Search

This paper discusses the requirements for the propulsion system of supersonic cruise aircraft that are quiet enough to fly over land and operate from civil airports, have trans-pacific range in the order of 11,112 km (6000 nmi), and payload in the order of 4545 kg (10,000 lb.). It is concluded that the resulting requirements for both the fuel consumption and engine thrust/weight ratio for such aircraft will require high compressor exit and turbine inlet temperatures, together with bypass ratios that are significantly higher than typical supersonic-capable engines. Several technologies for improving both the fuel consumption and weight of the propulsion system are suggested. Some of these directly reduce engine weight while others, by improving individual component performance, will enable higher bypass ratios. The latter should therefore also indirectly reduce the bare engine weight. It is emphasized, however, that these specific technologies require considerable further development. While the use of higher bypass ratio is a significant departure from more usual engines designed for supersonic cruise, it is nonetheless considered to be a practical option for an aircraft of this kind. [ABSTRACT FROM AUTHOR]

This paper discusses the structure of the flow within the engine inlet of an uninhabited combat air vehicle (UCAV). The UCAV features a top-mounted, serpentine inlet leading to an engine buried within the fuselage. The performance of the inlet is found to depend strongly on a flow separation that occurs within the inlet. Both the time-averaged and the unsteady structure of this separation is studied, and an argument relating the inlet performance to the behavior of this separation is suggested. The results presented in this paper also suggest that there are considerable aerodynamic limitations to further shortening or narrowing of the inlet. Since there are substantial, system level benefits from using a smaller inlet, the case for separated flow control therefore appears clear. [ABSTRACT FROM AUTHOR]

This paper describes an investigation into the effect that passing wakes have on a separation bubble that exists on the pressure surface and near the leading edge of a low-pressure turbine blade. Previous experimental studies have shown that the behavior of this separation is strongly incidence dependent and that it responds to its disturbance environment. The results presented in this paper examine the effect of wake passing in greater detail. Two-dimensional, Reynolds averaged, numerical predictions are first used to examine qualitatively the unsteady interaction between the wakes and the separation bubble. The separation is predicted to consist of spanwise vortices whose development is in phase with the wake passing. However, comparison with experiments shows that the numerical predictions exaggerate the coherence of these vortices and also overpredict the time-averaged length of the separation. Nonetheless, experiments strongly suggest that the predicted phase locking of the vortices in the separation onto the wake passing is physical. [ABSTRACT FROM AUTHOR]