A leeward wind turbine

Abstract

The present invention discloses a leeward type wind turbine, wherein a wind wheel (1) comprises a plurality of blades (1-1), the inner ends of the plurality of blades (1-1) are fixedly connected to the upper end of a wind wheel rotating mechanism, the plurality of blades (1-1) are distributed in a ring around the wind wheel rotating mechanism, and the vertical cross section of the wind wheel (1) presents an M shape when the wind is still. The leeward type wind wheel configuration is not restricted by "tower interference", and the blades can be designed to be softer than the windward type configuration; at the same time, the leeward M-type wind wheel automatically deforms as the wind speed increases, so that the blades are in a tensile stress state as much as possible within a wind speed range near the rated power, giving full play to the material strength of the blades, making the blades designed to be softer and lighter, and further reducing the cost of the blades and the whole machine. The leeward type wind wheel can automatically align with the incoming flow by virtue of its reset yaw moment, and generally has better yaw control performance than the windward type, and is also more suitable for super-large wind turbines under extreme weather conditions.

Description

Technical Field

[0001] The invention relates to a leeward type wind turbine, belonging to the technical field of wind turbines with leeward M-type wind wheels. Background Art

[0002] Wind energy is an important component of renewable energy. Since the 1870s, the number of wind turbines installed has increased rapidly. The size of wind turbines has increased significantly. As the installed capacity of onshore wind power in high wind speed areas has tended to be saturated, the development of low wind speed wind farms and distributed wind power is a recent hot spot in the wind power industry. One of the notable features of low wind speed wind turbines is that they have longer blades to increase the swept area. At the same time, offshore wind power is also developing rapidly, and the urgent need to reduce the cost of offshore wind power has driven the continuous increase in the length of wind turbine blades. The above two scenarios are a microcosm of the industry demand for the increasing diameter of wind turbine rotors. The power of a single wind turbine is expected to reach the 10-20MW level, and the rotor diameter will increase to the range of 150-250m.

[0003] As the blade length increases, the mass of the blade increases with the cube or subcubic length of the length. The mass of a single blade of a three-blade 20MW wind turbine will exceed 75,000 kg. The rapidly increasing blade mass also places higher demands on other parts of the wind turbine, such as the tower, main frame, gearbox, etc., resulting in a rapid increase in the difficulty of designing and manufacturing the whole machine and the total cost. After the blade length exceeds a certain threshold, the growth rate of power generation revenue brought by the blade lengthening will be lower than the growth rate of the whole machine cost, causing an increase in COE. Therefore, suppressing the trend of cubic or subcubic increase in blade mass is a guarantee for continued reduction in COE. The reduction of blade mass can be achieved through "internal" performance enhancement such as new materials and structural optimization, "external" force improvement such as reducing the aerodynamic load of the wind rotor and "constraint" conditions relaxation such as increasing the tip-tower anti-collision gap. The development and utilization of new materials is limited by cost, and structural optimization cannot fundamentally change the cubic increase law of mass. Under the premise of meeting the power generation requirements, reducing the ultimate load and fatigue load of the wind rotor can be achieved through adaptive blades, advanced control methods and accessories such as pitch control, trailing edge flaps, and trailing edge inserts. The rapid increase in the mass of long and flexible wind turbine blades is mainly to ensure blade stiffness, or the threshold of the blade tip-tower anti-collision clearance severely limits the possibility of blade weight reduction. Pre-bending blades to the windward direction, the cone angle and elevation angle design of the wind rotor are common means to increase the blade tip-tower clearance. However, these designs cannot support wind turbines to reach the 20MW level, and innovative designs must be carried out. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a leeward type wind turbine. The leeward type wind rotor configuration is not restricted by "tower interference", so that the blades can be designed to be softer than the windward type configuration; at the same time, the leeward M-type wind rotor automatically deforms with the increase of wind speed, so that the blades are in a tensile stress state as much as possible in a wind speed range near the rated power, giving full play to the material strength of the blades, making the blades designed to be softer and lighter, and further reducing the cost of the blades and the whole machine. In addition, the leeward type wind rotor can automatically align with the incoming flow by virtue of its reset yaw moment, and usually has better yaw control performance than the windward type, and is more suitable for super-large wind turbines under extreme weather conditions.

[0005] To achieve the above-mentioned purpose, the present invention provides a leeward wind turbine, including a wind rotor and a wind rotor rotating mechanism, the wind rotor including a plurality of blades, the inner ends of the plurality of blades being fixedly connected to the upper end of the wind rotor rotating mechanism, the plurality of blades being distributed in a ring around the wind rotor rotating mechanism, and the vertical cross-section of the wind rotor presents an M shape when the wind is still.

