A large-size free-piston driven high-enthalpy impulse wind tunnel device

Abstract

The application discloses a large-size free piston driven high-enthalpy pulse device, and relates to the field of wind tunnel test. The device contains four operation modes, i.e. a high-total-pressure high-enthalpy reflection type shock tunnel, a low-dissociation high-enthalpy straight-through type shock tube, an ultra-high-speed expansion tube and an ultra-high-speed expansion wind tunnel. The four operation modes expand the flight envelope simulated by the wind tunnel, so that the flight environment with extremely high dynamic pressure, extremely high temperature, extremely high speed and extremely high brightness can be simulated for a long time. The application not only can simulate the flight environment in a wide area and extremely high speed, but also can provide high-quality wind tunnel test aerodynamic data for aircraft development, and expand the test capacity of the high-enthalpy pulse device.

Description

Technical Field

[0001] This invention discloses a large-scale (2-4m scale) free piston-driven high-enthalpy pulse wind tunnel device, relating to the field of wind tunnel testing. This invention has four operating modes, not only providing an extremely high-pressure aerodynamic environment and allowing for adjustments to the pulse device's operating mode as needed, but also simulating the second cosmic velocity. Background Technology

[0002] With the development of advanced high-speed aircraft, there is a strong demand for extremely high-pressure and extremely high-speed flight environments. When an aircraft flies in the atmosphere, the physical phenomena of mechanical, thermal, optical, and electrical interactions with the atmosphere are unclear in terms of flow mechanisms. Physical modeling of phenomena such as high-enthalpy turbulence, transition, combustion, and acoustics is inappropriate, and simulations of incoming flow velocity (specific enthalpy) and dual-scale parameter ρL (ρ is density, L is characteristic length) are needed.

[0003] Compared to conventional high-speed aircraft, advanced high-speed aircraft face more severe challenges, primarily encountering flight environments with extremely high dynamic pressure, extremely high temperature, extremely high speed, and extremely high brightness. Therefore, ground simulation equipment needs to be able to match these conditions and provide data support for the flight environment required by advanced aircraft.

[0004] For free piston-driven high-enthalpy pulse wind tunnels, the simulation capability of the wind tunnel is limited by the wind tunnel operation mode. The simulated flight area has a narrow altitude and speed, the wind tunnel operation time is short, and it is affected by the chemical reaction of high-temperature air, making it impossible to accurately simulate the flight environment. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a large-size free piston driven high-enthalpy pulse wind tunnel device with four operating modes: high total pressure high-enthalpy reflection shock tunnel, low dissociation high-enthalpy straight-through shock tube, ultra-high speed expansion tube, and ultra-high speed expansion wind tunnel. The four operating modes expand the flight envelope of the wind tunnel simulation, enabling it to simulate flight environments with extremely high dynamic pressure, extremely high temperature, extremely high speed, and extremely high brightness for a longer period of time, thereby improving the wind tunnel's ability to simulate flight environments.

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

[0007] A large-size free piston driven high-enthalpy pulse wind tunnel device, the high-enthalpy pulse wind tunnel device has four operating modes: high total pressure high-enthalpy reflection shock tunnel mode, low dissociation high-enthalpy direct shock tube mode, ultra-high speed expansion tube mode, and ultra-high speed expansion wind tunnel mode.

[0008] The total pressure of the high total pressure and high enthalpy reflection shock tunnel mode is greater than 160 MPa, and the enthalpy value is greater than 15 MJ / kg; the air dissociation degree of the low dissociation and high enthalpy straight-through shock tube mode is less than 15%, and the enthalpy value is greater than 15 MJ / kg; the test gas velocity of the ultra-high speed expansion tube mode is greater than 9 km / s, and the test gas velocity of the ultra-high speed expansion wind tunnel mode is greater than 12 km / s.

[0009] Preferably, in the high total pressure and high enthalpy reflective shock tunnel mode, the wind tunnel device includes a free piston compressor, a free piston, a compression tube, a distributed counterweight, a large clamping membrane mechanism, a shock tube, a middle clamping membrane mechanism, a contraction-expansion nozzle and test section, a track system, a support system, and a free piston loading device.

[0010] The free piston compressor, free piston, compression tube, large clamping mechanism, shock tube, middle clamping mechanism, contraction-expansion nozzle, and test section are coaxially connected in sequence; distributed counterweights are loaded on the compression tube, large clamping mechanism, and shock tube to restrict the movement of the wind tunnel body;

[0011] The support system is placed on the track system to support the overall structure consisting of the free piston compressor, free piston, compression tube, distributed counterweight, large clamping mechanism, shock tube, middle clamping mechanism, contraction-expansion nozzle and test section;

[0012] The free piston loading device installs a free piston into the compression tube at the start of the test and removes the free piston from the compression tube after the test.

[0013] The total pressure that the end of the compression tube, the large clamping mechanism, and the end of the shock tube can withstand is greater than 160 MPa; after the incident shock wave is reflected at the end of the shock tube, it forms a high-temperature and high-pressure test gas, which flows through the contraction and expansion nozzle and enters the test section.

