Rotor performance enhancement via localized pitch control and its effects on hub vibrations and pitch link loads

Abstract

This paper presents an approach to enhance rotor performance and reduce vibration levels at the rotor hub by introducing local blade pitch variations at specific azimuthal locations. Two different variants of these “localized pitch control” (LPC) functions are presented and their effects both on rotor performance and vibrational loads are studied using parametric variation and subsequent numerical optimization of the respective LPC signals. The results are compared with those obtained from a conventional approach using 2/rev higher harmonic control (HHC). Numerical calculations were performed using the DLR’s comprehensive rotor code S4 with a modified Beddoes inflow-model simulating an isolated hingeless rotor at an advance ratio of µ = 0.382. In those simulations power reductions of up to 7.61 and 3.36% could be reached using two sets of different model rotor blades. Both for power reduction and simultaneous reduction of power and 4/rev vibrational loads, LPC performed slightly better than conventional 2/rev HHC but also resulted in higher actuation demands which have to be taken into account for real-world applications of LPC.