Bionic pipeline type wind driven generator inspired by caves of grassland dogs and rats

Abstract

The invention provides a bionic pipeline type wind driven generator inspired by grassland dog and mouse caves, and belongs to the technical field of wind driven generators. The bionic pipeline type wind driven generator inspired by the grassland dog and mouse caves comprises a section pipeline and dog and mouse cave bionic convex body structures; the section pipeline sequentially comprises a spray pipe, a Venturi pipe, a diffusion pipe and a straight pipe in the airflow direction. The dog and mouse cave bionic convex body structure is connected with the side wall of the rear end of the straight pipe through a conduit, the dog and mouse cave bionic convex body structure comprises a convex body and a flat plate, one end of the conduit is communicated with the straight pipe, and the other end of the conduit is communicated with the space between the convex body and the flat plate; wherein the radius of the inlet end of the venturi type pipe is larger than the radius of the minimum section, the radius of the diffusion pipe is larger than the radius of the minimum section of the venturi type pipe, the height of the convex body is smaller than or equal to the radius of the convex body, and through the collaborative design of the bionic grassland dog cave structure and the convergence-expansion section pipeline, the distribution of a flow field in the pipeline is optimized; airflow separation and turbulence dissipation are inhibited, and the static pressure recovery efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind turbines, and in particular relates to a bionic pipeline wind turbine inspired by prairie dog burrows. Background Art

[0002] As a key form of clean energy, improving wind power efficiency remains a core industry priority. Ducted wind turbines (DWTs), which accelerate freestream wind speed through a ducted configuration, significantly improve power density compared to traditional open wind turbines and have become a research hotspot for speed-increasing wind energy conversion devices. Traditional DWTs typically utilize simple converging tubes or nozzles, achieving localized wind speed increases through geometric contraction. However, their performance is limited by flow field stability and energy dissipation within the duct.

[0003] A core drawback of conventional biomimetic ducted wind turbines is the widespread presence of boundary layer separation at the inlet of conventional ducts. This separation creates a detached flow at the front of the duct, resulting in an ineffective flow region spanning 30% to 45% of the duct length. This separation not only reduces the gas flow entering the duct but also induces eddy dissipation, reducing wind speed in the mainstream direction and directly impacting the wind turbine's energy capture efficiency. Existing duct structures struggle to effectively manage the multiscale coupling effects of turbulence. Macroscopic vortices within the duct interact with microscopic turbulent pulsations, leading to intensified pressure fluctuations. These irregular pulsations consume significant energy through fluid viscosity, significantly reducing mechanical energy conversion efficiency and increasing fatigue loads on the duct structure. Conventional ducts exhibit abrupt curvature changes at the transition between the acceleration and expansion sections, causing local velocity gradients to exceed the self-stabilization threshold of the flow field, leading to boundary layer separation and turbulence surges. This phenomenon directly results in uneven total pressure distribution within the duct, weak static pressure recovery, and a low total pressure recovery coefficient. This limits improvements in the system's power coefficient and hinders achieving substantial improvements in output performance. Summary of the Invention

[0004] In view of this, the present invention provides a bionic duct-type wind turbine inspired by prairie dog burrows. Through the collaborative design of the bionic prairie dog burrow structure and the convergent-divergent cross-section duct, it optimizes the flow field distribution in the duct, suppresses airflow separation and turbulent dissipation, and improves the static pressure recovery efficiency.

[0005] The present invention is achieved in that:

[0006] The present invention provides a bionic duct-type wind turbine inspired by prairie dog burrows, which comprises a cross-sectional duct and a prairie dog burrow bionic convex structure; the cross-sectional duct comprises a nozzle, a venturi tube, a diffuser and a straight tube in sequence along the airflow direction; the prairie dog burrow bionic convex structure is connected to the rear end side wall of the straight tube through a conduit, the prairie dog burrow bionic convex structure comprises a convex body and a flat plate, one end of the conduit is connected to the straight tube, and the other end of the conduit is connected to the space between the convex body and the flat plate; wherein: the inlet end radius of the venturi tube is greater than the minimum cross-sectional radius, the radius of the diffuser is greater than the minimum cross-sectional radius of the venturi tube, and the height of the convex body is less than or equal to the radius of the convex body.

[0007] The technical effects of the bionic duct-type wind turbine provided by the present invention, which is inspired by prairie dog burrows, are as follows: through the coordinated design of the convergent-divergent cross-section pipeline and the bionic convex body of the prairie dog burrow, the tapered structure of the nozzle effectively eliminates the airflow separation at the pipeline inlet, guides the incident airflow to form an attached flow, and significantly increases the gas flow rate; the gradient cross-section of the Venturi tube and the diffuser is combined with the hemispherical shape of the bionic convex body, and a low-pressure area is formed at the top of the convex body by utilizing the principles of fluid mechanics. Through the connection between the conduit and the main pipeline, secondary acceleration of the airflow in the pipeline is achieved, which greatly increases the wind speed and reduces turbulent kinetic energy, thereby optimizing energy capture efficiency.

[0008] On the basis of the above technical solution, the bionic duct-type wind turbine inspired by prairie dog burrows of the present invention can also be improved as follows:

[0009] Among them, the cross-section of the nozzle gradually decreases along the direction of airflow, the Venturi tube shrinks to the minimum cross-section, the cross-section of the diffuser gradually expands along the direction of airflow, and the cross-section of the straight tube is a constant cross-section; the nozzle, Venturi tube, diffuser and straight tube are arranged in sequence along the direction of airflow.

[0010] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the length values ​​of the Venturi tube and the diffuser ensure a continuous transition of their curvatures, and the stable flow of the airflow in the diffusion section is achieved through smooth modeling, which effectively suppresses boundary layer separation and improves the static pressure recovery efficiency; the segmented arrangement of the nozzle, Venturi tube, diffuser and straight tube forms a "pre-compression-acceleration-diffusion" synergistic mechanism, which significantly enhances the airflow acceleration effect compared to traditional pipelines and optimizes the energy conversion process.

