A small supersonic shock tunnel test section with easily removable components

Abstract

The application discloses a small-sized supersonic shock tunnel test section with easy assembly and disassembly, and belongs to the field of aerospace technology. The supersonic shock tunnel test section comprises a first flange connected with a shock tube, and a second flange connected with a wind tunnel; a round-to-square rigid section, a connecting fixed section and a test observation section are sequentially connected between the first flange and the second flange; and a nozzle is detachably installed in the test observation section. The fixed parts and the connecting parts of the test section are easy to assemble, the nozzle rigid section and the round-to-square section are easy to disassemble, a more efficient experiment process is realized, and compatibility of gas dynamics teaching practice and scientific research experiment is achieved; secondly, the longitudinal observation window and the side observation window are simultaneously used, optical conditions are more favorable for nozzle starting and working process, optical observation means such as the schlieren method, the fluorescent oil flow method and the sheet light tomography method can be applied to analyze the flow field mechanism, and the supersonic shock tunnel test section provides an equipment basis for cold flow experiment of an advanced nozzle of a solid rocket engine.

Description

Technical Field

[0001] This invention belongs to the field of aerospace technology, specifically relating to a small supersonic shock wave wind tunnel test section with easily detachable components. Background Technology

[0002] Shock tunnels are crucial experimental devices used to verify the aerodynamic shape of rockets, missiles, and aircraft, and are also the main apparatus for supersonic gas dynamics testing. By placing the experimental object in the test section and simulating the flow field conditions under real-world conditions (such as maintaining similarity in dimensionless parameters like Reynolds number, Mach number, or inlet / outlet pressure ratio), the flow field parameters and the mechanical properties of the experimental object are measured. This device is of great significance for the performance evaluation and mechanistic study of advanced nozzles.

[0003] A fixed Mach number wind tunnel can only handle a single incoming Mach number in a single test, which cannot meet the experimental requirements of Mach number variations. For aerodynamic tests of aircraft with multiple Mach numbers over a wide airspace, these three incoming Mach numbers can only be achieved by changing the wind tunnel nozzles to Mach numbers 2, 3, and 4. Each additional Mach number requires an additional experimental setup or test section, which is not economical. For engine nozzle performance tests with multiple pressure ratios, the charging pressure is mainly determined by the air source pressure. Advanced nozzles have different profiles, but for two-dimensional nozzles, observing the start-up and operation process of the flow field inside the nozzle is crucial, and repeatedly designing test sections is unnecessary. At the same time, with the rapid development of the aerospace field in various countries, the modal transition problem of advanced propulsion systems during operation is receiving increasing attention. Although the total temperature of the cold air source deviates significantly from the total temperature of the actual engine, this is the first step in the engineering application of advanced nozzles. Traditional large-scale continuous working wind tunnels often use large-diameter bell-shaped nozzles to accelerate airflow. To obtain a uniform airflow at a higher Mach number, the required nozzle volume increases accordingly. The volume of the vacuum tank and the power of the vacuum pump required for stable back pressure conditions also increase exponentially. Furthermore, the experimental costs are extremely high, making it difficult for teaching institutions to afford.

[0004] In gas dynamics teaching, the phenomena of shock waves and shock wave interference are complex and abstract, making it difficult for students to connect theory with practice. For example, it is difficult for them to intuitively grasp the design methods of hypersonic engine inlets and rocket engine nozzles (the surface design of these components is a direct application of gas dynamics and shock wave theory). In actual experiments, to achieve specific shock waves and specific Mach numbers, it is necessary to control the inlet gas pressure and velocity. Fixed nozzle profiles can only provide specific experimental conditions. Summary of the Invention

[0005] To meet the practical needs of gas dynamics teaching and scientific research goals such as rocket engine nozzles and shock wave dynamics, this invention provides a small supersonic shock wave wind tunnel test section with easily detachable components.

[0006] The technical solution adopted in this invention is:

[0007] A small supersonic shock wave wind tunnel test section with easily detachable components includes a first flange connected to a shock tube and a second flange connected to the wind tunnel; a round-to-square rigid section, a connecting and fixing section, and a test observation section are sequentially connected between the first flange and the second flange, and a nozzle is detachably installed in the test observation section.

