Since wind power has become the largest application area of carbon fiber, people in related industries have paid close attention to it. At first, people focused on the automobile field, but it has not developed for various reasons. Inadvertently, a sudden rise in the field of wind power. This is because the application of carbon fiber materials in the field of wind power has developed low-cost, production processes and applications suitable for mass production (see why wind power has become a breakthrough for carbon fiber applications?). This is fundamentally due to the design change of wind power. It is design innovation that has made a significant leap in the application of carbon fiber in wind power.
So what breakthroughs have been made in the design of wind power in recent years?
Fan design changes
The picture above shows the early fan equipment, which was mainly used for agricultural water extraction, power of the mill, etc., while the real first fan for industry was invented by American Charles F. Brush.
Look at the complexity of the original industrial fan. Without mentioning anything else, so many blades are a headache. However, it is also understandable that the more intuitive the concept, the more blades, the more wind that comes into contact, and the higher the efficiency. Until the Danish Poul found that a fan that rotates quickly and has fewer blades is much more efficient than a fan that rotates at a low speed.
Later, many attempts were made, and the number of blades was finally set to three, which was the most effective. This set the shape for modern fans.
Changes in leaf design
From the earliest fans, the leaf shape of the blade is not particular. But with the development of aerodynamics, scientists have begun to pay attention to the research of leaf shape.
How the blade works
Initially, the design of the blade airfoil usually used aerospace advanced airfoil design method.
The aeronautical airfoil is used to design the blade shape. At first, the most widely used NACA series aeronautical airfoil, such as NACA44XX, NA-CA23XX, NACA63XX, and NASA LS. However, these airfoils are very sensitive to the roughness of the leading edge. Once the leading edge becomes rough due to pollution, the performance of the airfoil will be greatly reduced, and the annual output power loss is up to 30%. After realizing that aeronautical airfoils are not suitable for wind power blades, after the mid-1980s, developed countries in wind power began to study blade-specific airfoils and successfully developed wind-power blade-specific airfoil series such as the US Seri and NREL series , Denmark RISO-A series, Sweden FFA-W series and Netherlands DU series. These airfoils have their own advantages. The Seri series has low sensitivity to the surface roughness of the airfoil. The RISO-A series has good stall performance when approaching stall and low sensitivity to the leading edge roughness. The FFA-W series has good rear Stall performance. Fan-specific airfoil will be widely used in wind power blade design.
At present, there are many applications of DU and FFA-W airfoils in large blades. The DU airfoil limits the thickness of the upper surface and has performance characteristics such as low roughness sensitivity and low noise. The airfoil is widely used, from 29m to 100m in diameter, and the maximum power is from 350kW to 3.5MW, such as GE, Repower, Dewind, Suzlon, Gamesa, LM, NEG Mico, and domestic Dongfang Electric and other manufacturers' fan sets. This airfoil has been applied. The FFA-W airfoil has a maximum lift coefficient and lift-to-drag ratio, has good aerodynamic performance under stall conditions, and is not sensitive to the leading edge roughness. For example, LM has adopted Swedish FFA-W airfoil on large fan blades.
Different airfoils have their own characteristics, so different airfoil designs are used in different parts of the actual blades. For example, AAERPAC developed and produced APX45 blades, which are suitable for stall adjustment and pitch control. The blade tip airfoil is NACA632xx, the middle part of the blade is FFA airfoil, and the root part is DU airfoil. Mingyang Wind Power Group has designed and developed a 3MW blade with a blade length of 48.25 meters. The airfoil adopts a hybrid FFA-W airfoil and NACA airfoil. The blade tip adopts NACA63 airfoil.