Inlet and Aft Tonal Noise Predictions of a Full-Scale Turbofan Engine with Bifurcation and Inlet Distortion

Winkler, Julian; Reimann, Craig A.; Reba, Ramons; Ali, Amr A.; Gumke, Christopher

doi:10.2514/6.2017-3034

Cited by 16 publications

(13 citation statements)

References 13 publications

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“…Winkler and al. [39] also made similar observations. Contradictorily, the results presented by Namgoong and Arisetti [41] show the presence of a strong acoustic field produced by the ESS at 2nd harmonic BPF, which propagates up into the bypass duct.…”

Section: Comparison Of Numerical and Experimental Far Field Datasupporting

confidence: 62%

“…Research by Holewa et al [37] and by Redonnet and Druon [38] suggest that bifurcations and struts cause a richer modal content of the RSI tones due to several mechanisms: i) sound generation by the rotor wake (vortical) interaction with those structural elements, ii) scattering of the acoustic waves into new modes as they propagate through obstacles, and iii) impact of the potential field of the bifurcations on the rotor wake structure before they interact with the stator. This can not only jeopardize a cut-off fan design as shown by Winkler et al [39] but also result in a smoother directivity in the far field. In fact, the acoustic scattering at the bypass bifurcations suffices to significantly change the far field directivity as observed by Chen et al [40].…”

Section: Comparison Of Numerical and Experimental Far Field Datamentioning

confidence: 99%

See 1 more Smart Citation

The Challenge of Tonal Fan Noise Prediction for an Aircraft Engine in Flight

Kissner¹,

Guérin²,

Enghardt³

et al. 2019

Acta Acustica united with Acustica

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Expensive flyover tests are needed to verify that noise certification standards are fulfilled. Currently, no numerical alternative exists to perform a holistic "virtual fly-over" test. As a step towards enabling such evaluations in the future, the authors focus on an isolated noise source-the tonal rotor-stator-interaction (RSI) of the fan stage. A high-fidelity simulation relying on a state-of-the-art yet computationally efficient method is performed for a V2527 aircraft engine in approach conditions. The computational domain includes the noise generation in the fan stage, its propagation in the engine inlet and bypass duct, as well as its radiation into the far field. Installation effects due to bifurcations and struts in the duct, ESS (engine section stator), liners, and inflow distortions are not considered. Post-processing methods are introduced and applied to the numerical data to allow for a meaningful comparison of the results to microphone data recorded during flyover experiments. In particular, great care is taken to quantify the numerical dissipation of the simulation inside the nacelle and to enable a suitable correction of the numerical data. The numerical simulation cannot fully reproduce the experimental data indicating that its level of complexity is not yet sufficient. As there is no obvious cause for the mismatch, it would be necessary to incrementally increase the complexity of the simulation in order to pinpoint the most significant sources and effects.

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Section: Comparison Of Numerical and Experimental Far Field Datasupporting

confidence: 62%

Section: Comparison Of Numerical and Experimental Far Field Datamentioning

confidence: 99%

The Challenge of Tonal Fan Noise Prediction for an Aircraft Engine in Flight

Kissner¹,

Guérin²,

Enghardt³

et al. 2019

Acta Acustica united with Acustica

View full text Add to dashboard Cite

show abstract

“…Several recent studies have therefore focused on the impact of distortion on the noise emitted by turbofan engines [1][2][3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Shock Wave Generation and Radiation from a Turbofan Engine Under Flow Distortion

