Dear all,
I am currently working on a design project of an HAWT with a diameter of about 80 m. I was trying to select the best airfoils profiles for the various sections. There are no information about rotor with a diameter > than 50 m.
I was trying to understand the trend going from smaller rotors to larger rotors in terms of airfoils profiles, and it seems to exist in terms of shape, but not necessarily in terms of performance coefficients. Are there any suggestion to take into consideration when dealing with such massive rotors? Which profiles should I prefer?
Thank you for your time.
Hello Francesco,
you can take a look at the reference wind turbines developed and released by the IEA Wind Task 37 (IEAWindTask37 ยท GitHub). They all have rotors larger than 50 m, come with documentation, and model publicly available airfoils. The famous NREL 5MW also has a rotor diameter much bigger than 50 m (https://www.nrel.gov/docs/fy09osti/38060.pdf).
The design of airfoils for very large rotors is certainly a relevant topic of research and turbine manufacturers rely on their own datasets, which are usually characterized by high L/D ratios. Large rotors often use high t/c ratios, certainly >18% and sometimes >21%, to limit the growth in rotor mass. Really small turbines in the kW range were mainly stall controlled. This dictated a specific choice of airfols with mellow stall characteristics at the cost of performance (L/D). Once pitch control became standard, we could design airfoils with a sharper stall and higher performance (L/D). Flatback airfoils are also popular in very large blades, especially to compensate for max chord limitations. You can easily do a literature review on the topic of airfoil design, you will find a lot of publications. Francesco Grasso has nice publications in this area (although not super recent, so keep looking).
I hope this helps.
Best regards,
Pietro Bortolotti