Deflection of Turbofan Exhaust Streams for Enhanced Engine/Nacelle Integration

Abstract

An analytical and experimental description of how the fan exhaust of a modern turbofan can be dee ected into an annular cascade using only core bleed e ow is presented. Thrust reversing, emphasized herein, and/or vectoring is achieved without the need for fan duct blockers or other hardware devices to turn the e ow, allowing lighter, less complex, and lower loss exhaust systems for more efe cient up-andaway e ight. Two approaches for dee ecting fan e ow into an annular cascade, using two different models, are described, and test results are discussed. Results of a Euler analysis and its critical relationship with the testing are also described. Both methods use injected core e ow to turn the fan e ow. One method uses an annular air-curtain emanating from an annular injection slot located opposite the cascade and the other uses a similar slot in the nozzle throat to force upstream e ow into the cascade. Both approaches are impacted by engine core bleed limits. Injector jet arrangements to meet this requirement while providing adequate reverse thrust are described; analyses and test results are reviewed.