Structure of an array wind tunnel and method for simulating a wind field

Abstract

This invention relates to the structure of an array wind tunnel, comprising: several fan units installed in a matrix structure; each fan unit includes a duct, within which a pre-stage fan and a post-stage fan are installed at axial intervals, with a gap H between the inner wall of the duct and the edges of both the pre-stage and post-stage fans; several gap adjustment components are arranged circumferentially along the inner wall of the duct and located within the gaps; when the gap adjustment components expand, the gap H decreases; when the gap adjustment components contract, the gap H increases. This invention, by setting gap adjustment components on the inner wall of the duct, can dynamically compress the gap between the duct and the blade tips of the pre-stage and post-stage fans, effectively suppressing the generation of tip leakage vortices, while simultaneously utilizing the counter-rotating structure of the pre-stage and post-stage fans to completely eliminate rotational wakes. This hardware optimization significantly reduces aerodynamic losses and significantly improves the conversion rate of motor shaft power into effective axial airflow kinetic energy, achieving low-power operation from the fundamental level of fluid mechanics.

Description

Technical Field

[0001] This invention belongs to the field of aerodynamics technology, and relates to wind tunnels, particularly an array wind tunnel structure and a wind field simulation method. Background Technology

[0002] With the booming low-altitude economy, the demand for airworthiness certification and wind resistance testing of drones and various micro-aircraft has surged, leading to the development of various types of wind tunnels. Among them, array wind tunnels, composed of multiple small fans, are currently a research hotspot. However, existing array wind tunnels generally suffer from the following technical shortcomings:

[0003] 1. Existing wind tunnels mostly use industrial cooling fans directly, with a large fixed gap between the fan blade tip and the outer frame. When running at high speed, the pressure difference on both sides of the impeller will cause severe airflow backflow, forming a strong tip leakage vortex. This not only greatly reduces aerodynamic efficiency, but also damages the quality of the jet core area.

[0004] 2. The airflow from a single-stage axial fan is accompanied by a strong rotating tail, which causes parasitic crossflow in the downstream wind field, making it difficult to form a high-quality, flat test wind field over a short distance.

[0005] 3. In terms of control strategy, the fans of the array wind tunnel usually adopt overall synchronous speed regulation or simple on / off control. When simulating high turbulence wind fields, they often rely on the high speed operation of the entire array of fans, failing to optimize energy conversion efficiency from the perspective of fluid dynamics mechanism, resulting in high overall system energy consumption, which goes against the engineering development trend of energy conservation and emission reduction. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-energy-consumption, high-quality array wind tunnel structure and wind field simulation method.

[0007] To solve the above problems, the technical solution of the present invention is as follows:

[0008] A structure for an array wind tunnel includes:

[0009] Several fan units are installed together in a matrix structure;

[0010] The fan unit includes a duct, in which a pre-stage fan and a post-stage fan are installed at axial intervals. There is a gap H between the inner wall of the duct and the edges of the pre-stage fan and the post-stage fan.

[0011] Several gap adjustment components are arranged circumferentially along the inner wall of the duct and located within the gap;

[0012] When the gap adjusting component expands, the gap H decreases; when the gap adjusting component contracts, the gap H increases.

[0013] In a further embodiment, the pre-stage fan and the post-stage fan rotate in opposite directions.

[0014] In a further embodiment, the duct includes a front guide fan and a rear guide fan arranged sequentially, with the front fan and the rear fan located within the front guide fan and the rear guide fan, respectively.

[0015] In a further embodiment, several fan blades are fixedly installed at the front end of both the front guide fan and the rear guide fan. The fan blades are all arc-shaped structures, and the orientation of the arc-shaped structures is opposite to the orientation of the fan blades of the front-stage fan and the rear-stage fan, respectively.

[0016] In a further embodiment, the gap adjustment element is made of an airbag.

[0017] A method for simulating wind fields in an array wind tunnel, utilizing the structure of an array wind tunnel, includes the following steps:

[0018] Install several fan units;

[0019] Several fan units are divided into two groups;

[0020] Calculate the operating data of the two sets of fan units separately;

[0021] The corresponding fan unit is activated based on the operating data.

[0022] In a further embodiment, a plurality of fan units are installed, specifically including:

[0023] Several fan units are connected to several local motor controllers, which is suitable for controlling the independent rotation of each fan unit;

[0024] Several local motor controllers are connected to the main control node, and the main control node and several local motor controllers are all connected to the power supply.