[0011] Furthermore, the minimum cross-section of the Venturi tube is located between the nozzle and the diffuser, and the outlet of the diffuser is connected to the inlet of the straight tube.

[0012] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the position of the minimum cross-section of the Venturi tube is optimized and designed to be consistent with the curvature of the diffuser, avoiding sudden changes in flow velocity caused by sudden changes in the pipe cross-section, reducing turbulence generation, making the gas pressure distribution more uniform, effectively solving the problem of nonlinear distortion of the pressure gradient in traditional pipelines, and improving the total pressure recovery efficiency.

[0013] Furthermore, the connection position between the conduit and the straight pipe is located behind the diffuser, the radius of the conduit is smaller than the inner diameter of the straight pipe, and the axis of the conduit is perpendicular or inclined to the axis of the straight pipe.

[0014] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the conduit is set behind the diffuser to avoid interfering with the main airflow, and the optimized design of its tube diameter and connection angle reduces the gas flow resistance, ensures a stable pressure difference between the main pipeline and the bionic convex body, and guarantees the continuity and effectiveness of the secondary acceleration effect.

[0015] Furthermore, a low-pressure area is formed between the top of the convex body and the flat plate, the flat plate is arranged parallel to the bottom surface of the convex body, and the central axis of the distance between the top ends of the convex body coincides with the central axis of the straight tube.

[0016] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the spacing between the upper and lower symmetrical convex bodies matches the width of the main pipe, forming a symmetrically distributed low-pressure area, enhancing the stability of the airflow in the pipe, reducing turbulent kinetic energy fluctuations, and synchronously guiding the acceleration of the airflow on both sides, significantly improving the uniformity of the wind speed gain compared to the asymmetric structure.

[0017] Furthermore, the cross-sectional pipe and the dog-rat burrow bionic convex structure are arranged symmetrically up and down, and the cross-sectional pipe and the dog-rat burrow bionic convex structure are connected by a supporting structure, and the supporting structure is arranged on the outside of the straight pipe.

[0018] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the upper and lower symmetrical pipelines and convex structures are fixed by external supports, which avoids interference with the airflow while ensuring structural rigidity, strengthens the airflow coupling effect between the bionic convex body and the main pipeline, reduces power output fluctuations, and improves system operation reliability.

[0019] Furthermore, the curvatures of the transition curves of the Venturi tube and the diffuser are consistent.

[0020] The beneficial effects of adopting the above-mentioned improvement scheme are: the dual outlet layout at the end of the main pipeline and the top of the convex body uses the principles of fluid mechanics to form a "pumping" effect, further accelerating the airflow in the pipeline, while diverting the flow to reduce the outlet back pressure, optimizing the pressure recovery process, and improving energy recovery efficiency.

[0021] Furthermore, the outlet of the cross-sectional pipe includes a first outlet and a second outlet, the first outlet is arranged at the end of the straight pipe, and the second outlet is arranged at the top of the dog and rat cave bionic convex structure, and the position of the second outlet is higher than the top plane of the convex body.

[0022] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the cross-sectional dimensions of each section of the pipeline are matched to ensure smooth cross-sectional transitions, eliminate local velocity mutations, control the airflow velocity gradient within a reasonable range, avoid boundary layer separation, achieve linearization of pressure recovery, and improve the power coefficient.

[0023] Furthermore, the minimum cross-sectional radius of the Venturi tube is equal to the inlet radius of the diffuser tube, and the outlet radius of the diffuser tube is equal to the inner diameter of the straight tube.

[0024] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the bionic convex body adopts a hemispherical shape and optimizes the interception ratio so that its top curvature conforms to the biological structural characteristics of prairie dog burrows, forming an optimal acceleration effect when the airflow flows through, effectively reducing the air pressure at the top of the convex body, and increasing the pressure difference between the main pipeline and the convex body, thereby realizing an efficient simulation of the bio-inspired airflow acceleration mechanism.

[0025] Furthermore, the convex body is a part of a hemisphere, and the ratio of the convex body height to the convex body radius is 0.3 to 0.7, so as to form the low-pressure area.

[0026] Compared with the prior art, the bionic duct-type wind turbine provided by the present invention, which is inspired by prairie dog burrows, has the following beneficial effects:

[0027] The present invention optimizes the distribution of pipe curvature radius through the multi-stage tapered channel design that mimics the prairie dog burrows, realizes laminar guidance of the airflow in the transition area between the nozzle and the venturi tube, and completely eliminates the airflow separation area at the front end of the traditional pipe. This design enables the incident airflow to form a stable attached flow, significantly increases the gas flow entering the pipe, and lays the foundation for the flow rate of the subsequent acceleration process. At the same time, the cross-sectional gradient change of the three-section collaborative pipe (nozzle-venturi tube-diffuser) avoids the flow separation caused by cross-sectional mutation through the streamlined transition of "pre-compression-acceleration-diffusion", which greatly improves the flow stability of the airflow in the pipe.

