Take-off ground roll of propeller driven aircraft

Abstract

using a heater-burner to simulate the engine exhaust, seemed to indicate that the two-dimensional CD nozzle with exit aspect ratios less than 10 would not produce less IR signature than the equivalent axisymmetric nozzle (see Fig. 67 of Ref. 5). The effect of the engine swirl is expected to be more important when external streams are present, since in such cases external mixing due to shear is otherwise reduced because of the lowered velocity differences between the plume and external stream. In conclusion, a simple modeling technique has been developed to provide economical yet adequate prediction of two-dimensional-nozzle plume properties for IR signature analysis. Successful models were developed for ADEN, twodimensional CD, and two-dimensional plug nozzles with and without bypass flow and/or engine swirl. A 10-deg engine swirl was found to reduce the predicted plume temperature dramatically. Therefore the inherent engine swirl, though undesirable from the performance point of view, appears to be highly effective in reducing the IR signature of a twodimensional-nozzle plume.