Zero-interference high-efficiency safe low-starting-load supersonic wind tunnel start-stop operation method

Abstract

The application discloses a zero-interference high-efficiency safe low-starting-load supersonic wind tunnel start-stop operation method, relates to the field of supersonic wind tunnel operation, and adopts a test model support system with a normal degree of freedom, offsets a test model from an axial position to a biased position close to a wallboard before starting the wind tunnel, moves the model back to the axial test position to complete the test after the wind tunnel measurement system determines that a flow field is completely established, and offsets the model again to stop the wind tunnel after the test is completed. The model offsetting during the start-stop stage significantly reduces the starting load, the application does not need to add auxiliary devices, does not need to adjust the total pressure, and does not need to put the model, has the advantages of zero flow field interference, high operation efficiency, good safety, and the like, and can effectively reduce the operation risk of the wind tunnel, and improve the test data quality.

Description

Technical Field

[0001] This invention relates to the field of supersonic wind tunnel operation, and more specifically, to a method for starting and stopping a low-start-load supersonic wind tunnel with zero interference, high efficiency, and safety. Background Technology

[0002] Wind tunnels are indispensable ground testing facilities supporting the development of aerospace vehicles. Ensuring the safe commissioning and operation of wind tunnels is a key technical issue that needs to be focused on and resolved during the operation of supersonic wind tunnels. Excessive starting loads on the test model during the start-up and shutdown of supersonic wind tunnels (far exceeding the aerodynamic loads on the test model after wind tunnel startup), leading to significant vibrations of the wind tunnel test model, is a key problem that needs to be addressed during the start-up and shutdown of supersonic wind tunnels.

[0003] Domestic and international scholars have explored ways to reduce the aerodynamic loads borne by test models during wind tunnel start-up and shutdown, and have summarized and explored some test techniques for low start-up loads (referred to as load reduction techniques). Five typical and commonly used load reduction techniques are: 1) Low stable section total pressure start-up and shutdown: During wind tunnel start-up and shutdown, the total pressure in the stable section is reduced, and then adjusted back to the actual total pressure required for the test; 2) Adding model auxiliary devices: Adding auxiliary devices to the model during wind tunnel start-up and shutdown to enhance its strength and stiffness or change the local flow field around the model; 3) Using model deployment: Before wind tunnel start-up, the wind tunnel test model is retrieved into the wind tunnel chamber, and deployed after the supersonic flow field is established. Before shutdown, the model is retrieved into the wind tunnel chamber; 4) Optimizing the balance structure: By increasing the geometric dimensions of the balance, its structural strength and stiffness are enhanced, increasing the safety margin and impact resistance; 5) Low total pressure ratio start-up and shutdown techniques: The wind tunnel start-up pressure ratio is reduced by optimizing the geometry of the supersonic wind tunnel diffuser section and the combined operation mode of the wind tunnel power system.

[0004] The above methods have achieved certain results in reducing the starting load of the test model and improving the safety factor of the test model, but they also have certain limitations. 1) The low-stability-section total pressure start-stop technology has limited effectiveness in transient wind tunnels. For continuous wind tunnels, it significantly reduces operating efficiency, increases air consumption, and raises operating costs. 2) Adding model auxiliary devices presents significant challenges in terms of deployment, retraction, and sealing. Furthermore, the difficulty in eliminating the interference of these devices on the flow field affects the accuracy and precision of wind tunnel test results. 3) Model deployment technology is advantageous for slender, low-load test models but is difficult to implement for large-span, high-load models. The deployment process also generates dynamic disturbances in the wind tunnel flow field, impacting the operational safety of the continuous wind tunnel's power system. 4) Optimizing the balance structure primarily involves increasing its geometric dimensions. While increasing the balance's strength and stiffness, this significantly reduces its sensitivity and the quality of wind tunnel test data. 5) The low total pressure ratio start-stop technology has limited effectiveness. For example, optimizing the diffuser section's geometric design contributes little to reducing the operating pressure ratio (generally around 10%) and has no significant effect on reducing the starting load.

[0005] In summary, the existing load reduction technology has limitations such as severe interference, low efficiency, and poor safety. Therefore, there is an urgent need to develop a zero-interference, efficient, and safe method for starting and stopping supersonic wind tunnels under low starting load. Summary of the Invention

[0006] This invention aims to provide a zero-interference, efficient, and safe method for starting and stopping a supersonic wind tunnel with low starting load, in order to solve the following problems existing in the prior art: interference with the wind tunnel flow field; low efficiency and high operating costs during the start-up and shutdown process; large vibration of the test model, complex support structure design, and high safety risks; and decreased test data quality due to reduced sensitivity of auxiliary devices or balances. Ultimately, this invention aims to reduce the safety risks of wind tunnel operation, improve wind tunnel operating efficiency, and enhance the quality of wind tunnel test data.

