Radial and chordwise damped vibration absorbers embedded in the rotor blade are compared for rotor lag damping augmentation. Results show that the radial absorber is more effective in transferring damping to the rotor blade lag mode. The chordwise absorber needs to be at a more outboard location and have a larger mass to introduce levels of lag damping comparable to that introduced by the radial absorber. The 1/rev amplitude of a chordwise absorber at the blade tip, per degree of blade lead-lag motion in forward flight, is of the order of 35 % of the blade chord, and such a stroke might be difficult to accommodate. The 1/rev amplitude of a radial absorber at 70% span (having significantly lower mass than the chordwise absorber and producing comparable lag damping) is of the order of 4% of the rotor blade span. The static displacement of the radial absorber under centrifugal load needs to be limited using a frequency-dependent (high static stiffness, low dynamic stiffness) or nonlinear spring. The chordwise absorber can also undergo a large static displacement under the chordwise component of the centrifugal load if there is an offset from the feather axis, and this would again have to be limited using a strategy such as a frequency-dependent spring. Significant advantages of the radial absorber arehigher lag damping, lower absorber mass, space for absorber mass travel, and no chordwise travel of blade center of gravity reducing susceptibility to aeroelastic instability and dynamic pitch-link loads.


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    Title :

    Embedded absorbers for helicopter rotor lag damping


    Additional title:

    Eingebettete Absorber zur Dämpfung des Rotornachlaufs bei Hubschraubern


    Contributors:

    Published in:

    Journal of Sound and Vibration ; 325 , 4/5 ; 705-721


    Publication date :

    2009


    Size :

    17 Seiten, 27 Bilder, 3 Tabellen, 32 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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