A model transient force measurement system in a wind tunnel

Abstract

The present application relates to a kind of model transient force measuring systems in wind tunnel, mass is arranged in the cavity of model, and there is interval between the mass and model on any side, internal stress dynamic balance includes two measuring parts, each measuring part includes four balance sensitive beams which are in the same plane and are distributed in cross shape around mass or two balance sensitive beams which are distributed in one-word symmetrically, one end of balance sensitive beam is connected with the inside wall of the cavity of model, and the other end is connected with mass.Data collector is embedded in mass and is connected with the signal of measuring part.When model is subjected to aerodynamic load, acceleration difference is generated between mass and model, so that balance sensitive beam generates strain corresponding to aerodynamic load, and is transmitted to data collector.The upper limit of frequency response of the system can realize order leap compared with tail support balance force measuring system, and the structure is simple, not limited by model shape and release mode, suitable for instantaneous dynamic test scene.

Description

Technical Field

[0001] This invention relates to the field of wind tunnel force measurement and testing technology, and in particular to a transient force measurement system for a model inside a wind tunnel. Background Technology

[0002] Force measurement of models in wind tunnel testing is an important technique in ground-based experimental research. With technological advancements, many tests require the measurement of transient forces on models, such as shock tunnel free-flight aerodynamic measurement tests, multi-stage separation unsteady dynamic aerodynamic characteristic measurement tests, and other transient aerodynamic characteristic measurement tests during aircraft deformation processes (e.g., real-time changes in wingspan or sweep angle according to mission requirements throughout flight, with winglets capable of twisting, bending, and bifurcating like birds) or during strong maneuvers (similar to the cobra maneuver and right-angle turns of high-speed fighter jets). Therefore, high demands are placed on the transient response performance of the balance.

[0003] For shock tunnels, due to their operating principles, the test time for pulse wind tunnel equipment such as shock tunnels is very short, generally on the order of milliseconds. Currently, the commonly used force measurement technology in shock tunnels is the tail-supported internal balance method. The model is mounted on the internal balance, which is either mounted on a support rod or integrated with it. The support rod is mounted on a support device in the wind tunnel test section. When airflow acts on the model, the balance generates strain under aerodynamic load. Sensitive elements attached to the balance (such as semiconductor strain gauges or piezoelectric ceramic plates) convert the strain into an electrical signal output, which is recorded by data acquisition instruments. The aerodynamic load acting on the model and the balance's electrical signal output recorded by the data acquisition instruments have a linear relationship. Before the test, a specific relationship between the load and the balance output (balance usage formula) can be obtained through a balance calibration process. During the test, the aerodynamic load on the model is calculated using the balance output signal and the balance usage formula obtained during calibration.

[0004] Existing shock tunnel force measurement technology is essentially a static force measurement technology, based on Hooke's Law, which is incompatible with the dynamic force measurement scenario of shock tunnels, mainly in the following two aspects:

[0005] (1) The test frequency response of the existing tail support balance force measurement technology has a bottleneck and cannot meet the dynamic test requirements of pulse wind tunnel aerodynamic test.

[0006] The test frequency response refers to the range of measurable signal frequencies. Within this range, the output signal can reproduce the measured signal within an acceptable error range; otherwise, amplitude and phase deviations will occur. The frequency response of a shock tunnel force measurement system mainly depends on the model mass and support stiffness. Minimizing the model mass and increasing the support stiffness can raise the natural frequency of the model force measurement system, thereby increasing the upper limit of the frequency response. However, since the tail support cannot interfere with the flow field structure of the model, its minimum length and maximum diameter are strictly limited. Therefore, even if the model is made very small and its mass is reduced as much as possible, the lateral stiffness of the model force measurement system (which can be understood as the ability to resist bending deformation) cannot be increased much. The upper limit of the overall force measurement system's frequency response is difficult to exceed 100Hz, while millisecond-level (taking 5ms as an example) measurement tests require the force measurement system's frequency response to reach above 600Hz (the shorter the test time, the higher the frequency response requirement). This causes two problems: first, the model is very small, and the accuracy of detailed simulation is not high; second, the frequency response is insufficient, and the amplitude and phase of the output signal cannot accurately reflect the measured aerodynamic load, resulting in dynamic measurement errors.

[0007] (2) During the effective test time of the shock tunnel, the vibration generated by the high Mach high energy flow field impact model force measurement system cannot be effectively damped, which seriously interferes with the balance signal. The low frequency vibration interference caused by the support rod vibration even causes the effective signal to be distorted.

[0008] For multi-stage separation unsteady dynamic aerodynamic characteristic measurement tests, the CTS (Continuous Traction Theorem) testing technique is currently widely used. This technique mainly uses two support mechanisms to support the separated body separately. Generally, only one support mechanism has motion capability, while the other is fixed. The CTS mechanism supports the separated body model, and a balance is used to measure the aerodynamic loads of the separated body model in the disturbed flow field of the main model at its initial position and attitude. This is converted into aerodynamic coefficients. Combined with given flight separation conditions, the mass and moment of inertia of the separated body, the attitude of the main body, flight altitude, flight Mach number, and other relevant parameters, the six-free motion equations of the full-size separated body are solved at given time intervals to obtain the position and attitude of the separated body relative to the main body at the end of the next time interval. This is then converted into the position and attitude that the mechanism carrying the model should reach in the wind tunnel. The CTS mechanism then moves the model to the corresponding position and attitude according to the instructions. The balance is then used to measure the aerodynamic loads again, and the position and attitude of the separated body at the next point are calculated. This measurement and calculation is repeated point by point to obtain the motion trajectory of the full-size separated body. However, the CTS testing technique has the following shortcomings for the transient force measurement of the model in this type of test:

[0009] (1) Multibody separation CTS grid force measurement is essentially a quasi-static force measurement technology. The coupling of this aerodynamic data and the equation of motion cannot bring about the unsteady characteristics induced by the actual relative motion. It cannot truly simulate the unsteady dynamic process of the separation process (especially the initial stage of separation). The aerodynamic measurement results have certain deviations from the actual situation.