[0007] To achieve the above-mentioned objectives, this invention provides a method for starting and stopping a supersonic wind tunnel with zero interference, high efficiency, and safety under low starting load. The method includes:

[0008] Step S1: Construct a model support system, wherein the model support system has at least one normal degree of freedom, and the direction of the normal degree of freedom is perpendicular to the axis of the wind tunnel test section;

[0009] Step S2: Before the wind tunnel is started, the test model is moved from the axial position of the wind tunnel test section along the normal direction to an offset position using the model support system. The offset position is located between the axial position of the wind tunnel test section and the test section wall.

[0010] Step S3: Start the wind tunnel. After the flow field in the wind tunnel test section is established, use the model support system to move the test model from the offset position back to the test position at the axis of the wind tunnel test section for testing.

[0011] Step S4: After the test is completed, the test model is moved from the test station to the offset position using the model support system, and then the wind tunnel operation is stopped.

[0012] One problem with existing supersonic wind tunnel start-up and shutdown processes is the excessive starting load on the test model, leading to high model vibration and safety risks. Furthermore, a systematic solution that does not rely on additional devices or total pressure regulation is lacking. To address this issue, this method utilizes a support system with normal degrees of freedom to execute four steps: pre-start offset, flow field establishment and repositioning after start-up, post-test offset, and shutdown. This provides a complete and operable start-up and shutdown operation method, enabling model offsetting to reduce load during start-up and shutdown, and model repositioning to ensure experimental accuracy during the test phase. This results in overall zero-interference, efficient, and safe operation.

[0013] Preferably, the offset position is determined by pre-calculation, such that the maximum aerodynamic load borne by the test model during wind tunnel start-up and shutdown is lower than the position where it bears the maximum aerodynamic load when it is at the axial position.

[0014] In this invention, pre-calculation is introduced. By comparing the maximum aerodynamic load on the model under different offset positions, any offset position with a lower load than the axis position can be determined. This allows us to obtain the optimal offset position that minimizes the starting load, thereby maximizing the load reduction capability of the invention.

[0015] Preferably, the offset position is the center position between the axis of the wind tunnel test section and the lower wall panel of the test section. This provides a preferred offset position (center of the axis and lower wall panel) that balances safety and load reduction, significantly reducing the load while avoiding the risk of the model scraping against the wall panel due to excessive contact.

[0016] Preferably, the model support system also has three rotational degrees of freedom: pitch, roll, and yaw, used to adjust the attitude angle of the test model at the test station. In addition to the normal degree of freedom, the support system integrates pitch, roll, and yaw rotational degrees of freedom, enabling the system to perform both start / stop offset load reduction and test attitude adjustment functions.

[0017] Preferably, in step S3, the wind tunnel measurement system monitors whether the Mach number of the test section reaches a predetermined value to determine whether the flow field of the wind tunnel test section has been successfully established. Utilizing the wind tunnel's own measurement system to monitor whether the Mach number of the test section reaches the predetermined value serves as the criterion for determining the establishment of the flow field. This provides an objective and automated judgment basis, ensuring the accurate timing of the model's return from the offset position to the test position, balancing safety and efficiency.

[0018] Preferably, the method is applied to a continuous supersonic wind tunnel. This invention is particularly suitable for continuous supersonic wind tunnels because these tunnels have long operating times and high efficiency requirements, and the zero-interference and high-efficiency characteristics of this invention are of greatest value in such wind tunnels.

[0019] The core principle of this method, which is to reduce the starting load by biasing the test model, is a load reduction mechanism that is independent of the total pressure adjustment of the wind tunnel, the addition of auxiliary devices, and the model deployment method.

[0020] The maximum aerodynamic load that the test model experiences during wind tunnel start-up and shutdown is reduced by at least 30% compared to when it is placed on the wind tunnel axis, thanks to the offset operation.

[0021] The specific normal distance of the offset position is pre-optimized and determined by performing transient numerical simulation of the wind tunnel startup process on an integrated geometric model that includes the wind tunnel nozzle section, test section, test model and diffuser section, and comparing and analyzing the aerodynamic loads on the test model under different offset distances.