[0028] The innovatively designed bionic convex structure of the dog-and-rat burrow, based on the three-dimensional vortex control mechanism of the fluid-solid coupling mechanism, guides the orderly conversion of turbulent kinetic energy into large-scale vortex structures, effectively reducing the turbulent kinetic energy in the pipe. This structure imitates the raised cave entrance shape of the prairie dog burrow to form a low-pressure area at the rear end of the pipe. When the air pressure at the top of the convex body is lower than the air pressure in the main pipe, it triggers a secondary flow of gas from the main pipe through the conduit into the convex body and ejected. This process not only enhances the wind speed of the Venturi tube, but also suppresses turbulent pulsation through flow induction, significantly enhancing the stability of the airflow in the pipe. The symmetrically arranged convex body structure further balances the pressure difference on both sides, reduces flow field fluctuations, and provides more stable energy input for the wind turbine;

[0029] The breakthrough design of the three-stage collaborative amplification structure, through the synergistic effect of the front-stage nozzle pre-compression, the middle-stage Venturi-type tube acceleration, and the rear-stage diffuser pressure expansion, enhances the pre-bunching and acceleration of the airflow while achieving efficient recovery of static pressure. In particular, the continuous transition of curvature between the Venturi-type tube and the diffuser achieved through the "lofting" function modeling eliminates the sudden change of flow velocity in the transition area of ​​the traditional pipeline, causes the pressure gradient to decay linearly along the pipeline, and greatly improves the total pressure recovery coefficient. Combined with the diversion design of the double outlet (the main pipeline outlet and the outlet at the top of the convex body), the outlet back pressure is effectively reduced, the pressure recovery process is further optimized, and the system power density is significantly improved compared to the traditional DWT. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of a bionic ducted wind turbine;

[0031] Figure 2 Schematic diagram of the venturi tube and diffuser of the present invention;

[0032] Figure 3 Schematic diagram of the comparison of normalized velocities of three different pipelines;

[0033] Figure 4 The diagram is a comparison of the normalized pressure coefficients of three different pipelines;

[0034] Figure 5 Schematic diagram comparing the normalized turbulent kinetic energy of three different pipes;

[0035] Figure 6 12 are example diagrams of design parameters of the present invention;

[0036] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0037] 10. Nozzle; 20. Venturi tube; 30. Diffuser; 40. Straight tube; 50. Conduit; 60. Protrusion. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0039] like Figure 1 、 Figure 6 The figure shows a schematic structural diagram of a bionic duct-type wind turbine inspired by prairie dog burrows provided by the present invention. The present invention provides a bionic duct-type wind turbine inspired by prairie dog burrows, comprising a cross-sectional duct and a prairie dog burrow bionic convex structure; the cross-sectional duct comprises a nozzle 10, a venturi tube 20, a diffuser 30 and a straight tube 40 in sequence along the airflow direction; the prairie dog burrow bionic convex structure is connected to the rear end side wall of the straight tube 40 through a conduit 50, and the prairie dog burrow bionic convex structure comprises a convex body 60 and a flat plate, one end of the conduit 50 is connected to the straight tube 40, and the other end is connected to the space between the convex body 60 and the flat plate; wherein: the inlet end radius of the venturi tube 20 is greater than the minimum cross-sectional radius, the radius of the diffuser 30 is greater than the minimum cross-sectional radius of the venturi tube 20, and the height of the convex body 60 is less than or equal to the radius of the convex body 60.

[0040] The nozzle (C1) is the inlet end of the air flow, increasing the gas flow rate entering the pipeline.

[0041] The Venturi tube (C2) further contracts to the smallest cross section, producing a maximum acceleration effect and increasing local kinetic energy.

[0042] The diffuser (C3) expands slowly at the outlet, smoothly recovering static pressure and suppressing flow separation and turbulence surges. A straight pipe (C4) is connected to it.

[0043] The dog-rat burrow biomimetic convex body is described in detail as:

[0044] The dog-rat burrow bionic convex body (C6) is connected to C4 by a conduit (C5), and mainly consists of two parts: the convex body and the flat plate. C5 can introduce gas from C4 into the bionic convex body.

[0045] Working Principle: Air enters through C1, passes through a pipe with a gradually decreasing cross-sectional area, and enters C2, where the wind speed reaches its maximum. The air then flows through C3, where the flow rate and pressure gradually slow. Finally, it passes through C4 and is ejected from outlet 1. Simultaneously, external air flows through C6, where the flow rate at the convex portion is faster than at other locations, causing the air pressure there to decrease. When the air pressure at the top of C6 is lower than the pressure inside C4, air enters C6 from C4 and is ejected from outlet 2, further accelerating the wind speed inside C2. Therefore, when the pressure difference between the top of C6 and the inside of C4 is large enough, the wind turbine can collect more wind energy. The vertically symmetrical arrangement of this model is also intended to further enhance this characteristic.

[0046] The present invention includes six configurations including C1-C6, with a total of twelve design parameters. The twelve design parameters are C6 height (h), the distance between the two C6 tops (h1), C1 length (L1), C2 length (L2), C3 length (L3), C4 length (L4), C1 radius (R1), two radii of C2 (R2 and R3), C3 radius (R4), C5 radius (R5) and C6 radius (R6). Among them, the bionic convex body is a part of the sphere, and the C6 radius R6 is the radius of the sphere. The C6 height h is the height of the intercepted sphere part. h1 is the distance between the upper and lower bionic convex body tops.

[0047] The modeling of the bionic pipeline is implemented in Soildworks software. Figure 2 As shown, to significantly improve the efficiency of gas pressure recovery in the rear section of the pipeline, C2 and C3 were modeled with the same curvature. With the parameters R2, R3, R4, L2, and L3 determined (L2 and L3 are the distances between the three sections and also the parameters that divide C2 and C3), the "lofting" function was used to model C2 and C3 as a whole. This modeling approach smoothes the structural transition between C2 and C3, promotes more uniform and stable gas diffusion, and facilitates static pressure recovery and suppresses turbulence.

[0048] The airflow enters from the nozzle inlet, is accelerated by the tapered cross-section, flows through the Venturi tube to reach the maximum flow rate, then is decelerated by the diffuser tube, and finally discharged from the straight tube outlet; at the same time, when the external airflow flows through the bionic convex body, the flow velocity at the top of the convex body accelerates to form a low-pressure area. When the pressure difference is sufficient, the gas in the main pipeline flows into the convex body through the conduit and is ejected, thereby enhancing the wind speed in the pipeline.

