An axially windowed high speed wind tunnel

Abstract

The application discloses a high-speed wind tunnel with an axial window, comprising a nozzle section, an experiment section and an S-shaped flow channel which are connected in sequence; the nozzle section is linearly connected with the experiment section, one end of the S-shaped flow channel is smoothly connected with the downstream end of the experiment section, and the other end extends backward and upward in an S shape; a concave cavity is arranged on the bottom profile of the S-shaped flow channel, and a side wall surface of the concave cavity is provided with an observation window facing the experiment section. The application is applied to the field of aerodynamics, and the axial window of the high-speed wind tunnel is realized by the ingenious combination of the S-shaped flow channel and the concave cavity, so that the flow field of the experiment section can be directly observed in the opposite direction of the flow.

Description

Technical Field

[0001] This invention relates to the field of aerodynamic equipment technology, specifically a high-speed wind tunnel with axially opening windows. Background Technology

[0002] High-speed (sonic / hypersonic) wind tunnels are crucial equipment for researching and engineering high-speed aircraft flow mechanisms. The most important components of the wind tunnel's main structure are the nozzle section and the test section. The nozzle section accelerates the incoming flow, creating a uniform supersonic / hypersonic flow, providing the high-speed airflow experimental environment for the test section. Experimental models or actual aircraft are placed inside the test section to replicate the flow field during actual flight. To observe the flow field, optical observation windows are typically installed on the four walls of the test section, such as… Figure 1 As shown.

[0003] Opening windows on the experimental section wall allows for observation of the experimental model and flow field only from the side. For three-dimensional flow fields, observing from back to front against the flow direction provides a better view of the three-dimensional structure, which is more advantageous for research. When the experimental model obstructs the flow field, such as in a three-dimensional supersonic / hypersonic inlet, observation from the side window is impossible. In this case, the back-to-front observation method becomes more valuable. There are three main existing methods. One is to use a Scheimpflug mechanism, allowing the camera to observe from back to front against the flow direction. This is achieved when the observed plane, the lens's equivalent plane, and the CCD chip intersect in space along a line (from...). Figure 2 If the light is a point in the two-dimensional schematic diagram, then theoretically it can be clearly imaged on the CCD chip; secondly, a reflector is set downstream of the experimental model to reflect the light of the observed flow field out of the observation window at a 90-degree angle, and then the observation is carried out; thirdly, a large vacuum chamber is set downstream of the experimental section, and the camera is placed in the vacuum chamber to directly carry out countercurrent observation.

[0004] The Scheimpflug mechanism solution does not completely solve the problem of model occlusion of the flow field, and the oblique light passing through the observation window will cause the image to be blurry. As for the mirror solution, the mirror is placed directly in the airflow, which will cause the mirror to vibrate, and the particulate matter in the airflow can easily cause contamination and damage to the mirror. The vacuum chamber solution occupies a large area, and the camera is placed directly in the airflow, which can also easily damage the camera, and the vibration will lead to unclear images. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a high-speed wind tunnel with axially openable windows. By ingeniously combining an S-curve flow channel and a concave cavity, the high-speed wind tunnel can achieve axially openable windows, thereby allowing direct observation of the flow field in the experimental section against the flow direction.

[0006] To achieve the above objectives, the present invention provides a high-speed wind tunnel with axially openable windows, comprising a nozzle section, an experimental section and an S-bend flow channel connected in sequence.

[0007] The nozzle section is connected to the experimental section in a straight line. One end of the S-curve flow channel is smoothly connected to the downstream end of the experimental section, and the other end extends backward and upward in an S-shape.

[0008] The bottom surface of the S-bend flow channel is provided with a cavity, and the side wall of the cavity is provided with an observation window facing the experimental section.

[0009] In one embodiment, the S-bend flow channel is a three-dimensional rectangular cross-section S-bend flow channel formed by a top profile, a bottom profile, a left side profile, and a right side profile;

[0010] The top and bottom surfaces are both curved surface structures with an S-shaped profile, while the left and right sides are both planar structures.

[0011] In one embodiment, the top surface profile includes a first arc segment, a first straight line segment, and a second arc segment connected in sequence, wherein the center of the first arc segment is located above the top surface and the center of the second arc segment is located below the top surface.