[0022] One or more technical solutions provided by this invention have at least the following technical effects or advantages:

[0023] Zero interference: No auxiliary devices need to be added to the test section, and the total operating pressure of the wind tunnel is not changed. Therefore, there is no additional interference to the wind tunnel flow field, ensuring the authenticity and accuracy of the test data.

[0024] High efficiency: No need to adjust the total pressure or operate the auxiliary devices during start-up and shutdown; the process can be completed simply by moving the model through the support system, which greatly shortens the test preparation and completion time and improves the wind tunnel operation efficiency.

[0025] Safety: It significantly reduces the maximum aerodynamic load on the test model during start-up and shutdown, thereby reducing model vibration, lowering the requirements for the strength and stiffness of the supporting structure, and greatly improving the safety of wind tunnel start-up and shutdown operation.

[0026] It has good versatility: it is applicable to all kinds of supersonic wind tunnels (especially continuous wind tunnels) and has no special restrictions on the shape of the model (slender body or large wingspan). Attached Figure Description

[0027] The accompanying drawings, which are provided to further illustrate embodiments of the invention and constitute a part of this invention, are not intended to limit the scope of the invention.

[0028] Figure 1 This is a schematic diagram of a four-degree-of-freedom support system;

[0029] Figure 2 This is a schematic diagram showing the experimental model in its experimental position.

[0030] Figure 3 This is a schematic diagram showing the test model in the start / stop position;

[0031] Figure 4 A schematic diagram of the start-up and shutdown operation method for a low-start-load supersonic wind tunnel with zero interference, high efficiency and safety. Detailed Implementation

[0032] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, where there is no conflict, the embodiments of the present invention and the features thereof can be combined with each other.

[0033] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0034] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0035] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0036] Example 1;

[0037] Please refer to Figure 4 , Figure 4This invention provides a flowchart illustrating a zero-interference, efficient, and safe method for starting and stopping a supersonic wind tunnel under low start-up load. The method includes:

[0038] Step S1: Construct a model support system, wherein the model support system has at least one normal degree of freedom, and the direction of the normal degree of freedom is perpendicular to the axis of the wind tunnel test section;

[0039] Step S2: Before the wind tunnel is started, the test model is moved from the axial position of the wind tunnel test section along the normal direction to an offset position using the model support system. The offset position is located between the axial position of the wind tunnel test section and the test section wall.

[0040] Step S3: Start the wind tunnel. After the flow field in the wind tunnel test section is established, use the model support system to move the test model from the offset position back to the test position at the axis of the wind tunnel test section for testing.

[0041] Step S4: After the test is completed, the test model is moved from the test station to the offset position using the model support system, and then the wind tunnel operation is stopped.

[0042] The core technical principle of this invention is based on the applicant's research and discovery: during the start-up and shutdown of a supersonic wind tunnel, offsetting the test model along the normal direction (perpendicular to the wind tunnel axis) and bringing it closer to the test section wall can significantly reduce the start-up load on the model. The underlying mechanism is that during the start-up of a supersonic wind tunnel, complex shock wave and expansion wave systems are formed within the flow field. When the test model is located on the wind tunnel axis (the conventional test position), it faces the core mainstream region, and the shock wave impact on the model is most intense. However, when the model is offset closer to the wall: the model enters the wall boundary layer or near-wall region, resulting in a decrease in local flow velocity and dynamic pressure; the structure of the shock wave system changes after reflection from the wall, reducing the peak pressure in the wave system region where the model is located; and the asymmetry of the flow around the model leads to a decrease in net aerodynamic load. This principle is independent of traditional mechanisms such as reducing total pressure and adding auxiliary devices; it is a purely geometric position adjustment method for load reduction, therefore it does not generate any additional interference to the wind tunnel flow field and does not affect the normal operating efficiency of the wind tunnel.

[0043] The present invention achieves its objective through the following technical solutions:

[0044] This invention designs and provides a test model support system with a normal degree of freedom z. This normal degree of freedom is perpendicular to the wind tunnel axis, enabling the test model to move precisely along the normal direction between the wind tunnel axis and the wall panel. In addition, the system also retains three rotational degrees of freedom: pitch, roll, and yaw, to ensure the model's ability to adjust its attitude at the test site.

[0045] Start-stop bias strategy:

[0046] Before starting the wind tunnel, the test model is moved from the axial position to an offset position (between the axis and the wall panel, such as the center position) using this support system. After the wind tunnel starts up and the flow field is fully established (the Mach number is monitored by the wind tunnel measurement system to reach the predetermined value), the model is moved back to the test position at the axial position to complete the test. After the test, before shutting down, the model is moved back to the same offset position, and then the wind tunnel is shut down.

