Wind tunnel measurements of blade/vane ratio and spacing effects on fan noise

Woodward, Richard P.; Glaser, F. W.

doi:10.2514/3.44828

Cited by 10 publications

(2 citation statements)

References 19 publications

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“…Thus the increased tip axial spacing in this earlier study would tend to enhance the apparent noise reduction of the swept and leaned stator.) Smith and House 11 conclude that the rotor-stator interaction tone level relates to rotor-stator spacing as 10 log 10 (x/c) 2 , where x/c is the ratio of rotor-stator spacing to axial rotor chord length at the tip diameter. This relationship gives a reduction of 6 dB per doubling of rotor-stator separation.…”

Section: Acoustic Performancementioning

confidence: 99%

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Benefits of stator sweep and lean for a high tip speed fan

Woodward

Gazzaniga²,

Bartos³

et al. 2002

40th AIAA Aerospace Sciences Meeting &Amp; Exhibit

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A model high-speed fan stage was acoustically tested in the NASA Glenn 9-by 15-Foot Low Speed Wind Tunnel at takeoff/approach flight conditions. The fan was designed for a corrected rotor tip speed of 442 m/s (1450 ft/s), and had a powered core, or booster stage, giving the model a nominal bypass ratio of 5. The model also had a simulated engine pylon and nozzle bifurcation contained within the bypass duct. The fan was tested with three stator sets to evaluate acoustic benefits associated with a swept and leaned stator and with an swept integral vane/frame stator which incorporated some of the swept and leaned features as well as eliminated some of the downstream support structure. The baseline fan with the wide chord rotor and baseline stator approximated a current GEAE CF6 engine. A flyover effective perceived noise level (EPNL) code was used to generate relative EPNL values for the various configurations. Flyover effective perceived noise levels (EPNL) were computed from the model data to help project noise benefits. A tone removal study was also performed. The swept and leaned stator showed a 3 EPNdB reduction at lower fan speeds relative to the baseline stator; while the swept integral vane/frame stator showed lowest noise levels at intermediate fan speeds. Removal of the bypass blade passage frequency rotor tone (BPF) showed a 4 EPNdB reduction for the baseline and swept and leaned stators, and a 6 EPNdB reduction for the swept integral vane/ frame stator. Therefore, selective tone removal techniques such as active noise control and/or tuned liner could be particularly effective in reducing noise levels for certain fan speeds.

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Section: Acoustic Performancementioning

confidence: 99%

“…Traditional methods of reducing this interaction noise have been to select blade/vane ratios to satisfy the cutoff criterion for propagation of the fundamental rotor tone 1 and increased axial spacing between the rotor and stator. 2 Increased rotor-stator axial spacing may somewhat degrade the fan aerodynamic performance and increase the overall engine weight.…”

mentioning

confidence: 99%