Bladeless wind turbines should be the newest type.
The principle behind Vortex wind power generation is the Karman vortex effect in fluid dynamics, which refers to the fact that when a constant incoming flow bypasses certain objects under certain conditions, the two sides of the object fall periodically. Double linear vortices with opposite directions of rotation and regular arrangement are produced after nonlinear action, a Karman vortex street is formed. For example, water flowing through the pillars of a bridge and wind blowing through towers, chimneys, cables, etc. will form Karman vortices. Once the vortices are large enough, they can cause the structure to oscillate. Vortex takes advantage of this aerodynamic instability to maximize oscillation and capture mechanical energy, then use this mechanical energy to generate electricity. Of course, theThe design of this device is completely different from that of a conventional turbine. It mainly consists of a fixed mast, a generator and a hollow, lightweight, semi-rigid fiberglass cylinder on top. Vortex automatically changes stiffness and “synchronizes” with wind speed to maintain resonance without any mechanical or human intervention. The use of the vortex spill effect for wind power generation represents a technological leap forward in wind power that will produce power more efficiently, cheaper and more environmentally friendly. 'environment. The technology has attracted interest from Harvard University as well as SunEdison's TerraForm renewable energy division, Power, Inc. and Dat Venture.
Vortex Theory of Lift-Type Vertical Axis Wind Turbines
Nowadays, new energy is a very popular trend. There exists ane company Vortex Bladeless in Spain. A bladeless fan has been developed, which does not require particularly large and bulky materials, is less expensive and makes very little noise.
It uses the kinetic energy of the wind to be captured, thus using an induction generator or a piezoelectric generator to convert the kinetic energy of the wind into electrical energy.
The principle uses the Karman vortex effect, which is an important phenomenon in fluid mechanics. It is often found in nature. When the constant flow under certain conditions bypasses certain objects, the object periodically breaks away from both sides. Double-row linear vortices with opposite directions of rotation and a regular arrangement. After non-linear action, a Karman vortex street is formed.
Speaking of Carmen Vortex Street, there is another real-life event. In 1940, a suspension bridge with a main span of 853.4 meterswas built above Tacoma Canyon in Washington State, United States, at a cost of US$6.4. It took 4 months to complete it. Later, on November 7 of the same year, a wind with a speed of 19 meters per second was encountered. Although the wind was not very strong, the bridge experienced violent torsional and amplitude vibrations. became larger and larger until the bridge deck tilted 45 degrees. At about 100 degrees, the downrods were pushed aside one by one, causing the bridge's steel girders to break and collapse, falling into the canyon. He happened to be filming a film on the bridge, recording the initial vibration of the bridge. The entire process of final destruction, it then became the United States Federal Highway Administration investigating the cause of the accident. When people investigated the accident and collected historical data, they were surprised to notice that the vibraBridge damage caused by wind damaged at least 11 suspension bridges between 1818 and the end of the 19th century.
After World War II, research was conducted into the causes of wind damage on the Tacoma Bridge. Von Kármán wrote in his book "The Development of Aerodynamics" in 1954 that the destruction of the Tacoma Narrows Bridge was caused by the resonance of periodic vortices. The designers wanted to build a less expensive structure and used flat sheets to replace the trusses as side walls. . Unfortunately, these flat plates caused vortices to emit, causing the bridge body to begin twisting vibrations. The damage to the bridge was caused by the resonance of vibrations with the emission of vortices.
To put it simply and easily, it is the vibration caused by the change in speed of the fluid passing through the obstacle, which causes it to generate electricity.
The vortex theory was developed in the late 1970s and early 1980s. As with the horizontal axis wind turbine, the wake vortex system of The elevator-type vertical axis wind turbine is first established, and then the Biot-Saffa theorem is used to calculate the induced speed generated by the wake vortex system. By superimposing the induced velocity on the incoming wind speed, the velocity flow field everywhere near the wind rotor is established.
Assume a vertical axis wind turbine with thin lifting blades. The blades do not move in a circular path around the axis, but are constrained to move at a constant speed along a square path. The angle of attack of the road is 0. When a blade advances from the leeward side, according to Kelvin's theorem, in order to maintain conservation of circulation, it must escape a starting vortex and a pair of vorticesleak. When the blade moves forward, the lift force is assumed to be 0 and the attached vortex is released. Continuing on the windward side, the situation is similar.
As the tip speed ratio and number of blades increase, the longitudinal vortex component of the tail vortex disappears, forming an annular vortex system.
As the blade rotates around a fixed axis, its angle of attack changes continuously, that is, the circulation around the blade does not change, so the vortex is continually rejected in the wake of the wind wheel.