Active Vibration and Noise Alleviation in Rotorcraft Using Microflaps.

Helicopter Vibration and Noise Reduction Using Microflaps;Aerospace Engineering;Engineering;Aerospace Engineering

Padthe, Ashwani KumarEpureanu, Bogdan ;

University of Michigan

关键词: Helicopter Vibration and Noise Reduction Using Microflaps;    Aerospace Engineering;    Engineering;    Aerospace Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/89750/akpadthe_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

This work presents a comprehensive analysis of active Gurney flaps, or microflaps,for on blade control of noise and vibration in rotorcraft. The initial portionof the work considered the two-dimensional unsteady aerodynamic characteristicsof three different oscillating microflap configurations using a compressiblecomputational fluid dynamics (CFD) flow solver. Among these the configurationmost suitable for rotorcraft applications was chosen. An unsteady reducedorder aerodynamic model (ROM) was developed for the microflap using the RationalFunction Approximation approach and CFD based oscillatory aerodynamicload data. The resulting ROM is a state-space, time-domain model that accountsfor unsteadiness, compressibility and time-varying freestream effects. The ROMwas validated against direct CFD calculations for a wide range of flow conditionsshowing excellent agreement.Subsequently, the ROM was then incorporated into a comprehensive rotorcraftsimulation code featuring a free-wake model, an acoustic prediction tool, and fullycoupled flap-lag-torsional blade dynamics. The higher harmonic control (HHC)algorithm was used to simulate closed-loop active control with a 1.5% chord microflapon a hingeless rotor configuration resembling the MBB BO-105. Three spanwiseconfigurations, single, dual, and a five-microflap configuration were considered.Results indicate that the microflap can achieve reductions ranging from 3-6dB in the blade-vortex interaction (BVI) noise. Vibration reduction ranging from70-90% was also demonstrated at both low-speed and high-speed flight conditions.It was also found that reduction in BVI noise results in an increase in vibrations andvice versa, a trend also noted in previous active control studies.Next, simultaneous BVI noise and vibration reduction was studied. A reductionof 2-3 dB in the advancing and retreating side noise combined with a 55%reduction in the vibratory loads was achieved using the five-microflap configuration.The 1.5% chord microflap was also compared to a 20% chord plain trailingedgeflap showing similar effectiveness in reducing vibration and noise. Finally,a new approach for dealing with actuator saturation in the HHC algorithm wasdeveloped using nonlinear constrained optimization techniques. The optimizationapproach takes less computational time compared to the previous approacheswhile yielding better performance in the case of multiple control surfaces.