US 4,155,221 A · Turbofan engine having variable geometry fan duct

Abstract

This invention is an improved turbofan engine having a variable geometry fan duct which reduces stator source noise emitted from the engine. Attached to the inner wall of the fan casing near the fan stators is a pneumatically actuated annular membrane having two operating positions. In the cruise position, the membrane is forced radially inward to press against the radially outermost tips of the fan stators. In the second position, used during approach and takeoff, the membrane is drawn against a recessed portion in the fan casing, thereby creating an annular passageway between the stator tips and the casing. When the membrane is in this position, turbulent flow from the rotor blade tips which would normally impinge on the stators is directed through the annular passageway.

Claims9

Dependent claims

A gas turbine engine of the type commonly known as a turbofan comprising:

a core engine;
a centerbody enclosing said core engine and having an outer wall;
a fan rotor located near the forward end of said core engine;
a fan casing having an inner wall enclosing said rotor and forming an annular duct between said inner wall thereof and the outer wall of said centerbody for the passage of air through the engine;
a row of fan stators located downstream of said rotor, attached to said centerbody, and extending radially outward therefrom, each of said stators having a radially outermost tip located radially inward of said inner wall and defining a gap therebetween;
and,
a flexible membrane circumferentially disposed about the inner wall of said fan casing radially outward said tips of said fan stators and having an inner and outer surface.

4 more elements

Dependencies are inferred from the claim text.

Turbofan engine having variable geometry fan duct

Life of this patent

Turbofan engine having variable geometry fan duct

Life of this patent

Abstract

Claims9