Noise Reduction Potential of Phase Control for Distributed Propulsion Vehicles

Pascioni, Kyle A.; Rizzi, Stephen A.; Schiller, Noah H.

doi:10.2514/6.2019-1069

Cited by 30 publications

(9 citation statements)

References 10 publications

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“…Pascioni, Rizzi, and Schiller demonstrated the potential of rotor phasing to reduce the noise of multi-rotor aircraft, although the phase synchronization must be accurately controlled. 194 Further evidence for this was provided in previous work by the authors, in which interference patterns in the noise directivity of multiple constant speed rotors were observed due to coherent phase relations between the rotors; in contrast, the noise of the variable speed rotors did not add coherently (Ref. 192, Figures 21 and 22).…”

Section: Full Vehicle Noise Characterizationmentioning

confidence: 71%

Challenges and opportunities for low noise electric aircraft

Greenwood

Brentner

Rau

et al. 2022

International Journal of Aeroacoustics

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A new class of electric aircraft is being developed to transport people and goods as a part of the urban and regional transportation infrastructure. To gain public acceptance of these operations, these aircraft need to be much quieter than conventional airplanes and helicopters. This article seeks to review and summarize the aeroacoustic research relevant to this new category of aircraft. First, a brief review of the history of electric aircraft is provided, with an emphasis on how these aircraft differ from conventional aircraft. Next, the physics of rotor noise generation are reviewed, and the noise sources most likely to be of concern for electric aircraft are highlighted. These are divided into deterministic and nondeterministic sources of noise. Deterministic noise is expected to be dominated by the unsteady loading noise caused by the aerodynamic interactions between components. Nondeterministic noise will be generated by the interaction of the rotor or propeller blades with turbulence from ingested wakes, the atmosphere, and self-generated in the boundary layer. The literature for these noise sources is reviewed with a focus on applicability to electric aircraft. Challenges faced by the aeroacoustician in understanding the noise generation of electric aircraft are then identified, as well as the new opportunities for the prediction and reduction of electric aircraft noise that may be enabled by advances in computational aeroacoustics, flight simulation, and autonomy.

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Section: Full Vehicle Noise Characterizationmentioning

confidence: 71%

Challenges and opportunities for low noise electric aircraft

Greenwood

Brentner

Rau

et al. 2022

International Journal of Aeroacoustics

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“…Huff et al [92] reported that the noise generated by the electric motor system alone was 8-20 dB below the fan noise for a regional jet-sized aircraft, and 17-29 dB lower than that of a single-aisle commercial transport class aircraft. While the proximity of the propulsive system with the airframe is normally a source of important tonal noise, the multiplicity of propulsors opens interesting perspectives for noise control via an adequate clocking of the propellers [90,93]. The flexibility offered by DEP systems permits placing the propulsors over the airframe in such a way to enhance noise shielding effects.…”

Section: Noise Mitigation For Dep Systemsmentioning

confidence: 99%

The Enabling Technologies for a Quasi-Zero Emissions Commuter Aircraft

et al. 2022

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The desire for greener aircraft pushes both academic and industrial research into developing technologies, manufacturing, and operational strategies providing emissions abatement. At time of writing, there are no certified electric aircraft for passengers’ transport. This is due to the requirements of lightness, reliability, safety, comfort, and operational capability of the fast air transport, which are not completely met by the state-of-the-art technology. Recent studies have shown that new aero-propulsive technologies do not provide significant fuel burn reduction, unless the operational ranges are limited to short regional routes or the electric storage capability is unrealistically high, and that this little advantage comes at increased gross weight and operational costs. Therefore, a significant impact into aviation emissions reduction can only be obtained with a revolutionary design, which integrates disruptive technologies starting from the preliminary design phase. This paper reviews the recent advances in propulsions, aerodynamics, and structures to present the enabling technologies for a low emissions aircraft, with a focus on the commuter category. In fact, it is the opinion of the European Community, which has financed several projects, that advances on the small air transport will be a fundamental step to assess the results and pave the way for large greener airplanes.

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“…[33][34][35] Moreover, multirotor systems have the potential to influence the BPF modulation by way of controling the relative phase between the rotors. 36 Finally, BPF modulation aspects are critical for achieving realistic auralizations of rotorcraft noise, 37 and likewise, BPF modulation characteristics will benefit future extensions of noise prediction tools. [38][39][40][41]…”

Section: B Present Contribution and Outlinementioning

confidence: 99%

Quantifying modulation in the acoustic field of a small-scale rotor using bispectral analysis

Baars

Bullard

Mohamed

2021

AIAA Scitech 2021 Forum

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This paper describes a methodology to quantify inter-frequency modulation in the acoustic field of a small-scale rotor. How the blade passing frequency modulates the intensity of the higher-frequency (broadband) noise content is of specific interest, as this modulation is a major factor in the human perception of rotor noise from advanced air mobility vehicles and drones. A proposed modulation-parameter is based on post-processing steps that are applicable to a single acoustic time series. First, an auto-bispectral analysis assesses the dominant nonlinear, quadratic inter-frequency coupling between the blade passing frequency and the higher-frequency noise content. Secondly, the degree of modulation is determined using a robust parameter: a correlation parameter between the (low-frequency) modulating BPF signal and an envelope of the (higher-frequency) carrier signal. Provided that a single parameter is obtained for a given acoustic time series, the directivity pattern of the modulation strength can be inferred from data available from standard acoustic measurement campaigns. For illustration, an 11 inch diameter single-rotor in hover is considered, with acoustic data taken at 420 microphone positions within a plane perpendicular to the rotor disk. It is revealed that modulation is confined to a sector θ ≈ (10 • , −45 • ), where θ = 0 • is the rotor plane and negative angles are in the direction of the rotor-induced flow. The strongest modulation appears around θ ≈ −15 • . This work aids in quantifying the phenomenological description of modulation, namely that it results from the periodic advance and retreat of certain rotor blade's noise sources, relative to a stationary observer.

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Noise Reduction Potential of Phase Control for Distributed Propulsion Vehicles

Cited by 30 publications

References 10 publications

Challenges and opportunities for low noise electric aircraft

Challenges and opportunities for low noise electric aircraft

The Enabling Technologies for a Quasi-Zero Emissions Commuter Aircraft

Quantifying modulation in the acoustic field of a small-scale rotor using bispectral analysis

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