OPTIMIZATION THEORY APPLIED TO HIGHER HARMONIC CONTROL OF CIRCULATION CONTROLLED ROTORS

The feasibility of using numerical optimization techniques to determine control inputs to a high speed rotor system employing circulation control aerodynamics was investigated. The objective was to determine the azimuthal loading distribution (cyclic pressure waveform) which would be optimum with respect to performance parameters such as compressor power, mass flow, or peak cyclic pressure. An optimization code, COPES/CONMIN, is coupled with an empirically derived model of the rotor based on cyclic control perturbation derivatives. For specific flight conditions, solutions were obtained for optimum cyclic waveforms. These control inputs were experimentally verified, producing up to a 20 percent reduction in compressor power as compared to the standard one-per-revolution cyclic control. Influences on blade loading are presented along with investigations of blade response to higher harmonic control inputs. The mathematical concepts and procedures used should be applicable to conventional (unblown) rotors.