Closed cavity for optimizing local peak heat flow and design method thereof

Abstract

The invention relates to the technical field of aerodynamics, in particular to a closed cavity for optimizing local peak heat flow and a design method of the closed cavity. The closed concave cavity comprises a closed concave cavity body with an opening in the top, the opening face and the bottom face of the closed concave cavity body are parallel, the opening face and the bottom face are rectangular, the bottom area of the closed concave cavity body is larger than the opening area, and the included angle between the tail end of the closed concave cavity body and the bottom face is larger than 90 degrees. On the basis of an original concave cavity, based on a high heat flow generation mechanism, by changing the geometric configuration of the closed concave cavity, the flow direction vortex is adjusted, the tail end interference strength is reduced, then the peak value of local heat flow is reduced, local peak heat flow is improved, and the local peak heat flow can be simply and efficiently reduced.

Description

Technical Field

[0001] The invention relates to the technical field of aerodynamics, and in particular to a closed cavity for optimizing local peak heat flow and a design method thereof. Background Art

[0002] For new hypersonic strategic missiles, geometric structures such as cavities are unavoidable during the design and production process. The presence of cavities may change the flow state on the surface of the aircraft, causing flow transitions and increasing local peak heat flux. Excessive peak heat flux may cause local ablation, change the aerodynamic shape, cause the surface flow state and aerodynamic heat of the missile to deviate from the design, and affect the aerodynamic performance and landing point accuracy; in severe cases, it may cause the failure of the heat protection structure, causing safety accidents and seriously threatening flight safety.

[0003] For hypersonic cavity flow, the cavity flow is divided into three types: open, transitional and closed cavities according to the different length-to-depth ratios of the cavity. Open cavity: The flow above the cavity is a zone. The flow flows over the cavity, and the flow forms a large-scale closed vortex structure inside the cavity; it is compressed by the closed flow inside the cavity at the front wall, forming a compression wave; at the rear wall of the cavity, it is affected by the geometric compression surface to form a shock wave structure. Transition cavity: The flow above the cavity is divided into two zones. When the flow passes through the cavity, it goes deep into the bottom of the cavity, forming an incident shock wave and a departing shock wave. The two shock waves merge above the flow, and the shock foot is affected by the flow to form a bifurcated shock wave; at the front wall, the flow is mainly expanded into the cavity, forming an expansion shock wave, and a small-scale vortex structure is formed in the corner area of ​​the cavity; at the rear wall, the flow is mainly compressed by the rear wall, forming a compression wave, and a small-scale vortex structure is formed in the corner area. Closed cavity: The flow above the cavity is divided into three zones. The main flow field characteristics are similar to those of the transition cavity. The flow penetrates deeper into the bottom, and the incident shock wave and the departing shock wave are clearly separated. A smaller vortex structure is formed in the front wall and the rear corner area. There is an expansion wave in the upper corner area of ​​the front wall, and a compression wave in the corner area of ​​the rear wall.

[0004] In the design of high-speed aircraft, closed cavity structures often face the problem of poor local thermal environment. The high heat flux of the closed cavity is mainly distributed at the bottom downstream and the tail end. The high heat flux mechanism at the bottom downstream is mainly generated by the flow vortex structure at the bottom, and the high heat flux at the tail end is mainly generated by shock wave interference. The complex flow characteristics of high-speed airflow in the cavity cause a large amount of heat to accumulate in local areas, causing the temperature of the cavity wall to rise sharply. This will not only pose a serious threat to the structural integrity of the aircraft, but may also affect the normal operation of its internal equipment, thereby reducing the overall performance and reliability of the aircraft.

[0005] Therefore, there is an urgent need to provide a closed cavity that optimizes the local peak heat flux. Summary of the invention

[0006] The first purpose of the present invention is to provide a closed cavity for optimizing the local peak heat flux, which can solve the above-mentioned technical problems, adjust the flow vortex and reduce the tail end interference intensity, thereby reducing the peak value of the local heat flux.

[0007] A second object of the present invention is to provide a method for optimizing a closed cavity.

[0008] The present invention provides a closed cavity for optimizing local peak heat flux, comprising a closed cavity with a top opening, wherein the opening surface and the bottom surface of the closed cavity are parallel, and the opening surface and the bottom surface are both rectangular, the bottom area of ​​the closed cavity is larger than the opening area, and the angle between the tail end of the closed cavity and the bottom surface is greater than 90°.

[0009] Preferably, the cross section of the closed cavity is an isosceles trapezoid.

[0010] Preferably, the angle between the side wall and the bottom surface of the closed cavity is 130°-140°

[0011] Preferably, the included angle between the side wall and the bottom surface of the closed cavity is 135°.

[0012] Preferably, the angle between the tail end of the closed cavity and the bottom surface is 130°-140°

[0013] Preferably, the angle between the rear end of the closed cavity and the bottom surface is 135°.

[0014] Preferably, the length L of the closed cavity is greater than the depth D of the closed cavity.

[0015] Preferably, the length-to-depth ratio of the closed cavity is: L / D=15.

[0016] The present invention also provides a design method for a closed cavity for optimizing local peak heat flux, comprising the following steps: a. optimizing the geometric shape of the closed cavity; b. numerically simulating the optimized cavity configuration using computational fluid dynamics software; and c. verifying the optimization results through wind tunnel testing.

[0017] Preferably, the specific steps of step c are: conducting actual tests on the optimized closed cavity through wind tunnel experiments, and comparing and verifying the results with numerical simulation results.