[0010] (2) The multi-body separation CTS mesh force measurement technology has limitations such as the inability to perform multi-body maneuvers simultaneously, the inability to get too close, and spatial interference constraints on model supports.

[0011] For the measurement technology of aerodynamic characteristics of hypersonic aerodynamic deformable aircraft, current research mainly relies on CFD calculations to conduct qualitative research. Ground tests can only be conducted on several deformable configurations of the aircraft, and there is a lack of effective means to measure the transient aerodynamic characteristics during the deformation process.

[0012] There are currently no good ground-based test and measurement methods for the transient aerodynamic characteristics of hypersonic vehicles during strong maneuvers. Summary of the Invention

[0013] The purpose of this invention is to provide a transient force measurement system for models in a wind tunnel, which meets the requirements for transient force measurement of models in wind tunnel tests.

[0014] To achieve the above objectives, in a first aspect, the present invention provides a transient force measurement system for a model inside a wind tunnel, comprising:

[0015] A mass block is placed inside the cavity of the model, and there is a gap between each side of the mass block and the model.

[0016] The internal stress dynamic balance includes multiple balance sensitive beams, which form two measuring sections. The two measuring sections are distributed at intervals along the front-back direction of the model, and the number of balance sensitive beams in the two measuring sections is the same.

[0017] Each measuring unit includes four balance beams, which are located on the same plane and arranged in a cross shape around the mass block. One end of each balance beam is connected to the inner wall of the model's cavity, and the other end is connected to the mass block; or

[0018] Each measuring unit includes two balance sensitive beams, which are located on the same plane and are symmetrically distributed in a straight line around the mass block. One end of the balance sensitive beam is connected to the inner wall of the cavity of the model, and the other end is connected to the mass block.

[0019] The data acquisition unit is embedded in the mass block and is connected to the measurement unit for signal transmission.

[0020] When the model is subjected to aerodynamic loads, an acceleration difference is generated between the mass block and the model, causing the balance sensitive beam to produce strain corresponding to the aerodynamic load, and the strain data is transmitted to the data acquisition device.

[0021] In the first aspect, optionally, each measuring unit further includes a first connecting ring and a second connecting ring, the outer wall of the first connecting ring being tightly attached to the inner wall of the cavity of the model, the second connecting ring being sleeved on the mass block and tightly attached to the mass block, and one end of each balance sensitive beam being connected to the inner wall of the first connecting ring and the other end being connected to the outer wall of the second connecting ring.

[0022] In the first aspect, based on the implementation with the second connecting ring, the transient force measurement system of the model in the wind tunnel may optionally include a cable passage that passes through the mass block and communicates with the data acquisition unit, through which the cable of the measurement unit passes and is connected to the data acquisition unit.

[0023] In the first aspect, optionally, the dynamic balance of internal stress further includes a connecting shell, which is sleeved on the outside of the mass block, and the shape and size of the connecting shell match the shape of the mass block at the sleeve location, so that the connecting shell is tightly sleeved on the outside of the mass block.

[0024] Each measuring unit also includes a first connecting ring, the outer wall of which is in close contact with the inner wall of the cavity of the model. One end of each balance sensitive beam is connected to the inner wall of the first connecting ring, and the other end is connected to the outer wall of the connecting shell.

[0025] In the first aspect, based on the embodiment with a connecting shell, optionally, the connecting shell is designed in three sections along the axial direction, consisting of a first section shell, a second section shell, and a third section shell from one end to the other. The internal shape and size of the first section shell and the third section shell match the shape and size of the corresponding mass block, so that the first section shell and the third section shell are tightly attached to the mass block, and there is a gap between the second section shell and the corresponding mass block.

[0026] In the first aspect, based on the implementation with a connecting shell, the transient force measurement system for the model inside the wind tunnel may optionally include a cable passage that passes through the connecting shell and the mass block and communicates with the data acquisition unit, allowing the cables of the measurement unit to pass through and connect to the data acquisition unit.

[0027] Secondly, the present invention also provides another transient force measurement system for a model in a wind tunnel, comprising:

[0028] A mass block is placed inside the cavity of the model, and there is a gap between each side of the mass block and the model.

[0029] The internal stress dynamic balance includes a measuring unit comprising four balance-sensitive beams. These beams are located in the same plane and arranged in a cross shape around a mass block. One end of each beam is connected to the inner wall of the model's cavity, and the other end is connected to the mass block.

[0030] The measuring unit includes two balance sensitive beams, which are located on the same plane and are symmetrically distributed in a straight line around the mass block. One end of the balance sensitive beam is connected to the inner wall of the cavity of the model, and the other end is connected to the mass block.

[0031] The data acquisition unit is embedded in the mass block and is connected to the measurement unit for signal transmission.

[0032] When the model is subjected to aerodynamic loads, an acceleration difference is generated between the mass block and the model, causing the balance sensitive beam to produce strain corresponding to the aerodynamic load, and the strain data is transmitted to the data acquisition device.

[0033] In the second aspect, optionally, the transient force measurement system for the model in the wind tunnel also includes a cable passage that passes through the mass block and is connected to the data acquisition unit, through which the cable of the measurement unit passes and is connected to the data acquisition unit.

[0034] Thirdly, the present invention provides yet another transient force measurement system for a model inside a wind tunnel, comprising:

[0035] A mass block is placed inside the cavity of the model, and there is a gap between each side of the mass block and the model.