[0014] Preferably, the lengths of the compression tube end L2 and the shock tube end L1 satisfy the following conditions:

[0015]

[0016] in This refers to the compression ratio, ranging from 40 to 60. This refers to the length of the compressed tube; The length of the shock tube. The reflectance coefficient ranges from 20 to 30.

[0017] Compression tube end wall thickness and the thickness of the shock tube end wall Calculated by the following formula:

[0018]

[0019]

[0020] in To calculate pressure, ≥160MPa; This refers to the inner diameter of the compression pipe. For load combination systems; The design stress strength of the selected material; This is the inner diameter of the shock tube.

[0021] Preferably, the ends of the compression tube and the shock tube adopt a serrated section structure, and the serrated section of the ends of the compression tube and the shock tube is an open nut structure, wherein the stress borne by the nut is less than the allowable stress of the material. The critical cross-sectional area of ​​the threaded section of the screw with an open nut structure is A7. d7 is the minor diameter of the screw thread;

[0022] The axial surface stress at the critical section is calculated using the following formula. :

[0023]

[0024] in, F This refers to the axial stress borne by the screw. W T This is the torsional section modulus of the screw thread section. T This refers to the torque borne by the screw.

[0025] Preferably, in the low dissociation high enthalpy direct-through shock tube mode, the wind tunnel device includes a free piston compressor, a free piston, a compression tube, a distributed counterweight, a large clamping mechanism, a shock tube, a middle clamping mechanism, a test section, a track system, a support system, and a heavy piston loading device.

[0026] The free piston compressor, free piston, compression tube, large clamping mechanism, shock tube, middle clamping mechanism and test section are coaxially connected in sequence; distributed counterweights are loaded on the compression tube, large clamping mechanism and shock tube to restrict the movement of the wind tunnel body;

[0027] The support system is placed on the track system to support the overall structure consisting of the free piston compressor, free piston, compression tube, distributed counterweight, large clamping mechanism, shock tube, middle clamping mechanism and test section;

[0028] The free piston loading device installs a free piston into the compression tube at the start of the test and removes the free piston from the compression tube after the test.

[0029] The incident shock wave is not reflected at the end of the shock tube, and directly forms a low-dissociation test gas with an air dissociation degree of less than 15%, which enters the test section.

[0030] Preferably, in the ultra-high speed expansion tube mode, the wind tunnel device includes a free piston compressor, a free piston, a compression tube, a distributed counterweight, a large clamping mechanism, a shock tube, a medium clamping mechanism, an acceleration tube, a small clamping mechanism, a test section, a track system, a support system, and a heavy piston loading device.

[0031] The free piston compressor, free piston, compression tube, large clamping mechanism, shock tube, medium clamping mechanism acceleration tube, small clamping mechanism and test section are coaxially connected in sequence; distributed counterweights are loaded on the compression tube, large clamping mechanism and shock tube to restrict the movement of the wind tunnel body;

[0032] The support system is placed on the track system to support the overall structure consisting of the free piston compressor, free piston, compression tube, distributed counterweight, large clamping mechanism, shock tube, middle clamping mechanism and test section;

[0033] The free piston loading device installs a free piston into the compression tube at the start of the test and removes the free piston from the compression tube after the test.

[0034] The intensity of the incident shock wave formed in the shock tube is further increased in the acceleration tube, forming a high-speed airflow that enters the test section.

[0035] Preferably, in the ultra-high speed expansion wind tunnel mode, the wind tunnel device includes a free piston compressor, a free piston, a compression tube, a distributed counterweight, a large clamping mechanism, a shock tube, a medium clamping mechanism, an acceleration tube, a small clamping mechanism, a non-shrinkage expansion nozzle, a test section, a track system, a support system, and a heavy piston loading device.

[0036] The free piston compressor, free piston, compression tube, large clamping mechanism, shock tube, medium clamping mechanism, acceleration tube, small clamping mechanism, non-shrinkage expansion nozzle, and test section are coaxially connected in sequence; distributed counterweights are loaded on the compression tube, large clamping mechanism, and shock tube to restrict the movement of the wind tunnel body;

[0037] The support system is placed on the track system to support the overall structure consisting of the free piston compressor, free piston, compression tube, distributed counterweight, large clamping mechanism, shock tube, middle clamping mechanism and test section;

[0038] The free piston loading device installs a free piston into the compression tube at the start of the test and removes the free piston from the compression tube after the test.

[0039] The intensity of the incident shock wave formed in the shock tube is further increased in the acceleration tube, forming a high-speed airflow. The high-speed airflow is further increased in the non-contracting expansion nozzle, forming an ultra-high-speed airflow, which enters the test section.

[0040] Preferably, the minimum ventilation cross-sectional area A1 of the ejector core in the free piston compressor is more than 1.5 times the cross-sectional area A4 of the compression tube, that is...

[0041] A1 ≥ 1.5A4;

[0042] A1 = n × d1 × L

[0043] A4 = 0.25π × D6 × D6

[0044] Among them, the number of ventilation holes in the transmitter core is n, and D6 is the inner diameter of the compression pipe.

