A supersonic wind tunnel diffuser for a ramjet test stand

Abstract

This invention discloses a supersonic wind tunnel diffuser for a ramjet engine test bench, which solves the technical problems of high design difficulty, high control requirements, high production cost and reduced equipment lifespan caused by wide operating conditions design, as well as multiple model designs. By independently setting the contraction section, straight section, expansion section and cooling section of the supersonic wind tunnel diffuser, and setting the straight section to N, and by designing a universal flange assembly, the design effect of variable layout and adjustable length is achieved, which can meet the test requirements of different engine specifications and greatly reduce the test cost.

Description

Technical Field

[0001] This invention relates to a supersonic wind tunnel diffuser, and more specifically to a supersonic wind tunnel diffuser for a ramjet engine test bench. Background Technology

[0002] On the test bench for the pre-research model of the ramjet engine, when recovering and processing the supersonic high-temperature exhaust gas discharged from the engine, a supersonic wind tunnel diffuser is used to decelerate and pressurize the supersonic airflow to subsonic speed. This is to prevent the supersonic high-temperature exhaust gas from directly impacting the ground and equipment, which could cause serious thermal damage and mechanical destruction, such as burning the test bench structure or damaging the measuring equipment.

[0003] Supersonic wind tunnel diffusers mainly consist of cylindrical diffusers and secondary throat diffusers. The secondary throat diffuser comprises a contraction section, a secondary throat, and an expansion section. The secondary throat structure addresses shock wave loss during supersonic airflow diffusion. First, the inlet section receives the upstream flow (usually supersonic), guiding it smoothly into the diffuser to "capture" and control the shock wave position, preventing premature shock wave formation and energy loss in the expansion section. Then, the airflow is decelerated to subsonic speeds through the secondary throat, and finally, through the expansion section, it is further decelerated and pressurized, outputting gas at the same pressure as the outlet environment. Cylindrical diffusers, unlike secondary throat diffusers, do not include a contraction section.

[0004] Because the test benches for pre-research ramjet engines test the ramjet engines, the dimensions of the tested ramjet engines vary considerably, and the engine flow is complex and variable. Even for engines of the same size, the operating conditions vary significantly at different test phases, with substantial differences in flow rate, pressure, and temperature. Therefore, existing supersonic wind tunnel diffusers generally adopt either a wide operating range design or a design of multiple models and types of supersonic wind tunnel diffusers.

[0005] Adopting a wide operating range design requires precise calculation and optimization of the flow channel shape, size, and matching relationships of various parts, which is challenging and demands higher control standards. Designing multiple models of secondary throat supersonic diffusers to suit different engines would result in excessively high production costs. Changing engine dimensions would necessitate replacing the entire secondary throat supersonic diffuser, leading to frequent disassembly and replacement of equipment, reducing its lifespan, and posing significant safety hazards. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of high design difficulty, high control requirements, high production cost and reduced equipment lifespan caused by wide operating condition design, as well as the problem of high production cost and reduced equipment lifespan caused by multi-model design, and to provide a supersonic wind tunnel diffuser for ramjet engine test bench.

[0007] A supersonic wind tunnel diffuser for a ramjet engine test rig is characterized by comprising independently configured expansion sections, cooling sections, an air ejector system, multiple flange assemblies, multiple bridging cooling assemblies, and N straight sections. ;

[0008] The inlet of one of the N straight sections is connected to the outlet of the ramjet engine to be tested, and its outlet is detachably connected to the inlet of the expansion section via a flange assembly; or, at least two of the N straight sections are sequentially connected via the flange assembly to form a straight section combination, the inlet of the first straight section in the straight section combination is connected to the outlet of the ramjet engine to be tested, and the outlet of the last straight section is detachably connected to the inlet of the expansion section via a flange assembly.

[0009] The outlet of the expansion section is detachably connected to the inlet of the cooling section via a flange assembly; the outlet of the cooling section is connected to the inlet of the air ejector system to reduce the outlet pressure of the cooling section.

[0010] Each flange assembly includes a flange and a flange cooling assembly. The N straight sections, expansion sections, and cooling sections each include an inner shell and an outer shell. The cavity between each inner shell and outer shell forms an independent cooling jacket. The flange is disposed on the connection port of the corresponding straight section, expansion section, or cooling section. The flange cooling assembly is connected to the corresponding flange and disposed on the outside of the corresponding inner shell. Its inlet is connected to the corresponding independent cooling jacket, and its outlet is connected to an external drain pipe for cooling the flange.