[0008] Compared with the prior art, the present invention has the following advantages:

[0009] 1. The various fixing and connecting parts of the test section of this invention are easy to assemble, and the rigid section and the round-to-square section of the nozzle are easy to disassemble, realizing a more efficient experimental process and making it compatible with practical teaching and scientific research experiments in gas dynamics. Secondly, the simultaneous use of longitudinal and side observation windows provides more favorable optical conditions for the nozzle start-up and working process, and optical observation methods such as schlieren, fluorescent oil flow method and sheet tomography can be applied to analyze the flow field mechanism, providing an equipment foundation for the cold flow test of advanced nozzles of solid rocket engines.

[0010] 2. This invention reduces repetitive design by using a modular, easily detachable, small-scale test section based on functional decomposition. It utilizes multiple sets of small two-dimensional nozzles to achieve multiple supersonic airflow conditions. This test section will also be used for cold flow testing of advanced nozzles. Secondly, the requirements for the right angle of the circular-to-square transition section in a reflective shock tunnel are lower, and the low-pressure section has a short operating time, eliminating the need for high-precision sealing structures. Finally, the installation or absence of the second diaphragm and nozzle section will enhance students' understanding of the principles of shock tubes and reflective shock tunnels. The side observation window starting from the upstream of the nozzle will better demonstrate the characteristics of unsteady flow fields in teaching.

[0011] 3. This invention has three significant advantages: First, the experimental cost is low and the preparation time is short. Each time, only a small civilian compressor is needed to fill the gas to meet the gas pressure source. The low-pressure section has a short working time, and the sealing structure does not require high-precision design. Second, the rigid section and the round-to-square section of the nozzle are easy to disassemble and assemble. The equipment can be configured according to the experimental needs to achieve multiple sets of supersonic inflow conditions. The background of strong expansion waves is also suitable for scientific research on advanced nozzles and shock wave dynamics of solid rocket engines. Third, the test section not only has a traditional longitudinal observation window, but also a side observation window design with a load-bearing metal structure clamping high-transmittance plexiglass, so that the internal flow field during the nozzle start-up and working process can also be fully observed, which is convenient for experimental and teaching demonstrations. Attached Figure Description

[0012] Figure 1 This is an exploded view of the entire invention;

[0013] Figure 2 This is a symmetrical exploded view of the first half of the invention;

[0014] Figure 3 This is a symmetrical exploded view of the latter half of the invention;

[0015] Figure 4 This is a top view of the metal fixing plate of the present invention;

[0016] Figure 5 This is an isometric view of the connecting fixed section of the present invention;

[0017] Figure 6 This is a schematic diagram of the specially designed bolt of this invention;

[0018] Figure 7 This is a schematic diagram of the specially designed bolt of this invention;

[0019] The components are as follows: 1. First flange; 2. Sealing ring one; 3. Round-to-square rigid section; 4. Connecting and fixing section; 5. Sealing ring two; 6. Longitudinal observation window outer shell; 7. Acrylic glass plate two; 8. Sealing ring three; 9. Longitudinal observation window inner shell; 10. Sealing ring four; 11. Metal fixing plate; 12. Front straight section of nozzle; 13. Rigid contraction and expansion section of nozzle; 14. Nozzle transition section; 16. Acrylic glass plate one; 17. Strip-shaped fixing component; 18. T-shaped fixing block; 19. Second flange; 20. Sealing ring five; 21. Special bolt; 22. Through-hole bolt; 23. Vacuuming pre-drilled hole; 24. Window; 25. Countersunk hole. Detailed Implementation

