Abstract: The profile of the valve stop of a discharge valve is configured such that the portion facing the free length of the valve member has an increasing radius portion and a decreasing radius portion.

Abstract: A sound absorbing structure 38, 52 for a gas turbine engine 10 is disclosed. The sound absorbing structure 52 includes a wall element 54 and a casing 34 of the engine or nacelle 12. The casing is spaced from the wall element leaving a cavity 62 therebetween which is compartmentalized by partitions 64, 66. In one embodiment the partitions are attached to either the wall element or the casing element. In another embodiment the partitions are all attached to the wall element and spaced from the casing element or are all attached to the casing element and spaced from the wall element. In another embodiment the partitions are alternately spaced from the casing element and the wall element such that every other partition 64a is spaced from the wall and the remaining partitions 64b are spaced from the casing.

Abstract: This invention relates to acoustic liners having a plurality of cavities defining Helmholtz resonators in which the adjacent cavities are asymmetrical causing a pressure imbalance across the coupling means (tube, slot or aperture) between these cavities in the frequency range of interest. Such liners are particularly useful in turbofan engine noise reduction applications where low frequencies are encountered.

Abstract: This invention relates to acoustic liners having a plurality of cavities defining Helmholtz resonators in which the adjacent cavities are asymmetrical causing a pressure imbalance across the coupling means (tube, slot or aperture) between these cavities in the frequency range of interest. Such liners are particularly useful in turbofan engine noise reduction applications where low frequencies are encountered.