The Application of Circulation Control by Blowing to Helicopter Rotors

Abstract

Summary:A review of some methods of obtaining augmented lift coefficients in aerofoil sections precedes a description of lift by circulation control by blowing. The basic aerodynamic characteristics are considered as a prelude to a comparison of the merits of their application to helicopter rotors.In calculating the performance of a helicopter rotor which uses high lift coefficients, the determination of the induced power has demanded an extension of the performance estimation curves normally used. A theoretical model has been developed to calculate the induced power factor which suggests a large increase in this parameter for rotor thrust coefficients above the current helicopter operating regime. Experimental results up to thrust coefficients of 0·1 which confirm the theoretical results are presented.Some tentative ideas on the application of circulation control to produce a high speed helicopter are considered.