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Research Papers

Aeroelastic Tailoring of Helicopter Blades

[+] Author and Article Information
Donatien Cornette

Dynamics Department,
Airbus Helicopters,
Marignane Cedex F-13725, France
e-mail: donatien.cornette@isae.fr

Benjamin Kerdreux

Dynamics Engineer
Dynamics Department,
Airbus Helicopters,
Marignane Cedex F-13725, France
e-mail: benjamin.kerdreux@airbus.com

Guilhem Michon

Associate Professor
Université de Toulouse, ISAE,
ICA (Institut Clément Ader),
Toulouse F-31055, France
e-mail: guilhem.michon@isae.fr

Yves Gourinat

Professor
Université de Toulouse, ISAE,
ICA (Institut Clément Ader),
Toulouse F-31055, France
e-mail: yves.gourinat@isae.fr

Pitch corresponds to the rigid rotation along the spanwise axis imposed by the control system, flap is the out-of-plane motion of the blade, lead-lag corresponds to the in-plane motion and torsion deals with the elastic rotation of blade around the spanwise axis. The notation nΩ, corresponding to the nth harmonic of rotation speed, is a pulsation and represents an event that occurs n times per revolution (n/rev).

1Corresponding author.

2Pitch corresponds to the rigid rotation along the spanwise axis imposed by the control system, flap is the out-of-plane motion of the blade, lead-lag corresponds to the in-plane motion and torsion deals with the elastic rotation of blade around the spanwise axis. The notation nΩ, corresponding to the nth harmonic of rotation speed, is a pulsation and represents an event that occurs n times per revolution (n/rev).

Contributed by the Design Engineering Division of ASME for publication in the JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS. Manuscript received March 12, 2014; final manuscript received May 1, 2014; published online April 9, 2015. Assoc. Editor: José L. Escalona.

J. Comput. Nonlinear Dynam 10(6), 061001 (Nov 01, 2015) (12 pages) Paper No: CND-14-1073; doi: 10.1115/1.4027717 History: Received March 12, 2014; Revised May 01, 2014; Online April 09, 2015

The dynamic loads transmitted from the rotor to the airframe are responsible for vibrations, discomfort and alternate stress on components. A new and promising way to minimize vibration is to reduce dynamic loads at their source by performing an aeroelastic optimization of the rotor. This optimization uses couplings between the flapwise-bending motion and the torsion motion. The impacts of elastic couplings (composite anisotropy) and inertial couplings (center-of-gravity offset) on blade dynamic behavior and on dynamic loads are evaluated in this paper. First, analytical results, based on a purely linear modal approach, are given to understand the influence of these couplings on blade dynamic behavior. Then, a complete nonlinear aeroelastic model of the rotor, including elastic and inertial couplings, is derived. Finally, this last model is used to improve a simplified but representative blade (homogeneous beam with constant chord) and results are presented.

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References

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Figures

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Fig. 2

Blue edge™ planform

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Fig. 3

Assumed mode method

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Fig. 5

Induced flow at μ = 0.3

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Fig. 6

Modal shear loads at 4 Ω and 5 Ω normalized by the total shear load: TzinΩ/TznΩ. (a) Tzi4Ω and (b) Tzi5Ω.

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Fig. 7

Modal shear loads at 4 Ω and 5 Ω for a mass without center-of-gravity offset compared to the initial case without mass (dotted line). (a) Tzi4Ω - ωθ1 = 5.3Ω and (b) Tzi5Ω - ωθ1 = 5.3Ω.

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Fig. 8

Modal shear loads at 4 Ω and 5 Ω normalized by the total shear load for a mass position toward the leading edge compared to the case without the mass chordwise offset (dotted line). (a) Tzi4Ω - ωθ1 = 4.3 Ω, (b) Tzi4Ω - ωθ1 = 5.3 Ω, (c) Tzi5Ω - ωθ1 = 4.3 Ω, and (d) Tzi5Ω - ωθ1 = 5.3 Ω.

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Fig. 9

Modal shear loads at 4 Ω and 5 Ω normalized by the total shear load for a mass position toward the trailing edge compared to the case without the mass chordwise offset (dotted line). (a) Tzi4Ω - ωθ1 = 4.3 Ω, (b) Tzi4Ω - ωθ1 = 5.3 Ω, (c) Tzi5Ω - ωθ1 = 4.3 Ω, and (d) Tzi5Ω - ωθ1 = 5.3 Ω.

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Fig. 10

Modal shear loads at 4 Ω and 5 Ω normalized by the total shear load for a mass position toward the leading edge and with bending-torsion stiffness, compared to the case without bending-torsion stiffness and with a mass chordwise offset (dotted line). (a) Tzi4Ω - K45 < 0, (b) Tzi4Ω - K45 > 0, (c) Tzi5Ω - K45 < 0, and (d) Tzi5Ω - K45 > 0.

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Fig. 11

Third flapwise-bending mode aerodynamic generalized load at 4 Ω and 5 Ω compared to the case without bending-torsion stiffness and with a mass chordwise offset (dotted line). (a) Qβ˜34Ω - K45 < 0, (b) Qβ˜34Ω - K45 > 0, (c) Qβ˜35Ω - K45 < 0, and (d) Qβ˜35Ω - K45 > 0.

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