Four-degree-of-freedom model supporting mechanism used in severe environment and wind tunnel test device

Abstract

The invention relates to a four-degree-of-freedom model supporting mechanism used in a severe environment and a wind tunnel test device in the technical field of wind tunnel tests. The invention discloses a four-degree-of-freedom model supporting mechanism used in a severe environment. The four-degree-of-freedom model supporting mechanism comprises a supporting mechanism body, a composite heat-proof mechanism and a thermal deformation compensation assembly. The supporting mechanism body is provided with a driving mechanism for adjusting the pose of the tested model. The composite heat-proof mechanism comprises a cooling cover, an air supply assembly, an exhaust pipe and a cooling pipe. The thermal deformation compensation assembly comprises a pre-tightening pull rod and a plurality of spring assemblies. Through the overall structural design and optimization, an extremely stable bearing system is constructed, and an accurate and stable attitude reference is provided for a test. In addition, through the design of the composite heat-proof mechanism, a low-temperature island is constructed for core driving and transmission parts, pneumatic heat can be effectively isolated, and the operation reliability of precise elements such as a motor at high temperature is ensured.

Description

Technical Field

[0001] This invention relates to the field of wind tunnel testing technology, and in particular to a four-degree-of-freedom model support mechanism and wind tunnel testing device for use in harsh environments. Background Technology

[0002] Hypersonic vehicles possess significant advantages such as strong three-dimensional maneuverability and reentry endurance, enabling them to adapt to various complex and variable flight trajectories, perform rapid strike missions, and achieve a high penetration success rate, effectively limiting the functionality of anti-missile systems. While hypersonic vehicles exhibit exceptional flight performance, their aerodynamic design faces significant challenges. Therefore, research on hypersonic vehicle flight coupling dynamic wind tunnel testing technology is of great practical significance for vehicle design. During supersonic flight, the surface temperature of a vehicle can reach extremely high levels. At Mach 3, the temperature at the front of the vehicle can reach 330°C, and at Mach 8, the surface temperature can rise to over 1000°C. For the SR-72 aircraft, designed for speeds up to Mach 6, the maximum surface temperature can exceed 3000°C. Simultaneously, during supersonic flight, the compression of air by the object itself cannot propagate rapidly, gradually accumulating on the windward side to form a shock wave, generating a unique and powerful drag.

[0003] To support the experimental model in the predetermined position during wind tunnel testing, existing support mechanisms typically employ a fixed steel frame. However, this traditional fixed frame cannot achieve the intended attitude changes. To simulate attitude changes such as yaw and pitch of an aircraft, the usual practice is to install an adjustment mechanism on top of the traditional fixed frame. However, ordinary adjustment mechanisms cannot meet the harsh environment of high load and high temperature. Problems such as heat protection of components under high temperature, easy deformation of the structure under high load, insufficient transmission accuracy, and low maintenance efficiency are all issues that urgently need to be addressed. Summary of the Invention

[0004] To address the technical problems of traditional support mechanisms either being unable to perform attitude adjustment or being prone to damage and lacking precision in harsh environments after adding attitude adjustment functions, this invention provides a four-degree-of-freedom model support mechanism and wind tunnel testing device for harsh environments.

[0005] In a first aspect, the present invention proposes a four-degree-of-freedom model support mechanism for harsh environments, which includes: a support mechanism body, a composite heat protection mechanism, and a thermal deformation compensation component.

[0006] The support mechanism is equipped with a drive mechanism that adjusts the pose of the model under test.

[0007] The composite heat protection mechanism includes: a cooling cover, an air supply component, an exhaust pipe, and a cooling pipe; the cooling cover is wrapped around the drive mechanism, and a sealed space is formed inside the cooling cover; the air supply component is used to supply cooling air into the cooling cover and form a cooling protective air film layer on the drive mechanism; one end of the exhaust pipe is connected to the cooling cover, and the other end is connected to the outside of the wind tunnel test section; the cooling pipe is embedded in the support mechanism body.

[0008] The thermal deformation compensation component includes: several pre-tightening rods that are slidably connected to the support mechanism body, and spring assemblies set at both ends of the pre-tightening rods; the thermal deformation compensation component is used to maintain the stability of the support mechanism body at room temperature, and to compensate for the deformation of the support mechanism body at high temperature through the elastic deformation of the spring assemblies.

