Wind turbine blade
By designing trapezoidal blades with a tip chord length greater than the root chord length, and combining optimized parameters, the problems of low power generation efficiency and high cost of small-sized, low-wind-speed wind turbines have been solved, achieving more efficient and stable wind power generation.
Patent Information
- Application Number
- CN202423157250.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-20
- Publication Date
- 2025-12-09
- Estimated Expiration
- 2034-12-20
AI Technical Summary
The existing design of small-sized, low-wind-speed wind turbine blades follows the design concept of large wind turbines, resulting in low power generation efficiency, high development costs, and increased blade weight.
Design a wind turbine blade with a tip chord length greater than the root chord length and a trapezoidal blade body. Optimize the blade's aerodynamic performance by combining optimized leading-edge radius, trailing-edge radius, maximum thickness, and twist angle.
It improves power generation efficiency in low wind speed environments, reduces noise and vibration, enhances the stability and reliability of wind turbines, and lowers production costs.
Smart Images
Figure CN223647954U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to wind turbine technical field especially is a kind of wind turbine blade. BACKGROUND
[0002] Wind turbine provides a clean, renewable energy source, reduce environmental pollution, for energy security, economic growth, global energy transformation etc. Made a great contribution. And its research in China is mostly based on large wind turbine, relatively less for small size low wind speed wind turbine research. Compared with large wind turbine, small size low wind speed wind turbine has the advantages of small land occupation, low cost, low wind speed condition can better output power, etc. In wind-solar complementary street lamp, city landscape etc. Wind turbine blade is the most basic and key component in wind turbine, its good design, reliable quality and superior performance are one of the determinants of guaranteeing the normal and stable operation of unit.
[0003] Due to the relatively long length of the blade of large wind turbine, the centrifugal force is large when rotating, considering the structural strength of the blade, the tip chord length is relatively short compared to the chord length of other airfoil sections. For small size low wind speed generator, even if the chord length of the tip is appropriately lengthened, the structural strength requirement of the blade can be met. However, the current small size low wind speed wind turbine still continues the design idea of large wind turbine blade, which greatly reduces the power generation efficiency of small wind turbine. In addition, using the design method suitable for large blade for small size low wind speed wind turbine blade design requires increasing the length of the blade and the swept area of the blade, and improving the wind capturing capacity of the blade. This method will increase the weight of the blade and increase the cost of wind power development. SUMMARY
[0004] To solve the technical problems of low wind speed wind turbine blade low power generation efficiency and high development cost, the utility model provides a wind turbine blade.
[0005] A wind turbine blade for low wind speed wind turbine, comprising:
[0006] A blade stem;
[0007] A blade body, comprising:
[0008] A blade root connected to the blade stem;
[0009] A blade tip located at the end of the blade body away from the blade root, which presents a non-contracted blunt surface, wherein
[0010] In any one cross section of the blade body parallel to the blunt surface where the blade tip is located, there is a chord length of the cross section, and the chord length at the blade tip is greater than the chord length at the blade root, so that the blade body presents a trapezoidal shape when it is unfolded, gradually widening from the blade root to the blade tip.
[0011] Preferably, the blade body further comprises a leading edge, which is the side of the blade that the airflow first contacts when the blade is in operation, and the leading edge corresponds to the chord length c of any section of the blade body, and the following relationship exists: the leading edge radius r1 is 0.024c-0.030c.
[0012] Preferably, the leading edge radius r1 is 0.028c.
[0013] Preferably, the blade body further comprises a trailing edge, which is the side of the blade that the airflow leaves the blade when the blade is in operation, and the trailing edge corresponds to the chord length c of any section of the blade body, and the following relationship exists: the trailing edge radius r2 is 0.010c-0.015c.
[0014] Preferably, the trailing edge radius r2 is 0.012c.
[0015] Preferably, the blade body is curved in the width direction, and the upper and lower surfaces of the blade body have different curvatures.
[0016] Preferably, any section of the blade body has a maximum thickness t, and the maximum thickness t and the chord length c of the section have the following relationship: the maximum thickness t is 0.20c-0.30c.
[0017] Preferably, the maximum thickness t is 0.20c.
[0018] Preferably, the blade body is twisted in the length direction, and the twist angle of the twist is 6-10 degrees.
[0019] Preferably, the twist angle is 8 degrees.
