A New Approach To Rotor Blade Performance Design Improvement

Abstract

An optimal rotor always requires better hover and forward flight performance within the entire flight envelope. With recent advancements in composite material manufacturing technology, it is possible for engineers to produce flyable blades with variable chords. A new approach on how to select an optimal blade planform design is presented in this paper. The fundamental concept is to increase the aerodynamically efficient blade loading surface area, making it produce higher lift in a more effective manner. At the same time, it also reduces the aerodynamically inefficient blade air-loading area, making it produce less drag penalty during flight. This approach results in an overall higher blade aerodynamic efficiency with a planform having variable local blade chords along the radial direction. The shape of the blade differs greatly from that of a conventional design. Five blade planforms with good OGE hover performance are chosen to demonstrate the method. It is interesting to note that the results obtained from the best hover performance configuration has the worst forward flight performance. The modified 4:1 taper from 75% radius to the tip has the best forward flight performance among the five selected configurations. NOMENCLATURE