Downwind type small wind driven generator turbine

Abstract

The invention discloses a downwind type small wind driven generator turbine which comprises a rotor blade body axially swept back from a blade root to a blade tip, the front edge of the blade is provided with a bionic nodule structure changing in a sine rule, and the rear edge of the blade is provided with a sawtooth-shaped corrugated structure; the blades and the hub are connected to form a wind turbine rotor, the rotor is located on the downwind side of the tower, wind flow firstly passes through the tower and then acts on the rotor blades, the downwind layout enables the blades to be capable of natural feathering under the action of wind loads, therefore, dynamic load impact on the tower is reduced, and the yaw system structure is simplified. The tower shadow effect can be remarkably relieved through the whole sweepback type blades, and aerodynamic noise is reduced; the front edge nodules of the blades are bionic to fin limbs of the seat head whale, so that the lift-drag ratio can be effectively increased, broadband noise is reduced, and violent fluctuation of power and load is inhibited; sawtooth ripples on the rear edge of the blade imitate a comb-shaped structure on the rear edge of the flying feather of the owl, so that vortex shedding frequency concentration can be inhibited, and high-frequency noise can be remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of wind power generation technology, and more specifically, to a turbine for a downwind wind turbine, a wind turbine including the turbine, and blades for the turbine. Background Technology

[0002] A wind turbine is a device that converts wind energy into electrical energy. Its core component is the wind turbine (including the hub and blades). Based on the relative position of the wind turbine and the tower, wind turbines can be divided into upwind layout (the wind turbine is located upwind of the tower, and the airflow passes through the wind turbine before flowing through the tower) and downwind layout (the wind turbine is located downwind of the tower, and the airflow passes through the tower before flowing through the wind turbine).

[0003] Upwind configuration is currently the mainstream technical solution, but it has the following problems: a complex yaw system is required to keep the rotor always facing the wind; the blades are subjected to large cyclic loads during operation, which adversely affects the fatigue life of the tower and blade roots. In contrast, downwind configuration has self-aligning characteristics, which can simplify or even eliminate the yaw system. At the same time, the blades can naturally feather under wind loads, which theoretically reduces structural loads.

[0004] However, downwind configurations present a key problem in practical applications: because the rotor is located in the tower's wake region, the blades are periodically affected by the tower shadow effect during rotation, leading to increased aerodynamic load fluctuations. This not only affects power generation efficiency but also causes vibration and noise problems, often resulting in forced removal after installation in urban residential areas or on rooftops. Therefore, how to adapt to the non-uniform inflow conditions downwind through the aerodynamic design of the blades themselves is a crucial technical challenge that urgently needs to be addressed in this field.

[0005] Furthermore, various blade aerodynamic improvement schemes have emerged in the prior art. For example, patent CN200510088166.4 discloses a blade with a sweep angle, which has a forward sweep angle on the inner side and a backward sweep angle on the outer side to achieve load balance. Although this scheme improves the aerodynamic performance of the blade to some extent, its sweep angle distribution is relatively complex and it is not specifically optimized for downwind conditions. As another example, there are existing technologies that apply biomimetic nodules (leading edge protrusions) or trailing edge serrations to blades to improve aerodynamic performance or reduce noise. However, these schemes are usually applied individually without considering the synergistic effect between the features, and there is no indication of combining them with downwind layouts and overall swept blades. Summary of the Invention

[0006] Purpose of the invention: The present invention aims to provide a turbine, wind turbine generator and blade for downwind wind turbines, in order to solve the problems of large load fluctuation, low aerodynamic efficiency and high noise level caused by the tower shadow effect in the existing technology of downwind wind turbines, and to achieve comprehensive optimization of aerodynamic performance, structural load and noise control.

[0007] Technical solution To achieve the above objectives, the present invention provides a turbine for a downwind wind turbine, comprising: a hub; at least two blades mounted on the hub; the turbine being configured to be mounted on the downwind side of a tower such that airflow passes through the tower before contacting the blades; the blades having an integral axially continuous swept-back configuration from the blade root to the blade tip; the leading edge of the blades having a biomimetic nodal structure with a sinusoidal variation; and the trailing edge of the blades having a serrated corrugated structure.

[0008] Furthermore, the overall axially continuous sweep configuration is characterized by the following: along the blade span, the aerodynamic center line connecting each section of the blade is a smooth curve, and the projection of this curve onto the plane of rotation is a continuous arc in a single direction, without any reverse bending points. Preferably, the sweep angle of the overall axially continuous sweep configuration increases monotonically along the blade span, and the difference between the sweep angle at the blade tip and the sweep angle at the blade root is 15° to 35°.

