Flutter Stability of Rotors with Fluidic Pitch Links

Investigators - Shawn Treacy, Dr. Christopher D. Rahn, Dr. Edward C. Smith

Due to heavy vibration and loading at the hub, it is important to find ways to reduce rotorcraft vibration and increase performance in order to increase pilot comfort and component life. Replacing rigid pitch links on rotorcraft with fluidic pitch links has the potential to reduce vibratory hub loads and rotor power required. Dr. Lloyd Scarborough used a rotor aeroelastic simulation to show significant reductions in hub forces and moments as well as a modest decrease in rotor power. Dr. Jinhua Zhang expanded upon Scarborough’s work by adding a free-wake model to the aeroelastic simulation in order to explore low forward speed simulations. The results continued to show the potential for vibratory control.

Since fluidic pitch links were shown to provide performance and vibration benefits in isolation, the effect of fluidic pitch links on aeroelastic rotor stability was evaluated. A parametric study showed positive stability impacts for specific combinations of fluidic pitch link parameters. Moving forward, the stability and vibration studies will be combined and experimental validation will be pursued.

Rigid Pitch Link

Fluidic Pitch Link Model

Publications

1. Treacy, S.M., III, Rahn, C. D., Smith, E. C., and Marr, C., “Pitch-Flap Stability of an Articulated Rotor with Fluidic Pitch Links,” Proceedings of the AHS Technical Meeting on Aeromechanics Design for Vertical Lift, San Francisco, CA, January 20–22, 2016.

2. Zhang, J., Scarborough, L. H., III, Smith, E. C., Rahn, C. D., and Jolly, M. R., “Evaluation of Fluidic Pitch Links for Rotor Hub Vibration Controls,” Proceedings of the 40th European Rotorcraft Forum, Southampton, England, September 2–5, 2014.

3. Scarborough, L. H., III, Rahn, C. D., Smith, E. C., Koudela, K. L., and Jolly, M. R., “Impedance Tailored Fluidic Pitch Links for Passive Hub Vibration Control and Improved Rotor Efficiency,” Proceedings of the Fifth Decennial AHS Aeromechanics Specialists’ Conference, San Francisco, CA, January 22–24, 2014.

4. A. Lotfi-Gaskarimahalle, L. Scarborough, C. Rahn, and E. Smith, "Tunable fluidic composite mounts for vibration absorption," Journal of Vibration and Control, Published online before print June 21, 2013, doi: 10.1177/1077546313482340

5. A. Lotfi-Gaskarimahalle, L. Scarborough, C. Rahn, and E. Smith, "Passive and Switched Stiffness Vibration Controllers Using Fluidic Flexible Matrix Composites," ASME Journal of Vibration and Acoustics, Vol. 134, No. 2, 021001 (8 pp.), April 2012.

6. A. Lotfi-Gaskarimahalle, L. Scarborough, C. Rahn, and E. Smith, "Tunable fluidic composite mounts for vibration absorption," Journal of Vibration and Control, (accepted for publication), December 2012.

7. N. Kurczewski, L. Scarborough, C. Rahn, and E. Smith, "Coupled Fluidic Vibration Isolators For Rotorcraft Pitch Link Loads Reduction," 2012 ASME IDETC, DETC2012-70174, Chicago, IL, August 12-15, 2012.

8. L. Scarborough, C. Rahn, E. Smith, and K. Koudela, "Coupled Pitch Links for Multi-Harmonic Isolation Using Fluidic Circuits," 2012 ASME IDETC, DETC2012-70334, Chicago, IL, August 12-15, 2012.

9. L. Scarborough, C. Rahn, and E. Smith, "Fluidic Composite Tunable Vibration Isolators," ASME Journal of Vibration and Acoustics, Vol. 134, 011010 (7 pp.), 2012.

10. L. Scarborough, C. Rahn, and E. Smith, "Fluidic Composite Tunable Vibration Isolators," 2010 ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS2010-3683, September 2010, Philadelphia, PA.

11. A. Lotfi-Gaskarimahalle, L. Scarborough, C. Rahn, and E. Smith, "Passive and Switched Stiffness Vibration Controllers Using Fluidic Flexible Matrix Composites," ASME Journal of Vibration and Acoustics, (accepted, May 2010).