[0036] The internal stress dynamic balance includes multiple piezoelectric parts, which form two measuring parts. The two measuring parts are distributed at intervals along the front-back direction of the model, and the number of piezoelectric parts in the two measuring parts is the same.

[0037] Each measuring unit includes four piezoelectric units located on the same plane and arranged in a cross shape around the mass block. Each piezoelectric unit includes three stacked piezoelectric plates. One of the two piezoelectric plates at the two ends is connected to the inner wall of the cavity of the model, and the other is connected to the mass block; or

[0038] Each measuring unit includes two piezoelectric units located on the same plane and symmetrically distributed in a line around the mass block. Each piezoelectric unit includes two stacked piezoelectric plates, one of which is connected to the inner wall of the cavity of the model, and the other is connected to the mass block.

[0039] Setting the axis of the vertical model of the piezoelectric part;

[0040] The data acquisition unit is embedded in the mass block and is connected to the measurement unit for signal transmission.

[0041] When the model is subjected to aerodynamic load, an acceleration difference is generated between the mass block and the model, causing the piezoelectric element to produce strain corresponding to the aerodynamic load, and the strain data is transmitted to the data acquisition unit.

[0042] In the third aspect, optionally, the dynamic balance of internal stress also includes a connecting shell, which is sleeved on the outside of the mass block, and the shape and size of the connecting shell match the shape of the mass block at the sleeve location, so that the connecting shell is tightly sleeved on the outside of the mass block.

[0043] Based on the implementation of the connecting shell in the third aspect, optionally, the connecting shell is designed in three sections along the axial direction, consisting of a first section shell, a second section shell, and a third section shell from one end to the other. The internal shape and size of the first section shell and the third section shell match the shape and size of the corresponding mass block, so that the first section shell and the third section shell are tightly attached to the mass block, and there is a gap between the second section shell and the corresponding mass block.

[0044] Based on the implementation with a connecting shell in the third aspect, the transient force measurement system of the model in the wind tunnel may optionally include a cable passage that passes through the connecting shell and the mass block and communicates with the data acquisition unit, allowing the cable of the measurement unit to pass through and connect to the data acquisition unit.

[0045] Based on any of the first, second, or third embodiments, optionally, the mass block is divided into multiple segments along the axial direction, and the segments are detachably rigidly connected.

[0046] Based on the above implementation of the segmented design of mass blocks, optionally, in the two connected mass blocks, one mass block has a threaded post on its end face, and the other mass block has a threaded hole on its end face that mates with the threaded post. The two connected mass blocks are threadedly connected by the threaded post and the threaded hole.

[0047] Optionally, based on any of the first, second, or third embodiments, the inner wall of the cavity of the model is provided with reinforcing ribs.

[0048] The above-mentioned technical solution of the present invention has the following advantages: The transient force measurement system for a wind tunnel model provided by the present invention includes a mass block, a dynamic balance for internal stress, and a data acquisition unit. The mass block is placed inside the cavity of the model, and there is a gap between either side of the mass block and the model. The dynamic balance for internal stress includes two measuring parts. Each measuring part includes four balance sensitive beams located on the same plane and arranged in a cross shape around the mass block, or two balance sensitive beams located on the same plane and arranged symmetrically in a straight line around the mass block. One end of the balance sensitive beam is connected to the inner wall of the cavity of the model, and the other end is connected to the mass block. The data acquisition unit is embedded in the mass block and is connected to the measuring parts for signal transmission. When the model is subjected to aerodynamic loads, an acceleration difference is generated between the mass block and the model, causing the balance sensitive beam to generate strain corresponding to the aerodynamic load, and the strain data is transmitted to the data acquisition unit. Compared with the tail-support balance force measurement system, this measurement system can achieve a leap in the upper limit of frequency response, and its structure is simple, not limited by the shape of the model or the release method, and is suitable for instantaneous dynamic testing scenarios.

[0049] This invention provides another transient force measurement system for a wind tunnel model, comprising a mass block, a dynamic internal stress balance, and a data acquisition unit. The mass block is disposed within the cavity of the model, with a gap between either side of the mass block and the model. The dynamic internal stress balance includes two measuring units, each comprising four piezoelectric elements arranged in a cross shape around the mass block on the same plane, or two piezoelectric elements arranged symmetrically in a straight line around the mass block on the same plane. The piezoelectric elements are positioned perpendicular to the model's axis, with one end connected to the inner wall of the model's cavity and the other end connected to the mass block. The data acquisition unit is embedded within the mass block and connected to the measuring units via a signal connection. When the model is subjected to aerodynamic loads, an acceleration difference is generated between the mass block and the model, causing the piezoelectric elements to generate strains corresponding to the aerodynamic loads, and the strain data is transmitted to the data acquisition unit. This measurement system achieves a significant leap in frequency response compared to the tail-support balance force measurement system, and its simple structure, independence from model shape and release method, makes it suitable for instantaneous dynamic testing scenarios. Attached Figure Description

[0050] The accompanying drawings are provided for illustrative purposes only, and the proportions and quantities of the components in the drawings may not be consistent with the actual product.

[0051] Figure 1 This is a schematic diagram of the transient force measurement system for a model inside a wind tunnel in Embodiment 1 of the present invention;

[0052] Figure 2 This is a schematic diagram of the structure of a transient force measurement system for a wind tunnel model according to Embodiment 1 of the present invention;

[0053] Figure 3 yes Figure 2 A frontal view of the transient force measurement system for the model inside the wind tunnel;

[0054] Figure 4 yes Figure 2 A schematic diagram of the AA cross-section;

[0055] Figure 5 yes Figure 4 Schematic diagram of the BB section;

[0056] Figure 6 This is a schematic diagram of the structure of a transient force measurement system for a wind tunnel model installed inside the model, according to Embodiment 1 of the present invention;

[0057] Figure 7 yes Figure 6 A cross-sectional view along the centerline;

[0058] Figure 8 yes Figure 6 A schematic diagram of the structure of the model after removing the end caps;

[0059] Figure 9 This is a cross-sectional schematic diagram of a transient force measurement system for a wind tunnel model according to Embodiment 2 of the present invention;

[0060] Figure 10 This is a cross-sectional schematic diagram of a transient force measurement system for a wind tunnel model according to Embodiment 3 of the present invention;

[0061] Figure 11 This is a schematic diagram of the cross-section of a transient force measurement system for a wind tunnel model in Embodiment 4 of the present invention, cut along the axis of the sensitive beam of the balance.