[0009] Secondly, a wind tunnel testing apparatus is proposed, comprising an airflow generator and a four-degree-of-freedom model support mechanism for harsh environments, as described in the first aspect. The four-degree-of-freedom model support mechanism is used to mount the model under test and conduct wind tunnel tests in front of the airflow emitter.

[0010] The beneficial effects of this invention are as follows: This invention combines an asymmetric layout of "wall anchoring" with "mud core / concrete damping filling" to construct an extremely stable load-bearing system with high damping characteristics. This not only increases the upper limit of stiffness but also effectively dissipates the vibration energy generated by the impact of hypersonic airflow through internal friction, ensuring the stability of the model's attitude. Furthermore, the coupling effect of the "thermally symmetrical pre-tightening tie rod" automatically compensates for the thermal expansion of the columns and lifting platform under high temperatures, eliminating structural thermal stress and deformation. Combined with the ceramic patch design of the "composite thermal insulation support rod," it effectively blocks the conduction of heat to precision drive components, solving the problem of precision drift caused by high temperatures. Additionally, a composite thermal protection mechanism constructs a "low-temperature island" for the core components, and an innovative follow-up venting and sealing structure is designed. This ensures the safe operation of components such as motors in high-temperature external environments while avoiding secondary interference of cooling exhaust gas on the wind tunnel flow field. Thus, it can highly reproduce the complex maneuvering attitude of hypersonic flight under extreme conditions of high temperature, high load, and multi-degree-of-freedom adjustment, providing high-precision experimental conditions for aerodynamic coupling and stability research. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of a four-degree-of-freedom model support mechanism during installation in harsh environments; Figure 2 This is a schematic diagram of the structure of a four-degree-of-freedom model support mechanism after removing the composite heat protection mechanism, which is used in harsh environments. Figure 3 This is a schematic diagram of the internal box structure of the column and base; Figure 4 This is an exploded view of the base; Figure 5 This is a schematic diagram of the yaw mechanism; Figure 6 This is a schematic diagram of the angle-of-attack mechanism; Figure 7 This is a perspective installation diagram of the cooling pipes; Figure 8 This is a structural diagram of the column anchoring to the wall; Figure 9 This is a schematic diagram of the installation of a disc spring; Figure 10 This is a perspective view of the cooling shroud mounted on the motor.

[0012] In the diagram: 1. Wall; 2. Angle-attacking mechanism; 21. Model support rod; 22. Lever; 23. Electric push cylinder; 3. Cooling cover; 4. Butterfly spring; 5. Column; 51. Boss; 6. Base; 61. Splicing part; 61. Step groove; 62. Base plate; 7. Ground; 8. Cable chain; 9. Reinforcing rod; 10. Lifting platform; 11. Auxiliary support mechanism; 12. Bellows cover; 13. Yaw mechanism; 131. Rotary support platform; 132. Mounting seat; 14. Ball screw; 15. Servo motor; 16. Two-way bevel gearbox; 17. Transmission rod; 18. Bevel gearbox; 19. Guide rail; 20. Cooling pipe. Detailed Implementation

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.

[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0016] This invention, through overall structural design and optimization, constructs an extremely robust load-bearing system, effectively resisting the enormous loads and shock wave impacts generated by hypersonic airflow, ensuring minimal deformation of the model support system, and providing a precise and stable attitude reference for experiments. Its structural design and optimization mainly include the following aspects: 1. Overall structure and high-stiffness damping matrix.

[0017] Please refer to Figure 1 and Figure 2 This embodiment provides a support mechanism for a four-degree-of-freedom model in harsh environments, which includes a support mechanism body, a composite heat protection mechanism, and a thermal deformation compensation component. The support mechanism body includes: a base 6, two columns 5 connected to the base 6, a lifting platform 10 disposed between the two columns 5, a yaw mechanism 13 sliding on the lifting platform 10, an angle-of-attack mechanism 2 connected to the yaw mechanism 13, and several auxiliary support mechanisms 11.

