Hostname: page-component-cd9895bd7-gxg78 Total loading time: 0 Render date: 2024-12-27T12:24:25.510Z Has data issue: false hasContentIssue false
  • English
  • Français

Effects of rotor blade-tip geometry on helicopter trim and control response

Published online by Cambridge University Press:  10 April 2017

M. Rohin Kumar  and
C. Venkatesan
M. Rohin Kumar*
Affiliation:
Department of Aerospace Engineering, Indian Institute of Technology, Kanpur, India
C. Venkatesan
Affiliation:
Department of Aerospace Engineering, Indian Institute of Technology, Kanpur, India
*
kumar.rohin@gmail.com
Get access Rights & Permissions [Opens in a new window]

Abstract

For performance improvement and noise reduction, swept and anhedral tips have been incorporated in advanced-geometry rotor blades. While there are aerodynamic benefits to these advanced tip geometries, they come at the cost of complicated structural design and weight penalties. The effect of these tip shapes on loads, vibration and aeroelastic response are also unclear. In this study, a comprehensive helicopter aeroelastic analysis which includes rotor-fuselage coupling shall be described and the analysis results for rotor blades with straight tip, tip sweep and tip anhedral shall be presented and compared. The helicopter modelled is a conventional one with a hingeless single main rotor and single tail rotor. The blade undergoes flap, lag, torsion and axial deformations. Tip sweep, pretwist, precone, predroop, torque offset and root offset are included in the model. Aerodynamic model includes Peters-He dynamic wake theory for inflow and the modified ONERA dynamic stall theory for airloads calculations. The complete 6-dof nonlinear equilibrium equations of the fuselage are solved for analysing any general flight condition. Response to pilot control inputs is determined by integrating the full set of nonlinear equations of motion with respect to time. The effects of tip sweep and tip anhedral on structural dynamics, trim characteristics and vehicle response to pilot inputs are presented. It is shown that for blades with tip sweep and tip anhedral/dihedral, the 1/rev harmonics of the root loads reduce while the 4/rev harmonics of the hub loads increase in magnitude. Tip dihedral is shown to induce a reversal of yaw rate for lateral and longitudinal cyclic input.

Keywords

rotor blade tiprotor loadsrotary-wing aeroelasticity
Type
Research Article
Information
The Aeronautical Journal , Volume 121 , Issue 1239 , May 2017 , pp. 637 - 659
Copyright
Copyright © Royal Aeronautical Society 2017 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Footnotes

*

Corresponding author (currently DAAD Research Fellow at DLR, Braunschweig, Germany).

References

REFERENCES

1. Yen, J.G. Effects of blade tip shape on dynamics, cost, weight, aerodynamic performance, and aeroelastic response, J American Helicopter Soc, October 1994, 39, (4), pp 37-45.Google Scholar
2. Celi, R. and Friedmann, P.P. Structural optimization with aeroelastic constraints of rotor blades with straight and swept tips, AIAA J, 1992, 28, (5), pp 928-936.Google Scholar
3. Kim, K.C., and Chopra, I. Aeroelastic analysis of swept, anhedral, and tapered tip rotor blades, J American Helicopter Soc, 1992, 37, (1), pp 15-30.CrossRefGoogle Scholar
4. Bernardini, G., Piccione, E., Anobile, A., Serafini, J. and Gennaretti, M. Optimal design and acoustic assessment of low-vibration rotor blades, International J Rotating Machinery, 2016, 2016.Google Scholar
5. Yuan, K.A., Friedmann, P.P. and Venkatesan, C. A new aeroelastic model for composite rotor blades with straight and swept tips, 33rd AIAA Structural Dynamics & Materials Conference, AIAA 92-2259, April 1992, Dallas, Texas, US.Google Scholar
6. Yuan, K.A. and Friedmann, P.P. Aeroelasticity and structural optimization of composite helicopter rotor blades with swept tips, NASA CR-4665, 1995.CrossRefGoogle Scholar
7. Epps, J.J. and Chandra, R. The natural frequencies of rotating composite beams with tip sweep, J American Helicopter Soc, 1996, 41, (1), pp 29-36.CrossRefGoogle Scholar
8. Panda, B., Assembly of moderate-rotation finite elements used in helicopter rotor dynamics, J American Helicopter Soc, 1987, 32, (4), pp 63-69.Google Scholar
9. Johnson, W. A history of rotorcraft comprehensive analysis, NASA/TP-2012-216012, April 2012.Google Scholar
10. Laxman, V. and Venkatesan, C. Influence of dynamic stall and dynamic wake effects on helicopter trim and rotor loads, J American Helicopter Soc, July 2009, 54, (3).Google Scholar
11. Kumar, M.R. and Venkatesan, C. Rotorcraft aeroelastic analysis using dynamic wake/dynamic stall models and its validation, J Aeroelasticity and Structural Dynamics, 2013, 3, (1).Google Scholar
12. Kumar, M.R. and Venkatesan, C. Aeroelastic analysis of a helicopter in steady maneuver using dynamic wake/dynamic stall models, European Rotorcraft Forum, Moscow, Russia, September 2013.Google Scholar
13. Peters, D.A. and He, C.J. Correlation of measured induced velocities with a finite state wake model, J American Helicopter Soc, July 1991, 36, (3), pp 59-70.CrossRefGoogle Scholar
14. Petot, D., Differential equation modelling of dynamic stall, La Reserche Aerospatiale, Paper No. 1989-5, 1989, pp 59-72.Google Scholar
15. Laxman, V. and Venkatesan, C. Chaotic response of an aerofoil due to structural coupling and dynamic stall, AIAA J, January 2007, 45, pp 271-280.CrossRefGoogle Scholar
16. Padfield, G.D. Helicopter Flight Dynamics. John Wiley & Sons, 2008.Google Scholar
17. GSL – GNU Scientific Library, Available at URL: http://www.gnu.org/software/gsl/.Google Scholar
18. Hopkins, A.S. and Ormiston, R.A. An Examination of selected problems in rotor blade structural mechanics and dynamics, Proceedings of the American Helicopter Society 59th Annual Forum, Phoenix, Arizona, US, May 2003.Google Scholar
19. Bousman, W.G. Putting the aero back into aeroelasticity, Proceedings of the 8th Annual Workshop on Aeroelasticity of Rotorcraft Systems, University Park, Pennsylvania, US, 1999.Google Scholar
20. Yeo, H. and Johnson, W. Assessment of comprehensive analysis calculation of airloads on helicopter rotors, J Aircraft, September 2005, 42, (5), pp 1218-1228.Google Scholar
21. Kumar, M.R. and Venkatesan, C., Effects of blade configuration parameters on helicopter rotor structural dynamics and whirl tower loads, Aeronautical J, 2016, 120 (1224), pp 271-290.CrossRefGoogle Scholar