increasing, decreasing, or distributed systematically or randomly within each cycle.

[0021] In this embodiment, the unsteady flow process of fuel within the vortex recirculation chamber is as follows: the outlet section of the split channel is inclined, and two fuel jets from the same group enter the U-shaped vortex recirculation chamber as inclined, opposing jets, colliding with each other. Simultaneously, due to the special configuration of the U-shaped vortex recirculation chamber, the vortex characteristics generated by the fuel collision within the recirculation chamber are unstable. The two jets alternately form vortices at the bottom of the U-shaped chamber; when one jet deflects towards the bottom region of the U-shaped chamber, the other jet becomes the main body of the outlet jet. The two inclined jets interact through collision and vortex formation within the vortex recirculation chamber, creating periodic oscillations that transform steady flow into unsteady flow, increasing the complexity of the flow field and significantly enhancing internal heat transfer. After passing through the narrow square throat, a swept flow forms in the outlet expansion section.

[0022] In this implementation case, the working principle of the turbulence column in the flow divider is as follows: the turbulence column interferes with the flow path of the fluid, destroys the original laminar boundary layer, and causes the fluid to form a turbulent wake region behind the column. The thermal resistance of the turbulent boundary layer is smaller, which can significantly improve the convective heat transfer efficiency. The turbulence column itself, as a raised structure, directly increases the effective contact area of ​​the heat transfer surface, thereby increasing the total heat transfer.

[0023] In this embodiment, the computational domain includes the combustion chamber flow domain of the scramjet engine, the combustion chamber solid domain using the regenerative cooling structure, and the regenerative cooling structure flow domain. The combustion chamber inlet is given the total inlet pressure and airflow temperature, while the regenerative cooling structure inlet is given the fuel temperature and mass flow rate. The fuel mass flow rate corresponds to the combustion chamber fuel supply mass flow rate. The combustion chamber wall thickness δ is 4 mm, the flow splitter diameter is 0.8 mm, the total length is 8 mm, and the vortex recirculation chamber length is l. c It is 10mm long and the width is w. c The height h of the vortex reflux cavity and the gradually expanding outlet section is 8mm. c The diameter is 1.2mm, and the throat width at the outlet is w. t The diameter is 1.2mm, and the length of the gradually widening exit section is l. t The diameter is 3mm, and the height of the shunt cavity is h. f The height of the flow channel is 2mm, the spacing between the turbulence columns P is 5mm, the turning angle α between the outlet and inlet sections of the diversion channel is 60°, the angle β between the outlet section and the wall of the vortex return cavity is 75°, and the expansion angle γ of the gradually expanding outlet section is 60°. As a control, the rectangular cross-section long straight regenerative cooling channel has a height of 1.2mm and a width of 2.4mm, with multiple channels arranged at equal intervals along the circumference to maintain the same total heat exchange area as the novel regenerative cooling structure.

[0024] In this implementation case, the flow field and temperature field are calculated and solved using the commercial computing software Ansys Fluent.

[0025] In this implementation case, a numerical simulation of the computational model was performed using typical operating conditions of a scramjet engine combustion chamber. Traditional rectangular cross-section channels were arranged on the combustion chamber wall for regenerative cooling. During the simulated combustion, some areas of the combustion chamber wall experienced high heat loads, causing the wall temperature to exceed the material's temperature resistance limit. After replacing the combustion chamber with a new regenerative cooling structure, the average temperature of the combustion chamber wall decreased by approximately 20% when using the same mass flow rate of fuel for regenerative cooling. This reduction was particularly pronounced in the vortex recirculation chamber region, effectively utilizing fuel to cool the heat sink and improving the combustion chamber's cooling performance.

[0026] In this implementation case, after the introduction of circular or elliptical cross-section turbulence column structures into the flow divider cavity, the average temperature of the combustion chamber wall is reduced by about 5% compared to when no turbulence column structures are introduced.

Claims

1. A combustion chamber regenerative cooling structure, characterized in that, It includes a periodically alternating flow divider (1) and a cooling unit group. The flow divider (1) is provided with several turbulence columns (2). Each cooling unit includes a flow divider channel (3), a vortex return cavity (4) and a gradually expanding outlet section (5). The vortex return cavity (4) has a U-shaped cavity structure. The flow divider (1) is connected to both sides of the small head area of ​​the vortex return cavity (4) through two flow divider channels (3). The flow divider channel (3) includes an inlet section and an outlet section. The outlet section is inclinedly connected to the vortex return cavity (4). The gradually expanding outlet section (5) is located at the tail of the large head area of ​​the vortex return cavity (4). The tail of the gradually expanding outlet section (5) is connected to the next flow divider. When fuel enters the vortex return cavity from the flow divider channel, the two inclined jets collide and form a vortex in the vortex return cavity (4), generating periodic oscillations to achieve heat exchange. The cooling units are arranged in a staggered pattern, meaning that the outlet of each cooling unit is located between two adjacent downstream cooling units. The diversion channel (3) is a circular cross-section channel with a diameter of 0.15δ~0.25δ, where δ is the thickness of the combustion chamber wall. The inlet section of the diversion channel (3) is perpendicular to the rectangular diversion cavity. The turning angle α between the outlet section and the inlet section of the diversion channel (3) is 50°~70°. The angle β between the outlet section and the wall of the vortex return cavity is 60°~80°. The length of a single diversion channel (3) is 2δ~3δ.

2. The combustion chamber regenerative cooling structure according to claim 1, characterized in that, The length l of the vortex return cavity (4) c The width is 2δ~3δ, and the width is w. c The value is 1.5δ~2.5δ, and the height is h. c The height is the same as that of the gradually widening exit section, which is 0.2δ~0.4δ.

3. The combustion chamber regenerative cooling structure according to claim 1, characterized in that, The outlet throat of the vortex reflux chamber (4) is square, and the width of the outlet throat is w. t The flow length l of the gradually expanding outlet section (5) is 0.2δ~0.4δ. t The value is 0.5δ~1.0δ, and the expansion angle γ is 50°~80°.

4. The combustion chamber regenerative cooling structure according to claim 1, characterized in that, The flow divider (1) is a circumferential channel with a square cross-section and a channel height h. f The height of the diversion cavity is 0.5δ~0.7δ, which is greater than the height of the gradually expanding outlet section (5) and the diameter of the diversion channel (3).

5. The combustion chamber regenerative cooling structure according to claim 1, characterized in that, The turbulence column (2) is a column with a circular or elliptical cross section. The turbulence column is at the same height as the flow divider cavity and is arranged at equal intervals in the flow divider cavity. The spacing P is 1.0δ~1.5δ.

6. The combustion chamber regenerative cooling structure according to claim 1, characterized in that, The number of cooling units in the cooling unit group may be the same, increase, or decrease within each cycle.

7. The combustion chamber regenerative cooling structure according to claim 1, characterized in that, The sum of the areas of all vortex return cavities (4) in each cycle is the same, increases, or decreases.

8. The combustion chamber regenerative cooling structure according to any one of claims 1-7, characterized in that, It is applied to combustion chamber walls with a thickness δ of 3~10mm.

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