[0018] To construct a stable base capable of withstanding the impact of hypersonic airflow, the base 6, column 5, and lifting platform 10 all adopt a closed box-type casting structure, such as... Figure 3 As shown, the internal structure is equipped with transverse and longitudinal stiffening plates. The material used for the box body can be Q345B steel. Specifically, this embodiment introduces a high-damping filling technology: a cast clay core or a concrete-filled damping material is directly retained within the internal cavities of the base 6 and the column 5. This design utilizes the heterogeneity of the porous medium of the filling material, based on a composite loss factor theoretical model, to improve vibration reduction performance. When the support mechanism vibrates under shock wave impact, its single-cycle vibration energy dissipation... It can be represented as: In the formula, This represents the internal loss factor of the damping material. , These represent the minute stress and strain of the damping material under vibration. It is the coefficient of friction between the inner wall of the cavity and the interface of the damping material. N This is the normal contact pressure at the interface between the damping material and the inner wall of the cavity. X This represents the vibration displacement amplitude of the damping material. Compared to a purely hollow steel structure, retaining the cast clay core or filling it with damping material allows the damping material to vibrate when the column 5 and base 6 are impacted. The internal friction of the damping material and the friction between the damping material and the inner wall of the cavity cause the vibration energy to dissipate as heat, thus rapidly attenuating the high-frequency flutter caused by hypersonic airflow and ensuring the dynamic stability of the model's posture. Furthermore, as... Figure 4As shown, the base 6 is designed as a modular assembly mechanism, comprising two symmetrical splicing parts 61 and a base plate 62. Multiple connecting rods pass through the two splicing parts 61. The connecting rods are bolted to secure the two splicing parts 61 together, enabling a detachable connection. Stepped grooves 611 are provided at both ends of the contacting side of the two splicing parts 61. Two uprights 5 are respectively installed and positioned within the stepped grooves 611 at both ends. The base plate 62 is bolted to the bottom of the two splicing parts 61. The entire base 6 is modularly designed, facilitating on-site hoisting. The groove positioning between the base 6 and the uprights 5 further improves assembly feasibility and increases the reliability of connections between components. The base plate 62 is connected to the ground 7 using anchor bolts.

[0019] 2. Precision transmission and attitude adjustment.

[0020] Z-axis lifting (gravity direction): The lifting platform 10 is connected to the columns 5 via gravity-direction guide rails 19 on both sides. There are two guide rails 19, respectively located on opposite sides of the two columns 5. The drive mechanism of the lifting platform 10 includes: a motor 1, a double-direction bevel gearbox 16, two transmission rods 17, two bevel gearboxes 18, two ball screws 14, and two connecting blocks. The motor 1 and the double-direction bevel gearbox 16 are both connected to the base 6. The motor 1, as the drive source, can be a servo motor 15, ultimately driving the lifting platform 10 to lift. The input shaft of the double-direction bevel gearbox 16 is connected to the output shaft of the motor 1. The two transmission rods 17 are respectively connected to the two output shafts of the double-direction bevel gearbox 16. The two bevel gearboxes 18 are respectively connected to the two columns 5, and the input shafts of the two bevel gearboxes 18 are respectively connected to the two transmission rods 17. The two ball screws 14 are arranged in the gravity direction. These two ball screws 14 are respectively connected to the output shafts of the two bevel gearboxes 18. Two connecting blocks are respectively mounted on the two ball screws 14, and the lifting or lowering occurs accordingly with the forward and reverse rotation of the ball screws 14. The two connecting blocks are connected to the lifting platform 10. Alternatively, the lifting platform 10 can be moved directly by screwing the ball screws 14 to the lifting platform 10 without the connecting blocks. The configuration can be adjusted according to the actual situation. In this embodiment, the motor is sequentially connected to the double-direction bevel gearbox 16, two transmission rods 17, two bevel gearboxes 18, and two ball screws 14, forming a T-shaped structure. This greatly reduces transmission errors, ensures the synchronization accuracy of the ball screws 14 at both ends, and guarantees the stable lifting of the lifting platform 10 under heavy loads.

[0021] The yaw mechanism 13 can achieve rotational movement on a horizontal plane. For example... Figure 5As shown, the yaw mechanism 13 includes: a rotary support platform 131, a second motor, and a mounting base 132 that rotates around the Z-axis. The rotary support platform 131 is slidably connected to the upper surface of the lifting platform 10. The rotary support platform 131 can be a general-purpose component, such as a roller-type rotary support platform. The second motor, as the drive source of the yaw mechanism 13, can be a servo motor 15, used to drive the rotary support platform 131 to rotate along the Z-axis, and the second motor is mounted on the rotary support platform 131 and moves together with it. The mounting base 132 is connected to the rotating end of the rotary support platform 131.

