In recent years, a windmill used as a prime mover is generally called a wind turbine. There are many types of wind turbines successfully developed in various countries in the world. All types of wind turbines include at least blades (some are called blades), wheels, shafts, brackets (some are called towers) and other parts. Among them, the rotating part composed of the blade and the wheel is also called the wind wheel.
According to the relationship between the rotating shaft and the wind direction, wind turbines can be roughly divided into two categories: one is a horizontal axis wind turbine (the rotating axis of the wind rotor is parallel to the wind direction); the other is a vertical axis wind turbine (the rotating axis of the wind rotor is vertical on the ground or in the direction of airflow).
1. Horizontal axis wind turbine
Horizontal axis wind turbines are widely used. In order to make the wind direction face the rotation plane of the wind rotor, a direction adjusting device is generally required to control the wind.
1).Dutch wind turbine
The Dutch windmill was invented by the Dutch in the early 12th century, so it is called “Dutch windmill” and was widely used in Europe (especially the Netherlands, Belgium, Spain and other countries), with a maximum diameter of more than 20m.
This may be the earliest horizontal axis wind turbine to appear.
There are two types of Dutch windmills: one is that the windmill hut can rotate along with the wind direction; the other is only the roof on which the windmill is installed can rotate along with the wind direction.
2).Propeller wind turbine
The propeller-type horizontal axis wind turbine is the wind turbine with the most mature technology and the largest production volume. The airfoil of this wind turbine is similar to the airfoil of an airplane. Generally, it is mostly two-blade or three-blade, and there are also a small number of single-blade or four-blade or more.
The most used wind power generation is the propeller wind turbine, and its appearance is shown in Figure 2.
3). Multi-wing wind turbine
Multi-blade wind turbine (also called multi-blade wind turbine), whose appearance is shown in Figure 3, is generally equipped with about 20 blades, which is a typical low-speed high-torque wind turbine.
Pastures in the central and western United States mostly use it to lift water, and it also has a considerable number of applications in Mexico, Australia, Argentina and other places. There were once as many as millions in the 19th century.
The bicycle wheel wind turbine recently studied by the American Wind Turbine Company is also a multi-blade wind turbine, with 48 hollow blades in a radial configuration, which greatly improves the performance of the multi-blade wind turbine in the past.
4). Centrifugal throw-out wind turbine
Figure 4 is the schematic diagram of the centrifugal throw-out wind turbine, which uses hollow blades. When the wind rotor rotates under the action of the airflow, the air in the blade cavity is thrown out from the tip of the blade due to the centrifugal force, and “sucks” The incoming air flows in from the bottom of the tower. The air turbine coupled with the wind turbine is installed inside the tower bottom, and the accelerated airflow caused by the rotation of the wind wheel at the bottom of the tower is used to push the air turbine and drive the generator to generate electricity.
This design was invented by the French Antonio, so it is also called the Andreau wind turbine. This is a unique design that does not directly utilize natural wind. Due to the complex structure and the large friction loss of air flow in the channel, the overall efficiency of the device is very low. After World War II, the British Fleet Cable Company built this wind turbine in 1953, and no one has made it since. It consists of a hollow tower with a height of 26m and a perforated wind wheel with a diameter of 24.4m.
5). Turbine wind turbine
Turbine wind turbines are also called turbine wind turbines. As shown in Figure 5, their structure is similar to gas turbines and steam turbines, and consists of static blades and moving blades. Due to the short blades and high strength of this wind turbine, it is especially suitable for strong winds, such as the Antarctic and Arctic regions. The turbine-type wind power generation device developed by Professor Awano of Nihon University and used in Antarctica can withstand heavy snowstorms of 40~50m/s in Antarctica.
6). Compressed wind energy type wind turbine
Compressed wind energy type wind turbine (Figure 6) is a specially designed wind turbine. According to the design characteristics, it can be divided into wind collector type (a horn-shaped wind collector is installed on the windward side, and the wind energy is collected through the tightened bell mouth. Gather up and send it to the wind rotor), diffuser type (install a horn-shaped diffuser on the leeward side, and reduce the air pressure behind the wind rotor through the gradually released bell mouth) and wind collection and diffusion type (with the first two structures at the same time).