[0012] One end of the first arc segment is connected to the downstream end of the experimental segment and is tangent to the top surface of the experimental segment; the other end of the first arc segment is tangent to the first straight segment.

[0013] One end of the second arc segment is tangent to the first straight line segment, and the other end is tangent to the horizontal plane.

[0014] In one embodiment, the profile of the bottom surface includes a third arc segment, a second straight line segment, and a fourth arc segment connected in sequence, wherein the center of the third arc segment is located above the bottom surface, and the center of the fourth arc segment is located below the bottom surface.

[0015] One end of the third arc segment is connected to the downstream end of the experimental segment and is tangent to the bottom surface of the experimental segment; the other end of the third arc segment is tangent to the second straight segment.

[0016] One end of the fourth arc segment is tangent to the second straight line segment, and the other end is tangent to the horizontal plane;

[0017] The observation window is located on the bottom profile of the S-curve flow channel, corresponding to a portion of the second straight segment.

[0018] In one embodiment, the angle between the first straight line segment and the horizontal plane is α. e The angle between the second straight line segment and the horizontal plane is α. c ;

[0019] Where, α e >α c This ensures that the cross-sectional area of ​​the S-curve flow channel increases along the flow direction, thus ensuring the wind tunnel's start-up performance.

[0020] In one embodiment, a rectangular opening is provided on the bottom surface of the S-bend flow channel corresponding to a portion of the second straight segment, and the cavity is provided on the rectangular opening.

[0021] In one embodiment, the cavity includes a first mounting plate, a second mounting plate, and two side sealing plates;

[0022] One end of the first mounting plate is connected to the upstream end of the rectangular opening, the other end of the first mounting plate is connected to one end of the second mounting plate, and the other end of the second mounting plate is connected to the downstream end of the rectangular opening.

[0023] The first mounting plate is horizontally arranged and parallel to the axis of the experimental section, the second mounting plate is perpendicular to the axis of the experimental section, and the observation window is located on the second mounting plate.

[0024] One of the side sealing plates is connected to one side of the first mounting plate, one side of the second mounting plate, and one side of the rectangular opening, while the other side sealing plate is connected to the other side of the first mounting plate, the other side of the second mounting plate, and the other side of the rectangular opening.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] 1. The camera can be placed outside the wind tunnel for flow field observation, avoiding vibration and damage to the camera caused by airflow.

[0027] 2. When observing the flow field, the camera should be positioned perpendicular to the observation window to avoid light passing obliquely through the window, which could cause image blurring.

[0028] 3. During flow field observation, camera focusing and other operations are simpler and more direct.

[0029] 4. When conducting laser diagnostic experiments, the laser can be incident on the experimental section in the opposite direction of the flow through an axial window, making the experiment more flexible. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0031] Figure 1 Schematic diagram of opening windows in an existing wind tunnel;

[0032] Figure 2 This is a schematic diagram of observations using the Scheimpflug mechanism in existing technologies;

[0033] Figure 3 This is a schematic diagram of the overall structure of the high-speed wind tunnel in an embodiment of the present invention;

[0034] Figure 4 This is a first isometric view of the S-bend flow channel in an embodiment of the present invention;

[0035] Figure 5 This is a second isometric view of the S-bend flow channel in an embodiment of the present invention;

[0036] Figure 6 This is a cross-sectional view of the S-bend flow channel in an embodiment of the present invention;

[0037] Figure 7 This is a schematic diagram of the top and bottom profiles of the S-bend flow channel in an embodiment of the present invention.

[0038] Figure 8 This is a schematic diagram illustrating the working principle of the S-bend flow channel in an embodiment of the present invention.

[0039] Figure 9 This is a schematic diagram of the axial window opening on the S-bend flow channel in an embodiment of the present invention;

[0040] Figure 10 This is a schematic diagram of the aerodynamic profile of the three-dimensional S-bend flow channel in an embodiment of the present invention.

[0041] Reference numerals: Nozzle section 1, Experimental section 2, S-curve flow channel 3, Top profile 301, Bottom profile 302, Left side profile 303 and right side profile 304, Rectangular opening 305, Connecting flange 306, Cavity 4, First mounting plate 401, Second mounting plate 402, Side sealing plate 403, Observation window 5, First arc segment 601, First straight segment 602, Second arc segment 603, Third arc segment 604, Second straight segment 605, Fourth arc segment 606.