[0022] Please refer to Figure 6 The angle-of-attack mechanism 2 includes: a housing connected to the mounting base 132, a lever 22, an electric cylinder 23, and a model support rod 21. The lever 22 is hinged to the housing, and the plane in which the lever 22 rotates is parallel to the Z-axis. One end of the lever 22 extends outside the housing and connects to the model support rod 21. The model support rod 21 is used to mount the model under test. The electric cylinder 23, as the drive source of the angle-of-attack mechanism 2, is hinged inside the housing via a double trunnion. The output end of the electric cylinder 23 is hinged to the end of the lever 22 located inside the housing. The extension and retraction of the piston of the electric cylinder 23 drives the lever 22 to rotate, causing the model support rod 21 mounted on the lever 22 to rotate accordingly, thus achieving the pitching motion.

[0023] Auxiliary support mechanisms 11 are provided at each of the four corners of the lifting platform 10. The auxiliary support mechanisms 11 can share the vertical load of the lifting platform 10, ensuring normal movement of the lifting platform 10 in the Z-axis under heavy loads, while also reducing the impact of inertia on positioning and improving positioning accuracy. In this embodiment, the auxiliary support mechanism 11 includes a hydraulic cylinder, a pressure sensor, and a controller. The cylinder body of the hydraulic cylinder is connected to the base 6, and the piston is connected to the bottom of the lifting platform 10, or to a protruding connecting piece on the side of the lifting platform 10, to support the lifting platform 10 and ensure constant pressure. The pressure sensor is used to monitor the pressure of the lifting platform 10 on the hydraulic cylinder. The controller is used to compensate based on the pressure of the lifting platform 10 on the hydraulic cylinder. If the pressure increases, the supporting force of the hydraulic cylinder on the lifting platform 10 is reduced; conversely, if the pressure decreases, the supporting force of the hydraulic cylinder on the lifting platform 10 is increased. Through this design, when the lifting platform 10 moves, it can provide a certain supporting effect, reducing the power of the selected motor. Simultaneously, when the lifting platform 10 brakes, it can reduce the influence of inertial force, reducing the braking requirements of the motor. In addition, a pressure sensor is used to implement real-time pressure compensation, with a pressure feedback response time of ≤10ms and a pressure feedback accuracy of ±0.5%FS.

[0024] 3. Asymmetric wall anchoring structure and local reinforcement design.

[0025] To further enhance the strength and stiffness of the overall frame of the four-degree-of-freedom model support mechanism, this embodiment employs an asymmetric wall anchoring design. (See again...) Figure 1 and reference Figure 8 The left-side column 5 (the side closest to wall 1) is designed as an anchoring column, abutting against wall 1 of the laboratory and rigidly fixed to it by multiple expansion bolts (or heavy-duty expansion bolts), forming an "L-shaped" spatial stability support. This greatly enhances the model support mechanism's ability to withstand lateral overturning moments, meeting the testing requirements under harsh environments. This design fundamentally alters the boundary conditions of column 5: traditional gantry columns exhibit cantilever beam characteristics under lateral aerodynamic loads, with stiffness decreasing with the cube of the height. In this embodiment, anchoring to wall 1 transforms the structure into a statically indeterminate system with "fixed lower end support + lateral multi-point elastic support." The equivalent lateral stiffness of column 5 under lateral loads... Revised to: In the formula, EI The bending stiffness of column 5. H The equivalent stress height of column 5. k bolt This represents the equivalent stiffness of a single expansion bolt. h i For the first i The height of each expansion screw from the ground. n This represents the total number of expansion screws. No. i The angle between the axis of the expansion bolt and the direction of lateral force. This shows that the anchoring stiffness contribution of the expansion bolt is proportional to the square of the height. A huge anti-overturning moment is formed through the high anchoring point, thus achieving an ultra-high stiffness support effect at extremely low cost. Furthermore, while the column 5 is fixed to the base 6 at its base, a triangular reinforcing rib is also connected between the column 5 and the base 6, further improving the stability of the column 5 and thus enhancing the overall stability.

[0026] 4. Internal active thermal control structure.

[0027] Please refer to Figure 7To eliminate the impact of ambient temperature and conductive heat on the structural thermal deformation of the base 6 and column 5, cooling pipes 20 (liquid-cooled circulation pipes) are pre-embedded inside the box before the damping material is poured. Specifically, the cooling pipes 20 can be made of seamless 304 stainless steel, which has high pressure resistance and corrosion resistance, ensuring no leakage occurs throughout the entire lifespan of the concrete. The cooling pipes 20 are arranged in an internal serpentine pattern within the box and pass through pre-reserved holes in the transverse and longitudinal stiffening plates. When constant-temperature coolant is circulated through the cooling pipes 20, an "internal cold source" is formed, carrying away the heat conducted in through the outer wall of the box, keeping the internal core or concrete at a constant temperature, while simultaneously utilizing the heat capacity of the filling material to enhance the structure's resistance to thermal shock.