[0009] Furthermore, the biomimetic nodular structure is disposed in the inner region of the blade spanwise, from a first starting spanwise position to a first ending spanwise position. The relative radius r / R corresponding to the first starting spanwise position is 0.2 to 0.3, and the relative radius r / R corresponding to the first ending spanwise position is 0.65 to 0.85, where R is the distance from the rotation axis to the blade tip. The biomimetic nodular structure is distributed in a sinusoidal waveform along the spanwise direction of the blade leading edge, with its amplitude A being 0.025 to 0.1 relative to the local chord length c of the blade, and the wavelength λ being 3 to 8 relative to the amplitude A.

[0010] Furthermore, the serrated corrugated structure is disposed in the outer region of the blade spanwise, which extends from the second starting spanwise position to the blade tip, and the relative radius r / R corresponding to the second starting spanwise position is 0.65 to 0.85. The serration apex angle of the serration corrugated structure is no greater than 90°, the ratio of the serration height H_t to the local chord length c of the blade is 0.02 to 0.05, and the spacing between adjacent serrations is 1.2 to 2 times the serration height.

[0011] Furthermore, the first termination spanning position is less than or equal to the second starting spanning position, and the ratio of the maximum amplitude Amax of the biomimetic nodular structure to the maximum height Hmax of the sawtooth corrugated structure is 1.2 to 3.5.

[0012] Furthermore, an offset mechanism is provided between the hub and the tower, so that the rotation plane of the turbine maintains a preset offset distance from the center line of the tower, so as to ensure that the minimum gap between the blade and the outer wall of the tower during operation is not less than 1.5 times the blade chord length.

[0013] Furthermore, the blade has a tip speed ratio of 6 to 8 when operating at rated wind speed. Within this tip speed ratio range, the trailing edge serrated corrugated structure reduces the blade aerodynamic noise by at least 5 dB(A).

[0014] The present invention also provides a wind turbine, including a tower, a nacelle disposed on the top of the tower, and a turbine as described above, the turbine being mounted on the nacelle and located on the downwind side of the tower.

[0015] The present invention also provides a blade for a downwind wind turbine, the blade having the structural features of a blade as described above.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects.

[0017] Aerodynamic performance improvement: By adopting a blade configuration with continuous axial sweep from blade root to blade tip, combined with a biomimetic nodal structure at the leading edge, the blade can effectively delay flow separation and improve stall margin under non-uniform inflow (tower shadow region) conditions. CFD simulation results show that, under rated operating conditions, the wind energy utilization coefficient (Cp) of this invention is improved by about 3% to 5% compared with traditional upwind wind turbines, and by about 8 percentage points higher than the improvement value of simple swept blades under downwind conditions.

[0018] Structural load reduction: The overall continuous swept-back configuration and downwind layout create a synergistic effect, allowing the blades to smoothly adapt to the velocity gradient of the tower wake during rotation, significantly reducing the alternating load at the blade root. Simulation results show that the fatigue load at the blade root is reduced by approximately 12% to 15% compared to existing segmented swept-back blades.

[0019] Significantly reduced noise levels: By incorporating a trailing edge serrated corrugated structure on the outer section of the blade, the wake vortex is effectively broken up, reducing aerodynamic noise. Combined with the aerodynamic advantages of the downwind layout itself, the overall noise reduction effect can reach 5-8 dB(A) within the tip speed ratio range of 6-8, making it particularly suitable for noise-sensitive wind power applications such as urban residential areas.

[0020] Advantages of collaborative design: This invention integrates the leading-edge biomimetic nodule, trailing-edge sawtooth corrugations, and overall swept blade and downwind layout into a single design. In particular, by defining the connection between the end position of the nodule region and the beginning position of the sawtooth region, and defining the ratio between the maximum amplitude of the nodule and the maximum height of the sawtooth (1.2~3.5), the leading-edge flow control and trailing-edge wake breaking form an upstream-downstream synergy, achieving simultaneous optimization of aerodynamic efficiency and noise suppression, and producing an unexpected technical effect of "1+1>2".

[0021] Attached image description.

[0022] Figure 1 This is a schematic diagram of the overall structure of the turbine in an embodiment of the present invention.

[0023] Figure 2 for Figure 1 A side view of the middle blade, used to illustrate the overall axially continuous swept-back configuration.

[0024] Figure 3 for Figure 1 A schematic diagram of the spanwise zoning of the blade, used to illustrate the arrangement of biomimetic nodules and serrated corrugations.

[0025] Figure 4 for Figure 1 Enlarged view of the biomimetic nodular structure at the leading edge and the serrated corrugated structure at the trailing edge of the middle blade.

[0026] Figure 5 This is a schematic diagram of the overall structure of the turbine installed on the downwind side of the tower in an embodiment of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are only for explaining the invention and do not constitute a limitation on the scope of protection of this invention.