[0045] The width of the vent hole near the inner diameter of the compression tube on the cross-section of the launch core is d1, and the width of the vent hole near the outer diameter of the compression tube is d2, where d2 ≥ 2d1. The coordinates of any point on the cross-section of the venting part of the launch core are (…). x , y The following formula is used to determine:

[0046]

[0047] Where θ is the tangent of the inner surface of the vent near the outer diameter of the compression pipe. x The included angle of the axis, d3 is the wall thickness of the launch core, the x-axis direction is the direction from the intersection of the vent near the outer diameter of the compression tube and the outer diameter of the launch core section to the center of the launch core axis, and the y-axis is perpendicular to the x-axis direction.

[0048] Preferably, when the total pressure in the wind tunnel nozzle chamber exceeds 160MPa and the overall mass of the counterweight exceeds 280t, the overall displacement of the wind tunnel body is less than 80mm.

[0049] Preferably, the counterweights can be freely assembled and integrated, and the mass of each counterweight does not exceed 20t; at the counterweight installation position, the track system installed along the axial direction is a heavy-duty guide rail with a mass per unit area of ​​more than 100 tons, and friction sleepers are installed under the heavy-duty guide rail.

[0050] Preferably, the support system and the track system are connected by heavy-duty friction pulleys with a mass greater than 500 kg to increase the friction between the wind tunnel and the track system during wind tunnel operation.

[0051] Preferably, the optimal length of the shock tube Determined by the following formula:

[0052]

[0053] in, The Mach number of the incident shock wave in the shock tube. ≥5; This refers to the distance between the free piston and the end of the compression tube after the large clamping mechanism ruptures. The specific heat ratio of the driving gas in the compression tube; The inner diameter of the compression pipe. This is the inner diameter of the shock tube.

[0054] Preferably, the large clamping membrane mechanism is an open nut type, comprising three sections, which are connected by a 3 / 30 degree sawtooth thread, and the whole is mounted on a track in the form of a base; the distance between the first and second sections is 2m, and the distance between the second and third sections is 6m. The main membrane of the large clamping membrane mechanism can be placed at the leading edge of the first section, between the first and second sections, or between the second and third sections.

[0055] Preferably, the diameter of the main diaphragm of the large clamping mechanism is in the range of 0.8m to 1.5m, and the diameter of the diaphragm of the medium clamping mechanism is in the range of 0.5m to 0.8m.

[0056] Preferably, the diameter of the diaphragm in the small clamping mechanism is in the range of 0.2m to 0.5m.

[0057] Preferably, the inner diameter d9 of the accelerator tube and the inner diameter D5 of the shock tube satisfy 1≤d9 / D5≤2, and the length La of the accelerator tube satisfies 60≤La / d9≤100.

[0058] Preferably, the non-contraction expansion nozzle is a profile nozzle with no contraction section under wide operating conditions, with an inlet velocity range of 3km / s to 10km / s, no compression wave at the inlet, uniform outlet flow, and turbulent airflow in the nozzle.

[0059] The beneficial effects of this invention compared to the prior art are as follows:

[0060] (1) High-enthalpy pulse devices driven by free pistons with a range of 1m or more operate in either a high-total-pressure, high-enthalpy reflective shock tunnel or an ultra-high-speed expander tube mode. The wind tunnel simulation flight envelope is relatively narrow, limiting its simulation capabilities. To improve wind tunnel simulation capabilities, this invention designs four operating modes: a high-total-pressure, high-enthalpy reflective shock tunnel, a low-dissociation, high-enthalpy straight-through shock tube, an ultra-high-speed expander tube, and an ultra-high-speed expander tunnel. This invention not only simulates extreme flight environments over a wide area but also provides high-quality wind tunnel aerodynamic data for aircraft development, expanding the experimental capabilities of high-enthalpy pulse devices.

[0061] (2) Conventional free piston-driven high total pressure and high enthalpy reflective shock tunnels use an integral counterweight to limit wind tunnel displacement. However, the integral counterweight restricts the movement of the wind tunnel when it is not in operation, and cannot realize the four operating modes of the high enthalpy pulse device. This invention uses a distributed counterweight, which restricts the movement of the wind tunnel when it is in operation, and is easy to move when the wind tunnel is not in operation, thus realizing the four operating modes. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the present invention, wherein (a) is a schematic diagram of a high total pressure and high enthalpy reflection type shock tunnel, (b) is a schematic diagram of a low dissociation and high enthalpy straight-through type shock tube, (c) is a schematic diagram of an ultra-high speed expansion tube, and (d) is a schematic diagram of an ultra-high speed expansion wind tunnel.

[0063] Figure 2 This is a schematic diagram of the free piston compressor of the present invention;

[0064] Figure 3 This is a schematic diagram of the end of the compression tube and the end of the shock tube of the present invention, wherein (a) is the end of the shock tube and (b) is the end of the compression tube;

[0065] Figure 4 This is a schematic diagram of the movement of the main diaphragm in the large clamping mechanism of the present invention. Detailed Implementation

[0066] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0067] This invention proposes a large-size (2~4m range) free piston driven high enthalpy pulse wind tunnel device, with an outlet diameter of 2~4m for both contraction-expansion nozzles and non-contraction-expansion nozzles.

[0068] A large-size free piston driven high-enthalpy pulse wind tunnel device has four operating modes: a high total pressure and high enthalpy reflection shock tunnel, a low dissociation and high enthalpy straight-through shock tube, an ultra-high speed expansion tube, and an ultra-high speed expansion wind tunnel. The four operating modes expand the flight envelope of the wind tunnel simulation, enabling it to simulate flight environments with extremely high dynamic pressure, extremely high temperature, extremely high speed, and extremely high brightness for a longer period of time, thereby improving the simulation capability of the wind tunnel.

