Sound suppressor liner

• US 4,433,751 A
• Filed: 12/09/1981
• Issued: 02/28/1984
• Est. Priority Date: 12/09/1981
• Status: Expired due to Fees

• Current Assignee: Pratt & Whitney Aircraft of Canada Limited
• Original Assignee: Pratt & Whitney Aircraft of Canada Limited
• Inventors: Bonneau, Hilaire
• Primary Examiner(s): Fuller, Benjamin R.
• Application Number:
  US06/329,008
• Time in Patent Office: 811 Days
• Field of Search: 181/213, 181/250, 181/222, 181/224, 181/286, 181/288, 181/290, 181/292, 181/293, 181/269, 239/265.11, 60/264, 60/685, 60/687, 60/697, 428/116-118
• US Class Current: 181/213
• CPC Class Codes: F02K 1/827 Sound absorbing structures or liners

Abstract

A sound suppressor liner for aircraft exhaust passages is described which is based on the Helmholtz resonator principle including an inlet passage leading into a closed cavity wherein the inlet passages defined by a pair of curved walls with one wall being concave and the other wall being convex and the space between the walls gradually diminishing from the inlet of the inlet passage to the outlet within the cavity in a sense simulating an acoustic horn in reverse.

Claims

1. A suppressor liner comprising a first shell and a second shell spaced from the first shell with the second shell being permeable to sound and in contact with a gas path, sheet metal members forming a plurality of attenuator cells, each cell defining a cavity and having inlet passage means therein and constituting a battery of cells between the first shell and the second shell, the adjacent cells in the battery being formed by similarly formed sheet metal members with each member having a first concavely curved section relative to the second shell and forming a wall of the inlet passage of a first cell, a second continuing convexly curved section relative to the gas path and forming a portion of the cavity of a second cell with the first shell, an inwardly looped third section forming the convex wall of the inlet passage of the second cell such that each sheet metal member overlaps an adjacent member to form subsequent cells.

2. A sound suppressor liner adjacent a gas flow path, the liner including a first closed shell, a plurality of attenuator cells formed adjacent the first shell, each attenuator cell having wall means defining a cavity with the first shell and an inlet passage communicating at an inlet end with said gas flow path and leading into and communicating with said cavity, said wall means defining said inlet passage including at least a pair of curved walls with one wall being concave and the other being convex relative to the concave wall, with the space between the walls gradually diminishing from the inlet of the inlet passage towards the cavity, such that the curved walls simulate an acoustic horn, the volume of the cavity and the dimensions of the inlet passage are chosen as a function of the bandwidth of noise frequencies it is desired to attenuate.

3. A sound suppressor liner as defined in claim 2, wherein the liner includes a second shell which is permeable to sound and air and is in contact with the gas path and covers the inlets of the inlet passages of the attenuator cells.

4. A suppressor liner as defined in claim 3, wherein the second shell which is permeable to sound is made of fiber sheet material such as fibrous or porous metal.

5. A sound suppressor liner as defined in claim 3, wherein the second shell is a perforated sheet.