[0028] definition In this application, the total radius R of the blade is defined as the distance from the rotation axis of the wind turbine to the blade tip. The relative radius r / R is defined as the ratio of the distance r from a point on the blade to the rotation axis to the total radius R.

[0029] Example 1: Turbine Structure Reference Figure 1 and Figure 4 This embodiment provides a turbine 100 for a downwind wind turbine. The turbine 100 includes a hub 110 and three blades 120, which are uniformly mounted on the hub 110 in a circumferential direction.

[0030] The turbine 100 is configured to be installed on the leeward side of the tower 200. Specifically, the nacelle 300 is located on top of the tower 200, and the turbine 100 is mounted on the nacelle 300, located on the leeward side of the tower 200. When the airflow flows in the direction W, the airflow first passes through the tower 200 and then acts on the blades 120 of the turbine 100.

[0031] Reference Figure 2 The blade 120 has a continuous axial sweep configuration from the blade root 121 to the blade tip 122. Specifically, along the blade span, the aerodynamic center line connecting each section of the blade is a smooth curve. The projection of this curve onto the plane of rotation is a continuous arc in a single direction, without any reverse bending points. The sweep angle θ increases monotonically along the blade span, and the difference between the sweep angle θtip at the blade tip and the sweep angle θroot at the blade root is 20° (this value can be adjusted within the range of 15° to 35° according to the design conditions).

[0032] Example 2: Bionic nodule structure Reference Figure 3 and Figure 4 The leading edge of the blade 120 is provided with a biomimetic nodular structure 130. The biomimetic nodular structure 130 is disposed in the inner region of the blade spanwise, which extends from the first starting spanwise position a1 to the first ending spanwise position b1. In this embodiment, the relative radius r / R corresponding to the first starting spanwise position a1 is 0.25, and the relative radius r / R corresponding to the first ending spanwise position b1 is 0.75.

[0033] The biomimetic nodal structure 130 exhibits a sinusoidal waveform distribution along the spanwise direction of the blade's leading edge. The ratio of its amplitude A to the local chord length c is 0.05 (this ratio can be adjusted within the range of 0.025 to 0.1), and the ratio of wavelength λ to amplitude A is 5 (this ratio can be adjusted within the range of 3 to 8). The biomimetic nodal structure 130 improves the aerodynamic stability of the blade under non-uniform inflow conditions by generating flow-oriented vortices and delaying boundary layer separation.

[0034] Example 3: Sawtooth Corrugated Structure Reference Figure 3 and Figure 4 The trailing edge of the blade 120 is provided with a serrated corrugated structure 140. The serrated corrugated structure 140 is provided in the outer region of the blade spanwise, which starts from the second starting spanwise position a2 and ends at the blade tip 122. In this embodiment, the relative radius r / R corresponding to the second starting spanwise position a2 is 0.7.

[0035] The sawtooth corrugated structure 140 has a sawtooth apex angle α of 60° (not greater than 90°), a sawtooth height h to the local chord length c of the blade of 0.03 (this ratio can be adjusted within the range of 0.02 to 0.05), and a spacing d between adjacent sawtooths of 1.5 times the sawtooth height h (this ratio can be adjusted within the range of 1.2 to 2 times). The sawtooth corrugated structure 140 reduces aerodynamic noise through the broken trailing edge wake vortex.

[0036] Example 4: Collaborative Design Reference Figure 3 and Figure 4 In this embodiment, the first termination spanwise position b1 (r / R = 0.75) is equal to the second starting spanwise position a2 (r / R = 0.75), that is, the end position of the bionic nodule structure 130 and the start position of the sawtooth corrugated structure 140 are connected in the spanwise direction, which can work together to achieve the effect of enhancing efficiency and reducing noise.

[0037] The maximum amplitude Amax of the biomimetic nodular structure 130 is 0.08 times the local chord length, and the maximum height Hmax of the sawtooth corrugated structure 140 is 0.03 times the local chord length. The ratio between the two is 2.67 (this ratio is in the range of 1.2 to 3.5).

[0038] Through the aforementioned collaborative design, the flow-oriented vortices generated by the leading-edge nodule effectively interact with the trailing-edge serrations as they develop downstream: the nodule delays boundary layer separation, allowing the airflow to maintain a relatively good flow state upon reaching the trailing edge, while the serrations further break up the large-scale vortex structures in the wake, thus achieving simultaneous optimization of aerodynamic efficiency and noise reduction. Wind tunnel experiments show that, under rated operating conditions with a tip speed ratio of 7, the overall aerodynamic noise of this embodiment is reduced by approximately 3 dB(A) compared to the control blade with only trailing-edge serrations, while the wind energy utilization coefficient remains essentially unchanged.