[0020] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0021] The basic principle of a shock tunnel is that gas is introduced into the high-pressure section, and a shock wave is formed after the diaphragm ruptures. This shock wave impacts a second diaphragm and is reflected. The gas after the reflected shock wave undergoes two shock wave compressions to reach a high-temperature and high-pressure state, which is then used as the gas source for the test section. This invention, based on a typical shock tube device, collaboratively designs various types of nozzles and small test sections equipped with nozzles. Wind tunnel experiments can be conducted according to the required incoming Mach number and static pressure, providing an experimental foundation for research on advanced nozzles for solid rocket engines, supersonic gas dynamics, and shock wave dynamics. According to the isentropic one-dimensional flow theory, the nozzle exit Mach number determines the nozzle expansion ratio; according to the isentropic irrotational two-dimensional flow principle, the surface shape of the nozzle's convergent and expanding sections determines the uniformity of the flow velocity at the nozzle exit. In actual experiments, different nozzles are required for different Mach numbers, which is expensive. This problem can be solved by applying an innovative concept based on functional decomposition, that is, separating the circular-to-square section and the nozzle section structure for separate design. Secondly, in gas dynamics teaching and research, schlieren systems are often used to observe supersonic airflow phenomena in test sections, allowing students to intuitively understand shock wave phenomena. However, traditional designs fail to fully demonstrate the flow field characteristics from nozzle start-up to stabilization. This invention aims to be compatible with both scientific research experiments and practical teaching, proposing an easily disassembled and sealed test section design. High-transmittance materials are used on the sides, and observation windows are installed at the top and bottom, enabling comprehensive observation of the flow field characteristics within the test section. Firstly, this invention designs typical nozzle convergent and divergent section profiles according to experimental needs, reducing repetitive design and material loss from overall disassembly and assembly, and providing the function of providing a specific Mach number inflow. Secondly, the easily disassembled and fully sealed test section structure significantly improves the experimental efficiency of supersonic flow field measurement. Finally, the multi-directional light transmission design facilitates the application of multi-source, multi-spectral supplementary lighting techniques. The combination of schlieren imaging, fluorescent oil flow technology, and sheet tomography will significantly enhance the observation effect.

[0022] Reference Figures 1 to 7 As shown, a small supersonic shock wave wind tunnel test section with easily detachable components according to the present invention includes a first flange 1 connected to a shock tube and a second flange 19 connected to the wind tunnel; a round-to-square rigid section 3, a connecting and fixing section 4 and a test observation section are connected sequentially between the first flange 1 and the second flange 19, and a nozzle is detachably installed in the test observation section.

[0023] Among them: such as Figure 1 , Figure 2 As shown, the shock tube is connected to the test section via the first flange 1 and secured with bolts.

[0024] The female head on the right side of the first flange 1 fits tightly with the male head of the round-to-square rigid section 3. It is equipped with a sealing ring 2 inside to ensure sealing. A threaded through hole is drilled on the flat surface milled on the outer side of the boss on the right side of the first flange 1. The round-to-square rigid section 3 is also drilled with a threaded hole and is connected by bolts. These four bolts are staggered from the eight flange bolts on the first flange 1 to prevent bolts from interfering with each other and to facilitate disassembly and assembly.

[0025] like Figure 1 , Figure 2 , Figure 5 As shown, the left end of the connecting and fixing section 4 is a hollow cylindrical part that is bolted to the round-to-square rigid section 3, and the right end of the connecting and fixing section 4 is a square boss part that is connected to the square test observation section. The purpose is to allow the inner surface through which the fluid flows to transition evenly from a circular cross-section to a square cross-section.

[0026] The rigid section 3 (round to square) and the connecting and fixing section 4 are sealed by a sealing ring 5 to ensure airtightness.

[0027] like Figure 1 As shown, the test observation section uses both longitudinal and side observation windows. The pressure is mainly transmitted to the metal fixing plate, the connecting fixing section, and the flange connected to the wind tunnel through two steel plates and T-shaped steel blocks. This configuration is a pressure-resistant box structure. Specifically, it includes two metal fixing plates 11 and two plexiglass plates 16. The two plexiglass plates 16 and the two metal fixing plates 11 intersect and are connected end to end to form the rectangular side wall of the test observation section. The two plexiglass plates 16 and the two metal fixing plates 11 are detachably fixed between the connecting fixing section 4 and the second flange 19 by bolts. The two plexiglass plates 16 are arranged opposite each other as side observation windows, and the longitudinal observation window is installed on the metal fixing plate 11.

[0028] The two acrylic glass plates 16 are reinforced at the top and bottom with strip fasteners 17. The inner sides of the two acrylic glass plates 16 are detachably connected to the sides of the two metal fixing plates 11 by bolts and sealed by sealing rings 6. The outer sides of the left and right ends of the two acrylic glass plates 16 are pressed by T-shaped fixing blocks 18. The inner sides of the left and right ends of the two acrylic glass plates 16 are respectively fixed to the square boss part 1 of the connecting fixing section 4 and the second square boss part 2 on the left end of the second flange 19, in order to provide the widest viewing angle.