[0025] In a further embodiment, the installation of several fan units further includes:

[0026] Deploy nonlinear mapping and dead-zone compensation algorithms within the master node:

[0027] ;

[0028] In the formula, This refers to the actual instruction duty cycle. To activate the dead-time duty cycle, This represents the ideal linear duty cycle.

[0029] In a further embodiment, the plurality of fan units are divided into two groups, specifically including:

[0030] The two sets of fan units are staggered in both the horizontal and vertical directions, and each set of fan units has a different duty cycle.

[0031] In a further embodiment, the operating data of the two sets of fan units are calculated separately, specifically including:

[0032] When performing wind field simulation, low-frequency sine waves are applied to both sets of fan units:

[0033] ;

[0034] In the formula, The equation representing the duty cycle as a function of time is as follows: The average duty cycle corresponding to the base wind speed. For gust amplitude, The dominant frequency of gusts, For time, Spatial phase difference;

[0035] Operational data is generated using low-frequency sine waves.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] 1. This invention significantly improves aerodynamic conversion efficiency and reduces basic energy consumption: By incorporating a gap adjustment component on the inner wall of the duct, the gap between the duct and the blade tips of the pre- and post-stage fans can be dynamically compressed, effectively suppressing the generation of tip leakage vortices. Simultaneously, the counter-rotating structure of the pre- and post-stage fans completely eliminates rotational wakes. This hardware optimization significantly reduces aerodynamic losses and dramatically improves the conversion rate of motor shaft power into effective axial airflow energy, achieving low-power operation from the fundamental fluid dynamics perspective.

[0038] 2. This invention can efficiently generate high-intensity turbulence at low speeds, improving the overall energy efficiency ratio: The main control node of the control system applies a PWM modulation signal with spatial heterogeneity and spatiotemporal phase difference to adjacent fan units, actively exciting large-scale vortex structures by utilizing the shear layer instability between parallel jets; therefore, the system does not need to operate at full load across the entire array. Even under the condition of significantly reducing the total average speed, it can still quickly generate the required high-intensity turbulence and dynamic gust wind field in the downstream target area, greatly reducing system power consumption while ensuring wind field quality, and significantly improving the overall energy efficiency ratio.

[0039] 3. This invention enables high-quality wind field fusion over extremely short distances, simplifying wind tunnel structure: Based on the synergistic effect of duct rectification and control systems, multiple jets can be rapidly merged within a very short distance (e.g., within 1 meter) downstream of the outlet, forming a uniform flow field or a specific shear flow field. This eliminates the need for the large static pressure chamber and contraction section structure required by traditional wind tunnels, making the wind tunnel more compact and modular, significantly reducing construction and space costs, and is especially suitable for space-constrained laboratory or on-site wind field simulation scenarios.

[0040] 4. This invention can flexibly generate complex dynamic wind fields to adapt to various operating conditions: By performing spatiotemporal asymmetric PWM modulation on each fan unit, the phase difference and spatially heterogeneous parameters between adjacent fan units can be arbitrarily configured, thereby generating gust wind fields with different turbulence intensities, pulsation frequencies, and shear characteristics as needed. This method supports both low-energy steady-state uniform flow simulation and high-turbulence dynamic wind field simulation, possessing strong adaptability to operating conditions and control flexibility, providing a high-performance, low-cost experimental platform for fields such as wind engineering, aerospace power, and environmental fluid testing. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of an array wind tunnel;

[0042] Figure 2 An exploded view of a fan unit in an array wind tunnel structure;

[0043] Figure 3 A schematic diagram of the gap adjustment component of an array wind tunnel structure;

[0044] Figure 4 A flowchart of a wind field simulation method for an array wind tunnel;

[0045] Figure 5 This is a system schematic diagram of a wind field simulation method for an array wind tunnel;

[0046] Figure 6 A strategy diagram for a wind field simulation method in an array wind tunnel;

[0047] Figure 7 This is a schematic diagram of fan unit grouping for a wind field simulation method in an array wind tunnel.