[0069] A large-size free piston driven high-enthalpy pulse wind tunnel device, wherein a high-performance free piston compressor 1 drives a free piston 2 to move in a compression tube 3, and has four operating modes: high total pressure and high enthalpy reflection shock tunnel mode (total pressure greater than 160MPa, enthalpy value greater than 15MJ / kg), low dissociation and high enthalpy straight-through shock tube mode (air dissociation degree less than 15%), ultra-high speed expansion tube mode (test gas velocity greater than 9km / s), and ultra-high speed expansion wind tunnel mode (test gas velocity greater than 12km / s).

[0070] (I) High total pressure, high enthalpy reflective shock tunnel, the main components of which include: high-performance free piston compressor 1, free piston 2, compression tube 3, distributed counterweight 4, large clamping membrane mechanism 5, shock tube 6, middle clamping membrane mechanism 7, contraction-expansion nozzle 10 and test section 12, track system 13, support system 14, free piston loading device 15, see Figure 1 (a)

[0071] The free piston compressor 1, free piston 2, compression tube 3, large clamping mechanism 5, shock tube 6, middle clamping mechanism 7, contraction-expansion nozzle 10, and test section 12 are coaxially connected in sequence. Distributed counterweights 4 are loaded onto the compression tube 3, large clamping mechanism 5, and shock tube 6 to restrict the movement of the wind tunnel body. A support system 14 is placed on the track system 13 to support the overall structure consisting of the free piston compressor 1, free piston 2, compression tube 3, distributed counterweights 4, large clamping mechanism 5, shock tube 6, middle clamping mechanism 7, contraction-expansion nozzle 10, and test section 12. The free piston loading device 15 installs the free piston 2 into the compression tube 3 at the start of the test and removes the free piston 2 from the compression tube 3 after the test.

[0072] The ends of the compression tube 3, the large clamping mechanism 5, and the shock tube 6 need to be able to withstand high total pressure (total pressure greater than 160 MPa). After the incident shock wave is reflected at the end of the shock tube 6, the resulting high-temperature and high-pressure test gas flows through the contraction-expansion nozzle 10 and enters the test section 12.

[0073] (II) Low-dissociation, high-enthalpy straight-through shock tube, whose main components include: high-performance free piston compressor 1, free piston 2, compression tube 3, distributed counterweight 4, large clamping mechanism 5, shock tube 6, middle clamping mechanism 7, test section 12, track system 13, support system 14, and free piston loading device 15, see Figure 1 (b)

[0074] The free piston compressor 1, free piston 2, compression tube 3, large clamping mechanism 5, shock tube 6, middle clamping mechanism 7, and test section 12 are coaxially connected in sequence. Distributed counterweights 4 are loaded onto the compression tube 3, large clamping mechanism 5, and shock tube 6 to restrict the movement of the wind tunnel body. A support system 14 is placed on the track system 13 to support the overall structure consisting of the free piston compressor 1, free piston 2, compression tube 3, distributed counterweights 4, large clamping mechanism 5, shock tube 6, middle clamping mechanism 7, and test section 12. The free piston loading device 15 installs the free piston 2 into the compression tube 3 at the start of the test and removes the free piston 2 from the compression tube 3 after the test.

[0075] The incident shock wave is not reflected at the end of the shock tube 6, and the low dissociation test gas (air dissociation degree is less than 15%) is directly formed and enters the test section 12.

[0076] (III) Ultra-high-speed expansion tube, the main components of which include: high-performance free piston compressor 1, free piston 2, compression tube 3, distributed counterweight 4, large clamping mechanism 5, shock tube 6, medium clamping mechanism 7, acceleration tube 8, small clamping mechanism 9, test section 12, track system 13, support system 14, free piston loading device 15, see Figure 1 (c)

[0077] The free piston compressor 1, free piston 2, compression tube 3, large diaphragm mechanism 5, shock tube 6, middle diaphragm mechanism 7, acceleration tube 8, small diaphragm mechanism 9 and test section 12 are coaxially connected in sequence; the distributed counterweight 4 is loaded on the compression tube 3, large diaphragm mechanism 5 and shock tube 6 to restrict the movement of the wind tunnel body. The support system 14 is placed on the track system 13 and is used to support the overall structure composed of the free piston compressor 1, free piston 2, compression tube 3, distributed counterweight 4, large diaphragm mechanism 5, shock tube 6, middle diaphragm mechanism 7 and test section 12. The free piston loading device 15 installs the free piston 2 into the compression tube 3 at the beginning of the test and removes the free piston 2 from the compression tube 3 after the test is over.

[0078] The intensity of the incident shock wave formed in the shock tube 6 is increased again in the acceleration tube 8 to form a high-speed air flow (the test gas velocity is greater than 9 km / s) and enters the test section 12.