[0062] Figure 12 This is a cross-sectional schematic diagram of a transient force measurement system for a wind tunnel model according to Embodiment 5 of the present invention;

[0063] Figure 13 yes Figure 12 A schematic diagram of the CC section;

[0064] Figure 14 This is a cross-sectional schematic diagram of a transient force measurement system for a wind tunnel model according to Embodiment Six of the present invention;

[0065] Figure 15 yes Figure 14 DD cross-sectional schematic diagram.

[0066] In the picture:

[0067] 1: Model;

[0068] 11: Reinforcing ribs;

[0069] 2: Mass block;

[0070] 21: First block;

[0071] 22: Second block;

[0072] 3: Dynamic balance for internal stress;

[0073] 31: Balance sensitive beam;

[0074] 32: First connecting ring;

[0075] 33: Second connecting ring;

[0076] 34: Connecting shell;

[0077] 341: First shell segment;

[0078] 342: Second shell segment;

[0079] 343: Third shell segment;

[0080] 35: Cable crossing;

[0081] 36: Piezoelectric component;

[0082] 361: Piezoelectric element;

[0083] 4: Data acquisition device;

[0084] 5: End cap. Detailed Implementation

[0085] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0086] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0087] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0088] In this invention, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0089] The basic principle of the sensitive beam scheme adopted in this invention is as follows:

[0090] Inertia is a fundamental property of matter. See also Figure 1 As shown, a mass block 2 is installed inside model 1, and model 1 and mass block 2 are connected by a balance-sensitive beam 31. When model 1 is subjected to aerodynamic loads, due to inertia, model 1 and mass block 2 have different accelerations, resulting in an acceleration difference. The balance-sensitive beam 31 then generates strain that exhibits a specific stable relationship with the aerodynamic load. Compared to existing tail-support / belly-support balance force measurement technology, mass block 2 acts as the support end of a dynamic balance for internal stress. Furthermore, even in long-term static application scenarios, since model 1 is always subjected to aerodynamic loads and receives acceleration, while mass block 2 is never subjected to loads, the balance-sensitive beam 31 will always have internal stress.

[0091] It should be noted that the balance sensitive beam 31 itself is an existing component in stress balances, which is generally composed of strain gauges attached to a beam body capable of generating strain. In this embodiment, the configuration of the balance sensitive beam itself and its deformation decoupling principle are consistent with the existing technology.

[0092] The main differences between the present invention and existing tail-support balance technology are:

[0093] (1) Different measurement principles

[0094] Assuming the balance output is y under a certain static load, the load is x, and the static sensitivity of the balance is S, then the measurement principle of the tail-support balance force measurement technology is as follows:

[0095] y = Sx

[0096] Assuming the dynamic output of the balance is y(t), the unit impulse response function of the model, balance, and mass block force measurement system is g(t), and the dynamic load input is x(t), the measurement principle of this invention is as follows:

[0097]

[0098] Further theoretical models were used to observe the sensitivity and frequency response of the measurement system in this scheme:

[0099] Assume the mass of the mass block is m s The model quality is m f The stiffness of the sensitive beam of the balance is k. f Damping is C f Then the static sensitivity S and natural frequency ω of the balance itself f Damping ratio ζ f for:

[0100]

[0101] Let the mass ratio of the model to the mass block be... The equivalent stiffness k′ of the measurement system according to the present invention f and equivalent damping C′ f They are respectively:

[0102]

[0103]

[0104] The equivalent sensitivity S' and equivalent natural frequency ω' of the measurement system according to the present invention are then determined. f Equivalent damping ratio ζ' f for:

[0105]

[0106]

[0107]

[0108] As can be seen, the measurement sensitivity of traditional tail-support balance force measurement technology depends on the static sensitivity of the balance. However, the measurement sensitivity of the measurement system in this invention depends not only on the static sensitivity of the balance but also on the ratio of the model mass to the mass block mass. The upper limit of the measurement sensitivity of the measurement system in this invention is the static sensitivity of the balance; the smaller the ratio of the model mass to the mass block mass, the smaller the sensitivity attenuation. Simultaneously, it can be observed that the natural frequency of the measurement system in this invention depends on the natural frequency of the balance itself and the ratio of the model mass to the mass block mass. The natural frequency of the balance itself can easily reach the kHz level; the larger the ratio of the model mass to the mass block mass, the higher the natural frequency of the measurement system in this invention, i.e., the higher the upper limit of the frequency response. The natural frequency of the measurement system in this invention is no longer affected by the slender tail support rod, allowing for a significant leap in the upper limit of the measurement system's frequency response. This makes the measurement system of the present invention more suitable for instantaneous dynamic testing scenarios, such as shock tunnel free-flight aerodynamic measurement tests, multi-stage separation unsteady dynamic aerodynamic characteristic measurement tests, and other dynamic aerodynamic characteristic measurement tests such as during the deformation process of the aircraft (for example, during the entire flight process, the wingspan or sweep angle is changed in real time according to the mission requirements, while its winglets can perform twisting, bending, splitting and other operations like birds) or during the strong maneuvering of the aircraft (similar to the cobra maneuver, right-angle turn, etc. of high-speed fighter jets).

