Analysis of the adjustment methods of several vertical axis wind turbine airfoils
Wind turbines are diverse, but they can be divided into two categories:
1. The horizontal axis wind turbine, that is, the rotating shaft of the wind wheel is parallel to the wind direction;
2. The vertical axis wind turbine, that is, the rotating shaft of the wind wheel is perpendicular to the ground or the direction of the air flow.
Vertical axis wind turbine
This article mainly describes the vertical axis wind turbine. Vertical axis wind turbines (verTIcalaxiswindturbineVAWT) are mainly classified into resistance type and lift type.
The resistance type vertical axis wind turbine mainly uses the resistance generated by the air flowing through the blade as the driving force, and the lift type uses the lift generated by the air flowing through the blade as the driving force. As the blade rotates, the resistance decreases sharply with the increase of the rotational speed, and the lift increases instead. Therefore, the efficiency of the lift-type vertical-axis wind turbine is much higher than that of the resistance type.
There are several types of vertical-axis wind turbines that use resistance rotation, among which are wind turbines made of flat plates and cups, which are pure resistance devices; S-type windmills with partial lift, but mainly resistance devices. These devices have a large starting torque, but have a low tip speed ratio and provide a low power output with a certain size, weight and cost of the rotor.
The Darryl wind wheel was invented by the French G.J.M Darieu in the 1930s. In the 1970s, the Canadian National Academy of Sciences conducted extensive research on this and was the main competitor of horizontal-axis wind turbines. The Darryl type wind wheel is a lifting device. The curved blade has a profile of airfoil. Its starting torque is low, but the tip speed ratio can be high. It has a high power output for a given wind wheel weight and cost. . There are many types of Darrying wind turbines in the world, such as Φ type, Δ type, Y type and H type. These wind wheels can be designed as single, double, triple or multi-blade.
It has been more than 180 years since Darrier invented the lift-type vertical-axis wind turbine, but it has not been widely used, mainly because of its own shortcomings that hinder the application. The failure to self-start is an important shortcoming, but the main disadvantage is that the range of variation of the wind and the range of the load are too narrow, which also involves the disadvantage that it cannot be adjusted.