[0028] 5. Thermal deformation compensation components.

[0029] To address the accuracy drift caused by structural thermal expansion under high-temperature conditions, and to prevent damage to rigid connections due to excessive thermal stress, this embodiment incorporates a thermal deformation compensation component between the two columns 5. Please refer again to... Figure 1 and reference Figure 8 , Figure 9 The component includes: two sets of pre-tensioning rods 9 symmetrically arranged about the central plane of the lifting platform 10, and spring assemblies 4 set at both ends of the pre-tensioning rods 9. Specifically, the spring assemblies 4 can be disc springs. Each set of pre-tensioning rods 9 has two. The pre-tensioning rods 9 can be made of carbon fiber material with a coefficient of thermal expansion much smaller than that of the column 5 and the lifting platform 10. Taking the installation structure of one pre-tensioning rod 9 as an example, the two ends of the pre-tensioning rod 9 are connected to the boss 51 on the side wall of the column 5, and a high-stiffness disc spring is connected in series between the locking nut and the boss 51, and used in conjunction with the disc spring assembly, thus forming a stiffness design strategy of "high pre-tensioning force locking + thermoelastic breathing". During assembly, a preset axial preload is applied to the preload rod 9 by tightening the locking nut with a torque wrench. At this time, the disc spring is compressed, and its compression force is much greater than the pneumatic load, resulting in high rigidity of the mechanism. When pneumatic heating causes the column 5 and the lifting platform 10 to expand due to heat, the disc spring is further compressed. Utilizing the compression margin of the disc spring, the huge rigid thermal displacement is converted into a small elastic deformation, thereby significantly reducing additional thermal stress and preventing structural collapse.

[0030] To accurately quantify the setting range of axial preload and prevent thermal stress failure, a calculation model for tie rod preload based on thermoelastic deformation was established: During wind tunnel testing, due to the different coefficients of thermal expansion of the column 5, the lifting platform 10, and the pre-tensioned tie rod 9, a "thermal expansion difference" will occur when the temperature rises. ", can be represented as: In the formula:L This indicates the effective working length of the preloaded tie rod 9. , The linear expansion coefficients of the materials of column 5 (the same material as the lifting platform 10) and pre-tensioning rod 9 are respectively. , The maximum temperature rise of column 5 and preloaded tie rod 9 during the test are shown respectively (because the coefficient of thermal expansion of carbon fiber is much smaller than that of Q345B, the difference in thermal expansion is greater at the maximum temperature). After introducing the disc spring, the equivalent axial stiffness of column 5 is... The rigidity of the pre-tensioned tie rod 9 and the stiffness of the disc spring The series connection determines this. Because... The overall stiffness is mainly determined by the disc spring, that is: Based on the above model, in order to ensure that the preloaded tie rod 9 neither loosens nor yields under high-temperature conditions, the initial preload force is... The settings must satisfy the following thermo-mechanical coupling inequality: In the formula, F aero This represents the maximum aerodynamic load during wind tunnel testing. S To prevent loosening, a safety factor of 1.5 is used in this embodiment. A This is the cross-sectional area of ​​the preloaded tie rod 9. The strength utilization coefficient is set to 0.8 in this embodiment. This refers to the additional thermal load caused by the difference in thermal expansion.

[0031] 6. Composite heat protection mechanism.