[0048] In the diagram: 100, outer frame; 110, fan unit; 200, duct; 210, pre-stage fan; 220, rear duct fan; 230, post-stage fan; 240, front duct fan; 250, clearance adjustment component; 300, main control computer; 310, main control node; 320, local motor controller; 330, power supply. Detailed Implementation

[0049] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the 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, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0050] Example 1:

[0051] A structure of an array wind tunnel, such as Figures 1 to 3 As shown, the system includes an outer frame 100 and several fan units 110. The outer frame 100 is a rectangular frame structure, and the fan units 110 are fixedly installed inside the outer frame 100. The fan units 110 are fixedly installed together in a rectangular array. Specifically, there are 16 fan units 110 in total, arranged in a 4×4 pattern; the airflow direction of the fan units 110 is as follows... Figure 1 As indicated by the arrow in the diagram. Preferably, the outer frame 100 is made of 4040 and 2020 high-strength industrial aluminum profiles spliced ​​together. The side of the aluminum profile has grooves, and several slider nuts are installed in the grooves, which are suitable for installing several fan units 110.

[0052] like Figure 2As shown, the fan unit 110 includes a duct 200, a pre-stage fan 210, and a post-stage fan 230. The pre-stage fan 210 and the post-stage fan 230 are coaxially and rotatably mounted sequentially within the duct 200. The pre-stage fan 210 and the post-stage fan 230 are installed within the duct 200 using slots, bolts, or other quick-release mechanisms. The pre-stage fan 210 and the post-stage fan 230 rotate in opposite directions, forming a counter-rotating structure. The duct 200 has a length-to-diameter ratio between 0.5 and 1.5, providing both good aerodynamic rectification and ensuring the compactness of the equipment. The duct 200 includes a front guide fan 240 and a rear guide fan 220 fixedly mounted sequentially. Both the front guide fan 240 and the rear guide fan 220 are annular structures, and the pre-stage fan 210 and the post-stage fan 230 are rotatably mounted within the annular structures of the front guide fan 240 and the rear guide fan 220, respectively. Several fan blades are fixedly mounted on the front end face of both the front guide fan 240 and the rear guide fan 220. These blades are all arc-shaped, and their orientation is opposite to that of the blades of the pre-stage fan 210 and the rear-stage fan 230. Specifically, the blades of the front guide fan 240 and the rear guide fan 220 are opposite in orientation to the blades of the rear-stage fan 230. This design allows for more stable airflow when it contacts the blades of the pre-stage fan 210 and the rear-stage fan 230, reducing the high-frequency screeching caused by the instantaneous impact and cutting of the blade leading edges, and increasing the effective contact area between the airflow and the blades of the pre-stage fan 210 and the rear-stage fan 230. The pre-stage fan 210 accelerates the airflow, while the rear-stage fan 230 not only further pressurizes the airflow but also, in conjunction with the rear guide fan 220, eliminates the wake vortex generated by the pre-stage fan 210, converting rotational kinetic energy into axial kinetic energy. Specifically, the rear end of the front guide fan 240 is fixedly equipped with an annular structure, and the front end of the rear guide fan 220 has a corresponding groove, suitable for connecting the front guide fan 240 and the rear guide fan 220 together to form an integral duct 200. Both the front and rear ends of the front guide fan 240 and the rear guide fan 220 have horizontally arranged flanges, suitable for connecting the front guide fan 240 and the rear guide fan 220 together with bolts. Preferably, the duct 200 is manufactured by 3D printing or injection molding; both the pre-stage fan 210 and the rear fan 230 are 48V high-power brushless DC (BLDC) fans, with a single unit full-load power exceeding 200W.

[0053] like Figure 3As shown, gaps are left between the inner walls of the front guide fan 240 and the rear guide fan 220 and the edges of the front fan 210 and the rear fan 230, respectively. Several gap adjustment components 250 are fixedly installed circumferentially along the inner walls of the front guide fan 240 and the rear guide fan 220, i.e., the gap adjustment components 250 are located within the corresponding gaps between the edges of the front fan 210 and the rear fan 230, so that the gaps between the front guide fan 240 and the rear guide fan 220 and the front fan 210 and the rear fan 230 are updated to the gap H between the gap adjustment components 250 and the edges of the front fan 210 and the rear fan 230. Specifically, the number and installation position of the gap adjustment components 250 change according to the operating conditions. The gap adjustment component 250 is an airbag and is connected to a miniature air pump, suitable for controlling the inflation or deflation of the airbag according to usage requirements. When entering high turbulence simulation or high-load gust mode, the gap adjuster 250 inflates and expands, reducing the gap H to below 0.5mm; in low-speed uniform flow mode, the gap adjuster 250 deflates and contracts, increasing the gap H to ensure safe mechanical operation. The gap adjuster 250 effectively blocks the backflow of airflow between high and low pressure surfaces, improving the aerodynamic efficiency of the single fan unit 110 by more than 15%.