[0020] The above technical solution of the utility model has the following advantages compared with the prior art:
[0021] The above technical solution of the wind turbine blade of the utility model has the following advantages compared with the prior art: in the design of the wind turbine blade of the prior art, the chord length of the root is usually greater than the chord length of the tip, and the chord length of the tip of the utility model is greater than the chord length of the root, so that the blade body presents a trapezoidal shape that gradually widens from the root to the tip when it is unfolded. In the case that the total area of the blade does not change, appropriately lengthening the chord length of the tip and shortening the chord length of the root can more significantly increase the torque, thereby improving the power generation efficiency of the wind turbine in a low wind speed environment, and without additionally increasing the development cost of the wind turbine blade. The optimal chord length and twist angle combination obtained through accurate calculation effectively improves the aerodynamic performance of the blade, thereby significantly improving the overall efficiency of the wind turbine. This design not only improves the efficiency of the wind turbine, but also reduces the vibration and noise of the blade, enhances the stability and reliability of the wind turbine. BRIEF DESCRIPTION OF DRAWINGS
[0022] In order to make the content of the utility model more easily be clearly understood, the following according to the specific embodiment of the utility model and combining with the drawings, the utility model is further explained in detail.
[0023] Figure 1 It is the three-dimensional schematic view of the wind turbine blade of the utility model.
[0024] Figure 2 It is the two-dimensional plan view of the wind turbine blade of the utility model.
[0025] Figure 3 It is the section of the wind turbine blade of the utility model along the section line A-A. Figure 2
[0026] Figure 4 It is the torsion angle schematic view of the wind turbine blade of the utility model.
[0027] Figure 5 It is the output power variation curve of the wind turbine blade b of the utility model and the prior art blade a, c with wind speed.
[0028] The description of the drawing mark of the specification is as follows: 1, blade tip; 2, blade root; 3, blade stem; 4, blade body; 5, torsion angle. DETAILED DESCRIPTION
[0029] The utility model is further explained in combination with the drawings and specific embodiments, so that the person skilled in the art can better understand the utility model and can be implemented, but the embodiment is not as the limitation of the utility model.
[0030] As shown in the figure, the wind turbine blade of the utility model is used for low wind speed wind turbine, comprising: Figures 1-4
[0031] Blade stem 3;
[0032] Blade body 4, comprising:
[0033] Blade root 2 is connected to the blade stem 3;
[0034] Blade tip 1 is located at the end of the blade body 4 away from the blade root 2, and it presents a blunt surface of non-constriction, wherein
[0035] In the blade body 4, there is a chord length of the section parallel to the blunt surface where the blade tip 1 is located, and the chord length at the blade tip 1 is greater than the chord length at the blade root 2, so that the blade body 4 presents trapezoidal shape when unfolding gradually from the blade root 2 to the blade tip 1.
[0036] The low wind speed mainly refers to the numerical range of 2m / s-6m / s of wind speed.
[0037] According to the blade element momentum theory, the torque of a wind turbine can be expressed as follows for a wind turbine with N blades, a blade length of R, a blade height position of r, and a blade element chord length of c:
[0038]
[0039] (where p is the air density, w is the relative airflow velocity, and Ct is the tangential force coefficient)
[0040] As can be seen from the above formula, the torque acting on the blade element in the wind turbine plane is proportional to the wind turbine plane radius and the blade element chord length. Compared to lengthening the chord length of other airfoil sections, appropriately lengthening the chord length of the tip 1 can significantly increase the torque, thereby improving the performance of the blade. Therefore, under the condition that the total area of the blade is unchanged, appropriately lengthening the chord length of the tip 1 and shortening the chord length of the root 2 can significantly increase the torque, thereby improving the performance of the blade.
[0041] Three types of blades were designed according to the blade element momentum theory, including a blade a with equal chord lengths of the root 2 and the tip 1, a blade b with a chord length of the tip 1 greater than that of the root 2 according to the technical scheme of the present application, and a blade c with a chord length of the root 2 greater than that of the tip 1. The three types of blades have the same area, and the dimensions are shown in Table 1 below. The three groups of blades used in the experiment were obtained by laser cutting.