[0047] By employing the aforementioned operation procedure of offsetting during start-up and shutdown and repositioning during testing, this invention reduces model load during the high-load phases of wind tunnel start-up and shutdown using offsetting, while ensuring the model remains in the standard test position during the stable flow field testing phase to guarantee the validity of the test data. This solution fully achieves the invention's objectives of zero interference (no additional devices), high efficiency (no total pressure regulation), and safety (significantly reduced load).

[0048] The start-stop method in this embodiment of the invention includes the following steps:

[0049] (1) Based on the test section design scheme determined by the overall aerodynamic design scheme of the wind tunnel, design a section with pitch. , roll ,yaw and legal direction A model support system with four degrees of freedom, see Figure 1 (The model support system of a conventional supersonic wind tunnel cannot support degrees of freedom. When conducting wind tunnel tests, the test model is placed on the wind tunnel axis. See...) Figure 2 The purpose of increasing the normal degree of freedom is to allow the test model to be offset along the normal direction, thereby reducing the starting load by offsetting the test model along the normal direction. See details. Figure 1 , Figure 2 and Figure 3 The remaining three degrees of freedom are used to change the pitch, roll, and yaw angles of the test model during the experiment. Figures 2-3 In the diagram, 1 represents the upper wall panel of the test section, 2 represents the lower wall panel of the test section, 3 represents the incoming flow direction, 4 represents the test model, and 5 represents the wind tunnel axis. Figure 2 The experimental model is located at the experimental site. Figure 3 The experimental model is located in the start / stop position.

[0050] (2) Before starting the wind tunnel, place the test model at a position between the wind tunnel axis and the lower wall of the wind tunnel. The closer the test model is to the lower wall, the lower the starting load on the test model. Generally speaking, in order to ensure safety, the test model is placed at the center position between the wind tunnel axis and the lower wall. See Figure 3 ;

[0051] (3) Determine whether the flow field of the wind tunnel test section is fully established based on the wind tunnel measurement system (a measurement system will be built to support the wind tunnel after it is built, which is used to monitor the flow field state inside the wind tunnel). After confirming that the flow field of the test section is fully established (the Mach number of the test section reaches the predetermined Mach value), move the test model to the test position through the model support system and complete the prescribed test content.

[0052] (4) After the test, the wind tunnel test model is moved to a certain position between the wind tunnel axis and the lower wall of the test section (i.e., a certain distance away from the central axis of the test section) by the model support system. In order to take safety into account, the test model is placed at the center position between the wind tunnel axis and the lower wall before the wind tunnel is stopped.

[0053] The model support system described in this invention is an electromechanical integrated device used for fixing and manipulating the position of a test model in a supersonic wind tunnel test. The core feature of this system is that it possesses at least one linear motion degree of freedom along the normal direction (z-direction) of the wind tunnel test section, which is perpendicular to the wind tunnel axis and points inward perpendicular to the lower wall of the test section.

[0054] Conventional supersonic wind tunnel model support systems typically possess only three rotational degrees of freedom: pitch, roll, and yaw, with the test model fixed to the wind tunnel axis. This invention adds a normal translational degree of freedom to the conventional three-degree-of-freedom support system, creating a four-degree-of-freedom model support system. This addition of the normal degree of freedom allows the test model to move along the normal direction between the wind tunnel axis and the test section wall, providing a hardware foundation for subsequent offset load reduction strategies.

[0055] In this embodiment, the normal movement mechanism is implemented using a servo motor-driven ball screw in conjunction with linear guides. The specific structure is as follows: Two linear guides are mounted parallel to each other on a fixed base, with the guides perpendicular to the wind tunnel axis. The moving platform slides along the linear guides via a slider. The ball screw is mounted parallel to the two guides, with its ends supported by bearing seats. The servo motor is connected to the ball screw via a coupling, driving the screw to rotate. A nut seat is fixed to the bottom of the moving platform and works with the ball screw to convert the screw's rotational motion into the linear motion of the moving platform. The upper-level mechanisms (pitch, roll, and yaw mechanisms) are all mounted on the moving platform. Through precise control of the servo motor, the moving platform can reciprocate along the normal direction between the wind tunnel axis and the test section wall panel; the travel distance is determined according to the dimensions of the wind tunnel test section.