[0032] This closed-loop controlled composite heat protection mechanism can construct a "low-temperature island" for core drive mechanisms such as motors, reducers, and ball screws in a high-temperature flow field. Specifically, the composite heat protection mechanism includes: a cooling cover, an air supply assembly, and an exhaust pipe. Shaped cooling covers are designed to fit the specific shapes of the components in the drive mechanism, such as rectangular cooling covers covering motor one and motor two, and a bellows cover 12 covering the ball screw 14, to ensure that a relatively sealed space can be formed inside the cooling cover 3. Figure 10 As shown. Further, the cooling shroud 3 employs a three-layer composite material: the outer layer (3mm thick) is made of ceramic fiber, serving as the thickest main thermal barrier layer, utilizing its extremely low thermal conductivity to block external radiant heat. The middle layer (2mm thick) is made of graphene, utilizing its extremely high in-plane thermal conductivity to quickly and evenly distribute the transmitted heat laterally, preventing the accumulation of localized hot spots. The inner layer (1mm thick) is made of copper alloy, utilizing its high thermal conductivity to facilitate convective heat transfer in conjunction with internal airflow. According to Fourier's law of heat transfer, the heat flux through this composite wall surface... It can be controlled by the following formula: In the formula, T out This indicates the temperature of the high-temperature flow field outside the cooling shroud 3. T in This indicates the safe operating temperature of cooling shroud 3. , These represent the thickness of the outer layer and its low thermal conductivity, respectively. , These represent the thickness of the intermediate layer and its high thermal conductivity, respectively. , These represent the thickness and thermal conductivity of the inner layer, respectively. This design effectively reduces radial heat flux density by maximizing the thermal resistance of the ceramic layer, the heat homogenization effect of the graphene layer, and the efficient heat exchange of the internal copper alloy layer, ensuring that the internal wall temperature remains within a safe range even under extreme external temperatures. For the bellows cover 12, a "dynamic positive pressure ventilation" strategy is employed: injecting cooling gas maintains a slight positive pressure within the cooling cover 3, preventing the intrusion of high-temperature external dust and gas, while also preventing negative pressure adsorption or collapse of the bellows cover during high-speed stretching. The air supply components include: air ducts, electric valves, pressure gauges, and air flow meters. The air ducts connect to the cooling cover. The electric valves are used for controlled switching of the air ducts. The pressure gauges are used to monitor the pressure within the cooling cover. The air flow meters are used to monitor the flow rate within the air ducts. In the principle of the composite heat protection mechanism, an external cold source enters the cooling cover 3 through the air ducts, forming a cooling gas film on the component surface. Simultaneously, through integrated temperature sensors, electric valves, pressure gauges, and air flow meters, the system automatically adjusts the intake valve opening using a PID algorithm based on real-time temperature and pressure within the cooling shroud 3 and air flow rate in the air ducts, achieving on-demand cooling. For example, when the pressure detected by the pressure gauge is below a threshold, the electric valve opening is increased to increase the air intake of the cooling shroud. When the air flow meter detects a flow rate below a threshold, the air intake in the air ducts is increased. When the temperature detected by the temperature sensor is above a threshold, the intake valve opening is increased to increase the air intake of the cooling shroud. One end of the exhaust pipe is connected to the cooling shroud 3, and the other end is connected to the outside of the wind tunnel test section to prevent cooling exhaust gas from disrupting the wind tunnel flow field. Considering the Z-axis movement of the lifting platform 10, the exhaust pipe adopts a combination of "flexible corrugated pipe + engineering drag chain" and is arranged on the leeward side of the model support mechanism. The exhaust pipe rises and falls synchronously with the lifting platform 10, eventually merging into the exhaust manifold to lead the exhaust gas out of the test section. Furthermore, a labyrinth seal or magnetohydrodynamic seal is employed between the cooling shroud 3 and the rotating parts of the drive mechanism to ensure a slight positive pressure is maintained inside the cooling shroud 3. This prevents both backflow of external hot air and leakage of cooling air that could interfere with the flow field. This composite heat protection mechanism can maintain a component surface temperature ≤150℃ after continuous operation for one hour at 500℃, significantly improving the high-temperature resistance of the model support mechanism. The composite heat protection mechanism also boasts good durability and a long service life. Combined with the above structural design, compared to existing general model support mechanisms, it can meet the requirements of high temperature, high load, and multi-degree-of-freedom operating conditions. It also features a compact structure, low mass, high rigidity, high temperature resistance, modular assembly support, and strong expandability. Therefore, this invention can meet the requirements of high temperature, high load, and multi-degree-of-freedom operating conditions, highly reproducing the complex maneuvering attitudes of hypersonic flight, providing crucial experimental conditions for studying aerodynamic coupling and stability, and greatly enhancing the real value of the experimental data.

[0033] 7. Special thermal protection for model support rod 21.