[0042] Table 1 Dimensions of the three types of blades a, b, and c
[0043]
[0044] The pitch angle and other parameters of the wind turbine were set to be the same, and the three groups of blades were installed, respectively. The output power of the wind turbine at different wind speeds was measured, and the data is shown in Table 2. The output power curves of the three groups of blades with respect to the wind speed are shown in FIG. 1. Figure 5
[0045] Table 2 Output power of the three groups of blades at different wind speeds (unit: W)
[0046]
[0047] As can be seen, in the wind speed range of 4.34-5.76 m / s, the blade b with the chord length of the tip 1 greater than that of the root 2 has the maximum output power and the best performance, which verifies that the optimization design idea of appropriately lengthening the tip 1 and shortening the root 2 can improve the performance of the blade.
[0048] In the design process of the wind turbine blade, the parameters such as the leading edge radius r1, the trailing edge radius r2, and the maximum thickness t are also considered. The above parameters will be introduced one by one as follows.
[0049] The leading edge radius r1 refers to the radius of the leading edge of the wind turbine blade, i.e. the part where the air flow first contacts, relative to the center of the blade curvature. The leading edge radius r1 should not be too large or too small, a too large leading edge will cause air flow separation, resulting in a decrease in lift and efficiency of the blade; while a too small leading edge can cause unstable flow lines, generating strong vortex, thus increasing the drag and noise of the blade.
[0050] In an alternative embodiment, the blade body 4 further comprises a leading edge, which is the side where the air flow first contacts when the blade is in operation, the leading edge corresponds to the chord length c of any cross section of the blade body 4, and there is a relationship as follows: the leading edge radius r1 is 0.024c-0.030c. Preferably, the leading edge radius r1 is 0.028c.
[0051] The trailing edge radius r2 refers to the trailing edge of the wind turbine blade, i.e. the place where the air flow leaves the blade, relative to the curvature of the blade shape. The design of the trailing edge radius r2 should be coordinated with the design of the leading edge to ensure smooth transition of the air flow and reduce the generation of turbulence. In order to improve the efficiency of the blade, the trailing edge of the modern wind turbine blade is usually designed to be very smooth and sharp.
[0052] In an alternative embodiment, the blade body 4 further comprises a trailing edge, which is the side where the air flow leaves the blade when the blade is in operation, the trailing edge corresponds to the chord length c of any cross section of the blade body 4, and there is a relationship as follows: the trailing edge radius r2 is 0.010c-0.015c. Preferably, the trailing edge radius r2 is 0.012c.
[0053] The maximum thickness t refers to the maximum distance between the upper and lower surfaces perpendicular to the chord line, which is called the maximum thickness t. The thickness distribution of the blade will affect the aerodynamic performance, structural strength and stability of the wind turbine.
[0054] In an alternative embodiment, the blade body 4 is curved in the width direction, and the upper and lower surfaces of the blade body 4 have different curvatures.
[0055] In an alternative embodiment, any cross section of the blade body 4 has a maximum thickness t, and the relationship between the maximum thickness t and the chord length c of the cross section is: the maximum thickness t is 0.20c-0.30c. Preferably, the maximum thickness t is 0.20c.
[0056] Through the derivation of the blade element momentum theory, the relationship between the relative flow angle φ and the output power P can be obtained as follows:
[0057]
[0058] The relationship between the relative flow angle φ and the pitch angle β is as follows:
[0059]
[0060] Based on the above content analysis, the blade angle of attack alpha and the pitch angle beta (the sum of the local twist angle and the local pitch angle) will affect the blade output power, so it is known that the scheme of setting the twist angle 5 of the wind turbine blade has feasibility.
[0061] In an optional embodiment, the blade body 4 is twisted in the length direction, and the twist angle 5 of the twist is 6-10 degrees. Preferably, the twist angle 5 is 8 degrees.
[0062] In summary, through accurate calculation and analysis, it is determined that under the conditions of low wind speed and different wind directions, for the chord length c of any cross section on the blade body 4 of the wind turbine blade, the output power of the blade is relatively high when the leading edge radius r1 is 0.024c-0.030c, the trailing edge radius r2 is 0.010c-0.015c, the maximum thickness t is 0.20c-0.30c, and the twist angle 5 is 6-10 degrees. Preferably, the leading edge radius r1 is 0.028c, the trailing edge radius r2 is 0.012c, the maximum thickness t is 0.2c, and the twist angle 5 is 8 degrees. It should be noted that the above parameter range setting is only an example in the embodiment of the application, and in fact, the parameter settings of the leading edge radius r1, the trailing edge radius r2, the maximum thickness t, and the twist angle 5 are subject to the structural requirements of the wind turbine blade, and the settings of the leading edge radius r1, the trailing edge radius r2, the maximum thickness t, and the twist angle 5 are not specifically limited in the embodiment of the application.