[0018] Beneficial effects:

[0019] Based on the high heat flux generation mechanism on the basis of the original cavity, the present invention adjusts the flow vortex and reduces the tail end interference intensity by changing the geometric configuration of the closed cavity, thereby reducing the peak value of the local heat flux, achieving an improvement in the local peak heat flux, and being able to simply and efficiently reduce the local peak heat flux. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a schematic diagram of the original configuration of the concave cavity of the present invention;

[0022] Figure 2 A top view of the closed cavity configuration optimized for the present invention;

[0023] Figure 3 A front view of the closed cavity configuration optimized for the present invention;

[0024] Figure 4 A side view of the closed cavity configuration optimized for the present invention;

[0025] Figure 5 The heat flux distribution on the wall of the original cavity configuration obtained by numerical calculation of the present invention;

[0026] Figure 6 The heat flux distribution on the wall of the optimized closed cavity configuration obtained by numerical calculation in the present invention;

[0027] Figure 7 The heat flux distribution on the wall of the original cavity configuration obtained by the wind tunnel test of the present invention;

[0028] Figure 8 The heat flux distribution on the wall of the optimized closed cavity configuration is obtained from the wind tunnel test of the present invention. DETAILED DESCRIPTION

[0029] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example

[0033] like Figure 2-4 As shown, a closed cavity for optimizing local peak heat flux includes a closed cavity with an opening at the top, the opening surface and the bottom surface of the closed cavity are parallel, and the opening surface and the bottom surface are both rectangular, the sides of the opening surface and the bottom surface are parallel, the bottom area of ​​the closed cavity is larger than the opening area, and the angle between the tail end of the closed cavity and the bottom surface is larger than 90°.

[0034] The cross section of the closed cavity is an isosceles trapezoid. The angles between the side wall and the bottom surface of the closed cavity are 130°-140°, and preferably the angles between the side wall and the bottom surface of the closed cavity are 135°. The angle between the tail end and the bottom surface of the closed cavity is 130°-140°, and preferably the angle between the tail end and the bottom surface of the closed cavity is 135°. After the optimization of the present invention, the bottom area of ​​the closed cavity becomes smaller.

[0035] The length L of the closed cavity is greater than the depth D of the closed cavity. Preferably, the length-to-depth ratio of the closed cavity is: L / D=15.

[0036] The original cavity configuration is Figure 1 As shown, it is a rectangular structure.

[0037] A design method for a closed cavity for optimizing local peak heat flux comprises the following steps: a. optimizing the geometric shape of the closed cavity; b. numerically simulating the optimized cavity configuration using computational fluid dynamics software; and c. actually testing the optimized closed cavity through a wind tunnel experiment, and comparing and verifying the results with the numerical simulation results.

[0038] The conditions used for numerical simulation and wind tunnel test are: Mach number (Ma) is 5.95, Reynolds number (Re) is 3.53*10 7 / m, incoming flow temperature (Te) 60.60K.

[0039] The wall heat flux distribution of the original cavity configuration and the closed cavity configuration after optimization are shown in the figure below. Figure 5 , Figure 6 As shown in the figure, it can be seen that after the configuration is optimized, the high heat flux generated by the streamwise vortex on the bottom of the cavity is significantly suppressed; the high heat flux area near the tail end is also greatly reduced.

[0040] The heat flux distributions on the wall of the original cavity configuration and the optimized closed cavity configuration obtained from the wind tunnel test are shown in Figure 7 , Figure 8 As shown, it can be seen that after the configuration is optimized, the high heat flux generated by the streamwise vortex on the bottom of the cavity is significantly suppressed; the high heat flux area near the tail end is also greatly reduced.

[0041] The comparison results of the heat flux peak values ​​of the original cavity configuration and the optimized closed cavity configuration are shown in Table 1.

[0042] Table 1

[0043]

[0044] It can be seen from Table 1 that the temperature rise of the original configuration at 0.5s is 11.00°C, and the temperature rise of the optimized configuration of the present invention is 6.22°C, which is 43.45% lower. The peak heat flux of the original cavity configuration is 246.69KW / m 2 The peak heat flux of the optimized closed cavity configuration is 130.53KW / m 2 , the peak heat flux decreased by 47.04%.

[0045] 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 it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A closed cavity for optimizing local peak heat flow, characterized in that: A closed cavity with a top opening is provided, wherein the opening surface and the bottom surface of the closed cavity are parallel, and both the opening surface and the bottom surface are rectangular, the bottom area of ​​the closed cavity is larger than the opening area, and the angle between the tail end of the closed cavity and the bottom surface is larger than 90°.

2. The closed cavity according to claim 1, characterized in that: The cross section of the closed cavity is an isosceles trapezoid.

3. The closed cavity according to claim 1, characterized in that: The included angles between the side wall and the bottom surface of the closed cavity are both 130°-140°.

4. The closed cavity according to claim 3, characterized in that: The included angles between the side wall and the bottom surface of the closed cavity are both 135°.

5. The closed cavity according to claim 1, characterized in that: The angle between the tail end of the closed cavity and the bottom surface is 130°-140°.

6. The closed cavity according to claim 5, characterized in that: The angle between the tail end of the closed cavity and the bottom surface is 135°.

7. The closed cavity according to claim 1, characterized in that: The length L of the closed cavity is greater than the depth D of the closed cavity.

8. The closed cavity according to claim 7, characterized in that: The length-to-depth ratio of the closed cavity is: L / D=15.

9. A method for designing a closed cavity according to any one of claims 1 to 8, characterized in that: The following steps are involved: a. Optimize the geometry of the closed cavity; b. Use computational fluid dynamics software to perform numerical simulation on the optimized cavity configuration; c. Wind tunnel test verifies the optimization results.

10. The design method according to claim 9, characterized in that: The specific steps of step c are: conducting actual tests on the optimized closed cavity through wind tunnel experiments, and comparing and verifying with numerical simulation results.

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