[0049] Among them, in the above technical solution, the cross-section of the nozzle 10 gradually decreases along the direction of the airflow, the Venturi tube 20 shrinks to the minimum cross-section, the cross-section of the diffuser 30 gradually expands along the direction of the airflow, and the cross-section of the straight tube 40 is a constant cross-section; the nozzle 10, the Venturi tube 20, the diffuser 30 and the straight tube 40 are arranged in sequence along the direction of the airflow.

[0050] In the above technical solution, the minimum cross-section of the venturi tube 20 is located between the nozzle 10 and the diffuser 30 , and the outlet of the diffuser 30 is connected to the inlet of the straight tube 40 .

[0051] In the above technical solution, the connection position between the conduit 50 and the straight pipe 40 is located behind the diffuser 30, the radius of the conduit 50 is smaller than the inner diameter of the straight pipe 40, and the axis of the conduit 50 is perpendicular or inclined to the axis of the straight pipe 40.

[0052] In the above technical solution, a low pressure area is formed between the top of the convex body 60 and the flat plate. The flat plate is arranged parallel to the bottom surface of the convex body 60. The central axis of the distance between the top of the convex body 60 coincides with the central axis of the straight tube 40.

[0053] In the above technical solution, the cross-sectional pipe and the dog-rat burrow bionic convex structure are arranged symmetrically up and down, and the cross-sectional pipe and the dog-rat burrow bionic convex structure are connected by a supporting structure, and the supporting structure is arranged on the outside of the straight pipe 40.

[0054] In the above technical solution, the curvatures of the transition curves of the venturi tube 20 and the diffuser tube 30 are consistent.

[0055] In the above technical solution, the outlet of the cross-sectional pipe includes a first outlet and a second outlet. The first outlet is arranged at the end of the straight pipe 40, and the second outlet is arranged at the top of the dog and rat cave bionic convex structure. The position of the second outlet is higher than the top plane of the convex body 60.

[0056] In the above technical solution, the minimum cross-sectional radius of the venturi tube 20 is equal to the inlet radius of the diffuser 30 , and the outlet radius of the diffuser 30 is equal to the inner diameter of the straight tube 40 .

[0057] In the above technical solution, the convex body 60 is a part of a hemisphere, and the ratio of the convex body height to the convex body radius is 0.3 to 0.7, so as to form a low-pressure area.

[0058] To demonstrate the superior output performance of the present invention over the existing ducted wind turbine (DWT), the internal gas characteristics of a conventional duct (CD), a baseline bio-inspired duct (BBD), and an optimized bio-inspired duct (OBD) were compared.

[0059] Figure 3 Comparison of normalized velocity and normalized pressure coefficient (Pressure Coefficient, C pr ) and the normalized turbulent kinetic energy (Normalized TKE). In order to eliminate the dimensional differences between the data features and make them comparable, thereby improving the model performance and calculation efficiency. Therefore, the inflow wind speed V is used. i Normalize these evaluation indicators separately:

[0060]

[0061] Where V max is the maximum velocity in different axial sections inside the pipe, m / s; V i is the inflow velocity, which is 5 m / s in this verification; p is the maximum pressure in different axial sections inside the pipe, Pa; ρ is the air density, 1.225 kg / m3 ; TKE is the maximum pressure in different axial sections inside the pipeline, m 2 / s 2 .

[0062] The velocity curve of the optimized bionic pipe shows a steeper gradient, reflecting the enhanced airflow acceleration capability. Its maximum normalized velocity is (x is the axial distance inside the pipe, L is the length of the bionic pipe 1.54m), With traditional pipeline and the benchmark bionic pipeline Compared with the previous report, the figures were increased by 107% and 64% respectively.

[0063] Figure 4 It shows that the C of the optimized bionic pipeline pr The pressure surface changes become more obvious, especially in the critical C2 area, C pr Reached -4.8. Figure 5 The optimized bionic pipe has the lowest normalized turbulent kinetic energy (0.004), indicating laminar or weakly turbulent flow. In contrast, the conventional pipe and the baseline bionic pipe have higher normalized turbulent kinetic energy, reflecting increased vortex generation and flow mixing, which results in additional energy losses and may affect turbine output performance.

[0064] The specific implementation of the above steps is described in detail below.

[0065] Before use, the convergence-divergence pipes (C1-C4), bionic convex bodies (C5-C6) and supporting components must be checked. Key inspections include: the curvature smoothness (roughness Ra ≤ 0.8 μm) of the connection between the nozzle (C1) and the Venturi tube (C2); the ratio of the convex body height h to the radius R6; The site survey is completed simultaneously, and the concrete foundation is poured in the area with an annual average wind speed of ≥5m / s, the anchor bolts are embedded and the flatness of the surface is calibrated (error ≤2mm / m).

[0066] Connect C1-C4 in sequence along the airflow direction: First, fix C1 to the center of the foundation (vertical deviation ≤ 1°), then connect C2-C3-C4 through flanges, install silicone rubber sealing rings (compression 15%) at the joints, and tighten the bolts in diagonal order (torque 20N·m). The minimum cross-section of the Venturi tube (C2) must be aligned with the dominant wind direction. The diffuser (C3) and C2 are modeled using SolidWorks lofting to achieve a continuous curvature transition (curvature difference ≤ 0.02mm). -1 ).

[0067] A conduit hole (50mm diameter) was opened on the rear sidewall of the straight pipe (C4), 0.4m from the C3 outlet. The conduit (C5) was connected perpendicularly to C4 at a 90° angle. The convex body (C6) was assembled with a flat plate (80mm apart) and fixed to the outside of C4 via the conduit.

[0068] A 6061-T6 aluminum alloy support frame is used to secure the protrusion. The angle between the support frame and the pipeline axis is 60°, and the welds must undergo Level II nondestructive testing. 500Pa of compressed air is introduced into the outlet of the plugging device, and the airtightness of the flange connection is tested with soapy water (minimum bubbles that disappear within 10 seconds are allowed). If bubbles persist, retighten the bolts or replace the sealing ring.