[0109] The inventive concept is further illustrated below using the B-2 standard model as an example through specific embodiments. The model is a cone with an end cap at the rear.

[0110] Example 1

[0111] See Figures 2-8As shown, the transient force measurement system for a wind tunnel model provided in this embodiment of the invention includes a mass block 2, an internal stress dynamic balance 3, and a data acquisition device 4.

[0112] See Figure 7 As shown, mass block 2 is disposed within the cavity of model 1, and there is a gap between either side of mass block 2 and the model (including the end cap 5 at the rear of the model) (i.e., mass block 2 does not directly contact model 1). See also Figure 3 and Figure 4 As shown, in this embodiment, the mass block 2 is designed in two segments along the axial direction of model 1. Of course, in other embodiments, the mass block 2 can also be divided into three segments, four segments, etc.; it can also be a single integrated design. Taking the mass block 2 divided into two segments as an example, from the front end to the rear end of the model (… Figure 7 From left to right, the first segment 21 and the second segment 22 are respectively. The first segment 21 and the second segment 22 are detachably rigidly connected, that is, the two mass blocks are rigidly connected as one unit and can move synchronously. In this embodiment, the center of mass of the model can be easily adjusted by combining different materials, shapes or lengths of the two mass blocks.

[0113] In a preferred embodiment, see Figure 4 and Figure 7 As shown, the end face of the first segment 21 is provided with a threaded post, and the end face of the second segment 22 is provided with a threaded hole. The first segment 21 and the second segment 22 are connected by threaded post and threaded hole.

[0114] See Figures 2-5 As shown, in this embodiment, eight balance-sensitive beams 31 form two measuring sections, which are distributed at intervals along the axial direction of the model. Each measuring section contains four balance-sensitive beams 31, which are located on the same plane and arranged in a cross shape (cross-beam spoke structure) around the second segment 22. One end of each balance-sensitive beam 31 is connected to the inner wall of the cavity of the model 1, and the other end is connected to the mass block 2. It should be noted that, depending on the needs, both measuring sections can be located outside the second segment 22, both outside the first segment 21, or one outside the first segment 21 and the other outside the second segment 22. In this embodiment, both measuring sections are located outside the second segment 22, meaning one end of each balance-sensitive beam 31 is connected to the second segment 22.

[0115] In this embodiment, both the first block 21 and the second block 22 are frustoconical, but it is not required that the conical surface at the connection point after assembly must be smoothly transitioned. It should be noted that in some other embodiments, since the shapes of the models are different, the mass block 2 generally only needs to match the shape of the model, and the specific shape is not limited.

[0116] In this embodiment, the gap between the mass block 2 and the model 1 is to prevent them from contacting each other. This allows for a difference in acceleration between the two when the model is subjected to aerodynamic loads, causing the gap to change or tend to change, thus generating corresponding strain in the balance's sensitive beam 31. Ideally, the gap should ensure that they do not contact within the measurement range, but contact should occur under overload conditions. This provides overload protection, preventing plastic deformation of the balance's sensitive beam and damage during overload.

[0117] See Figure 2 , Figure 4 and Figure 4 As shown, the data acquisition unit 4 is embedded in the second segment 22 and connected to the measurement unit for receiving strain information from the balance-sensitive beam 31. Data is retrieved after the test.

[0118] It should be noted that in some other embodiments, the data acquisition device 4 may also be installed in other locations inside the model. However, to save space and facilitate arrangement, the data acquisition device 4 is preferably embedded in the mass block.

[0119] When model 1 is subjected to aerodynamic loads, under the influence of inertia, there is an acceleration difference between mass block 2 and model 1. This causes the balance sensitive beam 31 to produce a strain corresponding to the aerodynamic load, and the strain data is transmitted to the data acquisition unit 4. The acquired data is then processed to obtain the measurement results. It should be noted that the data processing and calculation are existing technologies and will not be elaborated upon here.

[0120] The internal stress dynamic balance 3 is fixed to the cavity of model 1 by mass block 2. In order to improve the overall force transmission characteristics, in one embodiment, see... Figures 2-4 As shown, the internal stress dynamic balance 3 also includes a connecting shell 34, which is fitted onto the outside of the second segment 22. The shape and size of the connecting shell match the shape and size of the second segment 22 (mainly the radial dimension; the axial dimension only needs to meet the distance between the measuring parts), so that the connecting shell 34 is tightly fitted onto the outside of the second segment 22. Each measuring part also includes a first connecting ring 32, the outer wall of which is tightly fitted against the inner wall of the cavity of model 1. One end of each balance sensitive beam 31 is connected to the inner wall of the first connecting ring 32, and the other end is connected to the outer wall of the connecting shell 34. This scheme can better ensure the assembly effect of the two measuring parts and improve the overall force transmission characteristics.

[0121] To facilitate the assembly of the connecting shell 34 and the mass block 2, in some embodiments, see [reference needed]. Figures 2-4 and Figure 7As shown, the connecting shell 34 is designed in three sections along the axial direction, consisting of a first shell 341, a second shell 342, and a third shell 343 from one end to the other. The internal shape and size of the first shell 341 and the third shell 343 match the shape and size of the corresponding mass block 2, ensuring that the first shell 341 and the third shell 343 are tightly fitted to the mass block 2. There is a gap between the second shell 342 and the corresponding mass block 2. This ensures a stable connection between the connecting shell 34 and the mass block 2 while avoiding excessive friction due to an excessively large contact surface, which would hinder installation and disassembly. Of course, in other embodiments, the second shell 342 can also be composed of multiple connecting plates spaced apart circumferentially, thus protecting the overall rigidity of the connecting shell 34 and similarly avoiding excessive friction due to an excessively large contact surface, which would hinder installation and disassembly.