[0063] Compared with the prior art, the utility model has the following beneficial effects:
[0064] First, an arbitrary cross section parallel to the blunt plane where the blade tip 1 is located is taken on the blade body 4, and there is a chord length of the cross section. The chord length at the blade tip 1 is greater than the chord length at the blade root 2, so that the blade body 4 presents a trapezoidal shape gradually widening from the blade root 2 to the blade tip 1 when it is unfolded. According to the blade element momentum theory, under the condition that the total area of the blade is unchanged, appropriately lengthening the chord length of the blade tip 1 and shortening the chord length of the blade root 2 can more significantly increase the torque, thereby improving the power generation efficiency of the wind turbine in a low wind speed environment. In addition, the total area of the blade being unchanged can reduce the use of unnecessary materials, reduce the complexity in the production process, and also does not increase the development cost of the wind turbine blade.
[0065] Secondly, by accurately calculating the best chord length and torsion angle 5 combination, the aerodynamic performance of the blade is effectively improved, thereby significantly improving the overall efficiency of the wind turbine. The larger front edge radius r1 can effectively reduce the separation of the wind flow and reduce the aerodynamic resistance of the blade; the smaller rear edge radius r2 helps to reduce the wake loss and reduce the induced resistance of the blade; the thickness setting can provide sufficient blade stiffness and strength, while not significantly increasing the resistance; the torsion angle 5 design helps to reduce the risk of turbulence and airflow separation during the operation of the wind turbine blade, reduce noise and vibration, and improve the stability and durability of the overall system. This design not only improves the efficiency of the wind turbine, but also reduces the vibration and noise of the blade, enhances the stability and reliability of the fan.
[0066] Obviously, the above embodiments are only examples for the sake of clarity, and are not limited to the embodiments. Based on the above description, those skilled in the art can make other different forms of changes or variations. Here, it is not necessary and impossible to enumerate all the embodiments. The obvious changes and variations derived therefrom are still within the protection scope of the present application.
Claims
1. A wind turbine blade for a low wind speed wind turbine, characterised in that, Comprising: a blade stem; a blade body comprising: a blade root connected to the blade stem; a blade tip at an end of the blade body away from the blade root, presenting a non-converging blunt surface, wherein for any cross section of the blade body parallel to the blunt surface of the blade tip, there is a chord length of the cross section, the chord length at the blade tip is greater than the chord length at the blade root, so that the blade body presents a trapezoidal shape when unfolded, gradually widening from the blade root to the blade tip.
2. A wind turbine blade according to claim 1, characterised in that The blade body further comprises a leading edge, which is a side of the blade body that is first contacted by the air flow when the blade is in operation, the leading edge corresponding to the chord length c of any cross section of the blade body, and there is a relationship that the leading edge radius r1 is 0.024c-0.030c.
3. A wind turbine blade according to claim 2, characterised in that The leading edge radius r1 is 0.028c.
4. A wind turbine blade according to claim 1, characterised in that The blade body further comprises a trailing edge, which is a side of the blade body that is away from the blade when the blade is in operation, the trailing edge corresponding to the chord length c of any cross section of the blade body, and there is a relationship that the trailing edge radius r2 is 0.010c-0.015c.
5. A wind turbine blade according to claim 4, characterised in that The trailing edge radius r2 is 0.012c.
6. A wind turbine blade according to claim 1, characterised in that The blade body presents a curvature in the width direction, and the upper and lower surfaces of the blade body have different curvatures.
7. A wind turbine blade according to claim 6, characterised in that For any cross section of the blade body, there is a maximum thickness t, and the relationship between the maximum thickness t and the chord length c of the cross section is that the maximum thickness t is 0.20c-0.30c.
8. A wind turbine blade according to claim 7, characterised in that The maximum thickness t is 0.20c.
9. A wind turbine blade according to claim 1, characterised in that The blade body presents a twist in the length direction, and the twist angle of the twist is 6-10 degrees.
10. A wind turbine blade according to claim 9, characterised in that The twist angle is 8 degrees.