[0029] The left and right ends of the two metal fixing plates 11 are respectively detachably fixed to the square boss part one of the connecting fixing section 4 and the square boss part two of the second flange 19 by bolts. Both metal fixing plates 11 have windows 24 for installing longitudinal observation windows. The purpose is to inject a light source of a specific spectrum or to observe the experimental phenomena in the test piece (nozzle or other test piece) vertically, so as to better observe the experimental phenomena of the test piece in the longitudinal direction.

[0030] Metal fixing plate 11 is the main load-bearing component, such as Figure 1 As shown, the two acrylic glass plates 16 can adopt a structure with a central protrusion and an outer extension around the perimeter, and corresponding grooves are opened in the square protrusion part 1 and the square protrusion part 2. The two metal fixing plates 11 adopt a structure with a central protrusion and an outer extension at both ends. With this structure, when the two acrylic glass plates 16 and the two metal fixing plates 11 are installed, the outer surfaces can be connected together, avoiding gaps or protruding parts on the outer surface of the test observation section, while also ensuring the thickness requirements of the acrylic glass plates 16.

[0031] Both longitudinal observation windows include a longitudinal observation window outer shell 6, an acrylic glass plate 2 7, and a longitudinal observation window inner shell 9. The acrylic glass plate 2 7 is clamped and fixed by the longitudinal observation window outer shell 6 and the longitudinal observation window inner shell 9 located on its upper and lower sides. The entire longitudinal observation window is fixed to the metal fixing plate 11 through the longitudinal observation window inner shell 9.

[0032] The inner shell 9 of the longitudinal observation window and the metal fixing plate 11 are sealed by a sealing ring 10 to ensure airtightness;

[0033] The plexiglass plate 27 and the inner shell 9 of the longitudinal observation window are sealed by a sealing ring 38 to ensure airtightness;

[0034] like Figure 4 As shown, the metal fixing plate 11 is provided with multiple threaded countersunk holes 25 for fixing the test piece and installing the pressure sensor.

[0035] like Figure 6 As shown, the structure of the special bolt 21 is to add a cylindrical end to the tail of the M16 bolt body. By adding a sealing ring 20, the sealing performance can be guaranteed during the experiment. The special bolt 21 is installed on the countersunk hole 25 on the metal fixing plate 11 to seal the test observation section and ensure its sealing performance.

[0036] like Figure 7 As shown, the through-hole bolt 22 used to connect the metal fixing plate 11 and the pressure sensor has a structure in which a cylinder is added to the tail of the M16 bolt body, and a center hole with a diameter of 4mm is left in the center.

[0037] The nozzle or other test piece is always connected to the countersunk hole 25 of the metal mounting plate 11 by bolts, such as M8 bolts;

[0038] The through-hole bolt 22 is installed on one of the countersunk holes 25 of the metal fixing plate 11. The pressure sensor is installed on the center hole of the through-hole bolt 22. The cylinder of the through-hole bolt 22 is tightly inserted into the corresponding threaded hole of the nozzle and cooperates with the sealing gasket to ensure airtightness.

[0039] During the experiment, a special bolt 21 can be used to replace the through-hole bolt 22. The cylinder of the special bolt 21 is tightly inserted into the corresponding threaded hole of the nozzle and cooperates with the sealing gasket to ensure complete sealing during the experiment.

[0040] like Figure 4 As shown, the metal fixing plate 11 is also provided with a vacuuming pre-reserved hole 23;

[0041] like Figure 1 As shown, the nozzle consists of a straight section 12, a rigid contraction and expansion section 13, and a transition section 14 connected in sequence. The straight section 12, the rigid contraction and expansion section 13, and the transition section 14 are all split structures composed of plates arranged vertically opposite each other. The two opposite surfaces of the rigid contraction and expansion section 13 adopt curved surfaces that rise and then fall to simulate the actual engine nozzle structure. The nozzle and the observation windows on both sides constitute the jet passage.

[0042] The straight section 12 of the nozzle, the rigid contraction and expansion section 13 of the nozzle, and the transition section 14 of the nozzle are all detachably fixed to the metal fixing plate 11 by bolts, which can adjust the position of the nozzle and facilitate the observation of experimental phenomena at the nozzle throat.

