Experimental investigation of the forward flight performance of a MAV-scale cycloidal rotor
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This paper describes the systematic measurements conducted to understand MAV-scale cycloidal rotor (cyclorotor) performance in forward flight. Experimental parametric studies were carried out in an open-jet wind tunnel using a custom built 3-component balance to determine the dependence of rotor performance on the amplitude of blade pitching and its phasing with respect to the wind direction, at different advance ratios. The effect of advance ratio was also studied for different blade kinematics. The effects of blade pitch amplitude and phasing were found to be strongly coupled and their impact on lift, thrust and power were found to vary for different advance ratios. At high forward speeds, the pitching amplitude was found to primarily impact rotor power and thrust whereas the phasing of pitch impacted the net lift. Rotor performance in trimmed flight conditions where the rotor was in level, steady flight was studied. The power requirements, lift-to-drag ratio and control parameters were determined for varying values of lift and rotational speeds corresponding to the trimmed flight conditions. The lift producing efficiency (lift per unit power) of the cyclorotor was found to increase with increasing advance ratio (up to = 0.77). The thrust producing efficiency (thrust per unit power) was found to remain relatively constant with increasing advance ratio (up to = 0.77). For a constant lift and rotational speed, the power requirements decreased with increasing forward speed. For higher values of lift, the power required to maintain trimmed conditions was higher at low speeds. However, the relative differences in power for different values of lift decreased with increasing forwards speeds. For a constant rotational speed of 1740 rpm and lift of 2.82 N, the minimum power occurred at 13 m/s ( = 0.94); the rotor power at 13 m/s was 36% lower than for hover and the lift-to-drag ratio was 1.73. Finally, decreasing the rotational speed (for a constant lift) led to significant decreases in power requirements. At higher flight speeds, the power requirements for the lower rotational speed increased faster than those of higher rotational speeds. 2012 by the authors. Published by the AHS International with permission. All rights reserved.
