Assessment of the relative performance of the by-pass engine and the orthodox double compound jet engine

Abstract

The by-pass engine can be described as a form of ducted fan engine in which the fan boosts the main compressor. Two possible forms of by-pass engine are described, and their estimated performance is compared with that of the orthodox double compound jet engine under various flight conditions, the calculations being extended to include the case of thrust boosting by means of exhaust reheat. It is concluded that the by-pass engine can offer an appreciable gain in respect of fuel economy over the orthodox double compound jet engine even at 650 m.p.h, in the stratosphere, at the expense, however, of increased frontal area for a given thrust.