[0011] The N straight sections, expansion sections, and cooling sections are each provided with a cooling medium inlet and a cooling medium outlet that communicate with the cooling interlayer. The bridging cooling assembly is used to connect two adjacent cooling interlayers through the cooling medium inlet and the cooling medium outlet.

[0012] Furthermore, the supersonic wind tunnel diffuser for the ramjet engine test bench also includes a contraction section; the inlet of one of the N straight sections is connected to the outlet of the ramjet engine to be tested through the contraction section; the inlet of the first straight section in the straight section combination is connected to the outlet of the ramjet engine to be tested through the contraction section; the outlet of the contraction section is detachably connected to the inlet of one of the N straight sections, or the inlet of the first straight section in the straight section combination, through a flange assembly.

[0013] The contraction section includes an inner shell and an outer shell, and the cavity between the inner shell and the outer shell forms an independent cooling interlayer; the contraction section is provided with a cooling medium inlet and a cooling medium outlet that communicate with the independent cooling interlayer;

[0014] The cooling medium inlet on the contraction section and the cooling medium outlet on the adjacent straight section are connected to the two cooling layers through the bridging cooling assembly.

[0015] Further, let R2 be the diameter of the throat of the ramjet engine under test, and S2 be the radial cross-sectional area; let R1 be the diameter of the straight section, and S1 be the radial cross-sectional area. , ,in, The value range is 56~120. The value range is 7.48 to 10.95;

[0016] Define the length of the i-th straight segment among N straight segments as . ,in, ,but .

[0017] Furthermore, the supersonic wind tunnel diffuser for the ramjet engine test bench also includes a support seat set on a preset support position, which is located on the straight section and / or the cooling section;

[0018] The support base includes a first support plate, a second support plate, and a third support plate arranged in parallel and radially along a preset support position, and each of the three supports has a through hole at its center.

[0019] The dimensions of the central through holes of the first and second support plates are adapted to the dimensions of the outer shell, and the dimensions of the central through hole of the third support plate are adapted to the dimensions of the inner shell. An annular notch is provided on the outer shell between the first and second support plates along its circumference. The third support plate passes through the annular notch, is fitted onto the inner shell, and is fixedly connected to the inner shell. The annular notch is sealed by two annular arc-shaped transition sections. One side of the arc-shaped transition section is fixedly connected to the third support plate, and the other side is fixedly connected to the inner shell. The inner walls of the through holes of the first and second support plates are fixedly connected to the outer shell. The outer walls of the first, second, and third support plates are connected by an annular support plate, and a bottom support is provided at the lower part of the annular support plate.

[0020] The third support plate has a through hole in the part of its structure located within the notch, allowing the cooling medium to flow from one side of the third support plate to the other.

[0021] Furthermore, of the two interconnected flanges, one flange has an annular sealing groove on its surface, and a first sealing gasket is disposed within the annular sealing groove; the other flange has an annular boss on its surface, and the annular boss is adapted to the annular sealing groove to seal the connection between the two flanges.

[0022] Furthermore, there are two annular sealing grooves, one of which has a rigid sealing gasket and the other has a rubber sealing gasket.

[0023] Furthermore, the flange cooling assembly includes an annular outer wall disposed at the connection between the flange and the inner shell. The annular outer wall is arranged circumferentially along the inner shell, and the accommodating space between it and the inner shell forms a flange cooling chamber for accommodating the cooling medium for cooling the flange.

[0024] The annular outer wall is provided with a drainage interface connected to the outlet, and the drainage interface is connected to an external drainage pipe.

[0025] The inlet of the flange cooling chamber is connected to its corresponding independent cooling jacket, so that the cooling medium in the independent cooling jacket can flow into the flange cooling chamber to cool the flange.

[0026] Furthermore, the bridging cooling assembly includes a bridging bend, on which the cooling medium inlet and cooling medium outlet on the contraction section, the straight section, the expansion section, and the cooling section are all located on its lower side, and the two ends of the bridging bend are respectively connected to two adjacent cooling medium inlets and cooling medium outlets.