The device utilizes an air collector or diffuser installed outside the wind turbine impeller to increase the air density passing through the wind rotor, or to increase the air pressure difference on both sides of the wind rotor, thereby improving the effect of wind energy absorption. However, the wind turbine with this structure still has installation and cost problems to be solved.
2. vertical axis wind turbines
Vertical axis wind turbine, the rotation axis of the wind rotor is perpendicular to the ground or the direction of airflow. Compared with the horizontal axis wind turbine, the advantage of the vertical axis wind turbine is that the wind from all directions can be utilized without changing the direction of the wind rotor as the wind direction changes. Due to the symmetry of the structure, this type of wind turbine generally does not need a wind facing device, and the transmission system can be closer to the ground, so the structure is simple, easy to maintain, and also reduces the gyro force when the wind rotor is facing the wind.
1). Sabinus type wind turbine (S type wind turbine)
The Sabonius-type wind turbine was invented by Finnish engineer Savonius in 1924, and is often referred to as the s-type wind turbine in my country. This kind of wind turbine is usually composed of two semi-cylindrical blades, but there are also 3-4 blades. The schematic diagram of its basic structure is shown in Figure 7. It is mainly driven by the resistance difference between the blades on both sides, and has a large starting torque and can generate a large torque. However, given the size, quality and cost of the wind turbine, the power output of the s-type wind turbine is relatively low, and the maximum efficiency does not exceed 10%. In order to increase the power, such wind turbines are often stacked on top of each other, as shown in Figure 8. Some people in developing countries use it to lift water, generate electricity, etc.
2). Darieu type wind turbine (D type wind turbine)
Darrieu wind turbine is a vertical axis wind turbine invented by French engineer G. Darrieus in 1925, often referred to as D-type wind turbine. The common structure, as shown in Figure 9(a), looks like a huge egg beater, with 2~3 blades bent into a bow shape, and the two ends are connected to the top and bottom of the vertical axis, respectively. There are also other styles of Darieu wind turbines such as H-shaped structure. As shown in Figure 9(b), Darieu wind turbines are the most advanced among modern vertical axis wind turbines. For a given rotor mass and cost, has a higher power output, but its starting torque is low. At present, the Darrieu wind turbine is the main competitor of the horizontal axis wind turbine.
3).S type and D type combined type
The Darieu wind turbine is simple in installation and low in cost, but has poor starting performance. Therefore, some people use a D-type wind turbine with good output performance and an S-type wind turbine with good starting performance, as shown in Figure 10.
The structure and principle of the Gorlov vertical axis wind turbine is similar to that of the D-type wind turbine, but it adopts a twisted design, as shown in Figure 11.
4). Rotary turbine wind turbine
The rotary turbine wind turbine is a cross-flow wind turbine propelled by a pressure difference. Its principle is inspired by the ventilator. Rotary turbine power generators have complex structures and high prices. Some of them can change the pitch, have good starting performance, can maintain a certain speed, and have high efficiency. A multi-blade rotating turbine wind turbine is shown in Figure 12 .
3. new wind turbines
1). Cyclone wind turbine
The cyclone type wind turbine (Figure 13) was pioneered by James Ian of Grumman Space Company in the United States. The efficiency of this cyclone-type wind turbine is said to be much more powerful than that of traditional wind turbines.
2). Building wind turbines
With the development of modernization and urbanization, there are more and more high-rise buildings in cities and they are getting taller. These high-rise buildings interfere with local airflow and form a special wind-gathering effect. These high-rise buildings have a lot of energy, and they are in the energy-using center, and a lot of energy can be obtained by making full use of these wind energy. The most typical example is a building with a double tower structure. The narrow passage between them is prone to the “Venturi effect”, forming a tuyere phenomenon. Three institutions in the United Kingdom and scientists from the University of Stuttgart in Germany and the Netherlands have set out to design an office building (Figure 14) that can use the wind power generated by such high-rise buildings. Between the “twin towers” of the building, a The three sets of huge turbine generators, because the sections of the main buildings of the two towers are arc-shaped, can “squeeze” the phoenix to the middle and blow into the turbine, which greatly improves the working efficiency of the wind turbine. When the three sets of turbine blades work at the same time, the electricity generated can meet at least 1/5 of the electricity demand of the building. If the research is successful, it is expected to change the power supply structure of the city.