[0034] To prevent heat from the model under test from being conducted along the model support rod 21 to internal precision components, the model support rod 21 adopts a composite structure of "metal skeleton + ceramic armor". Zirconia ceramic sheets are adhered to the exposed portion of the model support rod 21 outside the shell and to the end face connected to the model under test to form a ceramic heat insulation layer. This ceramic heat insulation layer, on the one hand, utilizes its extremely low thermal conductivity to cut off thermal bridges and block heat conduction to the electric thruster 23. On the other hand, it reduces the temperature rise of the metal model support rod 21 body, thereby minimizing the thermal expansion deformation of the model support rod 21 and ensuring the accuracy of angle of attack control.

[0035] In one example, the four-degree-of-freedom model support mechanism manufactured for harsh environments meets the following relevant technical specifications and requirements: 1. Vertical Z-axis lifting stroke: -2000mm to +500mm.

[0036] 2. The yaw mechanism moves from -500mm to +1500mm.

[0037] 3. Angle of attack direction α The angle range is ±30°.

[0038] 4. Yaw direction β The angle range is ±30°.

[0039] 5. The equivalent load of the wind tunnel test flow field is 20kN, and the overall mechanical deformation angle of the lifting platform 10 and its structure is less than 0.1%.

[0040] 6. The operating temperature of the drive structure and transmission structure shall be controlled below 150°C.

[0041] Based on the above conditions, the height of the two columns 5 is designed to be 4500mm, the width of the base 6 is 5500mm, and the width of the lifting platform 10 is 3500mm. The electric thruster 23 is designed with a stroke of 600mm and a thrust of 50kN, and is capable of meeting the angle of attack requirements. α The lever ratio is 3:1, meaning that the upper part of the rotation center of lever 22 is 1.8m long and the lower part is 0.6m long, and the driving force of the angle of attack is ≥3×20kN=60kN.

[0042] In another embodiment, a wind tunnel testing apparatus is also proposed, comprising: an airflow generator and a four-degree-of-freedom model support mechanism for harsh environments as described in the above embodiment. The four-degree-of-freedom model support mechanism is used to mount the model under test and conduct wind tunnel tests in front of the airflow generator. When in use, it is installed in a right-angled space area against a wall (part of the wall has an opening for wind tunnel testing), or on other relatively stable low mounds or fortifications, which can greatly enhance its strength and rigidity, meeting the testing requirements under wind tunnel testing conditions.

[0043] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0044] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A four degree of freedom model support mechanism for use in harsh environments, characterized by, It comprises: Support mechanism body, composite heat protection mechanism, thermal deformation compensation assembly; Wherein, the support mechanism body is provided with a driving mechanism for adjusting the pose of the measured model; The composite heat protection mechanism comprises: a cooling cover, a gas supply assembly, an exhaust pipe, and a cooling pipe; the cooling cover is wrapped around the driving mechanism, and a closed space is formed inside the cooling cover; the gas supply assembly is used to deliver cooling air into the cooling cover and form a cooling protective gas film layer on the surface of the driving mechanism; one end of the exhaust pipe is connected to the cooling cover, and the other end is connected to the outside of the wind tunnel test section; the cooling pipe is embedded in the support mechanism body; The thermal deformation compensation assembly comprises: a plurality of pre-tightening rods slidingly connected with the support mechanism body, and spring assemblies arranged at both ends of the pre-tightening rods; the thermal deformation compensation assembly is used to maintain the stability of the support mechanism body at room temperature, and compensate for the deformation amount of the support mechanism body at high temperature through the elastic deformation of the spring assemblies.

2. The four-degree-of-freedom model support mechanism for use in harsh environments of claim 1, wherein, The cooling cover comprises three layers of composite materials; wherein, the outer layer is made of ceramic fiber material, the middle layer is made of graphene material, and the inner layer is made of copper alloy material; And / or, the thickness of the outer layer is set to 3mm, the thickness of the middle layer is set to 2mm, and the thickness of the inner layer is set to 1mm.

3. The four-degree-of-freedom model support mechanism for use in harsh environments of claim 1, wherein, The gas supply assembly comprises: an air pipe, an electric valve, a pressure instrument, an air flow instrument, and a temperature sensor; the air pipe is connected to the cooling cover; the electric valve is used to control the opening and closing of the air pipe; the pressure instrument is used to monitor the pressure in the cooling cover; the air flow instrument is used to monitor the flow in the air pipe; the temperature sensor is used to monitor the temperature in the cooling cover; When the pressure monitored by the pressure instrument is less than a threshold value, the opening degree of the electric valve is increased to increase the air intake of the cooling cover; when the flow monitored by the air flow instrument is less than a threshold value, the air intake in the air pipe is increased; when the temperature monitored by the temperature sensor is greater than a threshold value, the opening degree of the air intake valve is increased to increase the air intake of the cooling cover.

