According to the position of the axis of the wind turbine, wind turbines can be divided into horizontal axis wind turbines and vertical axis wind turbines.
(1) Horizontal axis wind turbine: The wind rotor of the horizontal axis wind turbine rotates around a horizontal axis. The rotor axis is parallel to the wind direction. The wind rotor blades are installed radially and. are aligned with the vertical axis of rotation and forming an angle to the plane of rotation of the wind wheel (called installation angle). The number of wind rotor blades is 1 to 10 (usually 3, 5 or 6). It has a high wind energy utilization rate when operating at high speed, but requires high wind speed when starting.
(2) Vertical axis wind turbine: The wind wheel of the vertical axis wind turbine rotates around a vertical axis and the axis of the wind wheel is perpendicular to the wind direction. The advantage is that it can accept wind from any direction, so when the wind direction changes, there is no need to counter the wind.
For the design of horizontal axis wind turbine blades, the blade-impulse element theory is commonly used. The main methods include Glauert method, Wilson method, etc. However, because the blade element theory ignores the flow interference between each blade element, and at the same time ignores the airfoil resistance when designing blades using blade element theory, this simplification inevitably leads to inaccuracy in the results. This simplification has little impact. on the design of the blade shape, but has a greater impact on the wind energy utilization rate of the wind wheel. At the same time, the interference between the blades of the wind wheel is also very strong, and the entire flow is very complex. It is impossible to get resultsaccurate based solely on blade element theory.
The design of vertical-axis wind turbine blades was formerly based on the horizontal-axis design method and relied on blade element theory. Since the flow of vertical axis wind turbine is more complex than that of horizontal axis, it is a typical large separation unsteady flow and is not suitable for analysis and design using blade element theory. This is also an important reason for the vertical axis. The wind turbine has not been developed for a long time.
When the blades of the horizontal axis wind turbine rotate once, they are affected by the combined effects of the force of inertia and gravity. The direction of the inertial force changes at any time, but the direction of gravity always remains. unchanged. In this way, the blades move. They are subjected to an alternating load, whichis very detrimental to the fatigue life of the blade. In addition, horizontal axis generators are placed at an altitude of tens of meters, which brings a lot of inconvenience to the installation, maintenance and inspection of generators.
The blades of the vertical axis wind turbine are much better stressed during rotation than those of the horizontal axis. Since the direction of the force of inertia and gravity always remains unchanged, the blades are subjected to a constant load. The fatigue life is longer than that of horizontal axis wind rotors. At the same time, the vertical axis generator can be placed under the wind wheel or on the ground for easy installation and maintenance.
The leaves of wind power plants measure between 34 meters and 88 meters long. The length of a wind turbine's blades varies depending on the size and model of the wind turbine. Small wind turbines have blade lengths of severalmeters, while large commercial wind turbines can have blade lengths of several tens of meters. MW) Generators with blade lengths between 34 and 45 meters and corresponding tower heights (hub heights) of 65 to 100 meters for wind power of 2 MWFor wind turbines, the blade length is between 48 and 59 meters, and the corresponding hub height is 80 and 100 meters. For 3 MW wind turbines, the blade length is between 44 and 59 meters, and the corresponding hub height is 80 and 110 meters, the longest known wind turbine blade length in the world has reached 88 meters, manufactured by a factory in Denmark. Wind power is the process of using wind energy to operate wind turbines and then converting the wind energy into electricity. This clean energy technology is widely used around the world as it helps reduce dependencyaway from fossil fuels and reducing greenhouse gas emissions.