Acoustic evaluation of the bell 699 rotor on the tiltrotor test rig in the national full-scale aerodynamics complex 40- by 80- foot wind tunnel

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Authors
Shelts, Kelly
Issue Date
2020-12
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Thesis
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en_US
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Abstract

Aircraft noise is a growing problem in the air travel industry [1]. Urban air mobility (UAM) is a new movement to use rotorcraft to fly in and between large cities to alleviate ground traffic congestion [2]. Aircraft noise will affect more people once vehicles start taking off and landing in cities. Tiltrotor vehicles are a promising concept for UAM because of their flight mode versatility. Modern tiltrotors rotate their rotors to take off vertically like a helicopter, then transition to fly forward like an airplane. Tiltrotors do not require runways while maintaining the speed and efficiency of airplanes. Tiltrotor aerodynamics are complex due to the changing flight modes, which creates complex aeroacoustic effects. Full-scale testing is needed to validate present and future acoustic prediction codes so simulations can be done to predict noise for future designs. The National Aeronautics and Space Administration (NASA) collaborated with the United States Army and Air Force to create the Tiltrotor Test Rig (TTR) to increase their proprotor testing capabilities. The TTR can test large, full-scale rotors at higher speeds than any other proprotor test rig. The TTR Checkout Test took place in the National Full-Scale Aerodynamics Complex (NFAC) from 2017 to 2018 to assess TTR function and capabilities. Microphones were used to record acoustic data during the checkout test matrix. This thesis presents and evaluates acoustic results from the TTR Checkout Test. The acoustic results were used to evaluate data processing methods and determine their effect on overall noise metrics in helicopter and airplane mode. Acoustic data quality was determined by evaluating background noise, result repeatability, and signal-to-noise ratio in all flight conditions. Acoustic relationships were identified with relationship to rotor shaft angle, blade loading, and wind tunnel speed.

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Thesis (M.S.)-- Wichita State University, College of Engineering, Dept. of Aerospace Engineering
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Wichita State University
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© Copyright 2020 by Kelly Shelts All Rights Reserved
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