A Parametric Study of the Structural Design for an Advanced Active Twist Rotor

摘要

A parametric study of the structural design for an Advanced Active Twist Rotor (AATR) was conducted by the U.S. Army Vehicle Technology Directorate at NASA Langley Research Center. The goal of this analytical study was to determine the impact of blade structural properties on active-twist performance. A baseline blade model was used to conduct a series of parametric studies to examine how blade active twist, rotor power required, blade loads, and vibratory hub loads are affected by blade torsional, flap-wise, and lag-wise stiffness; section mass and torsional inertia; and center of gravity and elastic axis location. The design variations were analyzed using the second-generation version of the Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD II). The study concluded that the vibration reduction capabilities of a rotor utilizing controlled, strain-induced twisting are improved through reductions in blade torsional stiffness, flap-wise stiffness, and blade mass; increases in torsional inertia, and an aft location of the blade section center of gravity. The capability of blade active twist to reduce rotor power required was found to be generally insensitive to changes in structural properties, providing a less than 0.5 percent reduction in power using 2P actuation at an advance ratio of 0.3. Rotor power required reduction capabilities using active twist were found to be enhanced by a flap-up/nose-down kinematic coupling which amplifies the 2P twist response by modifying the pitch component of the blade first elastic flap mode.