| 摘要 |
An acoustic panel for a fan casing of a gas turbine engine includes one or more Helmholtz resonators to absorb acoustic energy propagated upstream from the fan. By arranging that the periodic air flow out of the resonators has some axial momentum, by inclining the passages that exit from the necks of the resonators in a downstream direction, some of the energy in this air flow can be realised as a useful pressure rise in the direction of the air flow into the fan, rather than a pressure drop as in known acoustic panels.
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