Helicopter Rotor Performance Improvement by Piecewise Dynamic Twist of Rotor Blades

Abstract

Piecewise dynamic twist of rotor blades is studied as a method for reducing rotor power and improving rotor performance. A validated helicopter model is used to predict the rotor power at different flight states. The effects of the parameters of the piecewise dynamic twist, including the phase angle, amplitude, harmonic number, and location, on the rotor performance are investigated. The inboard blade locations with the 1/rev dynamic twist are the most efficient parts to reduce the rotor power at low advance ratios, and the outboard locations are better for high advance ratios. A 2/rev dynamic twist usually can save more power at high advance ratios. Larger twist actuation leads to larger rotor power reduction, while the actuation with fewer actuated piezoelectric patches is more efficient. The dynamic twist with six pairs of the actuated patches is appropriate which can balance the efficiency and power savings. By deploying a piecewise dynamic twist containing the 1/rev and 2/rev twists at the spanwise locations of 10%–40% and 60%–90% of the blade, the rotor power can be significantly reduced and the performance is improved, especially at high advance ratios. A power reduction of 9.0% can be obtained at an advance ratio of 0.375.