[0027] Furthermore, buffer chambers are provided in the contraction section, the straight section, the expansion section, and the cooling section;

[0028] The buffer chambers are located at both ends of the independent cooling jacket, and the radial cross-sectional area of ​​the buffer chambers is larger than that of the independent cooling jacket; the cooling medium inlet and the cooling medium outlet are both located on the buffer chambers.

[0029] The vertical wall of the buffer chamber is fixedly connected to the annular outer wall of the flange cooling assembly and to the inner shell. Multiple flow holes are provided on the vertical wall to transport part of the cooling medium in the buffer chamber to the flange cooling chamber.

[0030] Furthermore, both the buffer chamber and the flange cooling chamber are equipped with drainage plates.

[0031] Compared with the prior art, the present invention has the following beneficial technical effects:

[0032] 1. This invention discloses a supersonic wind tunnel diffuser for a ramjet engine test bench. By independently configuring the constant-straight section, expansion section, and cooling section of the supersonic wind tunnel diffuser, and by setting N constant-straight sections, a universal flange assembly is designed to achieve a variable layout and adjustable length, meeting the testing requirements of different engine specifications and greatly reducing testing costs. Furthermore, by adding an air ejector system, the outlet pressure of the cooling section is reduced, ensuring that the outlet gas of the cooling section meets the requirements.

[0033] 2. The present invention provides a supersonic wind tunnel diffuser for a ramjet engine test bench. By adding an independently configured contraction section and combining it with independently configured isostatic sections, expansion sections, and cooling sections, various types of secondary throat diffusers are obtained, which can meet the test requirements of more engine specifications and greatly reduce the test cost.

[0034] 3. The present invention provides a supersonic wind tunnel diffuser for a ramjet engine test bench. By integrating a flange cooling assembly and a flange on a flange assembly and setting a bridging cooling assembly, the cooling requirements of the flange are met. At the same time, the independent cooling jackets between the contraction section, N straight sections, expansion section and cooling section are bridging to form a complete cooling scheme, which meets the cooling requirements of each section in the distributed design. The structure is simple and easy to install.

[0035] 4. This invention provides a supersonic wind tunnel diffuser for a ramjet engine test bench. Because high-altitude engine simulation tests require maintaining a low-pressure vacuum at the nozzle exit, and the engine generates high-temperature combustion gases after operation, it is necessary to extract these gases to maintain a certain vacuum environment within the test chamber. Therefore, a supersonic wind tunnel diffuser for a ramjet engine test bench is required at the engine outlet. This is achieved by setting the ratio of the radial cross-sectional area of ​​the straight section to the radial cross-sectional area of ​​the engine throat under test to be in the range of 56~120, setting the ratio of the diameter of the straight section to the diameter of the engine throat under test to be in the range of 7.48~10.95, and setting the length-to-diameter ratio of the straight section to a value within a certain range. Within the range, it can fully utilize the kinetic energy of the airflow at the height of the jet nozzle outlet section to increase the pressure and decrease the speed of the gas, ensuring that there is no shock wave blockage in the diffuser of the supersonic wind tunnel used for ramjet engine test bench, with low total pressure loss and low starting pressure ratio.

[0036] 5. This invention provides a supersonic wind tunnel diffuser for a ramjet engine test rig. Due to the distributed design of the supersonic wind tunnel diffuser for a ramjet engine test rig, with sections connected by flange assemblies, especially in layouts with a long overall length, simply supporting and fixing at both ends would lead to structural instability, particularly at the connection points of straight sections. Therefore, a support base is designed at the support position to effectively support the supersonic wind tunnel diffuser. Furthermore, since both the inner and outer shells of each section are thin-walled structures, if the support base is directly installed on the outer shell, under stress, the outer shell at the support position will deform and move towards the inner shell. This would severely affect the cross-sectional area of ​​the cooling interlayer between the inner and outer shells, hindering the flow of the internal cooling medium and consequently impacting the cooling effect of the supersonic wind tunnel diffuser for the ramjet engine test rig. By designing two first and second support plates connected to the outer shell, and a third support plate connected to the inner shell, the supporting force can be distributed to the inner and outer shells, effectively avoiding the outer shell being subjected to force alone, which would affect the flow of cooling medium and improve the cooling effect of the supersonic wind tunnel diffuser used in ramjet engine test benches.

[0037] 6. The present invention provides a supersonic wind tunnel diffuser for a ramjet engine test bench, which connects a first support plate, a second support plate, and a third support plate together by setting an annular support plate, and sets a bottom support on the side near the bottom surface, resulting in better support and greater stability.