[0122] To facilitate the wire connection and wiring between the measuring unit and the data acquisition unit 4, in some embodiments, a wire passage 35 is also provided. The wire passage 35 passes through the connecting shell 34 and the mass block 2 and communicates with the data acquisition unit 4, allowing the measuring unit's cable to pass through and connect to the data acquisition unit 4.

[0123] To improve the overall stiffness of the model and ensure its overall force transmission characteristics, in some implementation methods, see [reference needed]. Figure 7 and Figure 8 As shown, a reinforcing rib 11 is provided on the inner wall of the cavity of model 1 to improve the overall rigidity of model 1. Especially for some models with poor rigidity or high measurement accuracy requirements, the reinforcing rib 11 on the inner wall of the cavity of the model has a better effect.

[0124] Example 2

[0125] See Figure 9 As shown, this second embodiment is basically the same as the first embodiment, and the similarities will not be repeated. The difference is that the measuring unit also includes a first connecting ring 32 and a second connecting ring 33. The outer wall of the first connecting ring 32 is tightly attached to the inner wall of the cavity of the model 1. The second connecting ring 33 is sleeved on the mass block 2 and is tightly attached to the mass block 2. One end of each balance sensitive beam 31 is connected to the inner wall of the first connecting ring 32, and the other end is connected to the outer wall of the second connecting ring 33. That is, one end of the balance sensitive beam 31 is connected to the model 1 through the first connecting ring 32, and the other end is connected to the mass block 2 through the second connecting ring 33. That is, the two measuring parts are connected to the mass block 2 by a connecting ring, instead of using a connecting shell 34 to connect them as a whole. Compared with the scheme in the first embodiment where the two measuring parts are connected by a connecting shell 34, this embodiment is simpler to assemble, but requires higher processing and assembly accuracy.

[0126] To facilitate the connection and arrangement of cables between the measuring unit and the data acquisition unit 4, in some embodiments, a cable passage 35 is provided. The cable passage 35 passes through the mass block 2 and is connected to the data acquisition unit 4, allowing the cables of the measuring unit to pass through and connect to the data acquisition unit 4.

[0127] Example 3

[0128] See Figure 10 As shown, this embodiment three is basically the same as embodiment one or embodiment two, and the similarities will not be repeated. The difference is that only one measuring unit is set. The position of the measuring unit in the axial direction of the model can be set as needed and is not limited here. Compared with the two measuring units in embodiment two, the structure of one measuring unit is simpler, but it requires the model to have better overall stiffness in order to minimize the attenuation of load transmission in the parts of the model far away from the sensitive beam (the front and rear ends of the model).

[0129] Example 4

[0130] See Figure 11 As shown, the scheme of this embodiment four is based on any of the embodiments in embodiments one to three. Each measuring unit is equipped with only two balance sensitive beams 31. The two balance sensitive beams 31 are located on the same plane and are symmetrically distributed in a straight line around the mass block 2. One end of the balance sensitive beam 31 is connected to the inner wall of the cavity of the model 1, and the other end is connected to the mass block 2. The schemes of embodiments one to three can realize six-component measurement. The scheme of this embodiment can realize three-component measurement.

[0131] Example 5

[0132] See Figure 12 and Figure 13 As shown, the main difference between Embodiment 5 and Embodiment 1 is that the sensitive component 31 of the internal stress dynamic balance 3 is replaced by the piezoelectric part 36. The other structures are basically the same and will not be described in detail here.

[0133] Taking three-component measurement as an example, piezoelectric plates 361 are installed between model 1 and mass block 2. Two piezoelectric plates 361 form a piezoelectric part 36, and two piezoelectric parts 36 are arranged symmetrically vertically to form a measuring part. Two measuring parts are set at intervals at the front and back positions. The axis of the piezoelectric part 36 is set perpendicular to the axis of model 1 to ensure that the piezoelectric part 36 is perpendicular to the axis of model 1. The two piezoelectric plates 361 of each piezoelectric part 36 are respectively of the compressive type (D33 of the piezoelectric plate is the main component and is only sensitive to tension and compression) and the shear type (D31 of the piezoelectric plate is the main component and is only sensitive to shear). One of the two piezoelectric plates 361 of each piezoelectric part 36 is connected to model 1, and the other is connected to mass block 2. For structures with arc surfaces at the connection, in one specific embodiment, a groove can be provided on the arc surface, the bottom of the groove is flat, and the end of the piezoelectric part 36 abuts against the bottom of the groove. When measuring axial force, the shear-type piezoelectric elements are sensitive to axial force. The outputs of the four shear-type piezoelectric elements in the two measuring sections are added together to generate the axial force output, while simultaneously neutralizing the interference generated by the normal force and pitch moment (electrical decoupling). When measuring normal force, the positive pressure piezoelectric element in the lower piezoelectric section 36 is compressed, resulting in a positive output, while the positive pressure piezoelectric element in the upper piezoelectric section 36 is compressed, resulting in a negative output. The sum of the outputs of the two lower positive pressure piezoelectric elements and the sum of the outputs of the two upper positive pressure piezoelectric elements are used as the normal force component output. When measuring pitch moment, the positive pressure piezoelectric elements at opposite corners are compressed on one side and stretched on the other. Assuming a pitch moment of upward movement, the upper left and lower right piezoelectric elements are compressed, resulting in a positive output, while the lower left and upper right piezoelectric elements are stretched, resulting in a negative output. The output of the positive piezoelectric element and the output of the negative piezoelectric element are used as the pitch moment component output. The pitch moment output is checked according to the pitch moment calculation formula under normal force conditions, or the normal force output is checked according to the normal force calculation formula under pitch moment conditions. Electrical decoupling of the normal force and pitch moment is achieved through the addition and subtraction of the outputs from the four positive pressure piezoelectric plates in the two measuring sections. (The normal force component output is only sensitive to the normal force; when only pitch moment acts and no pitch moment acts, the normal force component output is zero. Similarly, the pitch moment component is only sensitive to the pitch moment component; when only normal force acts and no pitch moment acts, the pitch moment component output is zero.) The measurement of the force, yaw moment component, and roll moment component is similar and will not be elaborated further. It should be noted that the application of piezoelectric plates to the balance itself is existing technology, and its structure and measurement principle are also existing technologies. The above is merely an example, and further details will not be provided here.

