Installation Effects on Contra-Rotating Open Rotor Noise

Ricouard, Julien; Julliard, Emmanuel; Regnier, Vincent; Parry, Anthony B.; Baralon, Stephane

doi:10.2514/6.2010-3795

Cited by 55 publications

(36 citation statements)

References 4 publications

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“…This is due to the impulsive blade-loading change during the pylon-wake encounter (Fig. 6), and was also observed before by other researchers [10]. The overall noise penalty was smallest in high thrust conditions (J ¼ 1:05, Fig.…”

Section: Symmetric Inflow Conditionssupporting

confidence: 67%

“…In all cases, significant tonal noise penalties were measured compared to the isolated propeller test case. Such noise penalties have been observed for both single-and contra-rotating propellers; for the latter, the phenomenon is dominated by the tones emitted by the first blade row [9,10]. The additional noise due to the pylon-wake interaction is a function of the operating conditions of the propeller.…”

Section: Introductionmentioning

confidence: 92%

“…Previous experimental work [6][7][8][9][10][11] focused on the aeroacoustic impact of the pylon-wake impingement for semi-installed pusher propellers. More recently, acoustic investigations were reported that extended the scope to complete aircraft configurations [12,13].…”

Section: Introductionmentioning

confidence: 99%

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APIAN-INF: an aerodynamic and aeroacoustic investigation of pylon-interaction effects for pusher propellers

et al. 2017

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Advanced propellers promise significant fuelburn savings compared to turbofans. When installed on the fuselage in a pusher configuration, the propeller interacts with the wake of the supporting pylon. This paper presents an experimental analysis of the aerodynamic and aeroacoustic characteristics of this pylon-propeller interaction. An isolated propeller was operated in undisturbed flow and in the wake of an upstream pylon at the large low-speed facility of the German-Dutch wind tunnels (DNW-LLF). Measurements of the pylon-wake characteristics showed that the wake width and velocity deficit decreased with increasing thrust due to the suction of the propeller. The installation of the pylon led to a tonal noise penalty of up to 24 dB, resulting from the periodic blade-loading fluctuations caused by the wake encounter. The noise penalty peaked in the upstream direction and became increasingly prominent with decreasing propeller thrust setting, due to the associated reduction of the steady blade loads. The integral propeller performance was not significantly altered by the pylon-wake encounter process. However, at sideslip angles of ±6°, the effective advance ratio of the propeller was modified by the circumferential velocity components induced by the pylon tip vortex. The propeller performance improved when the direction of rotation of the propeller was opposite to that of the pylon tip vortex. Under this condition, a reduction was measured in the noise emissions due to a favorable superposition of the angular-inflow and pylon-wake effects.Keywords Propulsion integration Á Pusher propellers Á Propeller noise Á Pylon-installation effects List of symbols BNumber of blades

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Section: Symmetric Inflow Conditionssupporting

confidence: 67%

Section: Introductionmentioning

confidence: 92%

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APIAN-INF: an aerodynamic and aeroacoustic investigation of pylon-interaction effects for pusher propellers

et al. 2017

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“…This causes periodic unsteady blade loading, as confirmed by flight tests [2,3] and numerical simulations [4]. The associated increase in tonal noise emissions has been substantiated both experimentally and numerically for single-rotating [5] and contra-rotating [4,6,7] propellers. It was found that the noise penalty due to the installation of the pylon is especially pronounced in the directions away from the propeller plane.…”

Section: Introductionmentioning

confidence: 64%

“…The interaction of the turbulent flow structures with the blades leads to random load fluctuations, which cause an increase in broadband noise emissions. However, previous experimental studies [7,8] have shown that this mechanism is relatively unimportant compared to the increase in tonal noise levels resulting from the mean velocity deficit in the pylon wake.…”

Section: Introductionmentioning

confidence: 78%

Mitigation of Pusher-Propeller Installation Effects by Pylon Trailing-Edge Blowing

Sinnige

Ragni

Eitelberg

et al. 2017

Journal of Aircraft

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This paper presents an experimental assessment of the working principles of pylon trailing-edge blowing for the mitigation of the interaction between a pusher propeller and its associated pylon. The experiments were performed at the Large Low-Speed Facility of the German-Dutch wind tunnels (DNW-LLF), using a powered propeller model and an upstream pylon equipped with a trailing-edge blowing system. In-flow microphone measurements demonstrated the impact of pylon installation on the propeller's tonal noise emissions, with increases of up to 16 dB relative to the isolated propeller. Analysis of the unsteady blade pressures showed that this installation effect is caused by the impulsive increase in blade loading during the pylon-wake passage.The efficacy of pylon trailing-edge blowing to reduce the momentum deficit in the pylon wake was confirmed by stereoscopic particle-image-velocimetry measurements between the pylon and the propeller. Consequently, application of the pylon-blowing system alleviated the pylon-installation effects at the source. At an intermediate thrust setting, the root-mean-square of the blade-load fluctuations due to the wake encounter was reduced by up to 60%, resulting in noise emissions approximately equal to those recorded for the isolated propeller.a Ph

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Noise reduction of a Counter Rotating Open Rotor through a locked blade row

Smith

Filippone

Bojdo

2020

Aerospace Science and Technology

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Counter Rotating Open Rotors (CROR) have the potential to significantly reduce aircraft emissions. However, there are a number of concerns surrounding their noise levels. In this contribution, we propose a number of novel configurations to reduce the noise of CROR for general aviation aircraft. In particular, we lock either fore or aft blade row on departure and approach, and keep the CROR trimmed at the same thrust as in design configuration (both rotors running). The CROR is switched back to design configuration at cruise to regain the high propulsive efficiency. To further reduce noise, two additional cases are investigated: 1.) folded aft rotor; 2.) increased diameter fore rotor (with locked-aft blade row). A low-order CROR trim code that has been developed to compute the aerodynamic and aeroacoustic performance of new design configurations is used in the numerical analysis. The results demonstrate significant noise gains for a number of blade count combinations during a constant altitude flyover. The analysis found that using a locked-fore and locked-aft configuration resulted in a maximum noise reduction of around 3 dB(A) (or 3 dB (EPNL)) and 3 dB(A) (or 6 dB (EPNL)) respectively. Folding the aft rotor backward could result in a maximum noise gain of around 12 dB(A). Increasing the fore rotor diameter by 30% was shown to reduce noise by a maximum of 8 dB(A) against an operative CROR of the same tip extension.

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Installation Effects on Contra-Rotating Open Rotor Noise

Cited by 55 publications

References 4 publications

APIAN-INF: an aerodynamic and aeroacoustic investigation of pylon-interaction effects for pusher propellers

APIAN-INF: an aerodynamic and aeroacoustic investigation of pylon-interaction effects for pusher propellers

Mitigation of Pusher-Propeller Installation Effects by Pylon Trailing-Edge Blowing

Noise reduction of a Counter Rotating Open Rotor through a locked blade row

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