[0056] The model support system of this invention contains four degrees of freedom, specifically:

[0057] Normal movement (z): The motion type is translational, which moves the test model in a straight line along a direction perpendicular to the wind tunnel axis. It is used to offset the model during the start-up and shutdown phases to reduce the start-up load.

[0058] Pitch (α): The motion type is rotation, which changes the pitch angle of the test model and is used for aerodynamic characteristic testing during the test phase.

[0059] Roll (β): The motion type is rotation, which changes the roll angle of the test model and is used for aerodynamic characteristic testing during the test phase.

[0060] Yaw (γ): The motion type is rotation. It changes the yaw angle of the test model and is used for aerodynamic characteristic testing during the test phase.

[0061] Before the wind tunnel is started: the test model is moved from the wind tunnel axis position to an offset position close to the lower wall plate (such as the center between the axis and the lower wall plate) by the normal drive mechanism.

[0062] After the flow field is established: the measurement system confirms that the Mach number of the test section has reached the predetermined value, and then the normal drive mechanism moves the model back to the test position on the axis. The pitch, roll and yaw degrees of freedom are used to adjust the attitude of the model and start the test.

[0063] Before wind tunnel shutdown: After the test, the model is moved to the offset position again by the normal drive mechanism, and then the wind tunnel is shut down.

[0064] Normal degree of freedom can be achieved by using linear drive mechanisms such as electric actuators, hydraulic cylinders, and ball screws, in conjunction with linear guides to achieve precise position control.

[0065] Integration with other degrees of freedom: The normal translation mechanism typically serves as a base upon which pitch, roll, and yaw mechanisms are mounted, forming a series structure. Motion decoupling between the degrees of freedom ensures independent control.

[0066] The model support system described in this invention is a four-degree-of-freedom model support system formed by adding a normal translational degree of freedom to the conventional three-degree-of-freedom (pitch, roll, yaw) model support system. The components and their specific structures are described below.

[0067] (I) Overall Architecture:

[0068] The model support system adopts a series structure, with each degree of freedom mechanism stacked sequentially, from bottom to top (or from the fixed end to the model end): normal movement mechanism (base level) → yaw mechanism → pitch mechanism → roll mechanism → model connection interface.

[0069] The advantages of using a series structure are: decoupling of motion of each degree of freedom, simple control, and easy to modify and upgrade on the basis of the existing three-degree-of-freedom support system - only a normal movement platform needs to be added between the base and the original three-degree-of-freedom mechanism, with low modification cost and low technical risk.

[0070] The connection sequence of each degree of freedom can be adjusted according to the specific spatial layout of the wind tunnel test section. For example, in the tail boom scheme, it is usually connected in the order of normal → pitch → yaw → roll.

[0071] (II) Specific structure of each degree of freedom:

[0072] 1. Normal movement mechanism:

[0073] The normal movement mechanism is the key difference between this invention and conventional support systems, and it is used to realize the linear movement of the test model along the normal direction of the wind tunnel test section.

[0074] The implementation methods of the normal movement mechanism include, but are not limited to, the following:

[0075] Method 1: Servo motor + ball screw + linear guide; This is the most common and mature method for achieving linear motion. The specific structure is as follows: Linear guide: Installed parallel to the base, with the guide direction perpendicular to the wind tunnel axis (i.e., the normal direction). Typically, two guides are used to provide sufficient load-bearing rigidity and motion stability. Slider: Installed on the moving platform, slidingly engaging with the linear guide, allowing for linear reciprocating motion on the guide. Ball screw: Installed parallel between the two guides, with both ends supported by bearing seats. Servo motor: Connected to the ball screw via a coupling, driving the screw's rotation. Nut seat: Fixed to the bottom of the moving platform, engaging with the ball screw to convert the screw's rotational motion into the moving platform's linear motion. Moving platform: Serves as the mounting base for the upper mechanisms (pitch, roll, yaw mechanisms), moving together with the nut seat. The advantages of this method are high positioning accuracy, smooth motion, and good controllability, making it suitable for wind tunnel testing scenarios with high positioning accuracy requirements.

[0076] Method 2: Servo motor + rack and pinion: Suitable for applications with large strokes. The rack is fixed to the base, and the gear is mounted on the moving platform. The servo motor drives the gear to move along the rack, thus moving the platform. This method has a simple structure, but its positioning accuracy is slightly lower than that of the ball screw solution.