[0042] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0044] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0045] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0046] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0047] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0048] like Figure 3 The image shows a high-speed wind tunnel with axially openable windows disclosed in this embodiment, which mainly includes a nozzle section 1, an experimental section 2, and an S-curve flow channel 3 connected in sequence.

[0049] Specifically, nozzle section 1 and experimental section 2 are connected in a straight line. One end of the S-bend flow channel 3 is smoothly connected to the downstream end of experimental section 2, and the other end of the S-bend flow channel 3 extends backward and upward in an S-shape. Nozzle section 1, experimental section 2, and S-bend flow channel 3 can be fixed together by flanges and bolts. A cavity 4 is provided on the bottom profile 302 of the S-bend flow channel 3, and an observation window 5 facing experimental section 2 is provided on the side wall of the cavity 4, i.e., the observation window 5 is located axially in experimental section 2. By utilizing the ingenious combination of the S-bend flow channel 3 and the cavity 4, an axial window is achieved in the high-speed wind tunnel, allowing direct observation of the flow field in experimental section 2 in the opposite direction of flow.

[0050] refer to Figure 4-6 The S-curve flow channel 3 is a three-dimensional rectangular cross-section S-curve flow channel 3 enclosed by a top profile 301, a bottom profile 302, a left side profile 303, and a right side profile 304. Among them, the top profile 301 and the bottom profile 302 are curved surface structures with an S-shaped profile, while the left side profile 303 and the right side profile 304 are planar structures.

[0051] In the specific implementation process, refer to Figure 3 The top surface 301 has a profile consisting of a first arc segment 601, a first straight segment 602, and a second arc segment 603 connected in sequence. The center of the first arc segment 601 is located above the top surface 301, and the center of the second arc segment 603 is located below the top surface 301. One end of the first arc segment 601 is connected to the downstream end of the experimental segment 2 and is tangent to the top surface of the experimental segment 2, while the other end of the first arc segment 601 is tangent to the first straight segment 602. One end of the second arc segment 603 is tangent to the first straight segment 602, and the other end is tangent to the horizontal plane. The profile of the bottom profile 302 includes a third circular arc segment 604, a second straight line segment 605, and a fourth circular arc segment 606 connected in sequence. The center of the third circular arc segment 604 is located above the bottom profile 302, and the center of the fourth circular arc segment 606 is located below the bottom profile 302. One end of the third circular arc segment 604 is connected to the downstream end of the experimental section 2 and is tangent to the bottom surface of the experimental section 2. The other end of the third circular arc segment 604 is tangent to the second straight line segment 605. One end of the fourth circular arc segment 606 is tangent to the second straight line segment 605, and the other end is tangent to the horizontal plane. The observation window 5 is set on the bottom profile 302 of the S-bend flow channel 3, corresponding to a portion of the profile of the second straight line segment 605.

[0052] refer to Figure 7 This is a schematic diagram of the top profile 301 and bottom profile 302 of the S-curve flow channel 3. Figure 7 In the diagram, e1e2 is the first circular arc segment 601, e2e3 is the first straight line segment 602, e3e4 is the second circular arc segment 603, c1c2 is the third circular arc segment 604, c2c3 is the second straight line segment 605, and c3c4 is the fourth circular arc segment 606.