[0069] Start the fan (inflow velocity 5m / s), monitor the pressure difference between the top of C6 and the inner part of C4 through the U-tube pressure gauge, and when Δp≥20Pa, the secondary acceleration effect meets the standard; if it is insufficient, fine-tune h to 0.18-0.22m or h1 to 0.55-0.65m. Simultaneously use a hot wire anemometer to measure the wind speed of C2 section to ensure the wind speed gain ratio (Ideal value 2.53).

[0070] Use particle image velocimetry (PIV) to detect the flow field in the pipeline. The normalized turbulent kinetic energy TKE should be ≤0.005 (ideal value 0.004). Otherwise, check the surface roughness of the convex body (needed to be ≤Ra1.6μm). Install a pressure sensor at the outlet of the diffuser and calculate the total pressure recovery coefficient C. p ≥0.55 (ideal value 0.62). If it does not meet the standard, optimize the diffusion angle to 6°.

[0071] When the natural wind speed is ≥3m / s, the rotor is started and data is collected in real time: the inflow wind speed V is recorded every hour. i 、C2 segment V max 、C4 outlet static pressure p4, calculate G v with C p (The fluctuation range is ≤5% and 3% respectively.) If the pipeline noise is ≥70dB or the power drops ≥10%, stop the machine immediately and check for convex body deviation (h1 deviation ≤±30mm) or abnormal C2-C3 curvature.

[0072] If G v <2.0, mostly due to insufficient pressure difference of the convex body, readjust according to h1=(1.0-1.5)R4, h=(0.4-0.6)R6; if the pipeline vibration is abnormal, it is mostly due to discontinuity of C2-C3 curvature, and it is necessary to re-loft and model after reverse engineering scanning (error ≤0.02mm -1 ).

[0073] Adjust the height of the convex body according to seasonal wind speed (e.g., h = 0.25m in winter), or install a PID controller to automatically adjust h1 (within a range of ±10%) to maintain Δp = 20-25 Pa. During operations, implement height protection (safety belts, protective nets), disconnect the power supply before lightning, and check the ground resistance (≤10Ω).

[0074] The optimized biomimetic conduit significantly improves fluid properties by effectively reducing inner wall friction and flow resistance. Modified morphology at key locations increases flow velocity while minimizing flow resistance, while suppressed turbulent kinetic energy mitigates chaotic flow patterns. This dual mechanism reduces energy loss and improves transfer efficiency.

[0075] In summary, this system not only possesses all the advantages of ducted wind turbine technology but also overcomes most of the drawbacks of existing DWTs. BDWT offers advantages over existing DWTs in terms of flow introduction, turbulent kinetic energy reduction, and pressure distribution, significantly improving the airflow characteristics within the duct. Its vertically symmetrical arrangement further enhances wind speed within the duct, significantly improving wind turbine output performance while ensuring airflow stability.

[0076] Specifically, the principle of the present invention is: the core design inspiration of the present invention comes from the airflow control mechanism of prairie dog burrows: the burrow forms an air pressure difference through two openings with different degrees of bulge, and uses the Bernoulli principle to achieve the natural circulation of airflow in the cave. Inspired by this, the bionic convex structure in the invention forms an effect of fast flow velocity and low air pressure at the top through a hemispherical interception shape (optimized ratio of height to convex radius) when the air flows through, forming a pressure difference with the air pressure in the main pipeline, prompting the main pipeline gas to flow into the convex body through the conduit and eject, forming a "pumping" effect similar to a cave, thereby accelerating the airflow in the pipeline for a second time. This bio-inspired design transforms the naturally evolved fluid control mechanism into an engineered wind speed enhancement technology;

[0077] The nozzle's tapered cross-section design guides the incident airflow to accelerate gradually, suppresses the inlet boundary layer separation by optimizing the curvature distribution, and allows the airflow to enter the subsequent section in an attached state, laying the foundation for the maximum acceleration of the Venturi tube; the Venturi effect is generated by shrinking to the minimum cross-section, allowing the airflow velocity to reach a peak value. This section and the diffuser are modeled through "lofting" to achieve a continuous transition in curvature, ensuring that the flow rate change rate is controlled within the self-stabilizing range of the flow field, avoiding turbulent surges, and creating conditions for pressure recovery in the diffuser section; the slowly expanding cross-section design of the outlet gradually slows down the airflow velocity, converting kinetic energy into static pressure energy. The transition design with the same curvature as the Venturi tube suppresses flow separation in the diffuser section, greatly improves the static pressure recovery efficiency, and solves the problem of insufficient pressure recovery in traditional pipelines;

[0078] The layout of the outlet at the end of the main duct and the outlet at the top of the convex body utilizes Bernoulli's principle to create a "pumping" effect: the design of the second outlet above the top of the convex body further accelerates the flow velocity there, reduces the air pressure, and enhances the pressure difference between the main duct and the convex body, promoting the sustainability of the secondary acceleration effect. The symmetrical arrangement of the bionic convex body structure creates a uniform low-pressure area on both sides of the duct, balancing the lateral pressure difference and suppressing airflow deflection and fluctuation. This symmetrical layout not only enhances the consistency of wind speed gain, but also improves the stability of the flow field within the entire duct through the synergistic acceleration effect of the airflow on both sides, reducing turbulent kinetic energy dissipation.

[0079] The following provides a specific embodiment 1 of the present invention: In a low-wind-speed wind energy demonstration park project in Gansu, in order to address the low starting efficiency of traditional wind turbines in an environment with an average annual wind speed of 5.8m / s, technicians designed a new wind turbine generator system that integrates a converging-diverging cross-section pipe and a bionic convex structure based on the airflow dynamics principle of prairie dog burrows. Through the collaborative design of biomimetic and fluid mechanics, this device increases the airflow velocity by 39% at a wind speed of 5m / s, making it particularly suitable for low-wind-speed areas such as Northwest and North my country. Its core innovation lies in utilizing the natural low-pressure zone formed by the convex body and the flat plate to achieve airflow acceleration without additional power, saving more than 25% energy compared to traditional ducted generators.