[0054] Example 2:

[0055] A method for simulating wind field in an array wind tunnel, such as Figures 4 to 7 As shown, it includes the following steps:

[0056] S101, Install several fan units 110:

[0057] like Figure 5As shown, several fan units 110 are fixedly installed together. These fan units 110 are connected to a control system, which in turn connects to a miniature air pump connected to a gap adjustment component 250. The control system includes a main control computer 300, a main control node 310, and several local motor controllers 320. Each local motor controller 320 controls one of the fan units 110. The main control computer 300 is sequentially connected to the main control node 310 and the local motor controllers 320, and both the main control node 310 and the local motor controllers 320 are connected to a power supply 330. Specifically, the power lines of the power supply 330 are directly connected to each local motor controller 320 using a star-grounded topology, avoiding ground loop noise caused by high current grounding. The local motor controllers 320 and the main control node 310 communicate over long distances via a CAN bus or RS485 differential signal. High-speed optocoupler isolation circuits are added to the PWM signal outputs from the control board of the local motor controller 320 to the power supply 330, effectively isolating the interference of 48V power-side voltage spikes on the logic side of the 3.3V / 5V microcontroller (MCU). The PWM signal lines use twisted-pair shielded wire, and the frequency is set between 20kHz and 25kHz to avoid electromagnetic noise from the motor caused by low-frequency PWM. Preferably, the local motor controller 320 can output high-frequency PWM frequency conversion signals with a carrier frequency of not less than 20kHz; the power supply 330 uses a 48V high-power switching power supply.

[0058] In order to accurately convert the target wind speed input to the master control node 310 into the underlying PWM signal, a nonlinear mapping and deadband compensation algorithm is deployed in the master control node 310, as shown in formula (1):

[0059] (1)

[0060] In the formula, This refers to the actual instruction duty cycle. To activate the dead-time duty cycle, This represents the ideal linear duty cycle.

[0061] Since high-power fans usually cannot start at low duty cycles (such as <10%), the system eliminates the low-speed control blind zone through nonlinear mapping and dead zone compensation algorithm, and achieves a smooth transition of wind speed from zero to full load.

[0062] S103. Divide several fan units 110 into two groups:

[0063] like Figure 6 As shown, determine whether high turbulence is required based on usage needs. If not, all fan units 110 are simultaneously activated, and the operating data of all fan units 110 are consistent, meaning all fan units 110 enter a uniform operating mode. If required, then:

[0064] like Figure 7 As shown, the fan units 110 in the array wind tunnel are divided into at least two groups. In this embodiment, they are divided into two groups, 1 and 2. The fan units 110 in the two groups are staggered in both the vertical and horizontal directions. High duty cycle and low duty cycle PWM signals are sent to the fan units 110 in different groups respectively. For example, the control system assigns a high duty cycle (e.g., 80%) to group 1 and a low duty cycle (e.g., 20%) to group 2. A huge velocity gradient is formed between adjacent parallel jets, inducing strong Kelvin-Helmholtz instability. The strong shear layer breaks up within a very short distance and spontaneously rolls up large-scale vortex structures. At this time, the average power consumption of the system is only equivalent to 50% of the full array operation, but the turbulence intensity in the target area can be increased by more than 30%.

[0065] After receiving the PWM signal, the local motor controller 320 performs nonlinear compensation for the motor start-up dead zone according to the pre-calibrated speed-duty cycle mapping curve to ensure that the air outlet speed of each fan unit 110 corresponds linearly to the control command.

[0066] S105. Calculate the operating data of the two sets of fan units 110 respectively:

[0067] The aerodynamic parameters of the target test environment are acquired, including the target average wind speed and the target turbulence intensity. Based on the aerodynamic parameters, the master control node 310 generates a spatiotemporally asymmetric distributed PWM control matrix. Adjacent fan units 110, i.e., fan units 110 belonging to different groups, output parallel jets with velocity steps based on the PWM control matrix. By utilizing the extreme velocity gradient between adjacent jets, the Kelvin-Helmholtz instability of the fluid is actively excited, and high-intensity turbulence is spontaneously generated downstream of the wind field through shear layer instability.

