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Numerical Prediction of Far-Field Combustion Noise from Aeronautical Engines

CFD Team, CERFACS and Safran Aircraft Engines, 31100 Toulouse, France
CFD Team, CERFACS and Safran Helicopter Engines, 31100 Toulouse, France
Dept. Génie Mécanique, Université de Sherbrooke, Sherbrooke, QC J1K2R1, Canada
Author to whom correspondence should be addressed.
Acoustics 2019, 1(1), 174-198;
Received: 29 December 2018 / Revised: 4 February 2019 / Accepted: 12 February 2019 / Published: 19 February 2019
A hybrid methodology combining a detailed Large Eddy Simulation of a combustion chamber sector, an analytical propagation model of the extracted acoustic and entropy waves at the combustor exit through the turbine stages, and a far-field acoustic propagation through a variable exhaust temperature field was shown to predict far-field combustion noise from helicopter and aircraft propulsion systems accurately for the first time. For the single-stream turboshaft engine, the validation was achieved from engine core to the turbine exit. Propagation to the far field was then performed through a modeled axisymmetric jet. Its temperature modified the acoustic propagation of combustion noise significantly and a simple analytical model based on the Snell–Descarte law was shown to predict the directivity for axisymmetric single jet exhaust accurately. Good agreement with measured far-field spectra for all turboshaft-engine regimes below 2 kHz stresses that combustion noise is most likely the dominant noise source at low frequencies in such engines. For the more complex dual-stream turbofan engine, two regime computations showed that direct noise is mostly generated by the unsteady flame dynamics and the indirect combustion noise by the temperature stratification induced by the dilution holes in the combustion chamber, as found previously in the turboshaft case. However, in the turboengine, direct noise was found dominant at the combustor exit for the low power case and equivalent contributions of both combustion noise sources for the high power case. The propagation to the far-field was achieved through the temperature field provided by a Reynolds-Averaged Navier–Stokes simulation. Good agreement with measured spectra was also found at low frequencies for the low power turboengine case. At high power, however, turboengine jet noise overcomes combustion noise at low frequencies. View Full-Text
Keywords: aeroacoustics; indirect and direct combustion noise; sound propagation; turboshaft engines; turbofan engines aeroacoustics; indirect and direct combustion noise; sound propagation; turboshaft engines; turbofan engines
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Férand, M.; Livebardon, T.; Moreau, S.; Sanjosé, M. Numerical Prediction of Far-Field Combustion Noise from Aeronautical Engines. Acoustics 2019, 1, 174-198.

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