[0039] Example 5: Safety Clearance Reference Figure 5 An offset mechanism (not shown in the figure) is provided between the hub 110 and the tower 200 to maintain a preset offset distance between the rotation plane of the turbine 100 and the centerline of the tower 200. This offset distance ensures that during operation, the minimum clearance between the blade tip and the outer wall of the tower 200 is not less than 1.5 times the blade chord length. This serves two purposes: firstly, to avoid collisions between the blades and the tower, ensuring operational safety; and secondly, to allow the turbine to have sufficient torque to rotate with the wind under downwind conditions.

[0040] Example 6: Whole Machine Application The turbine 100 is installed on the downwind side of the tower 200 to form a wind turbine generator 10. When the wind turbine generator 10 operates at rated wind speed, the blade tip speed ratio is controlled within the range of 6 to 8. Within this blade tip speed ratio range, the trailing edge sawtooth corrugated structure 140 reduces the aerodynamic noise of the blade by at least 5 dB(A), making it particularly suitable for noise-sensitive wind power applications in urban residential areas and near residential areas.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Those skilled in the art can make various improvements and modifications without departing from the spirit and principles of the invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A downwind small wind turbine, characterized in that, include: Wheel hub; And at least two blades, mounted on the hub; The turbine is configured to be installed on the downwind side of the tower, such that the airflow passes through the tower before contacting the blades; The blade has an integral axially continuous swept-back configuration from the leaf root to the leaf tip; The leading edge of the blade is provided with a biomimetic nodular structure that varies in a sinusoidal pattern; The trailing edge of the blade is provided with a serrated corrugated structure.

2. The turbine for a downwind wind turbine according to claim 1, characterized in that, The overall axial continuous swept-back configuration is characterized by the following: along the blade span, the aerodynamic center line connecting each section of the blade is a smooth curve, and the projection of this curve onto the plane of rotation is a continuous arc in a single direction without any reverse bending points.

3. The turbine for a downwind wind turbine according to claim 2, characterized in that, The sweep angle of the overall axially continuous sweep configuration increases monotonically along the blade span, and the difference between the sweep angle at the blade tip and the sweep angle at the blade root is 15° to 35°.

4. The turbine for a downwind wind turbine according to claim 1, characterized in that, The biomimetic nodular structure is disposed in the inner region of the blade spanwise, which extends from a first starting spanwise position to a first ending spanwise position. The relative radius r / R corresponding to the first starting spanwise position is 0.2 to 0.3, and the relative radius r / R corresponding to the first ending spanwise position is 0.65 to 0.85, where R is the distance from the rotation axis to the blade tip. The biomimetic nodular structure is distributed in a sinusoidal waveform along the spanwise direction of the blade leading edge, with the ratio of its amplitude A to the local chord length c of the blade being 0.025 to 0.1, and the ratio of wavelength λ to amplitude A being 3 to 8.

5. The turbine for a downwind wind turbine according to claim 1, characterized in that, The serrated corrugated structure is disposed in the outer region of the blade spanwise, which starts from the second starting spanwise position and ends at the blade tip. The relative radius r / R corresponding to the second starting spanwise position is 0.65 to 0.85, where R is the distance from the rotation axis to the blade tip. The serration apex angle of the serration corrugated structure is not greater than 90°, the ratio of the serration height H to the local chord length c of the blade is 0.02 to 0.05, and the spacing between adjacent serrations is 1.2 to 2 times the serration height.

6. The turbine for a downwind wind turbine according to claim 4 or 5, characterized in that, The first termination spanning position is less than or equal to the second starting spanning position, and the ratio of the maximum amplitude Amax of the biomimetic nodular structure to the maximum height Hmax of the sawtooth corrugated structure is 1.2 to 3.

5.

7. The turbine for a downwind wind turbine according to claim 1, characterized in that, An offset mechanism is provided between the hub and the tower, so that the rotation plane of the turbine maintains a preset offset distance from the center line of the tower, ensuring that the minimum gap between the blade and the outer wall of the tower during operation is not less than 1.5 times the blade chord length.

8. The turbine for a downwind wind turbine according to claim 1, characterized in that, The blade has a tip speed ratio of 6 to 8 when operating at rated wind speed. Within this tip speed ratio range, the trailing edge serrated corrugated structure reduces the blade aerodynamic noise by at least 5 dB(A).

9. A wind turbine generator, characterized in that, include: Tower; The nacelle is located at the top of the tower; And a turbine as claimed in any one of claims 1 to 8, the turbine being mounted on the nacelle and located on the leeward side of the tower.

10. A blade for a downwind wind turbine, characterized in that, The blade has the structural features of a blade as described in any one of claims 1 to 8.

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