Foa 



k 



Equivalent spin angle 

 Entrainment coefficient 



Density 



Thrust augmentation ratio 



A prime ( ' ) denotes the conditions of the primary flow when expanded isen- 

 tropically to pressure p^ . 



INTRODUCTION 



The simplest thrust augmenters are those in which the transfer of mechani- 

 cal energy from the driving "primary" to the induced "secondary" flow takes 

 place directly, i.e., through the work of mutually exerted forces at the inter- 

 faces between the two flows. 



With the exception of the conventional ejector, where the energy transfer is 

 effected through the work of shear forces, all devices of this class operate on 

 the basis of nonsteady flow processes. In these devices the transfer is effected 

 in whole or in part through "pressure exchange," i.e., through the work of inter- 

 face pressure forces; and this requires that the flow be nonsteady, because no 

 work is done by pressure forces acting on a stationary interface. 



The conventional steady-flow ejector is simple, but inefficient and bulky. 

 Its effectiveness as a thrust augmenter is low and deteriorates rapidly with in- 

 creasing forward speed (Ref. 1). Nonsteady -flow thrust augmenters— e.g., the 

 pulsating -flow ejector (Fig. 1)— are capable of higher energy transfer efficiencies 



1352 