[0068] When simulating a dynamic gust environment, a low-frequency sinusoidal modulation signal is superimposed on the basic setpoint of the distributed PWM control matrix, and a preset time phase difference is set between adjacent columns of fan units 110 to synthesize a wavefront gust with spatial propagation characteristics within the test area. Low-frequency sinusoidal modulation is applied to a specific group of fan units 110, as shown in formula (2):

[0069] (2)

[0070] In the formula, The equation represents the function equation for the duty cycle as a function of time. The average duty cycle corresponding to the base wind speed; This refers to the amplitude of gusts, for example, 20%; This is the dominant frequency of gusts, typically between 0.5Hz and 2Hz; For time, To achieve spatial phase difference, a gradually varying phase difference is set between different column fan units 110. It can generate wavefront gusts with lateral propagation characteristics.

[0071] S107. Start the corresponding fan unit 110 according to the operating data:

[0072] Based on actual usage requirements and in conjunction with formula (2), the operating data of fan unit 110 is calculated and input to local motor controller 320, thereby controlling the operation of the corresponding fan unit 110.

[0073] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A structure of an array wind tunnel, characterized by, include: Several fan units (110) are installed together in a matrix structure; The fan unit (110) includes a duct (200), in which a pre-stage fan (210) and a post-stage fan (230) are installed at axial intervals. There is a gap H between the inner wall of the duct (200) and the edges of the pre-stage fan (210) and the post-stage fan (230). A plurality of gap adjusting members (250) are arranged circumferentially along the inner wall of the duct (200) and located within the gap; When the gap adjusting member (250) expands, the gap H decreases; when the gap adjusting member (250) contracts, the gap H increases.

2. The structure of the array wind tunnel according to claim 1, characterized in that, The front-stage fan (210) and the rear-stage fan (230) rotate in opposite directions.

3. The structure of the array wind tunnel according to claim 1 or 2, characterized in that, The duct (200) includes a front guide fan (240) and a rear guide fan (220) arranged in sequence, with the front fan (210) and the rear fan (230) located inside the front guide fan (240) and the rear guide fan (220), respectively.

4. The structure of the array wind tunnel according to claim 3, characterized in that, The front ends of the front guide fan (240) and the rear guide fan (220) are each fixedly equipped with a number of fan blades. The fan blades are all arc-shaped structures, and the orientation of the arc-shaped structures is opposite to that of the fan blades of the front fan (210) and the rear fan (230).

5. The structure of the array wind tunnel according to claim 1 or 2, characterized by The gap adjustment element (250) is made of an airbag.

6. A method of simulating a wind field of an array wind tunnel, characterized by, Using the structure of the array wind tunnel as described in any one of claims 1 to 5, the following steps are included: Install several fan units (110); The fan units (110) are divided into two groups; Calculate the operating data of the two sets of fan units (110) respectively; The corresponding fan unit (110) is activated based on the operating data.

7. The wind field simulation method for an array wind tunnel according to claim 6, characterized in that, Install several fan units (110), specifically including: The fan units (110) are respectively connected to the local motor controllers (320), which are suitable for controlling the independent rotation of each fan unit (110); Several of the local motor controllers (320) are connected to the master control node (310), and the master control node (310) and the several local motor controllers (320) are connected to the power supply (330).

8. The wind field simulation method for an array wind tunnel according to claim 7, characterized in that, The system includes several fan units (110) and also includes: Deploy a nonlinear mapping and dead-zone compensation algorithm within the master control node (310): ； In the formula, This refers to the actual instruction duty cycle. To activate the dead-time duty cycle, This represents the ideal linear duty cycle.

9. The wind field simulation method for an array wind tunnel according to claim 8, characterized in that, The fan units (110) are divided into two groups, specifically including: The two sets of fan units (110) are staggered in both the horizontal and vertical directions, and the two sets of fan units (110) are respectively set with different duty cycles.

10. The wind field simulation method for an array wind tunnel according to claim 9, characterized in that, The operating data of the two sets of fan units (110) are calculated separately, specifically including: During the wind field simulation, low-frequency sine waves were applied to both sets of fan units (110): ； In the formula, The equation representing the duty cycle as a function of time is as follows: The average duty cycle corresponding to the base wind speed. For gust amplitude, The dominant frequency of gusts, For time, Spatial phase difference; The operating data is generated using the low-frequency sine wave.

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