Some practical issues in the computational design of airfoils for the helicopter main rotor blades

Abstract

Very important requirement for the helicopter rotor airfoils is zero, or nearly zero moment coefficient about the aerodynamic center. Unlike the old technologies used for metal blades, modern production involving application of plastic composites has imposed the necessity of adding a flat tab extension to the blade trailing edge, thus changing the original airfoil shape. Using computer program TRANPRO, the author has developed and verified an algorithm for numerical analysis in this design stage, applied it on asymmetrical reflex camber airfoils, determined the influence of angular tab positioning on the moment coefficient value and redesigned some existing airfoils to include properly positioned tabs that satisfy very low moment coefficient requirement. .Jedan od veoma vaznih zahteva koji aeroprofili rotora helikoptera treba da ispune jeste da koeficijent momenta oko aerodinamickog centra mora priblizno biti jednak nuli. Za razliku od starijih tehnologija, koriscenih u proizvodnji metalnih lopatica, savremene izvedbe koje se baziraju na primeni plasticnih kompozita zahtevaju da se na izlaznoj ivici doda ravan repic, cime se menja izvorni oblik aeroprofila. Uz pomoc kompjuterskog programa TRANPRO, autor je razvio i verifikavao algoritam za ovu fazu projektovanja, namenjen promeni na nesimetricnim aeroprofilima sa srednjom linijom u obliku latinicnog slova ?S?, kvantifikavao globalni uticaj ugaonog polozaja repica na promenu momenta oko aerodinamickog centra, a zatim reprojektovao nekoliko aeroprofila kojima je dodao repic na takav nacin da je zahtev za malom vrednoscu ovog koeficijenta momenta u potpunosti ispunjen. .