2020

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This paper presents aeroacoustic investigations on a full-scale Ultra High Bypass Ratio (UHBR) engine with inflow distortion at transonic conditions. Computational Fluid Dynamics (CFD) simulations are first realized to compute the shocks in the vicinity of the fan. These shocks are then radiated in the near-field thanks to Computational AeroAcoustics (CAA) simulations. The chaining between CFD and CAA simulations is done by injecting the shocks in terms of usual conservative variables using a non-reflecting boundary condition. The CAA solver is based on the non-linearized Euler equations which allows to define the CFD/CAA interface close to the fan where the propagation of shocks is highly non-linear. Both shock generation and propagation mechanisms are investigated and the effects of inflow distortion are highlighted by comparison with a baseline case without distortion. The flow distortion is shown to be responsible for a modification of shock amplitudes along the circumferential direction. Thus, azimuthal modes appear in addition to the rotor-locked mode present without distortion. A particular feature of the studied configuration is the presence of a supersonic flow region in the bottom part of the nacelle. This supersonic pocket blocks the shocks in the lower half of the nacelle and also modifies the angle at which they leave the nacelle in its upper half. Consequently, the far-field radiation (obtained using Kirchhoff's integral method) is mainly oriented skywards and towards the side of descending blades. Acoustic power estimates are provided to quantify these effects. Nomenclature a = speed of sound of the uniform far-field flow, m/s a 0 = time-averaged speed of sound, m/s B = number of rotor blades CDC = circumferential distortion coefficient

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“…This is typically the case during landing or take-off operations (angle of attack around 10°-15°) where airport neighbours are the most exposed to noise nuisance. Several recent studies have therefore focused on the impact of distortion on the noise emitted by turbofan engines [1][2][3][4][5][6][7][8]. They have shown that the tone noise characteristics can be significantly modified by: (a) introducing new acoustic sources caused by the distortion/fan blades interaction [3][4][5], (b) modifying the conventional fan-blade wakes/Outlet Guide Vanes (OGVs) interaction [3][4][5]8], and (c) modifying the generation and propagation of fan-blade shocks at transonic speeds [1][2][3][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

“…However, the associated computational cost is very high and the radiation of acoustic waves outside of the nacelle cannot be correctly captured over an important distance. Most of the studies [1,3,7] are therefore based on a two-step methodology where the CFD solution is chained to a Computational AeroAcoustics (CAA) solver to propagate and radiate the shocks. The latter methodology is chosen here using the CFD/CAA chaining strategy developed by Thisse et al [9,10].…”

Section: Introductionmentioning

confidence: 99%

Shockwave Generation and Radiation from an UHBR Engine with Flow Distortion Using a CFD/CAA Chaining Strategy

Daroukh¹,

Polacsek²,

Chelius³

2019

25th AIAA/CEAS Aeroacoustics Conference

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This paper presents aeroacoustic investigations on a full-scale Ultra High Bypass Ratio (UHBR) engine with inflow distortion at transonic conditions. Computational Fluid Dynamics (CFD) simulations are first realized to compute the shocks in the vicinity of the fan. The shocks are then radiated outside of the nacelle thanks to Computational AeroAcoustics (CAA) simulations. The same solver is used for both CFD and CAA simulations and the chaining is done by injecting the shocks in terms of usual conservative variables using a non-reflecting boundary condition. The CAA solver is based on the non-linearized Euler equations which allows to define the CFD/CAA interface close to the fan where the propagation of shocks is highly non-linear. Both shock generation and shock propagation mechanisms are investigated and the effects of inflow distortion are highlighted by comparison with a baseline case without distortion. It is shown that the distortion, characterized by an acceleration of the flow at the bottom of the nacelle, is responsible for a modification of the shock amplitudes that depends on the circumferential position. Thus, azimuthal modes appear in addition to the rotor-locked mode present without distortion. The near-field radiation is also highly impacted with most of the noise being directed towards the sky. This is due to the blockage of shocks by a supersonic flow region in the bottom of the nacelle. The radiation is in addition highly heterogeneous in the other directions because of the various angles of the shocks that leave the nacelle.

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Inlet and Aft Tonal Noise Predictions of a Full-Scale Turbofan Engine with Bifurcation and Inlet Distortion

Cited by 16 publications

References 13 publications

The Challenge of Tonal Fan Noise Prediction for an Aircraft Engine in Flight

The Challenge of Tonal Fan Noise Prediction for an Aircraft Engine in Flight

Shock Wave Generation and Radiation from a Turbofan Engine Under Flow Distortion

Shockwave Generation and Radiation from an UHBR Engine with Flow Distortion Using a CFD/CAA Chaining Strategy

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