The effect of secondary flow velocity profile on the static performance of low speed ejector thrust augmenters

Abstract

Jet thrust at low speeds is notoriously inefficient, and ejectors have often been proposed as thrust augmenters in the hope of increasing the mass flow and momentum flux for a given expenditure of energy. Henri Coanda reported the development of a successful thrust augmenter (the Coanda nozzle) for the propulsion of ambulance sledges in Russia during the Second World War, and useful thrust augmentations with this were reported by Sproule and Robinson and Reba. These reports raised interest in the technical press, and large scale experimental programmes have been mounted by Lockheed Aircraft, Cornell Aeronautical Laboratory, Hiller Aircraft and others. However, no clear conclusions seem to have resulted. Although recent published analyses of the performance of ideal ejector thrust augmenters stress the importance of size and energy input, no detailed analysis of the many different definitions of thrust augmentation which appear in the literature, or of their practical implications, seems to be available.