Comparison of Far-Field Noise for Three Significantly Different Model Turbofans

Woodward, Richard P.

doi:10.2514/6.2008-49

Cited by 2 publications

(3 citation statements)

References 7 publications

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“…Only the isolated fan is considered here because there are no published data of the fan interacting with a BWB-shaped shield. Comparisons are made with the Advanced Ducted Propulsor Fan 1 (ADP1) tests of Woodward 13 ; and the Allison Fan tests of Woodward et al 14 . Figure 19 compares the acoustic power level (PWL) of the UCI tests with the ADP1 tests.…”

Section: Comparison With Past Larger-scale Data For Isolated Fanmentioning

confidence: 99%

“…Given that jet noise is significantly reduced in these high-bypass engines, prediction of the fan noise sources becomes critical. Fan noise, of course, has been the topic of numerous experimental, theoretical and computational investigations, some cited in this paper [7][8][9][10][11][12][13][14] . In particular, a series of studies conducted under the fan source diagnostic test (SDT) program resulted in extensive acoustic and flow field data 8,9 and proposed methods to reduce rotor-stator interaction noise [12][13][14] .…”

Section: Introductionmentioning

confidence: 99%

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Experimental Simulation of Ducted Fan Acoustics at Very Small Scale

Truong

Papamoschou

2014

52nd Aerospace Sciences Meeting

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This study evaluated the feasibility of simulating the aerodynamics and acoustics of ducted fans using small-scale components (approximately 1/38 th scale). Enabling technologies include high-definition stereolithography and high-performance, compact DC brushless motors used in model aircraft. The 70-mm ducted fan featured a 14-bladed rotor and 24 stators, and operated at fan pressure ratio of 1.15 and rotor tip Mach number of 0.61. Its operation was thus representative of turbofan engines with very large bypass ratio. The far-field acoustics were surveyed in the downward and sideline planes. The acoustic results of the isolated ducted fan compare favorably with past large-scale experiments. In addition, the project provided initial data on the shielding of ducted-fan noise using a surface that approximated the shape of the blended wing body airplane. The BWB-shaped shield featured removable inboard fins and a moveable elevon, and translated axially to enable various positions of the nacelle relative to the elevon trailing edge. The EPNL reduction on the downward plane ranged from 7.6 dB with the engine at its nominal location to 10.4 dB with the engine moved forward by one fan diameter. Sideline EPNL reduction was marginal with the fins off and reached about 3.0 dB with the fins installed. Upward deflection of the elevon improved moderately the shielding.

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Section: Comparison With Past Larger-scale Data For Isolated Fanmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental Simulation of Ducted Fan Acoustics at Very Small Scale

Truong

Papamoschou

2014

52nd Aerospace Sciences Meeting

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“…[8][9][10][11][12][13][14][15] These experiments are obviously very expensive. The small scale paradigm enables significant cost and time savings in the acoustic evaluation of noise-reduction concepts.…”

Section: Introductionmentioning

confidence: 99%

Harmonic and Broadband Separation of Noise from a Small Ducted Fan

Truong

Papamoschou

2015

21st AIAA/CEAS Aeroacoustics Conference

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In the study of noise from propellers and ducted fans, rigorous signal decomposition into harmonic and broadband components is essential for the development of high-fidelity predictive models. Current spectral methods and phase averaging techniques lack the temporal resolution to compensate for fluctuations in operating condition intrinsic to real world experiments. In this paper we use a Vold-Kalman filter to extract the tonal and broadband content of noise from a small ducted fan simulating the conditions of an ultrahigh-bypass turbofan engine. The fan operated at pressure ratio of 1.15 and tip Mach number of 0.61. The investigation includes time traces, narrowband spectra, one-third octave spectra, and overall sound pressure level. The energies of the tonal and broadband components are similar at low frequency, while the broadband component dominates at high frequency. In addition, there are distinct differences in the directivities of the two components. The trends are in general agreement with NASA large-scale fan tests at transonic conditions. NomenclatureA = structural equation matrix BPF = blade passing frequency C k = complex phasor matrix f (t) = instantaneous frequency FPR = fan pressure ratio i = imaginary unit = √ −1 I = identity matrix J(x) = cost function r = weighting factor SPL = sound pressure level t = time x k (t) = time-varying (complex) envelope of order k y(t) = total measured acoustic signal ε(t) = error in structural equation fit η(t) = broadband or shaft-uncorrelated noise θ = polar angle relative to downstream axis φ = azimuthal angle ∇ p x k [n] = structural equation of order p () = round brackets denote continuous signals [] = square brackets denote discrete signals Subscripts and Superscripts H = Hermitian k = harmonic or order of signal T = transpose Downloaded by CARLETON UNIVERSITY LIBRARY on July 22, 2015 | http://arc.aiaa.org |

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Comparison of Far-Field Noise for Three Significantly Different Model Turbofans

Cited by 2 publications

References 7 publications

Experimental Simulation of Ducted Fan Acoustics at Very Small Scale

Experimental Simulation of Ducted Fan Acoustics at Very Small Scale

Harmonic and Broadband Separation of Noise from a Small Ducted Fan

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