[0006] Preferably, the wind wheel rotation mechanism includes a hub, a nacelle and a tower, the inner ends of a plurality of blades are fixedly connected to the leeward side of the hub in a ring-shaped manner with equal intervals, the windward side of the hub is rotatably connected to the nacelle, the nacelle is fixedly set at the upper end of the tower, and the lower end of the tower is fixedly set on the ground.

[0007] Preferably, when the wind speed of the external environment is lower than the rated wind speed, the vertical cross-section of the wind rotor presents an M-shape; as the wind speed of the external environment gradually increases, the load on the wind rotor gradually increases, and the vertical cross-section of the wind rotor gradually transitions from M-shape to V-shape. In the process of transitioning to V-shape, the vertical cross-section of the wind rotor presents a hat shape, called HAT type; when the wind speed of the external environment is at the rated wind speed, the vertical cross-section of the wind rotor presents a V-shape; when the wind speed of the external environment exceeds the rated wind speed, the vertical cross-section of the wind rotor is approximately U-shaped in the side view.

[0008] Preferably, the wind rotor and the hub have a common central axis of rotation, and the wind rotor rotation plane line is perpendicular to the central axis of rotation;

[0009] A rectangular coordinate system is established with the straight line where the blade stacking line of the inner end of the blade is located as the X-axis, and the straight line where the windward side is perpendicular to the X-axis direction as the Y-axis. The angle between the rotation center axis and the horizontal plane is the inclination angle θt, θt∈[-30°, 30°]. The angle between the blade stacking line where the inner end of the blade is located and the wind rotor rotation plane line is θb, θb∈[0°, 90°]. The bottom of the blade stacking line where the inner end of the blade is located coincides with the X-axis of the rectangular coordinate system.

[0010] Preferably, the bending shape of the blade is controlled by the blade stacking line, and the blade stacking line is controlled by a piecewise function; in the blade rectangular coordinate system composed of the X-axis and the Y-axis, the offset distance Y of the blade stacking line in the Y-axis direction at different spanwise positions X bend can be obtained by Equation 1:

[0011]

[0012] where X r = X / R is the relative spanwise position of the blade, X is the actual spanwise position of the blade, R is the projected length of the blade on the X-axis, A is the control index of the bending curve, A is any real number and A is not equal to 0; when Y bend > 0, both A and the actual deflection angle γ of the airfoil are positive values.

[0013] Preferably, the vertical force Q1 when upward is less than the vertical force Q2 when rotated to vertically downward, that is, Q1 < Q2. The included angle between the resultant force F1 and the horizontal line when the blade rotates to vertically upward is θ1, and the included angle between the resultant force F2 and the horizontal line when the blade rotates to vertically downward is θ2, and the included angles satisfy the relationship θ1 < θ2.

[0014] Preferably, it includes 2 - 4 blades, and the blades are annularly distributed around the hub.

[0015] Preferably, the horizontal distance L between the outer end top of the blade and the tower satisfies L > 0.25m.

[0016] The beneficial effects achieved by the present invention are as follows:

[0017] In the innovative design of the downwind wind turbine of the present invention, a specific curve form is adopted to construct the stacking line shape of the blade. The blade is installed on the hub at a certain angle to form a downwind M-shaped wind wheel. The wind wheel approximately presents an M shape or a hat shape in the unloaded or slightly loaded state, approximately presents a V shape near the rated wind speed, and approximately presents a U shape at high wind speeds, realizing load reduction and achieving automatic deformation of the downwind wind wheel without adding a wind wheel folding mechanism. The configuration of the downwind wind wheel is not restricted by "tower interference", and the blade can be designed to be more flexible than the upwind configuration; at the same time, the downwind M-shaped wind wheel automatically deforms as the wind speed increases, so that the blade is in a tensile stress state as much as possible in a certain wind speed range near the rated power, giving full play to the material strength of the blade, making the blade designed to be more flexible and lighter, and further reducing the cost of the blade and the whole machine. In addition, the downwind wind wheel can automatically align with the oncoming flow by virtue of its reset yaw moment, usually having better yaw control performance than the upwind type, and is also more suitable for super-large wind turbines under extreme meteorological conditions. Description of the Drawings

[0018] Figure 1It is a side view of the present invention when it is not started or is running at a speed lower than the rated wind speed;

[0019] Figure 2 Schematic diagram of different forms of wind wheel blade stacking lines of the present invention;

[0020] Figure 3 Schematic diagram of the offset of the blade stacking line along the Y-axis at different spanwise positions of the X-axis in the present invention;

[0021] Figure 4 Schematic diagram of several different blade stacking line forms controlled by piecewise function in the present invention;

[0022] Figure 5 It is a schematic diagram of the force on the blades when the blades are located at the top and the bottom when the wind wheel of the present invention presents a V-shape.