4. The four-degree-of-freedom model support mechanism for use in harsh environments of claim 1, wherein, A dynamic sealing structure is provided between the cooling cover and the rotating part of the driving mechanism; And / or, the cooling pipe is arranged in a serpentine shape in the support mechanism body.

5. The four-degree-of-freedom model support mechanism for use in harsh environments of claim 1, wherein, The pre-tightening rods are provided in two groups and symmetrically arranged on both sides of the support mechanism body; each group of pre-tightening rods is provided with 2; when at room temperature, the spring assemblies are in a partially compressed energy storage state to exert an axial tension on the pre-tightening rods.

6. The four-degree-of-freedom model support mechanism for use in harsh environments of claim 1, wherein, The bottom cavity of the support mechanism body is filled with damping material to improve the damping characteristics of the base and the column to consume vibration energy.

7. The four-degree-of-freedom model support mechanism for use in harsh environments of claim 1, wherein, The support mechanism body comprises: A base; Two columns connected to the base; one of the columns is provided as an anchor column for connecting with the wall to form an asymmetric anti-overturning support structure; A lifting platform provided between the two columns and lifting along the Z-axis; the Z-axis is the direction of gravity; A yaw mechanism sliding on the lifting platform; An attack angle mechanism connected to the yaw mechanism and rotating around the Z-axis; the lifting platform, the yaw mechanism, and the attack angle mechanism are moved by the driving mechanism.

8. The four-degree-of-freedom model support mechanism for use in harsh environments of claim 7, wherein, The driving mechanism acting on the lifting platform comprises: a motor one, a bidirectional bevel gear box, two transmission rods, two bevel gear boxes, two ball screws, and two connecting blocks; wherein the motor one is connected to the base; the input shaft of the bidirectional bevel gear box is connected to the output shaft of the motor one, for dividing the power of the motor one into two paths for synchronous output; the two transmission rods are correspondingly connected to the two output shafts of the bidirectional bevel gear box; the two bevel gear boxes are connected to the two columns respectively; the input shafts of the two bevel gear boxes are correspondingly connected to the two transmission rods respectively; the two ball screws are correspondingly connected to the output shafts of the two bevel gear boxes and are arranged along the Z-axis direction; the two connecting blocks are correspondingly arranged on the two ball screws for corresponding lifting with the forward and reverse rotation of the ball screws; and the two connecting blocks are connected to the lifting platform. The driving mechanism acting on the yaw mechanism comprises: a rotary support platform, a mounting seat, and a motor two; wherein the rotary support platform is slidingly connected to the lifting platform; the mounting seat is connected to the rotating end of the rotary support platform; and the motor two is installed on the rotary support platform for driving the rotary support platform to rotate along the Z-axis. The attack angle mechanism comprises: a housing, a lever, and a model support rod; wherein the housing is connected to the mounting seat; the lever is hinged to the housing, and the plane in which the lever rotates is a plane parallel to the Z-axis; one end of the lever extends out of the housing; and the model support rod is connected to the end of the lever outside the housing for installing the measured model. The driving mechanism acting on the attack angle mechanism is an electric push cylinder which is hinged to the housing; the output end of the electric push cylinder is hinged to the other end of the lever for driving the lever to rotate. And / or, the base, the column, and the lifting platform are all closed box type cast structures, and the interiors of them are all provided with transverse rib plates and longitudinal rib plates.

9. The four-degree-of-freedom model support mechanism for use in harsh environments of claim 7, wherein, The four-degree-of-freedom model support mechanism further comprises: a plurality of auxiliary support mechanisms. The auxiliary support mechanism comprises: a hydraulic cylinder, one end of which is connected to the base and the other end of which is connected to the lifting platform; a pressure sensor for monitoring the pressure of the lifting platform on the hydraulic cylinder; a controller for compensating according to the pressure of the lifting platform on the hydraulic cylinder; if the pressure increases, the support force of the hydraulic cylinder on the lifting platform is reduced, and vice versa, the support force of the hydraulic cylinder on the lifting platform is increased.

10. A wind tunnel test device comprising a flow generator, characterised in that The wind tunnel test device further comprises the four-degree-of-freedom model support mechanism for severe environments as claimed in any one of claims 1 to 9, which is used for installing the measured model and performing wind tunnel test in front of the airflow emitter.

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