[0053] refer to Figure 8 In a high-speed airflow, the airflow will generate an expansion wave as it passes through the first circular arc segment 601e1e2. To prevent the high-speed airflow from expanding too rapidly and separating, the radius R of the first circular arc segment 601e1e2 is... e1 It cannot be too small, that is, the radius R of the first arc segment 601e1e2 e1 The constraint is to prevent flow separation. However, the airflow passing through the third circular arc segment 604c1c2 will generate compression waves and converging shock waves. To avoid the supersonic airflow generating shock waves near the wall during compression, leading to boundary layer separation, the radius R of the second circular arc segment 603c1c2 is... c1 It also cannot be too small, that is, the radius R of the third arc segment 604c1c2 c1 The constraint is to prevent boundary layer separation. Boundary layer separation leads to reduced wind tunnel start-up performance and decreased back pressure resistance of the S-bend flow channel 3. The angle between the first straight segment 602 and the horizontal plane is α. e The angle between the second straight segment 605 and the horizontal plane is α. c Among them, the angle α of the straight line segment e >α c This ensures that the cross-sectional area of ​​the S-bend flow channel 3 increases along the flow direction, guaranteeing the wind tunnel's start-up performance. In practical implementation, the length of the second straight segment 605c2c3 is determined based on the constraint of the axial window size. If it's too long, the performance of the S-bend flow channel 3 will decrease; if it's too short, the window space will be insufficient. Therefore, the length constraint of the second straight segment 605c2c3 is to be as small as possible while meeting the window space requirements. The design constraints for the dimensions of the S-bend flow channel 3 are given above. In actual design, the final dimensions will be determined based on experience and CFD calculation results or experimental results.

[0054] It should be noted that although the top and bottom profiles of the S-bend flow channel 3 can also be designed for shock-free operation using characteristic lines, the actual wind tunnel test section 2 will place an experimental model, which will cause the airflow entering the S-bend flow channel 3 to be uneven and the average Mach number to change, deviating significantly from the design state. Therefore, it is not necessary to use characteristic lines for shock-free operation.

[0055] In this embodiment, a rectangular opening 305 is formed on the bottom profile 302 of the S-bend flow channel 3, corresponding to a portion of the second straight segment 605, and the cavity 4 is disposed on the rectangular opening 305. Specifically, the cavity 4 includes a first mounting plate 401, a second mounting plate 402, and two side sealing plates 403. Both the first mounting plate 401 and the second mounting plate 402 are rectangular plates, and both side sealing plates 403 are triangular plates. The widths of the first mounting plate 401 and the second mounting plate 402 are the same as the width of the rectangular opening 305. One end of the first mounting plate 401 is connected to the upstream end of the rectangular opening 305, and the other end of the first mounting plate 401 is connected to one end of the second mounting plate 402. The other end of the second mounting plate 402 is connected to the downstream end of the rectangular opening 305. The first mounting plate 401 is horizontally arranged and parallel to the axis of the experimental section 2, while the second mounting plate 402 is perpendicular to the axis of the experimental section 2 and the first mounting plate 401. The observation window 5 is fixedly mounted on the second mounting plate 402. One side sealing plate 403 covers the right-angled triangular opening formed by one side of the first mounting plate 401, one side of the second mounting plate 402, and one side of the rectangular opening 305. The other side sealing plate 403 covers the right-angled triangular opening formed by the other side of the first mounting plate 401, the other side of the second mounting plate 402, and the other side of the rectangular opening 305. In specific implementation, the various structural components of the cavity 4 can be fixed by welding, bolting, or integral molding. The cavity 4 and the surface of the S-bend flow channel 3 can be fixed by welding, bolting, or integral molding. For example, the first mounting plate 401 is welded to the two side sealing plates 403 or integrally molded, and one end of the first mounting plate 401 and the two side sealing plates 403 forms an observation port. The second mounting plate 402 has a square annular structure, and the observation window 5 is clamped between the observation port and the second mounting plate 402, and is fixed to the observation port and the second mounting plate 402 by bolts.

[0056] refer to Figure 9 This is a schematic diagram of the axial window opening on the S-bend flow channel 3. Two straight lines, c5c6 and c6c7, are designed on the S-bend, parallel and perpendicular to the wind tunnel axis, respectively. Line c5c6 is the first mounting plate 401, and line c6c7 is the second mounting plate 402. Lines c5c6 and c6c7 form a cavity 4 in the flow channel. (Reference) Figure 8 In high-speed airflow, this concave cavity 4 generates a recirculation zone, which is basically filled with low-speed airflow, thus having little impact on the mainstream. An observation window 5 is arranged on the straight line c6c7, allowing direct observation of experimental section 2 via a camera. The height l of the straight line c6c7 can be adaptively determined according to the needs of flow field observation.

