This paper examines the effectiveness of an embedded spanwise Coriolis absorber in a rotor blade in reducing the in-plane vibratory hub loads. Simulations based on a light, four-bladed, hingeless rotor helicopter similar to the BO-105 showed that in high-speed flight (140 kt), over 85% reductions in both 4/rev longitudinal and lateral hub shears could nominally be achieved using an absorber mass 3% of the blade mass situated at 60% span, oscillating at 3/rev with an amplitude of about 0.03 ft. If the baseline in-plane vibration levels of the helicopter are increased to 0.1 to 0.12 g, the reduction achieved with the same absorber mass are in the range of 60%-70% while the absorber motion increases to 0.15 ft. The phase of the 3/rev absorber motion is critically important to realizing hub vibration reduction, and the absorber tuning frequency is set to a value close to, but not exactly at 3/rev, to achieve correct phasing. The absorber reduced the 4/rev in-plane hub forces by reducing the magnitude of the 3/rev blade root drag shear while simultaneously reversing the phase of the 3/rev blade root radial shear. The reductions in vibratory hub forces observed at 140-kt high-speed flight condition were largely preserved as the flight speed was reduced to 100 kt cruise condition, without any need for retuning of the absorber.
Rotor vibration reduction using an embedded spanwise absorber
Schwingungsreduzierung bei Hubschrauberrotoren mit einem integrierten, spannweitigen Absorber
Journal of the American Helicopter Society ; 57 , 2 ; 022008/1-022008/12
2012
12 Seiten, 16 Bilder, 4 Tabellen, 19 Quellen
Article (Journal)
English
Rotor Vibration Reduction using an Embedded Spanwise Absorber
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