[0079] (4) Hypersonic expansion wind tunnel, the main components include: high-performance free piston compressor 1, free piston 2, compression tube 3, distributed counterweight 4, large diaphragm mechanism 5, shock tube 6, middle diaphragm mechanism 7, acceleration tube 8, small diaphragm mechanism 9, non-shrinking and expanding nozzle 11, test section 12, track system 13, support system 14, free piston loading device 15, see Figure 1 in Figure (d).

[0080] The free piston compressor 1, free piston 2, compression tube 3, large diaphragm mechanism 5, shock tube 6, middle diaphragm mechanism 7, acceleration tube 8, small diaphragm mechanism 9, non-shrinking and expanding nozzle 11 and test section 12 are coaxially connected in sequence; the distributed counterweight 4 is loaded on the compression tube 3, large diaphragm mechanism 5 and shock tube 6 to restrict the movement of the wind tunnel body. The support system 14 is placed on the track system 13 and is used to support the overall structure composed of the free piston compressor 1, free piston 2, compression tube 3, distributed counterweight 4, large diaphragm mechanism 5, shock tube 6, diaphragm mechanism 7 and test section 12. The free piston loading device 15 installs the free piston 2 into the compression tube 3 at the beginning of the test and removes the free piston 2 from the compression tube 3 after the test is over.

[0081] The test air flow in the acceleration tube 8 is increased again in the non-shrinking and expanding nozzle 11 to form a hypersonic test air flow (the test gas velocity is greater than 12 km / s) and enters the test section 12.

[0082] In this invention, the high-performance free piston compressor 1 has an emission gas pressure range of 1MPa to 50MPa; the free piston 2 has a mass of 200kg to 2000kg and a length of 500mm to 1000mm; the compression tube 3 has a length of 48 to 82m and an inner diameter of 600 to 1000mm; the distributed counterweights 4 each have a mass of less than 20t; the large clamping mechanism 5 withstands a pressure greater than 160MPa; the shock tube 6 has a length of 20 to 40m and an inner diameter of 0.2 to 0.4m; the medium clamping mechanism 7 withstands a pressure greater than 160MPa; the acceleration tube 8 has a length of 20 to 30m and an inner diameter of 0.2 to 0.6m; the small clamping mechanism 9 withstands a pressure greater than 160MPa; the contraction-expansion nozzle 10 has an outlet diameter of 1.2m to 3m; the non-contraction-expansion nozzle 11 has an outlet diameter of 0.8m to 3m; and the test section 12 has a length greater than 15m.

[0083] To prevent sonic throat congestion in the connecting pipe and improve piston launch efficiency, the minimum cross-sectional area A1 of the launch core in the high-performance free piston compressor 1 is at least 1.5 times the cross-sectional area A4 of the piston compression tube, i.e., A1 ≥ 1.5A4, where A1 = n × d1 × L A4 = 0.25π × D6 × D6. The number of vent holes in the transmitter core is n (in this invention, n = 8, see...). Figure 2 ).

[0084] The width of the vent hole near the inner diameter of the compression tube on the cross-section of the launch core is d1, and the width of the vent hole near the outer diameter of the compression tube is d2, where d2 ≥ 2d1. The coordinates of any point on the cross-section of the venting part of the launch core are (…). x , y The following formula is used to determine:

[0085]

[0086] Where θ is the tangent of the inner surface of the vent near the outer diameter of the compression pipe. x The included angle of the axis, d3 is the wall thickness of the launch core, the x-axis direction is the direction from the intersection of the vent near the outer diameter of the compression tube and the outer diameter of the launch core section to the center of the launch core axis, and the y-axis is perpendicular to the x-axis direction.

[0087] During high total pressure operation, the ends of compression tube 3 and shock tube 6 are subjected to high total temperature and pressure. According to the heavy piston motion theory and shock tube flow theory, only the ends of the compression tube and shock tube bear extremely high total temperature and pressure. Therefore, it is only necessary to thicken the pipes at the ends of compression tube 3 and shock tube 5 by increasing the wall thickness and corresponding length, and strengthening the connection points. Since the ends of compression tube 3 and shock tube 6 adopt a serrated segment structure, both can be used... Figure 3 This indicates the increase in wall thickness and length. Figure 3In the diagram, (a) represents the end of the shock tube, and (b) represents the end of the compression tube. The length L2 of the end of the compression tube 3 and the length L1 of the end of the shock tube 6 satisfy the following conditions:

[0088]

[0089] in This refers to the compression ratio, ranging from 40 to 60. This refers to the length of the compressed tube; The length of the shock tube. The reflection coefficient ranges from 20 to 30.

[0090] The wall thickness d6 at the end of compression tube 3 and the wall thickness d5 at the end of shock tube 6 can be calculated using the following formula.

[0091]

[0092] in P C To calculate pressure, P c≥160MPa; D i is the inner diameter of the pipe; K For load combination systems; S m The design stress intensity of the selected material; when the subscript i is 5, it is a shock tube, and when it is 6, it is a compression tube.

[0093] The serrated sections at the ends of compression tube 3 and shock tube 6 are open-nut type, and the stress on the nuts must be less than the allowable stress of the material. The critical cross-sectional area of ​​the screw thread section is A7. d7 is the minor diameter of the screw thread, which can be calculated using the following formula.

[0094]

[0095] in, δ ca represents the axial stress calculated at the critical section. F This refers to the axial stress borne by the screw. W T This is the torsional section modulus of the screw thread section. T This refers to the torque borne by the screw.