[0038] 7. This invention discloses a supersonic wind tunnel diffuser for a ramjet engine test bench. A concave-convex sealing structure is provided on the flange surface, and a first sealing gasket is placed within an annular sealing groove to improve the sealing performance at the connection. Furthermore, since the temperature is higher closer to the inner side of the flange, a rigid first sealing gasket is placed within an annular sealing groove near the inner side to meet both sealing performance and high-temperature resistance requirements. A rubber first sealing gasket is placed within an annular sealing groove further away from the outer side to enhance the secondary sealing effect. This combined sealing structure effectively improves both sealing performance and service life.

[0039] 8. This invention discloses a supersonic wind tunnel diffuser for a ramjet engine test bench. It includes a flange cooling chamber and a buffer chamber, both designed to effectively buffer the cooling medium flowing through the flange and the cooling medium that needs to pass through a bridging bend into the next independent cooling jacket, preventing impact on the connecting components. Multiple flow holes are provided on the vertical wall between the buffer chamber and the flange cooling assembly, allowing some of the cooling medium to flow into the flange cooling assembly for independent cooling of the flange. The cooling medium flows out through a drain port, eliminating the need for it to flow back into the independent cooling jacket, simplifying the structural design and improving the cooling effect.

[0040] 9. The present invention provides a supersonic wind tunnel diffuser for a ramjet engine test bench, wherein a flow guide plate is designed in the buffer chamber to effectively guide the cooling medium entering the buffer chamber, so that it can smoothly pass through the bridging bend into the next independent cooling jacket. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of an embodiment of a supersonic wind tunnel diffuser for a ramjet engine test bench according to the present invention (excluding the air ejector system).

[0042] Figure 2 for Figure 1 A magnified view of the structure at point A;

[0043] Figure 3 for Figure 1 A magnified view of the structure at point B;

[0044] Figure 4 This is the first combination form (excluding the air ejector system) of a supersonic wind tunnel diffuser for a ramjet engine test bench according to the present invention.

[0045] Figure 5 This is a second combination (excluding the air ejector system) of an embodiment of a supersonic wind tunnel diffuser for a ramjet engine test bench according to the present invention.

[0046] Figure 6 This is a third combination of the present invention (excluding the air ejector system) for a supersonic wind tunnel diffuser for a ramjet engine test bench.

[0047] Figure 7 This is a fourth combination of the present invention (excluding the air ejector system) for a supersonic wind tunnel diffuser for a ramjet engine test bench.

[0048] Figure 8 This is the fifth combination (excluding the air ejector system) of an embodiment of a supersonic wind tunnel diffuser for a ramjet engine test bench according to the present invention.

[0049] The annotations in the attached figures are explained as follows:

[0050] 1. Contraction section; 2. Straight section; 4. Expansion section; 5. Cooling section; 6. Support base; 7. Second sealing gasket; 8. Cooling medium inlet; 9. Cooling medium outlet; 10. Bridging bend; 11. Drainage plate; 12. Flange assembly; 13. Inner shell; 14. Outer shell; 15. Buffer chamber; 16. Flange cooling chamber; 17. Drainage interface; 18. First sealing gasket; 19. Vertical wall; 20. First support plate; 21. Second support plate; 22. Third support plate; 23. Arc-shaped transition section; 24. Annular support plate. Detailed Implementation

[0051] To make the objectives, advantages, and features of the present invention clearer, the following detailed description of a supersonic wind tunnel diffuser for a ramjet engine test bench, in conjunction with the accompanying drawings and specific embodiments, is provided. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0052] Example 1

[0053] like Figure 1-3 As shown, a supersonic wind tunnel diffuser for a ramjet engine test bench includes an independently configured contraction section 1, N straight sections 2, an expansion section 4, a cooling section 5, an air ejector system, multiple flange assemblies 12, multiple cross-connected cooling assemblies, and a support base 6 mounted on a preset support position. In this embodiment, N=2, such as... Figure 4-6 The combination shown is as follows. The location of the preset support position can be reasonably arranged according to the specific parameter requirements and gravity distribution of the supersonic wind tunnel diffuser used for the ramjet engine test bench. Since the straight section 2 is relatively special, a support seat 6 is generally set at the connection of each end of the straight section.

