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Monday, July 8 • 11:20 - 11:40
THE INFLUENCE OF THE COMBINED LINER DESIGN PARAMETERS ON TURBOFAN NOISE REDUCTION

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In previous work an experimental evaluation of the acoustic efficiency of the fan combined noise reduction system was performed at the model test facilities. Typically, an acoustic lining is installed in the engine intake and in the bypass duct downstream the outlet guide vanes. In model tests the combined liner reduced the fan noise by 2-3 dB more than the double-layer honeycomb liner of the same length at fan operation modes corresponding to rotational speeds in certification points. In current work the experimental study of the combined liner lattice design parameters was completed in the conditions of model duct with the flow and high SPL. The length of the combined liner was equal to three calibers consisted of 2-caliber double honeycomb liner and the lattice of half-caliber installed upstream and downstream the double honeycomb liner. The distance between lattice plates varied in the range from 5 - 20 mm, the installation angle of the plates varied from 0 to 60 degrees. It is shown that the lattice space changing within 5-10 mm results in additional PWL reduction by 3-5 dB for tonal noise and 2-2.5 dB for broadband noise due to the lattice element. If the lattice spacing is equal to 20 mm the benefit the lattice element installation is less. When the lattice plates installation angle changes from 0 up to 60 degrees relative to axis of model duct the benefit of the lattice element almost monotonously decreases. The maximum difference in the efficiency of the lattice element in this case reaches 2 dB. As a result of the experimental work it could be stated that the best configuration of the studied lattice element turned out to be a lattice of 5-10 mm spacing and 0 degrees of installation angle.

Moderators
RL

Robby Lapointe

Principle engineering specialist, Airbus Canada

Authors

Monday July 8, 2019 11:20 - 11:40 EDT
Westmount 3
  T03 Aero… aircrft noise & vibr., SS06 Aicraft Engine Noise