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1. Wooden blades and cloth skin blades
Near-micro and small wind turbines also use wooden blades, but wooden blades are not easy to be twisted.
2. Steel beam fiberglass skin blade
In modern times, the blade adopts steel pipe or D-shaped steel as the longitudinal beam, steel plate as the rib beam, and the structure is filled with foam plastic and covered with glass fiber reinforced plastic skin. It is generally used in large wind turbines.
3. Aluminum alloy extruded blades with equal chord length
The blades of equal chord length extruded from aluminum alloys are easy to manufacture, and can be produced in contact with each other, and can be twisted according to the design requirements. The shaft and flange connecting the blade root to the hub can be realized by welding or bolting.
4. FRP blades
FRP reinforced plastic has high strength, light weight and aging resistance. The surface can be re-wrapped with glass fiber and epoxy resin, and other parts are filled with foam plastic. The main function of foam in the blade is to reduce the quality of the blade while ensuring its stability, so that the blade can increase the wind catching area while satisfying the stiffness.
5. Carbon fiber composite blades
The stiffness of carbon fiber composite blades is two to three times that of FRP composite blades. Although the performance of carbon fiber composite materials is much better than that of glass fiber composite materials, the price is expensive, which affects its wide application in wind power generation. Therefore, major composite material companies around the world are conducting in-depth research on raw materials, process technology, quality control and other aspects in order to reduce costs.
The shape design and number of blades of wind turbine blades are determined only after complex theoretical calculations and wind tunnel experiments. The results show that, in general, the fewer blades of the wind rotor, the higher the rotation speed of the blades; the more blades, the lower the rotation speed of the rotor. Therefore, a rotor with less than three blades is generally considered to be a high-speed rotor, while a rotor with more than three blades is a low-speed rotor.
For an impeller with the same self-weight, the blades can be made longer, and the circle area drawn by the blades during rotation (the total surface area of the wind) is larger, so the speed is faster and the power generation efficiency is higher. On the contrary, if more blades are used, the blades can only be made shorter under the premise that the total area of the blades remains unchanged, the total area of the blades affected by the wind is smaller when the blades rotate, the speed is slower, and the power generation efficiency is also reduced. lower.
Pultruded FRP reinforced blades have good durability and corrosion resistance, acid, alkali and atmospheric corrosion resistance, no need for regular maintenance, uniform material, strong flexibility, consistent size, standard weight, smooth surface, etc. Mainly used for: wind turbines, wind water lifters, highway anti-glare boards.
Most rotor blades on large wind turbines are made of fiberglass reinforced plastic (GRP). Using carbon fiber or aramid as reinforcement is another option, but such blades are not economical for large wind turbines. Wood, epoxy wood, or epoxy wood fiber composites are not currently available in the rotor blade market, although there are currently developments in this area. Steel and aluminum alloys have problems such as weight and metal fatigue, respectively, and they are currently only used in small wind turbines.
The working principle and structure of the blower
Working principle and structure of blower Rotor: consists of shaft, impeller, bearing, synchronous gear, coupling, bushing, etc. Impeller: select involute profile, high volume utilization rate.
Bearings: Type 3000 double row radial spherical roller bearings are selected as the positioning end near the coupling end. 32000 type single row radial short cylindrical roller bearing is selected as the free end near the gear end to adapt to the axial displacement of the rotor during thermal expansion.
Synchronous gear: It is composed of a ring gear and a hub, which is easy to adjust the impeller clearance.
Body: It consists of a casing and left and right wall panels. The left and right wall panels and the bearing seats and sealing parts installed in the left and right wall panels can be used in common with each other.
Base: The medium and small fans are equipped with a common base, and the large fan is only equipped with a fan base, which is easy to install and debug. Lubrication: The gears are immersed and the bearings are splash lubricated. Good lubrication effect, safe and reliable.
Transmission mode: The coupling is mainly connected directly. If the performance specification requires, the V-belt pulley speed change method can also be used. The coupling adopts elastic coupling, which can alleviate the impact and compensate a small amount of axis deviation. In addition to the motor as the driver, the large flow fan can also use a steam turbine or other drivers. working principle
The working principle of centrifugal blower
The working principle of a centrifugal blower is similar to that of a centrifugal fan, except that the compression process of air is usually carried out by several working impellers (or several stages) under the action of centrifugal force. The blower has a rotor that rotates at a high speed. The blades on the rotor drive the air to move at a high speed. The centrifugal force makes the air flow to the fan outlet along the involute in the involute-shaped casing. The high-speed airflow has a certain wind pressure. Fresh air is fed from the center of the enclosure.
The working principle of the single-stage high-speed centrifugal fan is as follows: the prime mover drives the impeller to rotate at a high speed through the shaft, and the airflow enters the high-speed rotating impeller from the inlet axial direction and becomes a radial flow to be accelerated, and then enters the diffuser cavity, changing the flow direction and decelerating, This deceleration effect converts the kinetic energy in the high-speed rotating airflow into pressure energy (potential energy), so that the fan outlet maintains a stable pressure.
Theoretically speaking, the pressure-flow characteristic curve of a centrifugal blower is a straight line, but due to frictional resistance and other losses inside the fan, the actual pressure-flow characteristic curve decreases smoothly with the increase of flow rate, and the corresponding centrifugal fan’s power – The flow curve rises with increasing flow. When the fan runs at a constant speed, the operating point of the fan will move along the pressure-flow characteristic curve. The operating point of the fan during operation depends not only on its own performance, but also on the characteristics of the system. When the resistance of the pipeline network increases, the pipeline performance curve will become steeper. The basic principle of fan adjustment is to obtain the required working conditions by changing the performance curve of the fan itself or the characteristic curve of the external pipe network.
The principle and characteristics of frequency conversion control
With the continuous development of science and technology, AC motor speed regulation technology is widely used. Through a new generation of fully-controlled electronic components, the frequency converter is used to change the speed of the AC motor to control the flow of the fan, which can greatly reduce the energy loss caused by the previous mechanical control of the flow. Energy saving principle of frequency conversion regulation:
When the air volume needs to be reduced from Q1 to Q2, if the throttling adjustment method is adopted, the operating point is from A to B, the wind pressure increases to H2, and the shaft power P2 decreases, but the reduction is not too much.