Open Rotor Installed Aeroacoustic Testing with Conventional and Unconventional Airframes

Czech, Michael; Thomas, Russell H.

doi:10.2514/6.2013-2185

Cited by 29 publications

(24 citation statements)

References 4 publications

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“…Moreover, there is also scope for overall CROR geometry (including blade shape) optimization for maximizing the propeller efficiency at the top of climb and minimizing the interaction noise at take-off conditions as shown by Schnell et al 4 Despite the use of modern advanced theoretical and numerical development tools, experimental work is still essential and necessary. Several extensive campaigns were performed in recent years, for example Ricouard et al; 5 Elliott; 6 Czech and Thomas; 7 Zante; 8 Stephens and Envia; 9 Fernando and Leroux. 10 The wind tunnel tests for the evaluation of the installation effects of Noise EMissions of an open rotor advanced regional aircraft (WENEMOR) test campaign, Bennett et al, 11 was conducted as a response to a Clean Sky call for proposals under SP1-JTI-CLEAN SKY-2010-4 entitled ''Aero-acoustic noise emissions measure for advanced Regional Open Rotor A/C configuration'' and forms part of the Clean SkyIntegrated Technology Demonstrators under the heading of Green Regional Aircraft (GRA) of which Alenia Aermacchi, Italy and EADS CASA, Spain are the leaders.…”

Section: Introductionmentioning

confidence: 99%

Experimental observations of an installed-on-pylon contra-rotating open rotor with equal blade number in pusher and tractor configuration

Eret

Kennedy

Amoroso

et al. 2016

International Journal of Aeroacoustics

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Noise from contra-rotating open rotors is a major obstacle to the adoption of this fuel efficient technology as a viable aircraft propulsion system. A better understanding of both contra-rotating open rotor noise generation and reduction has been achieved due to ongoing extensive research. One of the most recent research activities is the WENEMOR (wind tunnel tests for the evaluation of the installation effects of Noise EMissions of an open rotor advanced regional aircraft) project, which has been developed in response to the requirements described in the Clean SkyIntegrated Technology Demonstrators under the heading of Green Regional Aircraft. The project investigates the airframe installation effects of a 1=7th scale model of a regional aircraft equipped with two contra-rotating open rotors of the same rotor diameter, the same rotational speed and equal blade number. For this case, the blade passing frequency of rotor-alone tones and the frequency of relevant interaction tones cannot be distinguished due to the equal blade count of the two rotors. This study presents the tone directivity plots up to 4 Â blade passing frequency of the isolated WENEMOR single pylon contra-rotating open rotor engine in both pusher and tractor configurations at various angles of incidence and flow velocities. A linear array of 13 microphones is deployed for the far field sound measurements. The tone directivity trends show the efficient on-axis acoustic radiation at all blade passing frequency tones with the contra-rotating open rotor tone at 2 Â blade passing frequency dominating in the vast majority of the tests. The main objective is to compare the acoustic emission of pusher and tractor configurations tested under the same flow velocities and angles of incidence. The results suggest that the pusher configuration of the isolated contra-rotating open rotor tends to be slightly louder than the tractor at 2 Â blade passing frequency. However, it is shown that the acoustic performance of the isolated contra-rotating open rotor is complicated and sensitive to any change in the flow velocity and the angle of incidence. The increasing flow velocity and the increasing angle of incidence show limited consistency in proportional trends in the directivity plots of sound pressure levels. It is anticipated that the findings will be different for a more realistic case of installedon-model contra-rotating open rotor.

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Section: Introductionmentioning

confidence: 99%

Experimental observations of an installed-on-pylon contra-rotating open rotor with equal blade number in pusher and tractor configuration

Eret

Kennedy

Amoroso

et al. 2016

International Journal of Aeroacoustics

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“…Czech and Thomas [30] tested a counter-rotating open rotor in the Boeing Low Speed Aeroacoustics Facility. Among other tests, the rotor was placed at angles of attack of 0, 7, 10, and 13 degrees relative to the incoming flow.…”

Section: Mean Flow Distortionmentioning

confidence: 99%

Aircraft System Noise Assessment of the NASA D8 Subsonic Transport Concept

Clark

Thomas

Guo³

2018

2018 AIAA/CEAS Aeroacoustics Conference

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A vehicle-level noise assessment has been performed for the NASA D8 concept aircraft (ND8) in the NASA Advanced Air Transport Technology Project portfolio. The NASA research-level Aircraft NOise Prediction Program (ANOPP-Research) was used to predict the noise from each source component on the ND8 to build up a noise estimate for the full aircraft. The propulsion airframe aeroacoustic (PAA) effects of the ND8, namely boundary layer ingestion (BLI) with its influence on fan noise, and the noise shielding, reflection, and diffraction mechanisms of the unconventional airframe, were empirically modeled using experimental data. Noise reduction technologies appropriate to the 2025-2035 time frame were included in this study. Including all technologies and PAA effects, the ND8 is predicted to have a cumulative margin to the Stage 4 certification metric of only 7.4 EPNdB. Boundary layer ingestion is predicted to have a detrimental impact on cumulative noise levels on the order of 15 EPNdB. Fan noise is seen to be the primary noise source at all three certification points, even if the BLI noise impact could be entirely suppressed. The impact of engine noise shielding by the airframe is limited by a lack of aft shielding and the presence of horizontal tail reflections in the aft direction. The physical constraint on engine size by the pi-tail is seen as a potential barrier to engine noise reduction through the corresponding limitation on fan bypass ratio. Mildly reduced climb performance (compared to similar reference aircraft) does not provide any benefit through increased noise propagation distance. If the boundary layer ingestion noise penalty could be suppressed such that BLI would have no effect on noise, the cumulative margin to Stage 4 would increase to 22.4 EPNdB, still below the NASA Mid Term goal of 32-42 EPNdB.

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“…Thus multiple rotor blades can chop the same elongated structures in the boundary layer resulting in a highly correlated noise spectra [9]. Additionally, as the rotor is generally installed in proximity to a fuselage, the reflected acoustic waves from the hard-wall could significantly increase the farfield noise [10,11].…”

Section: Introductionmentioning

confidence: 99%

An analytical model for predicting rotor broadband noise due to turbulent boundary layer ingestion

Karve

Angland

Nodé-Langlois

2018

Journal of Sound and Vibration

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Open Rotor Installed Aeroacoustic Testing with Conventional and Unconventional Airframes

Cited by 29 publications

References 4 publications

Experimental observations of an installed-on-pylon contra-rotating open rotor with equal blade number in pusher and tractor configuration

Experimental observations of an installed-on-pylon contra-rotating open rotor with equal blade number in pusher and tractor configuration

Aircraft System Noise Assessment of the NASA D8 Subsonic Transport Concept

An analytical model for predicting rotor broadband noise due to turbulent boundary layer ingestion

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