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Variable cycle jet engines for a Mach 2·7 supersonic civil transport

Abstract The aim of the work outlined in this paper is to compare three different variable cycle jet engine concepts for future SSTs. These engines are: the turbofan-turbojet, the mid-tandem fan engine and the double bypass engine. The comparison is carried out on the basis of unin-stalled and installed performance, handling and sizing issues. This preliminary analysis compares SFC, size, variable geometry and cycle changes for each engine. The installed performance was estimated by calculating the air friction, the pre-entry and the afterbody drags, together with the wave drag due to the shock waves. A sizing calculation was carried out for the whole nacelle. The uninstalled and installed fuel bill, for two standard missions, is also estimated. These preliminary results indicate that the turbofan-turbojet and the mid-tandem fan engines are quite similar in terms of general suitability. The mid-tandem fan appears to be an attractive proposition from the point of view of sizing, however, this comes with a small penalty in fuel consumption. The present double bypass engine was found to be the least attractive for the application, although the differences are small.