Rotating fan blades do not produce eddy currents
When I saw this picture, I remembered discussing a turbulence generated when the blades of the wind turbine turned at a wind power seminar 10 years ago, which would affect the efficiency of power generation. I proposed that the fan blades will not produce vortex when rotating, and someone told me that this is against aerodynamics.
To this end, I wrote this short article to explain my views. In 2016, Siemens sent me a message to collect papers and sent this short article.Maybe there was some misunderstanding in the expression, I did not receive a reply.
Rotating fan blades do not produce eddy currents
I saw a discussion about the fan blade wake in a book << Wind Energy Technology >>. This is what says: "The wake from the tip of a wind turbine blade is the same as the tail vortex of the wing tip. As shown in Figure 3.17, because the blade tip moves in a circle, it leaves a spiral tail Vortex. The downstream of this wake vortex creates convection with the wake velocity. "" Tony Bueton> America. "
People in real life often use habitual thinking, and they will have a habit of identifying with two similar but different properties without thinking about it. During the flight, the trailing edge of the wing will produce wake, which has been confirmed in aerodynamic experiments. Because the fan blades are similar to the wings of an aircraft, some people think that the fan blades will also generate wake when rotating, which affects the efficiency of power generation. When this idea was accepted by many wind power experts who did not think about it, that absurd understanding became the truth.
Whether the fan blades will generate vortex when the fan rotates, let's start with how the vortex is generated.
For example, in a normal driving car, the front of the car will be subjected to air resistance, and the rear of the air car will have a certain negative pressure compared to the front of the car. The surrounding air will fill this negative pressure, and the vortex will be generated. The speed is not the vortex behind the car, but the air resistance of the car on the head. There is a certainty that whether cars or airplanes have in common is driving and flying on their own power.
The fan will not rotate by itself. Only when driven by a certain wind speed, the blades of the fan will be pushed and rotated by the wind. When the fan blades are driven by the wind, there is no disturbance to the air. How can there be "eddy currents"? This is not the same as the aerodynamics formed by the trailing edge of an airplane wing in flight.
I have seen Siemens company show a peculiar fan blade. The trailing edge of the blade tip of the fan blade is serrated. It is said that this can well destroy the occurrence of vortex. I really want to have face-to-face discussions with authoritative experts from Siemens. It is estimated that this possibility is unlikely.
When it comes to affecting the power generation efficiency of wind turbines, I think it is also impossible to stick to habitual thinking. Scaling up the size of the fan in proportion does not solve the actual problem. The power generation efficiency of the fan is not improved, but it only takes up and consumes more resources. If it does not change, it may be replaced at some time in the future. Please believe that this is not a joke.
The article has some changes