[0134] Compared to the sensitive beam scheme in Example 1, the piezoelectric scheme has a more compact structure and higher stiffness, and its upper limit of frequency response and dynamic response characteristics are better than the strain-based scheme. However, it places higher demands on the manufacturing process and data acquisition instruments.

[0135] Example 6

[0136] See Figure 14 and Figure 15 As shown, this sixth embodiment, compared to the fifth embodiment, is a six-component measurement. The only differences are the number of piezoelectric parts 36 and the number of piezoelectric plates 361 within each piezoelectric part 36; the rest of the structure is the same and will not be repeated here. The specific differences are as follows: The measuring unit includes four piezoelectric parts 36, located on the same plane and arranged in a cross shape around the mass block 2. Each piezoelectric part 36 includes three stacked piezoelectric plates 361. One of the two piezoelectric plates 361 located at both ends is connected to the inner wall of the cavity of the model 1, and the other piezoelectric plate 361 is connected to the mass block 2. During the measurement process, the function of each piezoelectric plate 361 is the same as in the current design and will not be repeated here.

[0137] In summary, the transient force measurement system for a wind tunnel model of the present invention sets up a dynamic internal stress balance in the interval between the mass block and the model. When the model is subjected to aerodynamic loads, there is no acceleration difference between the model and the mass block, causing the sensitive component of the dynamic internal stress balance to change in a corresponding relationship with the aerodynamic load, and transmitting the data to the data acquisition unit to realize the transient force measurement of the model in the wind tunnel.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that not every embodiment contains only one independent technical solution, and in the absence of conflict between solutions, the various technical features mentioned in each embodiment can be combined in any way to form other implementation methods that can be understood by those skilled in the art.

[0139] Furthermore, without departing from the scope of the present invention, modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions of some of the technical features, shall not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A transient force measurement system for a model inside a wind tunnel, characterized in that, include: A mass block is disposed within the cavity of the model, and there is a gap between each side of the mass block and the model. The internal stress dynamic balance includes multiple balance sensitive beams, which form two measuring sections. The two measuring sections are distributed at intervals along the front-back direction of the model, and the number of balance sensitive beams in the two measuring sections is the same. Each of the measuring units includes four balance-sensitive beams, which are located on the same plane and arranged in a cross shape around the mass block. One end of each balance-sensitive beam is connected to the inner wall of the cavity of the model, and the other end is connected to the mass block; or Each of the measuring units includes two balance sensitive beams, which are located on the same plane and are symmetrically distributed in a straight line around the mass block. One end of each balance sensitive beam is connected to the inner wall of the cavity of the model, and the other end is connected to the mass block. A data acquisition unit is embedded within the mass block and is connected to the measurement unit via a signal connection. When the model is subjected to aerodynamic load, an acceleration difference is generated between the mass block and the model, causing the balance sensitive beam to produce a strain corresponding to the aerodynamic load, and the strain data is transmitted to the data acquisition device.

2. The transient force measurement system for a model inside a wind tunnel according to claim 1, characterized in that: Each of the measuring units further includes a first connecting ring and a second connecting ring. The outer wall of the first connecting ring is in close contact with the inner wall of the cavity of the model. The second connecting ring is sleeved on the mass block and is in close contact with the mass block. One end of each balance sensitive beam is connected to the inner wall of the first connecting ring, and the other end is connected to the outer wall of the second connecting ring.

3. The transient force measurement system for a model inside a wind tunnel according to claim 1, characterized in that: It also includes a cable passage that passes through the mass block and communicates with the data acquisition unit, allowing the cable of the measuring unit to pass through and connect to the data acquisition unit.

4. The transient force measurement system for a model inside a wind tunnel according to claim 1, characterized in that: The internal stress dynamic balance also includes a connecting shell, which is sleeved on the outside of the mass block, and the shape and size of the connecting shell match the shape of the mass block at the sleeve location, so that the connecting shell is tightly sleeved on the outside of the mass block. Each of the measuring units further includes a first connecting ring, the outer wall of which is in close contact with the inner wall of the cavity of the model, one end of each balance sensing beam is connected to the inner wall of the first connecting ring, and the other end is connected to the outer wall of the connecting shell.

5. The transient force measurement system for a model inside a wind tunnel according to claim 4, characterized in that: The connecting shell is designed in three sections along the axial direction, consisting of a first section, a second section, and a third section from one end to the other. The internal shape and size of the first and third sections match the shape and size of the corresponding mass blocks, so that the first and third sections are tightly fitted to the mass blocks, and there is a gap between the second section and the corresponding mass block.

6. The transient force measurement system for a model inside a wind tunnel according to claim 4, characterized in that: It also includes a cable passage that passes through the connecting shell and the mass block and communicates with the data acquisition unit, allowing the cable of the measuring unit to pass through and connect to the data acquisition unit.

7. The transient force measurement system for a model inside a wind tunnel according to claim 1, characterized in that: The mass block is divided into multiple segments along the axial direction, and the segments are detachably rigidly connected.

