Double-wall impingement cooling device and application

Abstract

The application relates to a double-wall impact cooling device and application, belonging to the field of aero-engines, which comprises a cold-side flat plate, a hot-side flat plate and hollow turbulence columns, the cold-side flat plate is located on one side of a cold gas channel and is provided with a plurality of impact holes, the hot-side flat plate is located on one side of a high-temperature gas channel, a plurality of hollow turbulence columns are arranged between the cold-side flat plate and the hot-side flat plate, an intermediate channel containing the hollow turbulence columns is formed, and the cold gas channel and the high-temperature gas channel are communicated through hollow holes in the hollow turbulence columns. The application fully utilizes the advantages of suction-strengthened impact convection cooling and the hollow holes easy to flow to form a gas film layer, reduces the temperature distribution and temperature gradient of the heat shield, and achieves the purpose of high-efficiency cooling.

Description

Technical Field

[0001] This invention belongs to the field of aero-engines, specifically relating to a double-walled impact cooling device and its application. Background Technology

[0002] When military aircraft take off short distances and maneuver quickly, they often obtain additional thrust through afterburning in addition to the maximum throttle opening of the engine. Due to the limited space of the afterburner, the still burning gas acts on the wall of the engine's converging section nozzle in the form of oblique impact, which can easily cause backflow of gas and lead to serious consequences. Studies have shown that the gas temperature in the tail nozzle will be as high as 2000K or more at this time [1]. In addition, the pressure gradient from the engine nozzle inlet to the outlet is large, which can easily cause strong suction of gas in the expansion section, exacerbating the backflow phenomenon in the convergent section.

[0003] Impact-based double-wall film cooling technology is one of the advanced cooling methods for high-temperature components in modern engines. Before the cold gas forms a film, it fully utilizes the high heat transfer coefficient of impact to achieve locally enhanced heat transfer. Existing literature compares the cooling performance of novel impact / divergent cooling plate heat shields, demonstrating their feasibility for application in afterburners. Comparative analyses were conducted with corrugated plate heat shields and single-layer flat plate heat shields under the same operating conditions, showing that the impact / divergent cooling plate heat shield has a better cooling effect. The double-wall structure provides structural reinforcement, and simultaneously provides some vibration damping while the film gas flows out, thus improving the lifespan and reliability of the afterburner.

[0004] Existing technologies utilize an impact + film cooling structure, and enhance heat transfer through film cooling pores penetrating both wall layers. While this structure achieves good heat transfer, the internal flow resistance within the double-walled structure is high, and it is significantly affected by changes in the total pressure ratio of the primary and secondary flows. It is difficult to achieve outflow at low pressure ratios, making it unsuitable for the converging section of engine nozzles. Existing turbulence column structures, while offering high cooling efficiency, are relatively complex, and their large opening ratio generates significant thermal stress.

[0005] Currently, both domestic and international researchers are exploring methods to reduce internal flow resistance in double-walled systems, such as adding pits to the target surface and altering the shape of the turbulence columns. However, these methods are limited by the significant turns and vortices encountered by the airflow under impact-film cooling conditions, resulting in substantial flow losses and limited effectiveness. Advanced aero-engines have relatively short afterburners, where the combustion flame obliquely impacts the converging section of the nozzle. Cooling gas used for film cooling of the wall surface is difficult to escape, making it challenging to effectively protect the wall. At this point, the wall temperature exceeds the temperature resistance limit of the metal material, easily causing ablation. Traditional porous flat plate structures have low cooling efficiency and struggle to effectively protect the converging section wall. Furthermore, the impact-film double-walled structure, due to its high internal flow resistance, is prone to backflow of combustion gases. Additionally, the low-pressure suction of combustion gases in the expansion section draws most of the cooling gas into the more temperate expansion section, wasting cooling gas and exacerbating backflow in the converging section. Summary of the Invention

[0006] The technical problem to be solved:

[0007] To avoid the shortcomings of existing technologies, this invention provides a double-walled impact cooling device, which adopts a double-walled structure combined with a hollow turbulence column. It fully utilizes the advantages of suction-enhanced impact convection cooling and the formation of an air film layer through easy outflow from the hollow holes, thereby reducing the temperature distribution and temperature gradient of the heat insulation screen and achieving the purpose of efficient cooling.