[0057] In the specific implementation process, the height of wind tunnel test section 2 will be adjusted accordingly. Figure 7The two-dimensional flow channel in the middle is stretched vertically to generate a three-dimensional rectangular cross-section S-bend flow channel 3. The cavities 4c5c6c7 are only used for opening windows and do not need to be designed to cover the entire height of the flow channel, thus minimizing the influence of the cavity 4 on the flow. Its height w is determined according to the required window size, thus obtaining... Figure 10 The three-dimensional S-curve flow channel aerodynamic profile is shown. Finally, in Figure 10 Based on this, the structural thickness of the S-bend flow channel 3 is designed, and connecting flanges 306 are designed at the inlet and outlet of the S-bend flow channel 3. Observation windows 5 are designed on the surface c6c7c′7c′6, thus completing the design. Figure 2-3 The three-dimensional configuration design of the S-bend flow channel 3 is shown.

[0058] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A high-speed wind tunnel with axially opening windows, characterized in that, It includes the nozzle section, the experimental section and the S-bend flow channel connected in sequence; The nozzle section is connected to the experimental section in a straight line. One end of the S-curve flow channel is smoothly connected to the downstream end of the experimental section, and the other end extends backward and upward in an S-shape. The bottom surface of the S-bend flow channel is provided with a cavity, and the side wall of the cavity is provided with an observation window facing the experimental section. The S-bend flow channel is a three-dimensional rectangular cross-section S-bend flow channel formed by a top surface, a bottom surface, a left side surface, and a right side surface; the profile of the bottom surface includes a third arc segment, a second straight line segment, and a fourth arc segment connected in sequence, with the center of the third arc segment located above the bottom surface and the center of the fourth arc segment located below the bottom surface; the observation window is located on a portion of the bottom surface of the S-bend flow channel corresponding to the second straight line segment.

2. The high-speed wind tunnel with axially openable windows according to claim 1, characterized in that, The top and bottom surfaces are both curved surface structures with an S-shaped profile, while the left and right sides are both planar structures.

3. The high-speed wind tunnel with axially openable windows according to claim 2, characterized in that, The top surface profile includes a first arc segment, a first straight line segment, and a second arc segment connected in sequence. The center of the first arc segment is located above the top surface, and the center of the second arc segment is located below the top surface. One end of the first arc segment is connected to the downstream end of the experimental segment and is tangent to the top surface of the experimental segment; the other end of the first arc segment is tangent to the first straight segment. One end of the second arc segment is tangent to the first straight line segment, and the other end is tangent to the horizontal plane.

4. The high-speed wind tunnel with axially openable windows according to claim 3, characterized in that, One end of the third arc segment is connected to the downstream end of the experimental segment and is tangent to the bottom surface of the experimental segment; the other end of the third arc segment is tangent to the second straight segment. One end of the fourth arc segment is tangent to the second straight line segment, and the other end is tangent to the horizontal plane.

5. The high-speed wind tunnel with axially openable windows according to claim 4, characterized in that, The angle between the first straight line segment and the horizontal plane is . α e The angle between the second straight line segment and the horizontal plane is α c ; in, α e > α c This ensures that the cross-sectional area of ​​the S-curve flow channel increases along the flow direction, thus ensuring the wind tunnel's start-up performance.

6. The high-speed wind tunnel with axially openable windows according to claim 5, characterized in that, A rectangular opening is provided on the bottom surface of the S-bend flow channel corresponding to a portion of the second straight segment, and the cavity is provided on the rectangular opening.

7. The high-speed wind tunnel with axially openable windows according to claim 6, characterized in that, The cavity includes a first mounting plate, a second mounting plate, and two side sealing plates; One end of the first mounting plate is connected to the upstream end of the rectangular opening, the other end of the first mounting plate is connected to one end of the second mounting plate, and the other end of the second mounting plate is connected to the downstream end of the rectangular opening. The first mounting plate is horizontally arranged and parallel to the axis of the experimental section, the second mounting plate is perpendicular to the axis of the experimental section, and the observation window is located on the second mounting plate. One of the side sealing plates is connected to one side of the first mounting plate, one side of the second mounting plate, and one side of the rectangular opening, while the other side sealing plate is connected to the other side of the first mounting plate, the other side of the second mounting plate, and the other side of the rectangular opening.

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