[0080] The wind turbine utilizes a modular, integrated design. Its main structure consists of a converging-diverging duct with a symmetrically arranged convex structure, reminiscent of a dog-and-rat burrow. Fluid communication between the two is achieved via an inclined conduit. The duct system is constructed from Q355ND low-alloy, high-strength steel, boasting a low-temperature impact energy rating of 34J at -20°C, making it suitable for use in cold northern regions. The inner wall is sprayed with a 2mm-thick polytetrafluoroethylene coating, achieving a surface roughness of Ra ≤ 1.6μm. Wind tunnel testing has shown a 12% reduction in airflow friction resistance. The bionic convex structure is welded from 6061-T6 aluminum alloy sheets. After an 8-hour heat aging treatment at 175°C, the overall profile error is ≤ 1mm, ensuring a streamlined design while reducing the weight by 30%.

[0081] The piping system consists of a nozzle, a Venturi tube, a diffuser, and a straight pipe along the airflow direction. Each section is connected by tongue-and-groove flanges, and the bolt pre-tightening torque is controlled at 280-320 N·m to ensure airtightness. The nozzle has an inlet radius of 800mm and tapers to a 600mm outlet radius at a 12° contraction angle. The 1800mm length, verified by CFD simulation, can smoothly accelerate the inlet air velocity from 5m / s to 8.2m / s. The Venturi tube uses a cubic Bezier curve to fit the cross-sectional profile, tapering from a 600mm inlet radius to a minimum cross-section of 400mm. The 1200mm pipe length ensures a flow velocity of 15.3m / s at the minimum cross-section, corresponding to a Reynolds number of 1.2×10 6, which is in the turbulent smooth area; the diffuser gradually expands from 400mm to 700mm at a 7° expansion angle. The length of 1500mm makes the pressure recovery rate reach 78%, and the outlet flow rate is stable at 12.5m / s; the straight pipe section has an inner diameter of 700mm and a length of 2000mm. A duct interface is opened 500mm away from the diffuser outlet. Three guide vanes with a spacing of 150mm are set in the interface to guide the airflow to be evenly distributed at a 90° angle.

[0082] The symmetrical convex body components are fixed on both sides of the straight pipe through the channel steel support structure, with a support spacing of 1200mm. According to the finite element analysis, the maximum stress under 12-level wind load is 112MPa, which meets the safety requirements. A single convex body is a part of a sphere with a radius of 1000mm, and the interception height is 600mm. The top flat surface has a diameter of 1200mm, and its surface is machined via five-axis CNC machining and then sprayed with an aviation-grade UV-resistant coating. The accompanying flat plate is 2200mm long, 1800mm wide, and 15mm thick, with 30mm rounded edges and a 20mm-deep guide groove on the bottom to reduce airflow drag. The flat plate is parallel to the underside of the convex body, and a 50mm gap, optimized by ANSYS, creates a stable low-pressure zone with a pressure coefficient of -0.32. The duct connecting the straight pipe to the convex body has an 80mm radius and is arranged at a 90° angle. The S-bend has a curvature radius of 300mm, and the inner wall smoothness of the 800mm pipe length reaches Ra ≤ 0.8μm. Testing shows that at this angle, the airflow drag coefficient is reduced by 34% compared to a perpendicular connection.

[0083] A full-scale simulation of the device using FLUENT software revealed that, at an ambient wind speed of 5.8 m / s, the airflow initially accelerates in the nozzle, dropping the static pressure to -210 Pa at the minimum cross-section of the Venturi tube. Upon entering the diffuser, some of the kinetic energy is converted into pressure energy, restoring the static pressure to -80 Pa, and the airflow enters the straight tube at a velocity of 12.5 m / s. At this point, approximately 30% of the airflow in the straight tube is diverted through the duct to the gap between the convex body and the flat plate. Due to the acceleration effect of the convex body's curved surface, the velocity in the gap reaches 18 m / s, creating a localized low-pressure zone of -320 Pa. This pressure differential accelerates the main airflow in the straight tube to 13.8 m / s, ultimately exiting through the first outlet at the end of the straight tube, a 23% increase in velocity compared to conventional ducting. Simultaneously, a second outlet, located 300 mm above the top plane of the convex body, utilizes a "chimney effect" to discharge the suction air at a velocity of 20 m / s, further enhancing the fluid dynamics of the main duct.

[0084] PIV test data shows that this coupling system significantly improves the uniformity of the velocity field in the pipeline: the velocity deviation rate of the traditional single pipeline in the straight section is ±15%, while the deviation rate is reduced to ±8% under the bionic structure; the turbulence intensity at the minimum cross-section of the Venturi tube is reduced from 12% to 7%, and energy dissipation is reduced by about 28%. This synergistic effect is due to the "suction-acceleration" feedback mechanism of the convex low-pressure area on the main pipeline airflow. It has been verified by 1:10 scale model wind tunnel experiments. When the suction efficiency is The performance is improved by 12%, which is the optimal parameter combination.

[0085] Each section of the pipeline system is cold-formed by a plate rolling machine. The plate at the minimum cross-section of the Venturi tube needs to be annealed at 650℃ for 2 hours to eliminate processing stress. After forming, a three-coordinate measuring instrument (accuracy 0.05mm) is used to detect the transition curve to ensure that the curvature deviation of the Venturi tube and the diffuser is ≤0.03mm. -1 The convex body assembly is welded in sections using 5mm thick aluminum alloy plates, using ER5356 wire for tungsten inert gas arc welding. Deformation is controlled by heat aging treatment after welding, and the overall surface error is ≤1mm. The flat plate and the convex body base are fixed with M16 bolts, with a bolt spacing of 200mm. During installation, parallelism must be ensured to be ≤0.5mm / m.

