Spanwise-segmented TEFs were examined for rotorcraft power reduction. Four TEFs extending from 50- 60%, 60-70%, 70-80% and 80-90% span were considered, and actuated at frequencies of up to 2/rev. A gradient-based optimization scheme was used to determine the optimal deployment of the TEFs that minimized total rotor power, while satisfying vehicle trim. The effect of the TEFs was examined at moderate to very high speeds, and for low through high aircraft grossweights. The studies were based on a UH-60A type aircraft. In the analysis lift and drag increments associated with TEF deployment (obtained from CFD computation) were added to airfoil properties of the base SC-1094R8 airfoil. A prescribed wake was used to calculate the inflow around the rotor disk and this allowed for a proper representation of the change in bound and trailed vorticity associated with local changes in lift when a MiTE was deployed. From the study it was observed that the most significant change in trim parameters associated with deployment of the TEFs was a reduction of rotor collective pitch. At high gross-weights and advance ratios reductions in rotor power of up to nearly 8% were observed for a 8 deg linear blade twist (is fairly representative of the twist seen on many rotor blades), and up to 5.65% when the nonlinear twist of the UH-60 was considered. The TEF actuation results in a more optimal airload distribution. In all cases, the tips were offloaded and lift was moved inboard. Although this resulted in a slight increase in drag inboard, the large reduction in drag along the outer rim of the rotor disk and the large moment arm result in a net reduction in rotor torque and power requirement. The power reduction was predominantly due to a reduction in rotor profile power, especially so at higher gross weights and advance ratios. The smaller reductions in power for the blade with the nonlinear twist are attributed to a better starting configuration (lower power requirement of the baseline), and the fact that at high speeds and gross weights, the optimal TEF deployment schedule increased the negative lift on the advancing blade tip and consequently the drag in those regions, which partially negated the overall benefits.
Rotor power reduction using multiple spanwise-segmented, optimally-actuated trailing-edge flaps
2009
15 Seiten, 19 Bilder, 12 Tabellen, 28 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
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