Structureborne noise control in advanced turboprop aircraft

Loeffler, I. J.

doi:10.2514/6.1987-530

Cited by 5 publications

(6 citation statements)

References 3 publications

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“…These vibrations are then perceived as additional noise inside the cabin, reducing passenger comfort. This phenomenon is known as structure-borne noise and has been extensively investigated in the 1980s, both experimentally [22][23][24][25][26] and analytically [27][28][29][30][31]. Its relevance was first outlined by the study of Miller et al [22], who identified the propeller blade-tip vortices as dominant sources of pressure fluctuations on the wing.…”

Section: Introductionmentioning

confidence: 99%

Unsteady Pylon Loading Caused by Propeller-Slipstream Impingement for Tip-Mounted Propellers

Sinnige¹,

Vries²,

Corte

et al. 2018

Journal of Aircraft

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An experimental analysis was performed of the unsteady aerodynamic loading caused by the impingement of a propeller slipstream on a downstream lifting surface. When installed on an aircraft, this unsteady loading results in vibrations that are transmitted to the fuselage and are perceived inside the cabin as structure-borne noise. A pylonmounted tractor-propeller configuration was installed in a low-speed wind tunnel at Delft University of Technology. Surface-microphone and particle-image-velocimetry measurements were taken to quantify the pressure fluctuations on the pylon and visualize the impingement phenomena. It was confirmed that the propeller tip vortex is the dominant source of pressure fluctuations on the pylon. Along the path of the tip vortex on the pylon, a periodic pressure response occurs with strong harmonics. The amplitude of the pressure fluctuations increases with increasing thrust setting, whereas the unsteady lift coefficient displays a nonmonotonic dependency on the propeller thrust. The lowest integral unsteady loads were obtained for cases with approximately integer ratios between the pylon chord and the wavelength of the perturbation associated with the propeller tip vortices. This implies that structure-borne-noise reductions might be obtained by matching the pylon chord with an integer multiple of the axial separation between the propeller tip vortices.

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Section: Introductionmentioning

confidence: 99%

Unsteady Pylon Loading Caused by Propeller-Slipstream Impingement for Tip-Mounted Propellers

Sinnige¹,

Vries²,

Corte

et al. 2018

Journal of Aircraft

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show abstract

“…[7][8][9][10] The unsteady pylon loads cause vibrations, which are transmitted into the structure of the aircraft and can be perceived by the passengers as structure-borne noise. 11 This noise source can be mitigated by modifying the transmission path of the vibrations, 12 or by decreasing the amplitude of the unsteady aerodynamic loading. A possible way to reduce the amplitude of the unsteady loading is to use a pylon with a flowpermeable leading edge, also referred to as passive porosity.…”

Section: Introductionmentioning

confidence: 99%

Impingement of a propeller-slipstream on a leading edge with a flow-permeable insert: A computational aeroacoustic study

Avallone

Casalino

Ragni

2018

International Journal of Aeroacoustics

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This manuscript describes an aeroacoustic computational study on the impingement of a tractorpropeller slipstream on the leading edge of a pylon. Both the flow and acoustic fields are studied for two pylon leading edges: a solid and a flow-permeable one. The computational set-up replicates experiments performed at Delft University of Technology. Computational results are validated against measurements. It is found that the installation of the flow-permeable leading-edge insert generates a thicker boundary layer on the retreating blade side of the pylon. This is caused by an aerodynamic asymmetry induced by the helicoidal motion of the propeller wake, which promotes a flow motion through the cavity from the advancing to the retreating blade side of the pylon. The flow-permeable leading-edge insert mitigates the amplitude of the surface pressure fluctuations only on the pylon-retreating blade side towards the trailing edge, thus reducing structure-borne noise. Furthermore, it causes a reduction of the near-field noise only for receiver angles oriented in the upstream direction at the pylon-retreating blade side. In this range of receiver angles, it is found that the flow-permeable leading-edge insert reduces the amplitude of the tonal peaks for the third and fourth blade passage frequency, but strongly increases the broadband noise for frequencies higher that the seventh blade passage frequency.

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“…Despite the lower or equal community noise levels compared with turbofans [12,14], a drawback of unducted propellers is increased cabin noise [16,17], in particular for flight Mach numbers ranging from 0.6 to 0.8. This noise is caused by an airborne contribution due to the unsteady pressure field induced by the rotating blades and the propeller-airframe interaction, and a structureborne contribution due to vibrations from the engines, propellers, and propeller-airframe interaction [18][19][20][21]. However, because of the significant propulsive efficiency benefit, as consistently demonstrated in several industrial and governmental research programs, propellers remain appealing for the next generation of energy-efficient aircraft.…”

Section: Aerodynamic Performance and Static Stability Characteristics...mentioning

confidence: 99%

Aerodynamic Performance and Static Stability Characteristics of Aircraft with Tail-Mounted Propellers

Arnhem

Vries

Sinnige

et al. 2022

Journal of Aircraft

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Structureborne noise control in advanced turboprop aircraft

Cited by 5 publications

References 3 publications

Unsteady Pylon Loading Caused by Propeller-Slipstream Impingement for Tip-Mounted Propellers

Unsteady Pylon Loading Caused by Propeller-Slipstream Impingement for Tip-Mounted Propellers

Impingement of a propeller-slipstream on a leading edge with a flow-permeable insert: A computational aeroacoustic study

Aerodynamic Performance and Static Stability Characteristics of Aircraft with Tail-Mounted Propellers

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