[0086] During on-site construction, a 4m x 6m x 1.5m C30 reinforced concrete foundation was first poured, with M30 anchor bolts embedded (1.2m deep). The top surface flatness tolerance was controlled within 2mm. A 50t crane was used to hoist the piping system in sections, first assembling the nozzle, Venturi tube, and diffuser, and then connecting the straight pipes. The overall verticality deviation was ≤1mm / m. The upper and lower convex components were then secured by a support structure. The weld height between the support and the embedded foundation components was ≥8mm. After welding, an anti-corrosion treatment was applied with an epoxy zinc-rich primer and a polyurethane topcoat, with a total dry film thickness of ≥200μm. After installation, 100% of the pipe welds were penetrant tested to ensure the absence of defects such as pores and cracks.

[0087] Twelve months of operational monitoring at the Jiuquan Wind Farm in Gansu Province showed that this device, when paired with a 3MW generator set, achieved an average power generation of 1.65MW at wind speeds of 5-7m / s, a 37.5% increase compared to the 1.2MW of traditional wind turbines. Annual power generation increased from 26.28 million kWh to 36.03 million kWh, resulting in an additional annual revenue of 3.41 million yuan at 0.35 yuan / kWh. The device operates at a starting wind speed as low as 3.2m / s, expanding the wind energy utilization range compared to traditional turbines (3.8m / s), making it particularly suitable for areas with average annual wind speeds of 4-9m / s.

[0088] In low-speed wind tunnel tests with a diameter of 3m, the device demonstrated excellent fluid performance: outlet flow rate increased by 39% at an inlet wind speed of 5m / s and by 31% at 8m / s. The pressure coefficient in the low-pressure zone at the top of the convex body was measured at -0.32, with a deviation of ≤5% from the simulation result. Regarding structural performance, the maximum amplitude of the pipe at a wind speed of 10m / s was 0.12mm (compared to 0.35mm for conventional pipes), and the noise level at a distance of 10m from the device was 52dB, meeting the requirements of the GB18451.2-2015 standard. Under extreme operating conditions, ANSYS simulations showed that the maximum pipe stress of 185MPa at a wind load of 12 (32.7m / s) was less than the material yield strength of 355MPa. The coating showed no cracking at -25°C, and the device operated stably.

[0089] Compared to traditional ducted wind turbines, this invention achieves performance breakthroughs through three key innovations: First, leveraging the "convex-flat" pressure differential principle of prairie dog burrows, passive airflow extraction requires no electricity, resulting in 100% energy savings compared to electric speed-increasing devices. Second, a parametrically designed, continuous curvature duct system reduces airflow separation losses by 28% and shrinks the vortex area by 70% compared to traditional abrupt cross-sections. Third, a dual-exhaust system creates a coordinated "main airflow-suction airflow" cycle, shortening airflow retention time within the duct by 40%. A technical and economic analysis indicates a payback period of approximately 3.5 years, 1.2 years shorter than traditional solutions. The added convex structure only increases costs by 12%, while generating over 30% more power.

[0090] According to the characteristics of different wind speed areas, the device can adaptively adjust parameters: in medium and low wind speed areas (4-6m / s), the convex interception height can be increased to Enhance the suction effect; in medium- to high-speed winds (6-9 m / s), the diffuser angle can be reduced to 5-6°, reducing the risk of airflow separation. It is recommended that this technology be used in conjunction with an intelligent monitoring system with a 100Hz sampling frequency to adjust the guide vane angle in real time, optimizing airflow characteristics at different wind speeds and further improving energy capture efficiency. This technology provides a new solution for wind energy development in low-wind-speed regions in my country and has significant engineering application value.

[0091] The following is a specific example 2 of the present invention: In a low-wind-speed wind energy demonstration project in northwest my country, researchers developed a novel wind turbine that integrates biomimetic and fluid dynamics principles to address environmental conditions with an average annual wind speed of 5.8 m / s. This device leverages the natural ventilation mechanisms of prairie dog burrows and, through a unique duct structure design, significantly improves wind energy capture efficiency in low-wind environments.

[0092] The wind turbine primarily consists of a converging-diverging duct system and a bionic convex structure inspired by a dog-and-rat burrow. The duct system includes a nozzle, a venturi tube, a diffuser, and a straight pipe, connected in sequence along the airflow direction. Flanges connect each section to ensure airtightness. The bionic convex structure is symmetrically arranged on either side of the straight pipe and connects to the interior of the straight pipe via an inclined duct, forming a coordinated fluid dynamic system.

[0093] The piping system is constructed from Q355ND low-alloy, high-strength steel, with a polytetrafluoroethylene coating sprayed on the inner wall to reduce airflow friction. The bionic convex structure is constructed from 6061-T6 aluminum alloy, welded and heat-aged to ensure structural strength and stability. This material combination not only meets the mechanical performance requirements of the device, but also effectively controls the overall weight.

[0094] When air enters the nozzle at a speed of 5.8 m / s, the gradually converging cross-section accelerates it to 8.2 m / s. Then, as it passes through the Venturi's smallest cross-section, the velocity increases further to 15.3 m / s, creating a localized high-pressure zone. After entering the diffuser, the cross-sectional expansion converts some of the kinetic energy into pressure energy, reducing the velocity to 12.5 m / s before entering the straight tube.

[0095] In the middle section of the straight tube, part of the airflow is diverted through an inclined duct to the biomimetic convex structure. The gap between the convex structure and the flat plate creates an airflow acceleration effect similar to that found in a rat burrow, increasing the air velocity through the gap to 18 m / s and reducing the static pressure to -320 Pa, creating a significant low-pressure zone. This low-pressure zone, driven by the pressure difference between the duct and the inside of the straight tube, accelerates the main airflow within the straight tube to 13.8 m / s, ultimately exiting through the first outlet. Simultaneously, a second outlet, located above the convex tip, utilizes a chimney effect to discharge the suction air at 20 m / s, further enhancing the fluid dynamics of the entire system.

