Noise reduction kit for turbofan engine

摘要

In a noise reduction kit for modifying a two spool axial flow turbofan engine (20) with multi-stage compressors and fan driven by multi-stage reaction turbines, and a thrust of at least about 18,000 lbs. at sea level, there is a fan (21,22) at the upstream end (66) of the core engine (20) for generating axial fan air flow through bypass ducts (26a,26b,26c;27a,27b,27c) terminating at a common nozzle (28), the common nozzle (28) having a mixing plane area (29) for each of the fan air flow and for the exhaust gas in a range between 700 and 800 square inches. A target thrust reverser (41) includes opposing doors (43,44) rotatable into position to block and divert the flow of exhaust gas for generating reverse thrust. A material layer (300) is located in a spacing between a tip of blades (302) for at least some of the fans (21) and a duct for the fans, thereby to reduce a normal clearance between the tip of blades (302) for a fan (21) and the duct (305). Mixing means for radially diverting fan air and permitting radially outward expansion of exhaust gas is provided coaxially downstream to the core engine (20). An acoustically dampened light bulb-shaped nose cone (51) is provided for coaxial attachment to an upstream end of the core engine (20). The axial flow front fan is axially separated from the inlet guide vane which is extended relatively forwardle. A bleed air valve (202), selectively operational to bleed air from the core engine (20) when the valve (202) is open, is ducted for directing bleed air to the vicinity of the common nozzle (28).