[0054] Let the diameter of the throat of the ramjet engine under test be R2 and its radial cross-sectional area be S2, and the diameter of the straight section 2 be R1 and its radial cross-sectional area be S1; then , ,in, The value range is 56~120. The value range is 7.48 to 10.95;

[0055] Define the length of the i-th straight segment in N equal straight segments as . ,in, ,but .

[0056] One of the two straight sections 2 has its inlet connected to the outlet of the ramjet engine under test via a contraction section 1, and its outlet is detachably connected to the inlet of the expansion section 4 via a flange assembly 12; or, the two straight sections 2 are connected sequentially via the flange assembly 12 to form a straight combined section, in which the inlet of the first straight section 2 is connected to the outlet of the ramjet engine under test via a contraction section 1, and the outlet of the second straight section 2 is detachably connected to the inlet of the expansion section 4 via the flange assembly 12.

[0057] The outlet of expansion section 4 is detachably connected to the inlet of cooling section 5 via flange assembly 12; the outlet of cooling section 5 is connected to the inlet of air ejector system to reduce the outlet pressure of cooling section 5.

[0058] Each flange assembly includes a flange and a flange cooling assembly. The contraction section 1, the N straight sections 2, the expansion section 4, and the cooling section 5 each include an inner shell 13 and an outer shell 14. The cavity between each inner shell 13 and the outer shell 14 forms an independent cooling jacket. The flange is set on the connection port of the corresponding contraction section 1, straight section 2, expansion section 4, or cooling section 5. The flange cooling assembly is connected to the corresponding flange and is set on the outside of the corresponding inner shell 13. Its inlet is connected to the corresponding independent cooling jacket, and its outlet is connected to an external drain pipe for cooling the flange.

[0059] The flange cooling assembly includes an annular outer wall disposed at the connection between the flange and the inner housing 13. The annular outer wall is arranged circumferentially along the inner housing 13, and the accommodating space between it and the inner housing 13 forms a flange cooling chamber 16 for accommodating the cooling medium for cooling the flange. The inlet of the flange cooling chamber 16 is connected to its corresponding independent cooling jacket, so that the cooling medium in the independent cooling jacket flows into the flange cooling chamber 16 to cool the flange.

[0060] A drain port 17 is provided that is connected to the outlet, and the drain port 17 is connected to an external drain pipe.

[0061] The contraction section 1, the straight section 2, the expansion section 4, and the cooling section 5 are all equipped with cooling medium inlets 8 and cooling medium outlets 9 that communicate with the cooling interlayer. The bridging cooling assembly includes a bridging bend 10, on which the cooling medium inlets 8 and cooling medium outlets 9 on the contraction section 1, the straight section 2, the expansion section 4, and the cooling section 5 are all located on their lower sides. The two ends of the bridging bend 10 are respectively connected to two adjacent cooling medium inlets 8 and cooling medium outlets 9.

[0062] The support base 6 includes a first support plate 20, a second support plate 21, and a third support plate 22 arranged in parallel and radially along a preset support position, as well as an annular support plate 24 connecting the three. The center of the first support plate 20, the second support plate 21, and the third support plate 22 all have through holes.

[0063] The dimensions of the central through holes of the first support plate 20 and the second support plate 21 are adapted to the dimensions of the outer shell 14, and the dimensions of the central through hole of the third support plate 22 are adapted to the dimensions of the inner shell 13. On the outer shell 14, between the first support plate 20 and the second support plate 21, an annular notch is provided along its circumference. The third support plate 22 passes through the annular notch, is fitted onto the inner shell 13, and is fixedly connected to the inner shell 13. The annular notch is sealed by two annular arc transition sections 23. One side of the arc transition section 23 is fixedly connected to the third support plate 22, and the other side is fixedly connected to the inner shell 13. The inner walls of the through holes of the first support plate 20 and the second support plate 21 are fixedly connected to the outer shell 14. The outer walls of the first support plate 20, the second support plate 21, and the third support plate 22 are connected by an annular support plate 24, and a bottom support is provided at the lower part of the annular support plate 24.

[0064] The third support plate 22 has a through hole in the part of its structure located within the notch, for the cooling medium to flow from one side of the third support plate 22 to the other side.

[0065] Two interconnected flanges, one of which has an annular sealing groove on its surface and a first sealing gasket 18 inside the annular sealing groove, and the other flange has an annular boss on its surface, which is adapted to the annular sealing groove to seal the connection between the two flanges.

