A Parametric Study of Counter Rotating Open Rotor Noise

Smith, Dale; Filippone, Antonio; Bojdo, Nicholas

doi:10.2514/6.2019-2570

Cited by 5 publications

(7 citation statements)

References 17 publications

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“…Figure 14 shows that for the operative CROR configuration, the noise decreases with increasing fore and aft blade count, agreeing with previous parametric studies carried out by both the authors [20] and the work of Parry & Vianello [19]. The exception to this occurs with equal blade counts as the acoustic interactions (i.e.…”

Section: Inoperative Fore Rotorsupporting

confidence: 87%

“…Therefore, for each case, the force per unit blade area is constant for each blade count combination considered. Hence, differences in noise levels arise from acoustic criteria only [20].…”

Section: Inoperative Fore Rotormentioning

confidence: 99%

“…A noise reduction was found when the torque of the aft rotor was greater than the fore. Noise emissions can also be carefully controlled by the fore and aft blade counts [19,20]. Reductions in noise have also been sought by changing the azimuthal spacing and axially staggering the rotor blades [21,22].…”

mentioning

confidence: 99%

“…In order to isolate the effects of increasing blade count, the blade solidity is held constant by scaling the blade chord for each case [20]. Therefore, noise reductions are from acoustic criteria only, and hence, we are considering only the aeroacoustic performance of each concept.…”

mentioning

confidence: 99%

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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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Section: Inoperative Fore Rotorsupporting

confidence: 87%

“…Therefore, for each case, the force per unit blade area is constant for each blade count combination considered. Hence, differences in noise levels arise from acoustic criteria only [20].…”

Section: Inoperative Fore Rotormentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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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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“…In Reference [23], numerical aeroacoustic analyses of innovative propeller geometries have been carried out, accounting for a single propeller mounted on a wing. In Reference [24] a parametric study for a single open rotor aimed at reducing noise has been reported whereas in Reference [25], a new method has been presented to estimate the influence of the number of blades on noise contribution. A further analysis on the installation effect for two consecutive propellers has been presented in Reference [26].…”

Section: Introductionmentioning

confidence: 99%

Numerical Characterisation of the Aeroacoustic Signature of Propeller Arrays for Distributed Electric Propulsion

et al. 2020

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This paper presents an investigation of the aerodynamic and aeroacoustic interaction of propellers for distributed electric propulsion applications. The rationale underlying the research is related to the key role that aeroacoustics plays in the establishment of the future commercial aviation scenario. The sustainable development of airborne transportation system is currently constrained by community noise, which limits the operations of existing airports and prevents the building of new ones. In addition, the substantial saturation of the existing noise abatement technologies inhibits the further development of the existing fleet, and imposes the adoption of disruptive configurations in terms of airframe layout and propulsion technology. Simulation-based data may help in clarifying many aspects related to the acoustic impact of such innovative concepts. Blended-wing-body equipped with distributed electric propulsion is one of the most promising, due to the beneficial effect of the substantial shielding induced by its geometry. Nevertheless, the novelty of the layout requires a thorough investigation of specific aspect for which no previous experience is available. Herein, the interaction between propellers is analysed for a fixed propeller geometry, as a function of their mutual distance and compared to the acoustic pattern of the isolated one. The aerodynamic results have been obtained using a boundary integral formulation for unsteady, incompressible, potential flows which accounts for the interaction between free wakes and propellers. For the aeroacoustic analyses, the Farassat 1A boundary integral formulation for the solution of the Ffowcs Williams and Hawkings equation has been used. These results provide an insight into the minimum distance between propellers to avoid aerodynamic/aeroacoustic interaction effects, which is an important starting point for the development of distributed propulsion systems.

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Aeroacoustics research in Europe: The CEAS-ASC report on 2019 highlights

Camussi

Bennett

2020

Journal of Sound and Vibration

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A Parametric Study of Counter Rotating Open Rotor Noise

Cited by 5 publications

References 17 publications

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

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

Numerical Characterisation of the Aeroacoustic Signature of Propeller Arrays for Distributed Electric Propulsion

Aeroacoustics research in Europe: The CEAS-ASC report on 2019 highlights

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