A cooled acoustic liner useful in a fluid handling duct includes a resonator chamber (52) with a neck (56), a face sheet (86), and a coolant plenum (80) residing between the face sheet (86) and the chamber (52). Coolant bypasses the resonator chamber (52), rather than flowing through it, resulting in better acoustic admittance than in liners in which coolant flows through the resonator chamber and neck. In one embodiment, the liner also includes a graze shield (88). Openings (40, 38) penetrate both the face sheet (86) and the shield (88) to establish a relatively low face sheet porosity and a relatively high shield porosity. The shielded embodiment of the invention helps prevent a loss of acoustic admittance due to fluid grazing past the liner. Another embodiment (Fig. 6B) that is not necessarily cooled, includes the resonator chamber (52), low porosity face sheet (86) and high porosity shield (88), but no coolant plenum for bypassing coolant around the resonator chamber. An associated method of retrofitting an acoustic treatment into a fluid handling module includes installing openings (40) in the module and mounting a resonator box (44) on the module so that inlets (54) to the resonator necks (56) register with the installed openings (40).

High admittance acoustic liner

A linear acoustic liner for an aircraft includes a cellular core having a first surface and an opposed second surface. A substantially imperforate back skin covers the first surface, and a perforate face skin covers the second surface of the core. The perforate face skin includes an outer face skin layer having a first plurality of spaced openings, an inner face skin layer having a second plurality of spaced openings, and a porous layer disposed between the outer face skin layer and the inner face skin layer. Each of the first plurality of spaced openings are substantially aligned with one of the second plurality of spaced openings.

Linear acoustic liner

A sandwich composite panel ( 2 ) provides a load bearing structural member as well as noise protection, especially for a helicopter fuselage cell or cabin. The panel ( 2 ) includes an inner honey-comb core ( 6 ) made up of hollow cell bodies ( 4 ) extending trans-versely and sandwiched between first and second cover skins ( 8, 10 ) of fiber composite material. In order to achieve a low weight, a simple manufacturing, and good noise absorption, at least one of the cover skins ( 8 ) adapted to face the main source of noise (H) is made up of an open mesh fiber composite net ( 12 ) and a flexible cover film ( 16 ) applied on the outer surface of this fiber composite net ( 12 ). The net ( 12 ) has a smaller mesh size than the inner cross-sectional size of the hollow cell bodies ( 4 ).

Noise attenuating sandwich composite panel

An axially asymmetric exhaust gas muffler has a perforated central exhaust duct that is circumscribed by a duality of reactive sound attenuating chambers in each of which is positioned a resonant sound attenuator.

Compact muffler apparatus and associated methods

A tip turbine engine (10) according to the present invention includes an engine support structure (12) for cantilevering a load bearing shaft from an engine support plane (P). An engine support structure (12) defines the engine support plane (P), which is perpendicular to an engine centerline (A). The shaft (60) is rotationally fixed, coaxial with the engine centerline (A), and structurally supported by the engine support structure (12) such that a load borne by the shaft (60) is transferred along the engine support plane.

Cantilevered tip turbine engine

A multi-layer acoustic lining, e.g. for a flow duct in a gas turbine aeroengine, includes Helmholtz-type and tube-type resonators sandwiched between backing and facing sheets. In the invention, the ends of the tube-type resonators abut the Helmholtz resonators but are acoustically divided from them by partition means in such a way that the tube-type resonators differ from each other in resonant frequency. Variation of resonant frequency in the tube-type resonators is achieved by variation of their lengths according to which portion of the partition means acoustically divides them from the Helmholtz-type resonators, the partition means being arranged either step-wise or inclinedly between the backing and facing sheets.

John F. Chapman

Papers

Multi-layer acoustic linings