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  • 1
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    Electric Motor Noise Testing (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: A brief update of the progress towards RVLT Milestone L490 Initial acoustic model for kW class electric motors. A quiet loading device has been created that will allow for acoustic testing of a motor with different loads applied. Testing has also begun on a larger motor, the Scorpion SII-4020. Description of the installation of this motor as well as initial measurements reported. These include acoustic spectra and beamforming for source localization.
    Keywords: Aeronautics (General)
    Type: GRC-E-DAA-TN62182 , Acoustics Technical Working Group; Oct 16, 2018 - Oct 17, 2018; Cleveland, OH; United States|Urban Mobility Noise Working Group Meeting; Oct 18, 2018; Cleveland, OH; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    1/3-Octave Analysis of Core/Combustor-Noise Measurements for the DGEN Aeropropulsion Research Turbofan with Application to Noise Prediction (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This work continues the analysis of data obtained during a 2017 NASA DGEN Aeropropulsion Research Turbofan (DART) core/combustor-noise baseline test in the NASA GRC Aero-Acoustic Propulsion Laboratory (AAPL). The DART is a cost-efficient testbed for the study of core-noise physics and mitigation. Acoustic data were simultaneously acquired using the AAPL overhead microphone array in the engine aft-quadrant farfield, a single midfield microphone, and two infinite-tube-probe sensors for unsteady pressures at the core-nozzle exit. The data are here examined on an 1/3-octave basis as a first step in extending and improving core-noise prediction capability.
    Keywords: Aeronautics (General)
    Type: GRC-E-DAA-TN68115 , AIAA/CEAS Aeroacoustics Conference; May 20, 2019 - May 23, 2019; Delft; Netherlands
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Impact of Azimuthally Controlled Fluidic Chevrons on Jet Noise (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The impact of azimuthally controlled air injection on broadband shock noise and mixing noise for single and dual stream jets was investigated. The single stream experiments focused on noise reduction for low supersonic jet exhausts. Dual stream experiments included high subsonic core and fan conditions and supersonic fan conditions with transonic core conditions. For the dual stream experiments, air was injected into the core stream. Significant reductions in broadband shock noise were achieved in a single jet with an injection mass flow equal to 1.2% of the core mass flow. Injection near the pylon produced greater broadband shock noise reductions than injection at other locations around the nozzle periphery. Air injection into the core stream did not result in broadband shock noise reduction in dual stream jets. Fluidic injection resulted in some mixing noise reductions for both the single and dual stream jets. For subsonic fan and core conditions, the lowest noise levels were obtained when injecting on the side of the nozzle closest to the microphone axis.
    Keywords: Aeronautics (General)
    Type: 14th AIAA CEAS Aeroacoustics Conference; May 05, 2008 - May 07, 2008; Vancouver; Canada
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Electric Motor Noise from Small Quadcopters: Part II - Source Characteristics (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The increased interest in electric motors for aircraft propulsion systems has driven interest in quantifying the contribution of electric motor noise to the overall sound levels and possibly human annoyance of the propulsion system. This work presents acoustic measurements of electric motors used for small quadcopters to quantify the sound produced by a number of outrunner motors with different types of controllers. Results are presented for loaded and unloaded motors as well as installed and uninstalled configurations. Motor resonance frequencies were measured and computed. Current probe measurements showed significant harmonic content in the supply current from the controllers for both the conventional and sinewave controllers. Acoustic results showed motor noise is typically radiated at frequencies near that for azimuthal vibration mode number 2 of the rotor which occurs at roughly 5000 Hz. Electric motor noise was evident in the spectra produced by many of the motor-controller combinations for motors loaded with propellers with levels often greater than those for the motor alone due to increases in the stator magnetic flux density with increased current. An installed quadcopter configuration produced increases in acoustic radiation over that of the uninstalled motor in a frequency range near the 1200 Hz azimuthal vibration mode 1 of the rotor.
    Keywords: Aeronautics (General)
    Type: GRC-E-DAA-TN57549 , AIAA Aviation Forum; Jun 25, 2018 - Jun 29, 2018; Atlanta, GA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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