[0077] Method 3: Hydraulic Cylinder Drive: Suitable for heavy-duty applications. The hydraulic cylinder body is fixed to the base, and the piston rod is connected to the moving platform. The normal movement of the moving platform is achieved by controlling the extension and retraction of the piston rod through the hydraulic system. This method has a large load-bearing capacity, but its control precision and response speed are not as good as the servo motor solution, and it requires a hydraulic station, making the system more complex.

[0078] Method 4: Electric Linear Actuator: The electric linear actuator integrates a motor, reducer, and lead screw, forming a compact linear actuator. Multiple electric linear actuators are arranged in parallel to synchronously drive the moving platform. This method is compact in structure, easy to install, and suitable for small wind tunnels. Method 1 (servo motor + ball screw + linear guide) is preferred due to its high precision, mature control, and convenient maintenance, making it the best match for the model positioning accuracy requirements of wind tunnel testing.

[0079] 2. Yaw mechanism:

[0080] The yaw mechanism is used to achieve the rotational motion of the test model about the vertical axis (yaw angle γ). Common implementation methods include: slewing bearing + servo motor + worm gear: The inner or outer ring of the slewing bearing is fixed to the moving platform of the normal movement mechanism, while the other ring acts as a rotating component, driven by a servo motor through a worm gear reducer to achieve precise control of the yaw angle. The worm gear has a self-locking characteristic, maintaining its position even when power is off. Direct drive motor (torque motor): Using a torque motor to directly drive the rotating platform results in a compact structure, no transmission backlash, and high precision, but at a higher cost.

[0081] 3. Pitch mechanism:

[0082] The pitch mechanism is used to achieve the rotational motion (pitch angle α) of the test model about a horizontal transverse axis. Common implementation methods include: Scimitar-type pitch mechanism: This uses a scimitar-shaped support, driven by a hydraulic or electric cylinder to move the scimitar along an arc-shaped guide rail, achieving pitch angle changes. This is the most common type of pitch mechanism in high-speed wind tunnels, offering good rigidity and minimal flow field interference. Hinge-type pitch mechanism: This uses a hinge connection, driven by a servo motor through a reducer, to achieve pitch angle changes. It is suitable for test models with smaller loads.

[0083] 4. Rolling mechanism:

[0084] The rolling mechanism is used to achieve the rotational motion (roll angle β) of the test model about its horizontal longitudinal axis (the model's own axis). Common implementation methods include: Direct drive by a hollow motor: The rolling motor adopts a hollow structure, and the model support rod passes through the hollow shaft of the motor. The motor directly drives the model support rod to rotate, achieving the rolling motion. This method features a compact structure, short transmission chain, and high precision. Servo motor + worm gear: Suitable for applications with large loads, the worm gear has a self-locking function and can be locked at any roll angle.

[0085] 5. Model connection interface:

[0086] The model connection interface is located at the very end of the support system and is used to connect and secure the test model. Common types include: Conical sleeve connection: This uses a standard tapered fit, fixing the model to the support rod with tension bolts, offering convenient assembly and disassembly and high repeatability. Balance-integrated interface: This integrates a force balance into the connection interface, allowing for the measurement of aerodynamic forces acting on the model while supporting it.

[0087] (III) Control System:

[0088] The model support system needs to be equipped with a corresponding control system to achieve precise motion control and position feedback for each degree of freedom. The control system typically includes:

[0089] Controller: Can be a PLC or motion control card, which receives motion commands from the host computer and sends control signals to each drive unit.

[0090] Drive unit: servo driver or hydraulic servo valve, used to drive motor or hydraulic cylinder.

[0091] Position feedback elements: encoder (mounted on the motor shaft), linear encoder or magnetic encoder (mounted on the linear motion axis), rotary transformer (mounted on the rotary axis), used to provide real-time feedback of position information of each degree of freedom to achieve closed-loop control.

[0092] Limit switches: installed at the travel limit positions of each motion axis for safety protection, preventing collisions caused by overtravel.

[0093] Host computer: Used for human-computer interaction, providing motion control interface, position monitoring and fault diagnosis functions.

[0094] The control system should have the following functions: independent and linked control of each degree of freedom; precise position control and repeatable positioning; adjustable motion speed; position memory and automatic return function (such as automatic return to the offset position or test position); and a linkage interface with the wind tunnel main control system, which can automatically trigger model position adjustment according to the wind tunnel start-up and shutdown status.

[0095] The following is the structure of a typical implementation (from top to bottom):

[0096] Model connection end: The test model is connected to the front end of the model support rod via a conical sleeve, and a force balance is installed at the rear end of the support rod.