[0023] The meaning of the marks in the attached drawings are: 1-wind rotor; 2-hub; 3-nacelle; 4-tower; 1-1-blade; 1-2-blade stacking line; 1-3-rotation center axis; 1-4-wind rotor rotation plane line. DETAILED DESCRIPTION

[0024] The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and are not intended to limit the protection scope of the present invention.

[0025] A leeward wind turbine includes a wind rotor 1 and a wind rotor rotating mechanism, wherein the wind rotor 1 includes a plurality of blades 1-1, wherein the inner ends of the plurality of blades 1-1 are fixedly connected to the upper end of the wind rotor rotating mechanism, and the plurality of blades 1-1 are annularly distributed around the wind rotor rotating mechanism, and when the wind is still, the vertical cross section of the wind rotor 1 presents an M shape. In the prior art, there are V-shaped cone-angle wind rotors, and the greatest feature of the wind rotor 1 of the present invention is that it is an M shape when still, and the wind rotor 1 will gradually deform as the wind speed increases.

[0026] Furthermore, the wind wheel rotation mechanism includes a hub 2, a nacelle 3 and a tower 4, the inner ends of a plurality of blades 1-1 are fixedly connected to the leeward side of the hub 2 in an annular manner with equal intervals, the windward side of the hub 2 is rotatably connected to the nacelle 3, the nacelle 3 is fixedly arranged at the upper end of the tower 4, and the lower end of the tower 4 is fixedly arranged on the ground.

[0027] Furthermore, when the wind speed of the external environment is lower than the rated wind speed, the vertical cross-section of the wind rotor 1 presents an M-shape; as the wind speed of the external environment gradually increases, the load on the wind rotor 1 gradually increases, and the vertical cross-section of the wind rotor 1 gradually transitions from the M-shape to the V-shape. In the process of transitioning to the V-shape, the vertical cross-section of the wind rotor 1 presents a hat shape, which is called a HAT shape; when the wind speed of the external environment is at the rated wind speed, the vertical cross-section of the wind rotor 1 presents a V-shape; when the wind speed of the external environment exceeds the rated wind speed, the vertical cross-section of the wind rotor 1 approximately presents a U-shape in the side view.

[0028] Furthermore, the wind wheel 1 and the hub 2 have a common rotational central axis 1-3, and the wind wheel rotation plane line 1-4 is perpendicular to the rotational central axis 1-3;

[0029] Taking the straight line where the blade stacking line 1-2 at the inner end of the blade 1-1 is located as the X-axis, and the straight line perpendicular to the X-axis direction on the windward side as the Y-axis, a rectangular coordinate system is established. The included angle between the rotational central axis 1-3 and the horizontal plane is the inclination angle θt, θt ∈ [-30°, 30°], and the included angle between the blade stacking line 1-2 where the inner end of the blade 1-1 is located and the wind wheel rotation plane line 1-4 is θb, θb ∈ [0°, 90°]. The bottom end of the blade stacking line 1-2 at the bottom end of the inner end of the blade 1-1 coincides with the X-axis of the rectangular coordinate system.

[0030] Furthermore, the bending shape of the blade 1-1 is controlled by the blade stacking line 1-2, and the blade stacking line 1-2 is controlled by a piecewise function; within the blade rectangular coordinate system composed of the X-axis and the Y-axis, the offset distance Y of the blade stacking line 1-2 in the Y-axis direction at different spanwise positions X bend can be obtained by Formula 1:

[0031]

[0032] where X r = X / R is the relative spanwise position of the blade, X is the actual spanwise position of the blade, R is the projected length of the blade on the X-axis, A is the control index of the bending curve, A is an arbitrary real number and A is not equal to 0. As Figure 4 shown, in the present invention, A takes values of -5, -1, 0.7, 1.5, 2, and 5; when Y bend > 0, both A and the actual deflection angle γ of the airfoil at the blade element take positive values.

[0033] Furthermore, the vertical force Q1 when upward is less than the vertical force Q2 when rotated to vertically downward, that is, Q1 < Q2. The included angle between the resultant force F1 and the horizontal line when the blade 1-1 rotates to vertically upward is θ1, and the included angle between the resultant force F2 and the horizontal line when the blade 1-1 rotates to vertically downward is θ2. The included angles satisfy the relationship θ1 < θ2.