[0096] Distributed counterweights 4 are installed on the compression tube 3 and shock tube 6. Based on dynamic calculations, when the total pressure in the wind tunnel nozzle sump exceeds 160 MPa, the overall mass of the counterweights needs to exceed 280 tons to ensure the overall displacement of the wind tunnel is less than 80 mm. The counterweights adopt a modular and integrated design. The total mass of the distributed counterweights 4 installed on the compression tube 3 is 200-220 tons, and the total mass of the distributed counterweights 4 installed on the shock tube 6 is 80-100 tons. The counterweights can be freely assembled and integrated, with each counterweight weighing no more than approximately 20 tons, meeting the operating conditions of the track system 13 and support system 14. At the counterweight installation location, the track system 13, installed axially, is a heavy-duty guide rail with a unit area bearing a mass greater than 100 tons. Friction sleepers are installed below the heavy-duty guide rail. The support system 14 is connected to the track system 13 by heavy-duty friction pulleys with a mass greater than 500 kg, increasing the friction between the support system 14 and the track system 13 during wind tunnel operation.

[0097] Optimal length of shock tube 6 X C Determined by the following formula

[0098]

[0099] in, Ma S The incident shock Mach number in shock tube 6 is... Ma S ≥5; Xrup is the distance between the piston and the end of the compression tube 3 after the large clamping mechanism ruptures; γ4 is the specific heat ratio of the driving gas in the compression tube 3.

[0100] The large clamping mechanism 5 is an open nut type, connected by a 3 / 30 degree sawtooth thread, and is divided into three sections. The whole is mounted on a track in the form of a base. The main diaphragm of the large clamping mechanism 5 is placed between the three sections. The main diaphragm of the large clamping mechanism 5 can be placed at the leading edge of the first section. Figure 4 (at point ① in the middle) and between the first and second paragraphs ( Figure 4 (at point ② in the middle) or between the second and third paragraphs ( Figure 4 (At point ③ in the middle). It can easily move downstream; the distances between the three sections are 2m and 6m respectively, requiring the main diaphragm to move downstream a distance greater than 8m to meet the requirements of long-term operation. The effective test time exceeds 20ms. See [link / reference]. Figure 4 Setting different travel distances is mainly to verify the actual operating conditions. This not only ensures the safety of the heavy piston, but also allows for the adjustment of the total temperature and pressure of the driving gas according to the operating status, thereby regulating the wind tunnel's operating state. Furthermore, it can delay the interference of the expansion wave system on the test airflow and extend the effective operating time of the wind tunnel.

[0101] The diameter of the main membrane placed in the large membrane clamping mechanism 5 ranges from 0.8m to 1.5m, the diameter of the medium membrane placed in the medium membrane clamping mechanism 7 ranges from 0.5m to 0.8m, and the diameter of the small membrane placed in the small membrane clamping mechanism 9 ranges from 0.2m to 0.5m.

[0102] When operating in ultra-high speed expansion tube and ultra-high speed expansion wind tunnel modes, the downstream of the membrane clamping mechanism 7 is connected to the acceleration tube 8. The inner diameter d9 of the acceleration tube 8 and the inner diameter D5 of the shock tube 6 satisfy 1≤d9 / D5≤2, and the length La of the acceleration tube 8 satisfies 60≤La / d9≤100.

[0103] When operating in the ultra-high speed expansion wind tunnel mode, the non-contraction expansion nozzle 11 is a wide-condition nozzle with no contraction section. The inlet velocity range is 3km / s to 10km / s. This nozzle needs to ensure that there is no compression wave at the nozzle inlet, the flow is uniform at the nozzle outlet, and the ultra-high speed airflow flows in the nozzle without turbulence.

[0104] The free piston loading device 15 can automatically load and unload heavy pistons 2 with a mass of 200kg~2000kg. It has a precise axial positioning function, and the robot can support the heavy piston for movement. It is easy for operators to control, and the display screen resolution meets the robot's operation and observation needs, thus improving the wind tunnel operation efficiency.

[0105] When the high-total-pressure, high-enthalpy reflective shock tunnel of this invention is operated, the simulated total pressure exceeds 160 MPa, the overall displacement of the wind tunnel body is less than 50 mm, and the effective test time exceeds 15 ms. When operating in the low-dissociation, high-enthalpy straight-through shock tube, the degree of dissociation of the high-enthalpy test gas flow is low. When operating in the ultra-high-speed expansion tube, it can simulate the second cosmic velocity. When operating in the ultra-high-speed expansion wind tunnel, the test gas flow can simulate the second cosmic velocity while further expanding the test area. The distributed counterweight requires an overall mass exceeding 280 tons, and the counterweight adopts a modular and integrated design. This invention not only provides high-quality wind tunnel aerodynamic data for simulating wide-area extreme flight environments but also expands the testing capabilities of high-enthalpy pulse devices by providing high-quality wind tunnel test aerodynamic data for aircraft development.