[0097] Rolling mechanism: hollow servo motor, the motor rotor is fixed to the model support rod, and the motor stator is fixed on the rolling bracket, driving the model to roll around its own axis.

[0098] Pitch Mechanism: A scimitar-type pitch mechanism, comprising a scimitar support and a pitch drive cylinder. The scimitar support is fixedly connected to the roll mechanism housing, and the pitch drive cylinder drives the scimitar to move along the arc guide rail, thereby achieving changes in the pitch angle.

[0099] Yaw mechanism: slewing bearing + worm gear reducer + servo motor, mounted on the normal moving platform, driving the upper mechanism to rotate around the vertical axis.

[0100] Normal movement mechanism: Two parallel linear guide rails are mounted on the fixed base, and the moving platform slides along the guide rails via a slider. A ball screw is mounted parallel between the two guide rails, and a servo motor drives the screw to rotate via a coupling, causing the moving platform to move linearly along the normal direction.

[0101] Base: Fixed to the foundation or mounting base outside the wind tunnel test section, providing a stable installation foundation for the entire support system.

[0102] It should be noted that the specific mechanical structure for achieving normal movement (such as a servo motor + ball screw + linear guide) is a conventional technique in this field. The inventive point of this invention does not lie in the specific structural form of the normal movement mechanism, but rather in: first, the discovery of a novel technique that can significantly reduce the starting load by using a normal offset test model; and second, the introduction of the normal degree of freedom into the model support system and its combination with the offset strategy of the supersonic wind tunnel start-up and shutdown process, forming a complete low-start-load start-up and shutdown operation method. Therefore, any mechanism capable of achieving linear movement of the test model along the normal direction falls within the protection scope of this invention.

[0103] In this method, the direction of the normal degree of freedom z is defined as: perpendicular to the axis of the wind tunnel test section, perpendicular to the lower wall of the test section, and pointing towards the interior of the test section. The positive direction of the normal is from the lower wall to the wind tunnel axis. When the test model moves along the normal, its vertical position in the test section changes, and it can stop at any position between the wind tunnel axis and the lower wall.

[0104] The purpose of setting the normal degree of freedom is to enable the test model to be offset from the axial position to a near-wall position during the wind tunnel start-up and shutdown phases, thereby reducing the start-up load on the model. After the flow field is established, the model can accurately return from the offset position to the test position at the axial position, ensuring the validity of the test data. This start-up and shutdown offset and test return operation process is the core innovation of this invention.

[0105] In this embodiment of the invention, the offset position refers to a specific normal position between the wind tunnel axis and the test section wall. To achieve optimal reduction of starting load while ensuring safety during model movement, the offset position is preferably determined through pre-calculation.

[0106] The specific method for numerical calculation is as follows:

[0107] (1) Construct an integrated numerical analysis model that includes the wind tunnel nozzle section, test section, test model and diffuser section. The model should fully reflect the changes in the flow channel geometry during the wind tunnel startup process (such as the matching relationship between the nozzle throat, test section and diffuser section), and be able to simulate the transient process of the supersonic flow field from establishment to stability.

[0108] (2) The integrated model is meshed, and local meshing is performed in areas where shock waves may occur (such as nozzle exit, around the model, and diffuser inlet) to ensure calculation accuracy.

[0109] (3) Using a solver based on the Reynolds-averaged Navier-Stokes equations (RANS) or large eddy simulation (LES), set the boundary conditions for the wind tunnel startup process: the total pressure in the steady section increases from low pressure to the total pressure required for the test over time (e.g., using a piecewise linear or exponentially increasing function), the outlet boundary conditions are set as pressure outlet or supersonic outlet, and the wall is set as a non-slip adiabatic wall.

[0110] (4) Place the test model in multiple different normal positions (including the axial position and multiple different offset distances), perform transient calculations, monitor the change curve of the aerodynamic load on the surface of the test model over time, and extract the maximum load value during the start-up process at each position.

[0111] (5) Compare the maximum starting load under different offset positions, and select a position that makes the maximum load significantly lower than the load at the axis position and leaves a sufficient safety gap (generally not less than 5% of the model reference length) between the model and the wall panel as the optimal offset position.

[0112] Through the above numerical calculations, an offset position that ensures both load reduction and safety can be determined for a specific wind tunnel and test model. For conventional wind tunnel configurations and typical models, general offset rules can also be obtained through a small number of calculations (for example, the center position between the axis and the wall panel is a safe and effective offset position).