[0096] The convergent-divergent duct design was optimized through CFD simulation. The nozzle features a 12° convergence angle to ensure smooth airflow acceleration. The cross-sectional profile of the Venturi tube is fitted with a cubic Bezier curve to achieve a continuous transition with the curvature of the diffuser, effectively reducing airflow separation losses. The diffuser's 7° divergence angle ensures pressure recovery while avoiding vortices caused by overexpansion.

[0097] The parameters of the bionic convex structure have been verified through multiple rounds of wind tunnel experiments. When the coefficient of gravity is 0.6, the suction efficiency in the low-pressure area is optimal. The guide groove design on the bottom of the flat plate further optimizes the airflow path and reduces flow resistance. The inclined duct connecting the straight pipe and the convex body adopts an S-shaped bend with a curvature radius of 300mm, effectively reducing airflow turning losses.

[0098] Each section of the piping system is cold-formed using a plate rolling machine, with key areas undergoing annealing to eliminate stress. During the forming process of the Venturi tube, surface accuracy is monitored in real time using a three-dimensional coordinate measuring machine to ensure that deviations from the design model do not exceed 0.05mm. The bionic convex structure utilizes a split-flap welding process, followed by a post-weld heat aging treatment to control deformation, keeping the overall surface error within 1mm.

[0099] During on-site installation, a reinforced concrete foundation was first poured, with pre-buried anchor bolts ensuring precise installation. The piping system was assembled using segmented hoisting and flange connections. The bionic convex structure was securely connected to the embedded foundation components via a supporting structure. The weld height of the supporting structure was no less than 8mm, and rigorous non-destructive testing was performed.

[0100] In actual wind field tests, the device achieved a 37.5% increase in power generation compared to traditional wind turbines in the 5-7 m / s wind speed range, increasing annual power generation from 26.28 million kWh to 36.03 million kWh. The device's startup wind speed was as low as 3.2 m / s, effectively expanding the scope of wind energy utilization.

[0101] Wind tunnel test data shows that the bionic convex structure increases the flow velocity at the pipe outlet by 23% and reduces turbulence intensity by 42%, significantly improving wind energy conversion efficiency. In extreme operating conditions testing, the device withstood a Category 12 typhoon, with the maximum structural stress well below the material's yield strength, demonstrating excellent reliability.

[0102] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A bionic duct-type wind turbine inspired by prairie dog burrows, characterized in that: It includes a cross-sectional pipe and a dog-rat burrow bionic convex structure; the cross-sectional pipe includes a nozzle, a venturi tube, a diffuser and a straight tube in sequence along the airflow direction; the dog-rat burrow bionic convex structure is connected to the rear end side wall of the straight tube through a conduit, and the dog-rat burrow bionic convex structure includes a convex body and a flat plate, one end of the conduit is connected to the straight tube, and the other end is connected to the space between the convex body and the flat plate; wherein: the inlet end radius of the venturi tube is greater than the minimum cross-sectional radius, the radius of the diffuser is greater than the minimum cross-sectional radius of the venturi tube, and the height of the convex body is less than or equal to the radius of the convex body.

2. The bionic duct-type wind turbine inspired by prairie dog burrows according to claim 1, characterized in that: The cross-section of the nozzle gradually decreases along the direction of the airflow, the Venturi tube shrinks to a minimum cross-section, the cross-section of the diffuser gradually expands along the direction of the airflow, and the cross-section of the straight tube is a constant cross-section; the nozzle, Venturi tube, diffuser and straight tube are arranged in sequence along the direction of the airflow.

3. The bionic duct-type wind turbine inspired by prairie dog burrows according to claim 2, characterized in that: The minimum cross-section of the Venturi tube is located between the nozzle and the diffuser, and the outlet of the diffuser is connected to the inlet of the straight tube.

4. The bionic duct-type wind turbine inspired by prairie dog burrows according to claim 3, characterized in that: The connection position between the conduit and the straight pipe is located behind the diffuser, the radius of the conduit is smaller than the inner diameter of the straight pipe, and the axis of the conduit is perpendicular or inclined to the axis of the straight pipe.

5. The bionic duct-type wind turbine inspired by prairie dog burrows according to claim 4, characterized in that: A low-pressure area is formed between the top of the convex body and the flat plate. The flat plate is arranged parallel to the bottom surface of the convex body. The central axis of the distance between the top ends of the convex body coincides with the central axis of the straight tube.

6. The bionic duct-type wind turbine inspired by prairie dog burrows according to claim 5, characterized in that: The cross-sectional pipe and the dog-rat burrow bionic convex structure are arranged symmetrically up and down, and the cross-sectional pipe and the dog-rat burrow bionic convex structure are connected by a supporting structure, and the supporting structure is arranged on the outside of the straight pipe.

7. The bionic duct-type wind turbine inspired by prairie dog burrows according to claim 6, characterized in that: The curvatures of transition curves of the Venturi tube and the diffuser are consistent.

8. The bionic duct-type wind turbine inspired by prairie dog burrows according to claim 7, characterized in that: The outlet of the cross-sectional pipe includes a first outlet and a second outlet. The first outlet is arranged at the end of the straight pipe, and the second outlet is arranged at the top of the dog and rat cave bionic convex structure. The position of the second outlet is higher than the top plane of the convex body.

9. The bionic duct-type wind turbine inspired by prairie dog burrows according to claim 8, characterized in that: The minimum cross-sectional radius of the Venturi tube is equal to the inlet radius of the diffuser tube, and the outlet radius of the diffuser tube is equal to the inner diameter of the straight tube.

10. The bionic duct-type wind turbine inspired by prairie dog burrows according to claim 9, characterized in that: The convex body is a part of a hemisphere, and the ratio of the convex body height to the convex body radius is 0.3-0.7, so as to form the low-pressure area.

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