[0034] Furthermore, it includes 2-4 blades 1-1, and the blades 1-1 are annularly distributed around the hub 2.

[0035] Furthermore, the horizontal distance L between the top end of the outer end of the blade 1-1 and the tower 4 satisfies L > 0.25 m.

[0036] The advantage of Formula (1) is that only one variable A is used to control the bending curve. When the control index |A| > 1, the formula represents a smoothly curved blade, and when |A| ≤ 1, it is a folded blade. It is stipulated that Y bendWhen >0, the actual deflection angle γ of both A and the blade element profile line takes a positive value.

[0037] This device adopts a leeward configuration, that is, the oncoming wind first flows through the tower 4 and the nacelle 3, and then flows through the leeward M-shaped wind turbine 1. The bending shape of the blade 1-1 is controlled by the blade stacking line 1-2. The wind turbine rotation plane line 1-4 is the straight line passing through the center of the hub 2 on the plane formed by the inner end rotation of the blade.

[0038] The wind turbine composed of several blades approximately presents an M shape in the side view when it is stationary or the wind speed is low. As the wind speed increases, the load on the wind turbine increases, and the wind turbine gradually transitions from an M shape to a V shape. During the transition process, it approximately presents a certain hat shape, called the HAT type. When at the rated wind speed, the wind turbine approximately presents a V shape. The resultant force on the blade 1-1 is parallel to the blade span direction, making the blade structure mainly承受 tensile force, while the load condition of the blades of traditional windward wind turbines is similar to that of a cantilever beam. When the wind speed is too high and exceeds the rated wind speed, the wind turbine approximately presents a U shape in the side view. At this time, the projected area of the wind turbine on the wind turbine rotation plane is greatly reduced, realizing the unloading function. The leeward M-shaped wind turbine 1 in this device presents different postures at different wind speeds, which can reduce the limit design load requirements or design strength requirements of the blade 1-1, making the blade 1-1 can be designed to be softer and lighter, and then the cost of the blade 1-1 can be reduced. At the same time, the costs of other components of the whole machine are also reduced due to the reduced load, and finally the cost of the whole machine is reduced; in the present invention, the rated wind speed refers to the external environmental wind speed when the wind turbine reaches the rated power generation.

[0039] When the blade 1-1 rotates to the position at high altitude, that is, above the hub 2, the thrust T1 exerted by the wind on the blade at the wind turbine radius r is greater than the thrust T2 when the blade 1-1 rotates to low altitude, that is, below the hub 2, that is, T1>T2; when the blade 1-1 rotates to point to the sky, in the ideal state, the gravity and the centrifugal force are approximately equal in value and opposite in direction; when the blade 1-1 rotates to point to the ground, the gravity and the centrifugal force are almost in the same direction. Under the combined action of the centrifugal force and the gravity, the vertical force Q1 on the blade 1-1 when it rotates to the vertical upward direction is less than the vertical force Q2 when it rotates to the vertical downward direction, that is, Q1<Q2. The included angle between the resultant force F1 on the blade 1-1 when it rotates to the vertical upward direction and the horizontal line is θ1, and the included angle between the resultant force F2 on the blade 1-1 when it rotates to the vertical downward direction and the horizontal line is θ2, and the included angles satisfy the relationship θ1<θ2.

[0040] θt is the angle between the rotation center axis 1-3 and the horizontal plane, θb is the angle between the Y axis of the coordinate system and the wind wheel rotation plane line 1-4, L is the horizontal distance between the top end of the blade (1-1) and the tower (4), θ1 is the angle between the resultant force F1 and the horizontal line, the angle between the resultant force F2 received by the blade 1-1 when it rotates vertically downward and the horizontal line is θ2, Q1 is the vertical force received by the blade when it rotates vertically upward, Q2 is the vertical force received by the blade when it rotates vertically downward, the resultant force received by the blade 1-1 when it rotates vertically upward is F1, and the resultant force received by the blade 1-1 when it rotates vertically downward is F2.

[0041] When the angle θt between the rotation center axis 1-3 and the horizontal plane is less than 0, the entire wind rotor presents a "lower head" posture, which is different from the "raised head" posture usually adopted by traditional windward wind rotors. When the wind rotor is approximately V-shaped, the inclination angle θt<0 makes the tangent of the blade stacking line 1-2 at the wind rotor radius r closer to the direction of the resultant force, thereby making the blade 1-1 bear as much tensile load as possible, giving full play to the performance of the material, so that the blade can be designed to be lighter, achieving the effect of further reducing costs.