[0106] This invention discloses a large-size free-piston driven high-enthalpy pulse device, relating to the field of wind tunnel testing. For free-piston driven high-enthalpy pulse wind tunnels, the simulation capability is limited by the wind tunnel's operating mode, resulting in a narrow simulated flight altitude and speed range, short operating time, and the influence of chemical reactions in high-temperature air, making it impossible to accurately simulate the flight environment. This invention proposes a large-size free-piston driven high-enthalpy pulse device, comprising four operating modes: a high-total-pressure high-enthalpy reflection shock tunnel, a low-dissociation high-enthalpy straight-through shock tube, an ultra-high-speed expansion tube, and an ultra-high-speed expansion wind tunnel. This invention not only enables the simulation of wide-area extreme flight environments but also provides high-quality wind tunnel aerodynamic data for aircraft development, expanding the testing capabilities of high-enthalpy pulse devices.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Those skilled in the art can make various modifications and substitutions to the present invention without creative effort, and all such modifications and substitutions should be covered within the scope of protection of the present invention.

Claims

1. A large-size free piston driven high-enthalpy pulse wind tunnel device, characterized in that: The high-enthalpy pulse wind tunnel device has four operating modes: high total pressure high-enthalpy reflection shock tunnel mode, low dissociation high-enthalpy direct shock tube mode, ultra-high speed expansion tube mode, and ultra-high speed expansion wind tunnel mode. The total pressure of the high total pressure and high enthalpy reflection shock tunnel mode is greater than 160 MPa, and the enthalpy value is greater than 15 MJ / kg; the air dissociation degree of the low dissociation and high enthalpy straight-through shock tube mode is less than 15%, and the enthalpy value is greater than 15 MJ / kg; the test gas velocity of the ultra-high speed expansion tube mode is greater than 9 km / s, and the test gas velocity of the ultra-high speed expansion wind tunnel mode is greater than 12 km / s. All four wind tunnel modes include a free piston compressor (1), a free piston (2), a compression tube (3), a distributed counterweight (4), a large clamping mechanism (5), a shock tube (6), a middle clamping mechanism (7), a test section (12), a track system (13), a support system (14), and a free piston loading device (15). The distributed counterweight (4) is loaded on the compression tube (3), the large clamping mechanism (5), and the shock tube (6) to restrict the movement of the wind tunnel body. The free piston loading device (15) installs the free piston (2) into the compression tube (3) at the beginning of the test and removes the free piston (2) from the compression tube (3) after the test. The minimum ventilation cross-sectional area A1 of the ejector core in the free piston compressor (1) is more than 1.5 times the cross-sectional area A4 of the compression tube, that is... A1 ≥ 1.5A4; A1 = n×d1× L A4 = 0.25π×D6×D6 Among them, the number of ventilation holes in the transmitter core is n, and D6 is the inner diameter of the compression pipe. The width of the vent hole near the inner diameter of the compression tube on the cross-section of the launch core is d1, and the width of the vent hole near the outer diameter of the compression tube is d2, where d2 ≥ 2d1. The coordinates of any point on the cross-section of the venting part of the launch core are (…). x , y The following formula is used to determine: Where θ is the tangent of the inner surface of the vent near the outer diameter of the compression pipe. x The included angle of the axis, d3 is the wall thickness of the launch core, the x-axis direction is the direction from the intersection of the vent near the outer diameter of the compression tube and the outer diameter of the launch core section to the center of the launch core axis, and the y-axis is perpendicular to the x-axis direction.

2. The large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 1, characterized in that: In the high total pressure and high enthalpy reflection shock tunnel mode, the wind tunnel device also includes a contraction-expansion nozzle (10). The free piston compressor (1), free piston (2), compression tube (3), large clamping mechanism (5), shock tube (6), middle clamping mechanism (7), contraction-expansion nozzle (10) and test section (12) are connected coaxially in sequence; The support system (14) is placed on the track system (13) to support the overall structure consisting of the free piston compressor (1), free piston (2), compression tube (3), distributed counterweight (4), large clamping mechanism (5), shock tube (6), middle clamping mechanism (7), contraction-expansion nozzle (10) and test section (12); The total pressure that the end of the compression tube (3), the large clamping mechanism (5), and the end of the shock tube (6) can withstand is greater than 160 MPa; after the incident shock wave is reflected at the end of the shock tube (6), it forms a high-temperature and high-pressure test gas, which flows through the contraction and expansion nozzle (10) and enters the test section (12).

3. The large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 2, characterized in that: The end length L2 of the compression tube (3) and the end length L1 of the shock tube (6) satisfy the following conditions: in This refers to the compression ratio, ranging from 40 to 60. This refers to the length of the compressed tube; The length of the shock tube. The reflectance coefficient ranges from 20 to 30. The wall thickness of the end of the compression tube (3) And shock tube (6) end tube wall thickness Calculated by the following formula: in To calculate pressure, ≥160MPa; This refers to the inner diameter of the compression pipe. For load combination systems; The design stress strength of the selected material; This is the inner diameter of the shock tube.

4. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 3, characterized in that: The ends of the compression tube (3) and the shock tube (6) adopt a serrated section structure, and the serrated sections of the ends of the compression tube (3) and the shock tube (6) are open nut structures, and the stress borne by the nut is less than the allowable stress of the material. The critical cross-sectional area of ​​the threaded section of the screw with an open nut structure is A7. d7 is the minor diameter of the screw thread; The axial surface stress at the critical section is calculated using the following formula. : in, F This refers to the axial stress borne by the screw. W T This is the torsional section modulus of the screw thread section. T This refers to the torque borne by the screw.

5. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 1, characterized in that: In the low dissociation high enthalpy direct shock tube mode, the free piston compressor (1), free piston (2), compression tube (3), large clamping mechanism (5), shock tube (6), middle clamping mechanism (7) and test section (12) are coaxially connected in sequence; The support system (14) is placed on the track system (13) to support the overall structure consisting of the free piston compressor (1), free piston (2), compression tube (3), distributed counterweight (4), large clamping mechanism (5), shock tube (6), middle clamping mechanism (7) and test section (12); The incident shock wave is not reflected at the end of the shock tube (6), and directly forms a low dissociation test gas with an air dissociation degree of less than 15%, which enters the test section (12).

6. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 1, characterized in that: In the ultra-high speed expansion tube mode, the wind tunnel device also includes an acceleration tube (8) and a small clamping mechanism (9); the free piston compressor (1), free piston (2), compression tube (3), large clamping mechanism (5), shock tube (6), medium clamping mechanism (7), acceleration tube (8), small clamping mechanism (9) and test section (12) are coaxially connected in sequence; The support system (14) is placed on the track system (13) to support the overall structure consisting of the free piston compressor (1), free piston (2), compression tube (3), distributed counterweight (4), large clamping mechanism (5), shock tube (6), middle clamping mechanism (7) and test section (12); The intensity of the incident shock wave formed in the shock tube (6) is increased again in the acceleration tube (8), forming a high-speed airflow that enters the test section (12).

7. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 1, characterized in that: In the ultra-high speed expansion wind tunnel mode, the wind tunnel device also includes an acceleration tube (8), a small clamping mechanism (9), and a non-shrinkage expansion nozzle (11); the free piston compressor (1), free piston (2), compression tube (3), large clamping mechanism (5), shock tube (6), medium clamping mechanism (7), acceleration tube (8), small clamping mechanism (9), non-shrinkage expansion nozzle (11), and test section (12) are coaxially connected in sequence; The support system (14) is placed on the track system (13) to support the overall structure consisting of the free piston compressor (1), free piston (2), compression tube (3), distributed counterweight (4), large clamping mechanism (5), shock tube (6), middle clamping mechanism (7) and test section (12); The intensity of the incident shock wave formed in the shock tube (6) is increased again in the acceleration tube (8), forming a high-speed airflow. The high-speed airflow is increased again in the non-contraction expansion nozzle (11), forming an ultra-high-speed airflow, which enters the test section (12).

8. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 2, 5, 6, or 7, characterized in that: When the total pressure in the wind tunnel nozzle chamber exceeds 160MPa and the overall mass of the distributed counterweight exceeds 280t, the overall displacement of the wind tunnel body is less than 80mm.

9. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 8, characterized in that: The distributed counterweights can be freely assembled and integrated, with each counterweight weighing no more than 20t; at the counterweight installation position, the track system (13) installed along the axial direction is a heavy-duty guide rail with a unit area bearing a mass greater than 100 tons, and friction sleepers are installed under the heavy-duty guide rail.

10. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 9, characterized in that: The support system (14) is connected to the track system (13) by a heavy friction pulley with a mass greater than 500 kg, which increases the friction between the wind tunnel and the track system (13) during operation.

11. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 2, 5, 6, or 7, characterized in that: Optimal length of shock tube (6) Determined by the following formula: in, The incident shock Mach number in the shock tube (6) is... ≥5; The distance between the free piston and the end of the compression tube (3) after the large clamping mechanism ruptures; The specific heat ratio of the driving gas in the compression tube (3); The inner diameter of the compression pipe. This is the inner diameter of the shock tube.

12. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 2, 5, 6, or 7, characterized in that: The large clamping membrane mechanism (5) is an open nut type, consisting of three sections. The sections are connected by a 3 / 30 degree sawtooth thread, and the whole is mounted on a track in the form of a base. The distance between the first and second sections is 2m, and the distance between the second and third sections is 6m. The main membrane of the large clamping membrane mechanism (5) can be placed at the leading edge of the first section, between the first and second sections, or between the second and third sections.

13. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 2, 5, 6, or 7, characterized in that: The main diaphragm diameter of the large clamping mechanism (5) ranges from 0.8m to 1.5m, and the diaphragm diameter of the medium clamping mechanism (7) ranges from 0.5m to 0.8m.

14. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 6 or 7, characterized in that: The diaphragm diameter of the small clamping mechanism (9) ranges from 0.2m to 0.5m.

15. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 6 or 7, characterized in that: The inner diameter d9 of the accelerator tube (8) and the inner diameter D5 of the shock tube (6) satisfy 1≤d9 / D5≤2, and the length La of the accelerator tube (8) satisfies 60≤La / d9≤100.

16. A large-size free piston driven high-enthalpy pulse wind tunnel device according to claim 7, characterized in that: The non-contraction expansion nozzle (11) is a profile nozzle with no contraction section under wide operating conditions. The inlet velocity range is 3km / s to 10km / s. There is no compression wave at the inlet, the outlet flow is uniform, and the airflow flows smoothly in the nozzle.

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