[0008] The technical solution of the present invention is: a double-walled impact cooling device, comprising a cold-side plate, a hot-side plate, and a hollow turbulence column, wherein the cold-side plate is located on one side of the cold air passage and has a plurality of impact holes thereon; the hot-side plate is located on one side of the high-temperature gas passage.

[0009] Several hollow baffle columns are provided between the cold-side plate and the hot-side plate to form an intermediate channel containing the hollow baffle columns, and the cold air channel and the high-temperature gas channel are connected through the hollow holes in the hollow baffle columns.

[0010] A further technical solution of the present invention is that the hollow turbulence column and the impact hole are arranged in an alternating manner.

[0011] A further technical solution of the present invention is: the diameter D of the hollow pores in the hollow turbulence column. i The hole inclination angle is 30°-90°, ranging from 0.5-5mm.

[0012] A further technical solution of the present invention is: the spanwise hole spacing P of the hollow hole. z and flow direction hole spacing S z The diameter D of the hollow pore is 3-10 times that of the pore. i The hollow holes are distributed in a rhomboid shape in the flow direction.

[0013] A further technical solution of the present invention is: the diameter D of the impact hole c The diameter D of the hollow pore is 1-1.2 times that of the pore. i .

[0014] A further technical solution of the present invention is: the average height H of the channel formed by the hot-side plate and the cold-side plate is 1-10 times the diameter D of the impact hole. c Inside.

[0015] A further technical solution of the present invention is that the cross-sectional shape of the hollow turbulence column is circular, elliptical, teardrop-shaped, or hyperbolic.

[0016] A further technical solution of the present invention is that the cross-sectional shape of the hollow hole of the hollow turbulence column is consistent with the radial cross-sectional shape of the hollow turbulence column.

[0017] An application of a double-walled impact cooling device is disclosed. The double-walled impact cooling device is applied to the engine nozzle. The cold-side plate and the outer wall of the nozzle form a cold air passage, and the hot-side plate forms the inner wall surface of the nozzle. The cold-side plate and the outer wall surface of the converging section of the nozzle are connected at the end to form a closed cavity. The total pressure outflow is used to reduce the backflow rate of combustion gas.

[0018] Beneficial effects

[0019] The beneficial effects of this invention are as follows: This invention provides a double-walled impact cooling device with hollow turbulence columns, which fully utilizes the advantages of suction-enhanced impact convection cooling and the easy outflow of air film layer formed by hollow holes, reducing the temperature distribution and temperature gradient of the heat insulation screen, and achieving the purpose of efficient cooling. The specific implementation principle is as follows: Figure 2 As shown, a portion of the cooling gas B flows out through the hollow hole 3 onto the hot-side plate on the gas side (D2), forming a gas film layer to reduce heat transfer from the mainstream gas A to the hot-side plate. Another portion of the cooling gas B, under the suction of the gas in the expansion section, impacts the hot-side plate 2 through the impact hole 5, and is then carried away by the turbulence of the hollow column array, removing heat from the hot-side plate 2 and the hollow column 4. The staggered arrangement of the impact holes and the gas film holes ensures uniform cooling of the entire hot-side plate, resulting in a small temperature gradient. The diameter of the impact holes is equal to or greater than the diameter of the hollow holes, ensuring the effectiveness of impact cooling and reducing internal flow resistance to some extent. The turbulence column 4 forms a 30-90° angle with the airflow C in the middle channel, making the flow cross-section elliptical, reducing internal flow resistance, and ensuring a small angle between the cooling gas flow D2 and the mainstream A, guaranteeing the cold gas's adhesion to the wall surface, thus achieving a higher cooling effect and reducing mixing losses in the nozzle. Figure 5As shown, the cold-side plate 1 and the outer wall 9 form a straight cold air channel in the wind wall, forcing the cold air to flow out from the hollow hole 3 and the impact hole 5, reducing the possibility of gas backflow; the combination of impact cooling and film cooling improves the cooling efficiency while avoiding the disadvantage of excessive flow resistance in the traditional double-wall impact + film structure. Figure 6 As shown, the cylindrical shapes of ellipse 13, teardrop 14, and hyperbolic 15 not only allow the gas film to adhere better to the gas surface and enhance the heat exchange effect, but also reduce the flow resistance of the internal column array.