[0066] There are two annular sealing grooves. The first sealing gasket 18 in the inner annular sealing groove is made of rigid material, while the first sealing gasket 18 in the other annular sealing groove is made of rubber.

[0067] Buffer chambers 15 are provided on the contraction section 1, the straight section 2, the expansion section 4, and the cooling section 5. The buffer chambers 15 are located at both ends of the independent cooling jacket, and the radial cross-sectional area of ​​the buffer chambers 15 is larger than that of the independent cooling jacket. The cooling medium inlet 8 and the cooling medium outlet 9 are both provided on the buffer chambers 15. The vertical wall 19 of the buffer chamber 15 is fixedly connected to the annular outer wall of the flange cooling assembly and to the inner shell 13. Multiple flow holes are provided on the vertical wall 19 for transporting part of the cooling medium in the buffer chamber 15 to the flange cooling chamber 16.

[0068] Both the buffer chamber 15 and the flange cooling chamber 16 are equipped with flow guide plates 11 for guiding the cooling medium and improving cooling efficiency.

[0069] Example 2

[0070] like Figure 7 , Figure 8As shown, this embodiment does not include the contraction section 1. Instead, the inlet of one of the two straight sections 2 is connected to the outlet of the ramjet engine to be tested, and its outlet is connected to the other of the two straight sections, or to the inlet of the expansion section 4. The other components and their connection relationships are the same as in embodiment 1.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A supersonic wind tunnel diffuser for a ramjet test stand, characterized by: It includes an independently configured expansion section (4), a cooling section (5), an air ejector system, multiple flange assemblies (12), multiple cross-connected cooling assemblies, N straight sections (2), and a support base (6) set on a preset support position, wherein, ; At least two of the N straight sections (2) are connected in sequence through the flange assembly (12) to form a straight combination section. The inlet of the first straight section (2) in the straight combination section is connected to the outlet of the ramjet engine to be tested, and the outlet of the last straight section (2) is detachably connected to the inlet of the expansion section (4) through the flange assembly (12). The outlet of the expansion section (4) and the inlet of the cooling section (5) are detachably connected via a flange assembly (12); the outlet of the cooling section (5) is connected to the inlet of the air ejector system to reduce the outlet pressure of the cooling section (5). Each of the flange assemblies (12) includes a flange and a flange cooling assembly. The N straight sections (2), expansion sections (4) and cooling sections (5) each include an inner shell (13) and an outer shell (14). The cavity between each inner shell (13) and the outer shell (14) forms an independent cooling jacket. The flange is set on the connection port of the corresponding straight section (2), expansion section (4) or cooling section (5). The flange cooling assembly is connected to the corresponding flange and is set on the outside of the corresponding inner shell (13). Its inlet is connected to the corresponding independent cooling jacket, and its outlet is connected to an external drain pipe for cooling the flange. The N straight sections (2), expansion sections (4) and cooling sections (5) are each provided with a cooling medium inlet (8) and a cooling medium outlet (9) that communicate with the cooling interlayer. The bridging cooling assembly is used to connect two adjacent cooling interlayers through the cooling medium inlet (8) and the cooling medium outlet (9). The preset support position is located on the straight section (2) and / or the cooling section (5); the support base (6) includes a first support plate (20), a second support plate (21) and a third support plate (22) arranged in parallel and radially along the preset support position, and each of the three has a through hole in its center; The dimensions of the central through holes of the first support plate (20) and the second support plate (21) are adapted to the dimensions of the outer shell (14), and the dimensions of the central through hole of the third support plate (22) are adapted to the dimensions of the inner shell (13). An annular notch is provided circumferentially on the outer shell (14) between the first support plate (20) and the second support plate (21). The third support plate (22) passes through the annular notch, is fitted onto the inner shell (13), and is fixedly connected to the inner shell (13). The annular notch passes through the two... A ring-shaped arc transition section (23) is used for sealing. One side of the arc transition section (23) is fixedly connected to the third support plate (22), and the other side is fixedly connected to the inner shell (13). The inner walls of the through holes of the first support plate (20) and the second support plate (21) are fixedly connected to the outer shell (14). The outer walls of the first support plate (20), the second support plate (21) and the third support plate (22) are connected by an annular support plate (24). The lower part of the annular support plate (24) is provided with a bottom support. The third support plate (22) has a through hole in the part of the structure located in the notch, so that the cooling medium can flow from one side of the third support plate (22) to the other side.

