Rotor blade lag damping using embedded chordwise absorbers.

摘要

The feasibility of helicopter blade lag damping using embedded chordwise absorbers is investigated. The basic feature of this approach is the use of tuned vibration absorbers along the blades. This concept, utilizing a portion of the leading edge weights that are already incorporated into the blade as a part of the mass of the absorbers, may have the potential to replace current blade lag dampers and reduce complexity, aerodynamic drag, and weight. The effectiveness of the embedded absorbers is evaluated by analyzing and testing blade lag damping and rotor system aeromechanical stability.; An aeromechanical stability analysis of the rotor system with embedded chordwise absorbers is developed. The rotor blade is modeled as an elastic beam undergoing axial, flapwise, lagwise, and torsional deflections. The fuselage is modeled as a rigid body with roll and pitch rotations about its center of mass. Each embedded absorber is modeled as a mass-spring pair. The rotor-absorber-fuselage system equations of motion are formulated using Hamilton's Principle and spatially discretized using the finite element method. The modal frequencies and damping of the system are found using complex eigenvalue solutions of the linearized equations.; A rigid blade-absorber model is developed to explore the dynamic response of the embedded absorbers, including the static and steady-state dynamic response, and to examine the effect of the embedded absorber on rotor blade aeroelastic stability, including flap-lag flutter, pitch-flap flutter, and pitch divergence.; A small-scale model rotor system with embedded absorbers is designed and constructed. A set of experiments measuring blade lag frequency and damping is conducted. The effects of some key issues, including absorber mass, location, and tuning frequency, are examined experimentally.; The analytical results are correlated with the experimental data. The theoretical lag frequencies and damping of the blade with embedded absorbers are in good agreement with the experimental data. The aeromechanical stability analysis of the rotor-fuselage system also shows a good agreement with the experimental data. The theoretical and experimental results both show promising blade lag damping augmentation using embedded chordwise absorbers. The blade damping augmentation using embedded chordwise absorber varies from 0.3% to 15% critical damping ratio, depending on blade and absorber parameters. The ground resonance stability analysis of the hingeless rotor system and articulated rotor system shows that the blade lag damping augmentation using embedded chordwise absorbers improves the ground resonance stability. (Abstract shortened by UMI.)