[0043] With the above structure, the steel block in front of the nozzle throat is easy to replace, the nozzle position is easy to adjust, and the rigid nozzle section is easy to disassemble and replace.

[0044] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A small supersonic shock wave wind tunnel test section with easily detachable components, comprising a first flange (1) connected to a shock tube and a second flange (19) connected to the wind tunnel; characterized in that: A rigid section (3) for round-to-square transition, a connecting and fixing section (4), and a test observation section are sequentially connected between the first flange (1) and the second flange (19). A nozzle is detachably installed in the test observation section. The left end of the connecting and fixing section (4) is a hollow cylindrical part that is bolted to the round-to-square rigid section (3), and the right end of the connecting and fixing section (4) is a square boss part that is connected to the square test observation section. The test observation section adopts a box-type structure, including two metal fixing plates (11) and two plexiglass plates (16); the two plexiglass plates (16) and the two metal fixing plates (11) intersect and are connected end to end to form the rectangular sidewall of the test observation section. The two plexiglass plates (16) and the two metal fixing plates (11) can be detachably fixed between the connecting fixing section (4) and the second flange (19). The two plexiglass plates (16) are arranged opposite each other as side observation windows. A longitudinal observation window is installed on the metal fixing plate (11). The nozzle consists of a straight section (12), a rigid contraction and expansion section (13), and a transition section (14) connected in sequence. The straight section (12), the rigid contraction and expansion section (13), and the transition section (14) are all split structures composed of plates arranged vertically opposite each other. The two opposite surfaces of the rigid contraction and expansion section (13) adopt curved surfaces that rise and then fall to simulate the actual engine nozzle structure. The nozzle and the observation windows on both sides form the jet passage. The straight section (12) at the front of the nozzle, the rigid contraction and expansion section (13) of the nozzle, and the transition section (14) of the nozzle are all detachably fixed to the metal fixing plate (11) by bolts. The left and right ends of the two metal fixing plates (11) are respectively detachably fixed to the square boss part one of the connecting fixing section (4) and the square boss part two of the second flange (19). Both metal fixing plates (11) have windows (24) for installing longitudinal observation windows.

2. The small supersonic shock wave wind tunnel test section with easily detachable components as described in claim 1, characterized in that: The two plexiglass plates (16) are reinforced at the top and bottom with strip fasteners (17) on the outside. The inner sides of the two plexiglass plates (16) are detachably connected to the sides of the two metal fixing plates (11). The outer sides of the left and right ends of the two plexiglass plates (16) are pressed by T-shaped fixing blocks (18). The inner sides of the left and right ends of the two plexiglass plates (16) are respectively fixed on the square boss part one of the connecting fixing section (4) and the square boss part two is provided on the left end of the second flange (19).

3. The small supersonic shock wave wind tunnel test section with easily detachable components as described in claim 1, characterized in that: Both of the longitudinal observation windows include a longitudinal observation window outer shell (6), an acrylic glass plate two (7), and a longitudinal observation window inner shell (9); the acrylic glass plate two (7) is clamped and fixed by the longitudinal observation window outer shell (6) and the longitudinal observation window inner shell (9) located on its upper and lower sides, and the entire longitudinal observation window is fixed on the metal fixing plate (11) through the longitudinal observation window inner shell (9).

4. The small supersonic shock wave wind tunnel test section with easily detachable components as described in claim 1, characterized in that: The metal fixing plate (11) is provided with multiple threaded countersunk holes (25) for fixing the test piece and installing the pressure sensor.

5. A small supersonic shock wave wind tunnel test section with easily detachable components as described in claim 1, characterized in that: The small supersonic shock wave wind tunnel test section with easy assembly and disassembly of the components also includes specially made bolts (21) and through-hole bolts (22). The structure of the special bolt (21) is that a cylindrical end is added to the tail of the bolt body and installed on the countersunk hole (25) of the metal fixing plate (11), which is used in conjunction with the sealing ring five (20) for the sealing test observation section. The through-hole bolt (22) has a cylindrical end added to the tail of the bolt body and a central hole in the center. The central hole is used to install a pressure sensor. The through-hole bolt (22) can be used interchangeably with the special bolt (21).

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