Deflection of turbofan exhaust streams for enhanced engine/nacelle integration

This paper presents the results of analytical and experimental work describing how the fan exhaust of a modern turbofan can be deflected into an annular cascade using only core bleed flow. Thrust reversing, emphasized here, and/or vectoring could be achieved without the need for blocker 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; test results are discussed. Results of an Euler analysis and its critical relationship with the testing also are described. Both methods use injected core flow to cause the fan flow to turn. One method uses an annular aircurtain emanating from an injection jet located opposite the cascade, and the other uses a similar jet in the nozzle throat, to force upstream flow into the cascade. Both approaches are impacted by engine core bleed limits, e.g., estimated W_b/W_f