Noise reducing air inlet for gas turbine engines

Abstract

A noise-suppressing air inlet having two coaxially arranged airflow channels to supply inlet air to a gas turbine engine is disclosed. The outer airflow channel has an annular cross-sectional geometry and is formed between the inner wall of a tubular outer cowling which forms the forward portion of the engine housing and the outer wall of a tubular inner cowling that is coaxially mounted within the outer cowling. The inner airflow channel is formed between the inner wall of the inner cowling and a forward projecting central hub of the gas turbine engine. Major portions of the walls of both the inner and outer cowling include sound attenuating panels to suppress noise propagating in the forward direction through both airflow channels of the air inlet. The inner cowling is supported within the outer cowling such that the leading edge of the inner cowling projects forwardly of the outer cowling leading edge. This support is provided by a number of radially extending, circumferentially spaced-apart struts located between the inner wall of the outer cowling and the outer wall of the inner cowling. The struts are aerodynamically contoured and have a hollow interior for the passage of tubing of an aircraft thermal anti-icing system. The two airflow channels are of a height dimension which provides near optimal noise suppression, thus resulting in minimal air inlet length and minimum length to diameter ratio for a given sound suppression level. Minimizing the length to diameter ratio reduces the airload on the inlet structure during various aircraft maneuvers, reduces the overall weight of the air inlet and, since the outer surface area of the air inlet is thereby minimized, results in less drag.