Application of wide and thin blades for wind turbines
Among the components of the wind power generator, the wind wheel and the blade are energy harvesting mechanisms of the wind power generator. At present, small and medium-sized wind turbines on the market generally use dead paddle wheels. There is only one fixed form of the blade on the wind wheel. No matter what kind of wind condition, the blade and the wind wheel will not have relative motion. This kind of dead paddle wheel will try its best to study the fan blade, study the blade material, make the blade material lighter and ensure the strength as much as possible; in addition, it takes a lot of effort to study the wing shape of the fan blade, as much as possible The blade wing structure conforms to the current aerodynamic principle and meets the existing theoretical requirements. It is expected to make a breakthrough in the design of the wing shape, so that the wind turbine has a lower starting wind speed and a relatively low rated wind speed.
It is not difficult to find that the current small wind turbine blade material is mostly FRP, and the blade form is basically characterized by wide roots and narrow and thin tips. The blades generally have their own shape characteristics, namely the wing shape. After the blade is assembled with the wind wheel, the different parts of the blade and the plane of the wind wheel are at different angles to make it easy to start as much as possible, and at the same time, there is a certain rotation speed during the rotation of the wind wheel.
Because there is no relative motion between the wind wheel and the blade, that is, there is no pitching action, it can only be studied on the wing shape of the blade, but the wing structure has its limit state after all, if it is a breakthrough in the performance of the wind wheel, simply Considering the wing shape is already incapable. The pitch wind wheel can solve the problem that the wind wheel needs different wing shape or blade windward state in different states. Simplifies the wing design of small wind turbines while improving performance.
The existing wind turbine blade has a relatively large root and a large angle; the top of the blade becomes narrower and smaller, and the angle is small. This design mainly considers the use of the root wing shape to obtain greater impulse and kinetic energy, which is easy to start; the upper part of the blade is narrowed and the angle becomes smaller. The main consideration is to reduce the air resistance during the rotation of the blade, so that the blade can be rotated more easily after starting. High speed. At the same time, the wide wing shape and narrow top shape help to ensure the strength of the existing material.
Several characteristics of the blade are discussed below:
1, blade angle
It has been found that when the angle of the blade of the wind turbine is large, it is easy to start and the starting wind speed is low; however, during the rotation after starting, the angle is greatly affected by the air resistance, the rotation speed is limited, and the rotation speed is not high. When the blade angle is small, it is not easy to start, and the starting wind speed is high; however, during the rotation after starting, the blade is subjected to small air resistance, the rotor rotates at a high speed, and it is easy to obtain a higher rotation speed. However, the angle of the blade of the wind turbine is relatively less affected by the gust, the wind speed is reduced, the rotation speed is rapidly decreased or even stopped.
2, blade quality
The small quality of the blade is easy to start, and the quality of the blade is not easy to start. The reason why the wind wheel is from stationary to rotating is that the air particles hit the blade continuously to bring the impulse to the blade. When the impulse reaches a certain level, the blade starts to move from the static state, so the blade quality is smaller and it is easier to obtain the required impulse at the start. Similarly, during the rotation process, the blade has a small mass and its required rotational kinetic energy is small, which is beneficial to the conversion of wind energy; the large mass itself requires a large rotational kinetic energy, which is not conducive to the conversion of wind energy. Therefore, in the case of ensuring the strength, the blade light will be more favorable for the start and rotation of the wind wheel.
3, the thickness of the blade
The blade thickness is not conducive to rotation, and the blade is thin to facilitate rotation. The wind turbine has the same airfoil shape, and the blade has a large air resistance during the rotation process, which is not conducive to the rotation of the wind wheel; the air resistance of the blade thin during the rotation is small, which is beneficial to the rotation of the wind wheel; meanwhile, if the same material, the blade thickness Its quality is also large, which is not conducive to the rotation of the wind wheel.
4, the width of the blade
The blade width is beneficial to the blade to obtain energy, and the narrow blade is beneficial to reduce the air resistance during the blade rotation. The two sets of wind turbine blades with the same pitch angle, the blade wide wind wheel is more likely to obtain wind energy during the starting process, the wind wheel is easy to start, and the starting wind speed is low; however, during the rotation of the wind wheel after starting, the blade width is wide and the air resistance is received. It is also large, it is not easy to obtain a high speed, the speed does not go up, and the speed is low. The narrow wind wheel of the blade is not easy to obtain wind energy during the starting process, the wind wheel is not easy to start, and the starting wind speed is high; however, during the rotation process after the wind wheel is started, the blade is narrow, and the air resistance is small, and it is easy to obtain as the wind speed increases. High speed.
5, the blade concavity
The blade is concave in the wind, which is beneficial to obtain wind energy; the blade is convex in the wind, which is not conducive to obtaining wind energy. When the external conditions are the same, when the wind turbine blade is concave in the wind, the wind passes through the surface of the blade, and the blade has greater resistance to the wind. The blade is more likely to capture air particles, and it is easier to obtain and absorb wind energy, and the convex surface of the blade is more favorable to the wind. The air resistance is reduced during the rotation of the wheel; when the windward blade is convex to the wind, the resistance of the blade to the wind is small, which is beneficial to the wind passing through the surface of the blade, which is not conducive to the capture of air particles by the blade, which is not conducive to the capture and absorption of wind energy by the blade.
6, the number of blades
The number of blades is more favorable for the wind wheel to obtain energy, the wind wheel is easy to start, and the rotation speed of the wind wheel is slow after starting; the number of blades is not favorable for the wind wheel to obtain energy, the wind wheel is relatively easy to start, and the rotation speed of the wind wheel is fast after starting. The blade has the same airfoil shape, and the wind turbine blade is more likely to capture the wind energy passing through the wind wheel. The wind wheel is easy to start and the starting wind speed is low; however, during the rotation of the wind wheel, there are many blades, and the air resistance is large, and the wind wheel is difficult. A very high speed is achieved. The number of blades of the wind wheel is not easy to obtain the required impulse at the start, the wind wheel is not easy to start, and the starting wind speed is high; however, during the rotation process, the blade has less air, less air resistance, and the wind wheel is easier to obtain. High speed.