8. The transient force measurement system for a model inside a wind tunnel according to claim 7, characterized in that: In the two connected mass blocks, one of the mass blocks has a threaded post on its end face, and the other mass block has a threaded hole on its end face that mates with the threaded post. The two connected mass blocks are threaded together by the threaded post and the threaded hole.

9. The transient force measurement system for a model inside a wind tunnel according to claim 1, characterized in that: The inner wall of the cavity of the model is equipped with reinforcing ribs.

10. A transient force measurement system for a model inside a wind tunnel, characterized in that, include: A mass block is disposed within the cavity of the model, and there is a gap between each side of the mass block and the model. An internal stress dynamic balance includes a measuring unit comprising four balance-sensitive beams. The four balance-sensitive beams are located in the same plane and arranged in a cross shape around the mass block. One end of each balance-sensitive beam is connected to the inner wall of the cavity of the model, and the other end is connected to the mass block; or The measuring unit includes two balance sensitive beams, which are located on the same plane and are symmetrically distributed in a straight line around the mass block. One end of each balance sensitive beam is connected to the inner wall of the cavity of the model, and the other end is connected to the mass block. A data acquisition unit is embedded within the mass block and is connected to the measurement unit via a signal connection. When the model is subjected to aerodynamic load, an acceleration difference is generated between the mass block and the model, causing the balance sensitive beam to produce a strain corresponding to the aerodynamic load, and the strain data is transmitted to the data acquisition device.

11. The transient force measurement system for a model inside a wind tunnel according to claim 10, characterized in that: The measuring unit further includes a first connecting ring and a second connecting ring. The outer wall of the first connecting ring is in close contact with the inner wall of the cavity of the model. The second connecting ring is sleeved on the mass block and is in close contact with the mass block. One end of each balance sensitive beam is connected to the inner wall of the first connecting ring, and the other end is connected to the outer wall of the second connecting ring.

12. The transient force measurement system for a model inside a wind tunnel according to claim 10, characterized in that: It also includes a cable passage that passes through the mass block and communicates with the data acquisition unit, allowing the cable of the measuring unit to pass through and connect to the data acquisition unit.

13. The transient force measurement system for a model inside a wind tunnel according to claim 10, characterized in that: The mass block is divided into multiple segments along the axial direction, and the segments are detachably rigidly connected.

14. The transient force measurement system for a wind tunnel model according to claim 13, characterized in that: In the two connected mass blocks, one of the mass blocks has a threaded post on its end face, and the other mass block has a threaded hole on its end face that mates with the threaded post. The two connected mass blocks are threaded together by the threaded post and the threaded hole.

15. The transient force measurement system for a wind tunnel model according to claim 10, characterized in that: The inner wall of the cavity of the model is equipped with reinforcing ribs.

16. A transient force measurement system for a model inside a wind tunnel, characterized in that, include: A mass block is disposed within the cavity of the model, and there is a gap between each side of the mass block and the model. The internal stress dynamic balance includes multiple piezoelectric parts, which form two measuring parts. The two measuring parts are distributed at intervals along the front-back direction of the model, and the number of piezoelectric parts in the two measuring parts is the same. Each measuring unit includes four piezoelectric parts, which are located on the same plane and arranged in a cross shape around the mass block. Each piezoelectric part includes three stacked piezoelectric plates, with one of the two piezoelectric plates at both ends connected to the inner wall of the cavity of the model, and the other connected to the mass block; or Each of the measuring units includes two piezoelectric units located on the same plane and symmetrically distributed in a line around the mass block. Each piezoelectric unit includes two stacked piezoelectric plates, one of which is connected to the inner wall of the cavity of the model, and the other is connected to the mass block. The piezoelectric part is positioned perpendicular to the axis of the model; A data acquisition unit is embedded within the mass block and is connected to the measurement unit via a signal connection. When the model is subjected to aerodynamic load, an acceleration difference is generated between the mass block and the model, causing the piezoelectric element to produce strain corresponding to the aerodynamic load, and the strain data is transmitted to the data acquisition device.

17. The transient force measurement system for a model inside a wind tunnel according to claim 16, characterized in that: The internal stress dynamic balance also includes a connecting shell, which is sleeved on the outside of the mass block, and the shape and size of the connecting shell match the shape of the mass block at the sleeve location, so that the connecting shell is tightly sleeved on the outside of the mass block. Each of the measuring units further includes a first connecting ring, the outer wall of which is in close contact with the inner wall of the cavity of the model, one end of each piezoelectric unit is connected to the inner wall of the first connecting ring, and the other end is connected to the outer wall of the connecting shell.

18. The transient force measurement system for a wind tunnel model according to claim 17, characterized in that: The connecting shell is designed in three sections along the axial direction, consisting of a first section, a second section, and a third section from one end to the other. The internal shape and size of the first and third sections match the shape and size of the corresponding mass blocks, so that the first and third sections are tightly fitted to the mass blocks, and there is a gap between the second section and the corresponding mass block.

19. The transient force measurement system for a wind tunnel model according to claim 17, characterized in that: It also includes a cable passage that passes through the connecting shell and the mass block and communicates with the data acquisition unit, allowing the cable of the measuring unit to pass through and connect to the data acquisition unit.

20. The transient force measurement system for a model inside a wind tunnel according to claim 16, characterized in that: The mass block is divided into multiple segments along the axial direction, and the segments are detachably rigidly connected.

21. The transient force measurement system for a model inside a wind tunnel according to claim 16, characterized in that: In the two connected mass blocks, one of the mass blocks has a threaded post on its end face, and the other mass block has a threaded hole on its end face that mates with the threaded post. The two connected mass blocks are threaded together by the threaded post and the threaded hole.

22. The transient force measurement system for a model inside a wind tunnel according to claim 16, characterized in that: The inner wall of the cavity of the model is equipped with reinforcing ribs.

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