[0020] Numerical verification, such as Figure 7 and 8 As shown in the figure, the distribution cloud map and line graph of the comprehensive cooling efficiency of an embodiment of the present invention and the traditional single-layer plate multi-oblique hole model with holes in the same position are compared. Under the same cold air consumption, the comprehensive cooling effect increases from 0.307 to 0.695, improving the comprehensive cooling efficiency to 2.26 times that of the traditional structure.

[0021] In summary, the advantages of this invention are: (1) less cooling air consumption and high cooling efficiency; (2) small temperature gradient of the heat insulation screen and low wall temperature; (3) small structural flow resistance and cold air total pressure outflow, which can avoid gas backflow. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a double-walled impact cooling device according to the present invention;

[0023] Figure 2 This is a schematic diagram of the flow of a double-walled impact cooling device according to the present invention;

[0024] Figure 3 This is a schematic diagram showing the characteristic dimensions of a double-walled impact cooling device according to the present invention;

[0025] Figure 4 This is a schematic diagram of the hole arrangement of a double-walled impact cooling device according to the present invention;

[0026] Figure 5 This is a schematic diagram illustrating the application scenario of the present invention in the convergent section of an engine nozzle;

[0027] Figure 6 This is a schematic diagram of the structural form of the hollow turbulence column in this invention;

[0028] Figure 7 This is a cloud map comparing the overall cooling efficiency of the embodiment of the present invention with that of a single-layer perforated plate model;

[0029] Figure 8 This is a line graph comparing the spanwise average comprehensive cooling efficiency of an embodiment of the present invention with that of a single-layer perforated plate model;

[0030] Explanation of reference numerals in the attached diagrams: 1. Cold-side plate; 2. Hot-side plate; 3. Inner hole of the column; 4. Hollow turbulence column; 5. Impact hole; 6. Outer wall of the afterburner; 7. Single-layer corrugated plate of the afterburner; 8. Main combustion gas duct; 9. Outer wall of the nozzle converging section; 10. Outer wall of the nozzle expanding section; 11. Impact-film double-wall cooling structure of the nozzle expanding section; 12. Circular hollow turbulence column; 13. Elliptical hollow turbulence column; 14. Teardrop-shaped hollow turbulence column; 15. Hyperbolic hollow turbulence column; A. Mainstream combustion gas; B. Outer duct cooling airflow; C. Cooling airflow between the double-layer plates; D1. Outflow from the impact hole; D2. Outflow from the hollow hole; D c Impact hole diameter; D i , Inner diameter of the hollow turbulence column; D o 1. Outer diameter of the hollow column causing turbulence; H; Average height of the channel between plates; P c Impact hole spacing; S c Impact hole discharge direction spacing; P z Spacing of hollow spoiler columns; S z , Spacing of the hollow turbulence columns in the direction of airflow. Detailed Implementation

[0031] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0032] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] This implementation case is a specific example of a double-walled impact cooling device with hollow turbulence columns being used in the expansion section of an engine nozzle.

[0034] The high-temperature, low-pressure gas discharged from the turbine is diffused and enters the main gas duct 8. It mixes with the fuel injected by the fuel nozzle and then reignites to form high-temperature gas, which has an oblique impact effect on the converging section of the nozzle. The temperature of the mainstream high-temperature gas A can reach 2200K, far exceeding the melting point of the material. Therefore, the nozzle wall needs to be cooled.

[0035] See Figure 1 , Figure 2 , Figure 3 , Figure 4This embodiment describes a double-walled impact cooling device with hollow turbulence columns, comprising a cold-side plate 1, a hot-side plate 2, and hollow turbulence columns 4 connecting the two plates. The cold-side plate contains staggered hollow holes 3 and impact holes 5. The cold-side plate 1 and the outer wall surface form a cold air channel, creating an intermediate channel for the impact jet between the two plates. The hot-side plate 2 forms the inner wall surface of the high-temperature component.

[0036] Figure 2 and Figure 5 The image shows the operation of a double-walled impact cooling device with hollow baffles in the nozzle convergent section. The double-walled impact cooling device with hollow baffles is connected to the single-layer corrugated plate of the afterburner through a transition corrugation. Cooling gas from the afterburner's outer duct enters the cold-side plate and forms a cooling airflow B with the outer duct formed by the outer wall of the nozzle convergent section. The end of the outer duct of the convergent section is closed, causing part of the cold gas to form an outflow D1 through the hollow column 3 and form an outflow gas film on the hot-side plate 2. The other part of the cold gas passes through the impact hole 5 to form an impact jet D2, which converges into a cooling airflow C. The airflow C is turbulent by the hollow baffle 4 in the middle channel, cooling the hot-side plate 2.