[0113] The wind tunnel measurement system described in this invention refers to an existing system consisting of a sensor network and data acquisition and processing components installed on a supersonic wind tunnel for real-time monitoring of the wind tunnel's operating status and the flow field quality of the test section. Its core function is to continuously monitor airflow parameters (especially Mach number) at key locations in the test section during wind tunnel startup. When the parameters reach predetermined values ​​and the fluctuation amplitude meets the flow field quality requirements, the system determines that the flow field is fully established, thereby triggering the model to move from the offset position to the test position.

[0114] Example 2;

[0115] Based on Embodiment 1, Embodiment 2 of the present invention will be described in conjunction with specific examples:

[0116] A supersonic wind tunnel is designed to operate at Mach 3.0, using a publicly disclosed aircraft as the test model. This invention aims to reduce the aerodynamic loads experienced by the test model during wind tunnel startup (the specific values ​​of the aerodynamic loads experienced by the test model during wind tunnel startup are calculated numerically). The specific implementation steps are as follows:

[0117] (1) A numerical analysis model including the wind tunnel nozzle section, test section, test model and overexpansion section was constructed. The computational fluid dynamics numerical simulation method known in the field was used to simulate the wind tunnel Ma3.0 start-up process and the maximum start-up load on the test model was found to be 0.409.

[0118] (2) Construct a numerical analysis model including the wind tunnel nozzle section, test section, test model, and super-expansion section (the difference between the two constructions in step (1) and step (2) is that the position of the test model is different. In step (1), the position of the test model is the test position, and in step (2), the position is the start-stop position). Offset test model, place the test model at the center between the wind tunnel axis and the lower wall of the test section (start-stop position), and use numerical methods to simulate the wind tunnel Ma3.0 working condition start-up process. The maximum start-up load on the test model is calculated to be 0.271.

[0119] According to the above specific implementation steps, during the start-up process of a supersonic wind tunnel under Ma3.0 conditions, the aerodynamic loads experienced by the test model placed on the test section axis and at the center position between the wind tunnel axis and the lower wall of the test section are as described in (1) and (2), respectively. It can be seen that through the present invention, under Ma3.0 conditions, the aerodynamic load experienced by the test model during the wind tunnel start-up process is reduced by 33.7%.

[0120] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0121] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A zero-interference, high-efficiency, and safe method for starting and stopping a supersonic wind tunnel with low starting load, characterized in that: The method includes: Step S1: Construct a model support system, wherein the model support system has at least one normal degree of freedom, and the direction of the normal degree of freedom is perpendicular to the axis of the wind tunnel test section; Step S2: Before the wind tunnel is started, the test model is moved from the axial position of the wind tunnel test section along the normal direction to an offset position using the model support system. The offset position is located between the axial position of the wind tunnel test section and the test section wall. Step S3: Start the wind tunnel. After the flow field in the wind tunnel test section is established, use the model support system to move the test model from the offset position back to the test position at the axis of the wind tunnel test section for testing. Step S4: After the test is completed, the test model is moved from the test station to the offset position using the model support system, and then the wind tunnel operation is stopped.

2. The zero-interference, high-efficiency, and safe low-start-load supersonic wind tunnel start-up and shutdown operation method according to claim 1, characterized in that, The offset position is determined through pre-calculation, such that the maximum aerodynamic load borne by the test model during wind tunnel start-up and shutdown is lower than the maximum aerodynamic load borne by the model when it is in the axial position.

3. The zero-interference, high-efficiency, and safe low-start-load supersonic wind tunnel start-up and shutdown operation method according to claim 1, characterized in that, The offset position is the center position between the axis of the wind tunnel test section and the lower wall of the test section.

4. The zero-interference, high-efficiency, and safe low-start-load supersonic wind tunnel start-up and shutdown operation method according to claim 1, characterized in that, The model support system also has three rotational degrees of freedom: pitch, roll, and yaw, which are used to adjust the attitude angle of the test model at the test station.

5. The zero-interference, high-efficiency, and safe low-start-load supersonic wind tunnel start-up and shutdown operation method according to claim 1, characterized in that, In step S3, the wind tunnel measurement system is used to monitor whether the Mach number of the test section reaches the predetermined value to determine whether the flow field of the wind tunnel test section has been successfully established.

6. The zero-interference, high-efficiency, and safe low-start-load supersonic wind tunnel start-up and shutdown operation method according to claim 1, characterized in that, The method is applied to a continuous supersonic wind tunnel.

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