Deflection of Turbofan Exhaust Streams for Enhanced Engine/Nacelle Integration

摘要

An analytical and experimental description of how the fan exhaust of a modern turbofan can be deflected into an annular cascade using only core bleed flow 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 flow, allowing lighter, less complex, and lower loss exhaust systems for more efficient up-and-away flight. Two approaches for deflecting fan flow 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 flow to turn the fan flow. 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 flow 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.