[0037] In this implementation case, the average height H of the passage between the two flat plates is 6mm, and the inner diameter D of the hollow column is... i The outer diameter D of the hollow column is 2mm. o The diameter is 4mm, the impact hole diameter is 2mm, and the spanwise spacing P of the hollow turbulence column array is 4mm. z The spacing S of the hollow turbulence column in the flow direction is 12mm. z The spacing P of the impact hole row is 12mm. c The diameter is 12mm, and the spacing S of the impact hole discharge direction is... c It is 12mm.

[0038] Because the cold-side plate and outer wall form a straight cold air channel that is sealed at the end, and the hollow holes have lower flow resistance compared to the double-walled impingement film structure, the risk of backflow of the gas can be reduced. Part of the cooling gas passes through the hollow holes and forms a film layer on the hot-side plate, significantly reducing the heat transfer from the gas to the hot-side plate. Another part of the cooling gas passes through the impingement holes, and under the strong suction of the nozzle expansion section, it impacts the hot-side plate, converging into a cooling airflow C that passes through the middle channel between the two plates. Under the action of the hollow turbulence column, convective heat transfer is enhanced, carrying away heat from the hot-side plate and further reducing its temperature, thus providing good protection for the inner wall of the entire expansion section. This implementation case was numerically compared with a single-layer multi-slanted hole plate structure with the same opening ratio and opening position. Specific calculation settings are shown in Table 1, and the cooling effect comparison between the implementation case and the single-layer multi-slanted hole plate model is shown in [Table 1]. Figure 7 and Figure 8 Under the same cooling air consumption, this implementation improves the overall cooling efficiency to 2.26 times that of the original structure.

[0039] Table 1. Implementation Cases and Numerical Calculation Methods for Single-Layer Perforated Plate Models

[0040]

[0041] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. An engine nozzle, characterized in that: The device includes a double-walled impact cooling system, which comprises a cold-side plate, a hot-side plate, and a hollow turbulence column. The cold-side plate is located on one side of the cold air passage and forms a cold air passage with the outer wall of the nozzle. Several impact holes are opened on it. The hot-side plate is located on one side of the high-temperature gas passage and serves as the inner wall surface of the nozzle. The cold-side plate and the outer wall surface of the converging section of the nozzle are connected at the end to form a closed cavity. The total pressure outflow is used to reduce the backflow rate of gas. Several hollow baffle columns are provided between the cold side plate and the hot side plate to form an intermediate channel containing hollow baffle columns, and the cold air channel is connected to the high temperature gas channel through the hollow holes in the hollow baffle columns. The hollow turbulence-disrupting columns and impact holes are arranged in an alternating pattern; The hollow pore diameter D of the hollow turbulence column i The hole inclination angle is 30°-90°, ranging from 0.5-5mm. The diameter D of the impact hole c The diameter D of the hollow pore is 1-1.2 times that of the pore. i ; A portion of the cooling gas passes through the hollow holes and forms a gas film layer on the hot-side plate, thereby significantly reducing the heat transfer from the combustion gas to the hot-side plate. Another portion of the cooling gas passes through the impact holes, and under the strong suction of the nozzle expansion section, it impacts the hot-side plate, converging into a cooling gas flow that passes through the middle channel between the two plates. Under the action of the hollow turbulence column, convective heat transfer is enhanced, carrying away the heat from the hot-side plate and further reducing the temperature of the hot-side plate, thus providing good protection for the inner wall of the entire expansion section.

2. The engine nozzle according to claim 1, characterized in that: The spanwise aperture P of the hollow hole z and flow direction hole spacing S z The diameter D of the hollow pore is 3-10 times that of the pore. i The hollow holes are distributed in a rhomboid shape in the flow direction.

3. The engine nozzle according to claim 1, characterized in that: The average height H of the channel formed by the hot-side plate and the cold-side plate is 1-10 times the diameter D of the impact hole. c Inside.

4. The engine nozzle according to claim 1, characterized in that: The cross-sectional shape of the hollow turbulence column is circular, elliptical, teardrop-shaped, or hyperbolic.

5. An engine nozzle according to claim 4, characterized in that: The hollow hole cross-section of the hollow turbulence column has the same shape as the radial cross-section of the hollow turbulence column.

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