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| Little knowledge ask! Why do common fans have only 3 blades? |
| Release time:2022-12-22 15:30:31| Viewed： |
Little knowledge ask! Why do common fans have only 3 blades?
One blade fan cannot be seen
......
Huaneng Puyang 500MW Wind Farm Project
The fans with 2, 4 and 6 blades
"Yang Jun uses several sails, and when the wind turns, it stops." -- Song Yingxing, Heavenly Creations
"Six sails are used to irrigate the fields with water, and Huaiyang Sea is used for it." -- Fang Yizhi's "Little Knowledge of Physics"
Human beings have used wind energy as energy for thousands of years. Before the invention of the steam engine, wind energy was an important source of power. Through wind sails, windmills and other forms, wind energy was used to achieve ship navigation, water supply, drinking and irrigation, drainage and farmland, surface grinding, sawing, etc. Zheng He and his huge sailing team sailed to the Western Ocean for seven times. Since the Ming Dynasty, windmills have been widely used in farmland irrigation, drainage and other aspects, which shows that China has long mastered the manufacture and application of wind sails and windmills.
Simulation of Ancient Chinese Windmills Used for Irrigation Farmland
However, the windmills we are most familiar with are still big windmills from the Netherlands, a developed country. These windmills use wind energy to transform into power to drain water, crush crops, process various raw materials, etc., and also form a unique cultural symbol of the Netherlands.
Dutch windmill
However, no matter what impression we have of the Dutch windmill or according to historical records in China, windmills using wind energy can have four blades, six blades or more. Why do modern wind turbines using wind power basically have only three blades?
Guangdong Yuedian Pingyuan Sishui 40 MW Wind Farm Project
Come and discuss the mystery
We know that the purpose of designing, manufacturing and operating wind turbine is to obtain the maximum benefit with the minimum investment under the same wind resource conditions. To put it bluntly, it is to reduce the cost of wind turbine as much as possible and maximize the power generation.
Youyou fans embellish the agricultural photovoltaic integrated photovoltaic project of Yuedian Zhanjiang Fengshou Company
First, from the perspective of power generation: P (mechanical power)=T (torque) × N (speed)/9.55
That is to say, the mechanical power is related to two parameters, one is the torque of the wind turbine and the other is the speed of the wind turbine.(Note: The torque of the wind turbine is also called "torque" because the mechanical components will have a certain degree of torsional deformation under the action of torque. In short, it is the amount of force required to rotate the wind turbine.)
When the design power is determined, the higher the rotor torque, the lower the rotor speed; The lower the rotor torque, the higher the rotor speed.
Is it better to choose high torque or low torque?
When the design power is determined, the same mechanical power is obtained. The higher the speed, the greater the tip speed ratio, the lower the torque, and the lower the manufacturing cost.
Fan structure diagram
Therefore, we should reduce the torque as much as possible, improve the tip speed ratio, obtain greater wind energy utilization coefficient, and obtain greater power generation.
The torque increases with the number of blades. In practical application, the torque of three blades is the lowest compared with four or more blades. The fewer the blades, the higher the speed, and the higher the tip speed ratio.
The fan with two blades
Fan with 2 blades
of course. But what we need to consider is that although the maximum tip speed ratio can be obtained by using two blades, the power generation efficiency decreases, because the torque of using two blades is low, and in low wind speed, the lower torque cannot reach the speed of power generation, so there is no power output.
Secondly, the fewer the blades, the higher the rated speed. The speed is high to a certain extent. The circumferential linear speed of the blade tip is large, which causes large wind resistance. The resistance torque limits the further improvement of power generation and speed.
Vietnam Ningshun Zhengsheng 50 MW Wind Power Project In addition, the fan with two blades is not as efficient as the fan with three blades because of the large gap between the blades. In order to improve the air catching efficiency, the rotor speed of the fan with two blades is usually higher than that of the fan with three blades, which will also increase the fan noise and magnify the visual impact.
AVIC Xiangzhou Baizhang 50 MW Wind Power Project
Therefore, too few blades are not good.
Three blades are convenient for the fan to maintain balance. When the number of blades is too large, the fan is difficult to balance, and the cost is high. Due to the large resistance, the multi blade fan will produce adverse factors that interfere with the rotation of the blade and reduce the energy conversion rate.
Jieyang Shenquan Second Offshore Wind Power Project of State Power Investment Corporation
Therefore, the fan with three blades can obtain the best tip speed ratio, so as to achieve the maximum energy acquisition and maximum power generation efficiency. At the same time, it has the advantages of good balance and low cost. After a long time of verification, the fan with three blades has become the most popular fan form today.
In Shaoguan Nanxiong Liniuping Phase III Wind Farm Project, which can be built in China, under the blue sky and white clouds, and on the top of green peaks, wind gusts slowly rotate, and clean and standardized green power is gathered here and continuously sent to the land of South Guangdong. Huadian Yangjiang Qingzhou Three 500 MW Offshore Wind Power Project, the first offshore deep-water offshore wind farm contracted by China Energy Construction Guangdong Thermal Power Co., Ltd., stands tall in rows on the vast sea and rotates with the wind.....
Huaneng Mengcheng Xutuan Phase II 50 MW Wind Farm Project
So, our The wind turbine adopts the form of three blades, which realizes the best balance of mechanical stability, power generation efficiency, manufacturing and installation feasibility, cost and benefit, and is the best implementation scheme for practical application.
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