2. The supersonic tunnel diffuser for ramjet test facility according to claim 1, characterized in that: It also includes a contraction section (1); the inlet of one of the N straight sections (2) is connected to the outlet of the ramjet engine to be tested through the contraction section (1); the inlet of the first straight section (2) in the straight combination section is connected to the outlet of the ramjet engine to be tested through the contraction section (1); the outlet of the contraction section (1) is detachably connected to the inlet of one of the N straight sections (2), or the inlet of the first straight section (2) in the straight combination section through a flange assembly (12); The contraction section (1) includes an inner shell (13) and an outer shell (14), and the cavity between the inner shell (13) and the outer shell (14) forms an independent cooling interlayer; the contraction section (1) is provided with a cooling medium inlet (8) and a cooling medium outlet (9) communicating with the independent cooling interlayer. The cooling medium inlet (8) on the contraction section (1) and the cooling medium outlet (9) on the adjacent straight section (2) are connected to the two cooling layers through the bridging cooling assembly.

3. The supersonic tunnel diffuser for a ramjet test facility of claim 2, wherein: Let the diameter of the throat of the test ramjet engine be R2 and its radial cross-sectional area be S2, and the diameter of the straight section (2) be R1 and its radial cross-sectional area be S1; then , ,in, The value range is 56~120. The value range is 7.48 to 10.95; Define the length of the i-th straight segment in N equal straight segments (2) as ,in, ,but .

4. The supersonic tunnel diffuser for a ramjet test facility of claim 1, wherein: Two interconnected flanges, one of which has an annular sealing groove on its surface and a first sealing gasket (18) inside the annular sealing groove, and the other flange has an annular boss on its surface, which is adapted to the annular sealing groove to seal the connection between the two flanges.

5. The supersonic tunnel diffuser for a ramjet test facility of claim 4, wherein: The annular sealing groove is two in number. The first sealing gasket (18) in the inner annular sealing groove is made of rigid material, while the first sealing gasket (18) in the other annular sealing groove is made of rubber.

6. The supersonic tunnel diffuser for a ramjet test facility of claim 2, wherein: The flange cooling assembly includes an annular outer wall disposed at the connection between the flange and the inner shell (13). The annular outer wall is arranged circumferentially along the inner shell (13), and the accommodating space between it and the inner shell (13) forms a flange cooling chamber (16) for accommodating the cooling medium for cooling the flange. The annular outer wall is provided with a drain port (17) that is connected to the outlet of the flange cooling assembly, and the drain port (17) is connected to an external drain pipe. The inlet of the flange cooling chamber (16) is connected to its corresponding independent cooling jacket, so that the cooling medium in the independent cooling jacket flows into the flange cooling chamber (16) to cool the flange.

7. The supersonic tunnel diffuser for a ramjet test facility of claim 6, wherein: The bridging cooling assembly includes a bridging bend (10), and the cooling medium inlet (8) and cooling medium outlet (9) on the contraction section (1), straight section (2), expansion section (4) and cooling section (5) are all located on its lower side. The two ends of the bridging bend (10) are respectively connected to two adjacent cooling medium inlets (8) and cooling medium outlets (9).

8. The supersonic wind tunnel diffuser for a ramjet engine test bench according to claim 7, characterized in that: The contraction section (1), the straight section (2), the expansion section (4) and the cooling section (5) are all provided with buffer chambers (15); The buffer chamber (15) is located at both ends of the independent cooling jacket, and the radial cross-sectional area of ​​the buffer chamber (15) is larger than the radial cross-sectional area of ​​the independent cooling jacket; the cooling medium inlet (8) and the cooling medium outlet (9) are both located on the buffer chamber (15); The vertical wall (19) of the buffer chamber (15) is fixedly connected to the annular outer wall of the flange cooling assembly and to the inner shell (13). The vertical wall (19) is provided with multiple flow holes for transporting part of the cooling medium in the buffer chamber (15) to the flange cooling chamber (16).

9. The supersonic tunnel diffuser for a ramjet test facility of claim 8, wherein: Both the buffer chamber (15) and the flange cooling chamber (16) are equipped with a flow guide plate (11).

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