[0042] When the angle θb between the Y axis of the blade coordinate system and the wind wheel rotation plane line 1 - 4 is greater than 0°, the hub 2 needs to be specially designed so that the blade 1 - 1 can be mounted on the hub 2 at the angle θb.

[0043] In summary, the present invention has a wide range of applications and can be used in land and offshore wind turbines. It plays an important role in reducing the weight and cost of large wind turbines and lowering COE. It is of great significance for the large-scale development of wind turbines and offshore wind farms.

[0044] It should be noted that the terms such as "upper", "lower", "left", "right", "front", "back", etc. cited in the invention are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0045] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A leeward wind turbine, characterized in that: The invention comprises a wind wheel (1) and a wind wheel rotating mechanism, wherein the wind wheel (1) comprises a plurality of blades (1-1), the inner ends of the plurality of blades (1-1) are fixedly connected to the upper end of the wind wheel rotating mechanism, the plurality of blades (1-1) are distributed in a ring around the wind wheel rotating mechanism, and when the wind is still, the vertical cross section of the wind wheel (1) presents an M shape; The wind wheel rotating mechanism comprises a hub (2), a nacelle (3) and a tower (4); the inner ends of a plurality of blades (1-1) are fixedly connected to the leeward side of the hub (2) at equal intervals in an annular manner; the windward side of the hub (2) is rotatably connected to the nacelle (3); the nacelle (3) is fixedly arranged at the upper end of the tower (4); and the lower end of the tower (4) is fixedly arranged on the ground; When the wind speed of the external environment is lower than the rated wind speed, the vertical cross-section of the wind rotor (1) presents an M shape; as the wind speed of the external environment gradually increases, the load on the wind rotor (1) gradually increases, and the vertical cross-section of the wind rotor (1) gradually transitions from the M shape to the V shape. During the transition to the V shape, the vertical cross-section of the wind rotor (1) presents a hat shape, referred to as a HAT shape; when the wind speed of the external environment is at the rated wind speed, the vertical cross-section of the wind rotor (1) presents a V shape; when the wind speed of the external environment exceeds the rated wind speed, the vertical cross-section of the wind rotor (1) presents an approximately U shape; The bending shape of the blade (1-1) is controlled by the blade stacking line (1-2), and the blade stacking line (1-2) is controlled by a piecewise function; in the blade rectangular coordinate system composed of the X axis and the Y axis, the blade stacking line (1-2) is offset by a distance Y along the Y axis at different spanwise positions X. bend From formula (1), we can get: （1） Where X r = X / R is the spanwise position relative to the blade, X is the spanwise position of the actual blade, R is the projection length of the blade on the X-axis, A is the control index of the bending profile, A is an arbitrary real number, and A is not equal to 0; The wind wheel (1) and the hub (2) have a common rotation center axis (1-3), and the wind wheel rotation plane line (1-4) is perpendicular to the rotation center axis (1-3); A rectangular coordinate system is established with the straight line where the blade stacking line (1-2) at the inner end of the blade (1-1) is located as the X-axis and the straight line where the windward side is perpendicular to the X-axis direction is located as the Y-axis.

2. A leeward wind turbine according to claim 1, characterized in that: The angle between the rotation center axis (1-3) and the horizontal plane is the inclination , The angle between the blade stacking line (1-2) where the inner end of the blade (1-1) is located and the wind wheel rotation plane line (1-4) is , , the bottom end of the blade stacking line (1-2) where the inner bottom end of the blade (1-1) is located coincides with the X-axis of the rectangular coordinate system.

3. A leeward wind turbine according to claim 1, characterized in that: When the blade is upward, the vertical force Q1 it receives is less than the vertical force Q2 when it rotates to the vertical downward, that is, Q1 < Q2. The included angle between the resultant force F1 received by the blade (1-1) when it rotates to the vertical upward and the horizontal line is , and the included angle between the resultant force F2 received by the blade (1-1) when it rotates to the vertical downward and the horizontal line is , and the included angles satisfy the relationship .

4. The leeward wind turbine according to claim 1, characterized in that: It comprises 2 to 4 blades (1-1), and the blades (1-1) are distributed in a ring shape around a hub (2).

5. The leeward wind turbine according to claim 1, characterized in that: The horizontal distance L between the top of the outer end of the blade (1-1) and the tower (4) satisfies L>0.25 m.

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