Noise reduction kit for jet turbine engines

Claim 1

A noise reduction kit for modifying a fan jet engine having a core engine generating axial exhaust gas flow through a downstream end thereof, an outer casing defining an annular bypass duct surrounding the core engine, a fan at the upstream end of the core engine for generating axial fan air flow through the bypass duct, a thrust reverser for selectively converting axial flow of exhaust gas and fan air into reverse thrust, and a tail pipe assembly disposed to axially receive and exhaust the exhaust gas and fan air, the kit comprising: a mixer having an upstream end and an annular mixer wall axially extending downstream therefrom, the wall being formed into a plurality of circumferentially alternating radially inward and radially outward lobes, the radially inward lobes defining cold chutes for radially inwardly diverting fan air and the radially outward lobes defining hot chutes for permitting radially outward expansion of exhaust gas; an annular mounting bracket for fixing the mixer to the casing in position downstream of and coaxial with the core engine; a fairing having an upstream end for coaxial attachment to the downstream end of the core engine and an annular, axially-extending fairing wall for attachment to the upstream end of the mixer, the fairing wall being shaped to aerodynamically conform to the lobes of the mixer to direct fan air to the cold chutes and exhaust gas to the hot chutes; and an annular spacer for axial disposition between the downstream end of the core engine and the thrust reverser, the spacer extending the axial flow path sufficiently to permit achieving generally smooth laminar flow of mixed exhaust gas and fan air downstream of the mixer.

Claim 7

A method of modifying a fan jet engine to reduce noise, the engine having a core engine generating axial exhaust gas flow through a downstream end thereof, an outer casing defining an annular bypass duct surrounding the core engine, a fan having blades at the upstream end of the core engine for generating axial fan air flow through the bypass duct, a nose cowl coaxially defining an air intake to the fan, a thrust reverser having clam shell doors moveable between stowed and closed positions for selectively diverting axial flow of exhaust gas and fan air into radially-opposed cascade vane assemblies defining gas exit areas for generating reverse thrust, and a tail pipe assembly disposed to axially receive and exhaust the exhaust gas and fan air, the method comprising the steps of: removing components of the engine from the upstream and downstream ends of the core engine; modifying the contour of each blade of the fan; installing coaxially downstream to the core engine mixing means for radially inwardly diverting fan air and for permitting radially outward expansion of exhaust gas to mix the fan air and exhaust gas; installing an annular spacer coaxially between the downstream end of the core engine and the thrust reverser, the spacer extending the axial flow path sufficiently to permit achieving generally smooth laminar flow of the mixed exhaust gas and fan air upstream of the thrust reverser; replacing the cascade assemblies with new cascade assemblies defining increased exit areas; installing a pair of radially-opposed seal fairings at the upstream end of the thrust reverser, each seal fairing being disposed to engage a respective one of the new cascade assemblies to direct gas flow thereto when the clam shell doors are in the closed position and to sealingly engage a respective one of the doors when in the stowed position; and modifying the clam shell doors to permit sealing engagement with the seal fairings when in the stowed position.

Claim 8

A method of modifying a fan jet engine to reduce noise, the engine having a core engine generating axial exhaust gas flow through a downstream end thereof, an outer casing defining an annular bypass duct surrounding the core engine, a fan having blades at the upstream end of the core engine for generating axial fan air flow through the bypass duct, a nose cowl coaxially defining an air intake to the fan, a thrust reverser having clam shell doors moveable between stowed and closed positions for selectively diverting axial flow of exhaust gas and fan air into radially-opposed cascade vane assemblies defining gas exit areas for generating reverse thrust, and a tail pipe assembly disposed to axially receive and exhaust the exhaust gas and fan air, the method comprising the steps of: removing components of the engine from the upstream and downstream ends of the core engine; modifying the contour of each blade of the fan; installing coaxially downstream to the core engine mixing means for radially inwardly diverting fan air and for permitting radially outward expansion of exhaust gas to mix the fan air and exhaust gas; installing an annular spacer coaxially between the downstream end of the core engine and the thrust reverser, the spacer extending the axial flow path sufficiently to permit achieving generally smooth laminar flow of the mixed exhaust gas and fan air upstream of the thrust reverser; replacing the cascade assemblies with new cascade assemblies defining increased exit areas; installing a pair of radially-opposed seal fairings at the upstream end of the thrust reverser, each seal fairing being disposed to engage a respective one of the new cascade assemblies to direct gas flow thereto when the clam shell doors are in the closed position and to sealingly engage a respective one of the doors when in the stowed position; and modifying the clam shell doors to permit sealing engagement with the seal fairings when in the stowed position.