Pallabazzer 



be obtained. Therefore the pumpjector provides thrust improvement with 

 regard to both water jet and hydrojector. 



5 POWER PLANT ANALYSIS 



5.1 Description 



As already mentioned, three different kinds of connection between propul- 

 sor and powerplant have been studied: 



(a) the hydrojector (Figs. 22 and 23), where a purely gas-dynamical 

 connection is realized; 



(b) the water jet (Fig. 24), with a purely mechanical connection; 



(c) the pumpjector (Figs. 25 and 26) which can be realized either 

 with both mechanical and gas-dynamical connections (Figs. 4b and 4c) or with 

 a purely gas-dynamical connection which acts by both pressure and mixing ex- 

 change (Fig. 4a). This propulsor can be considered as either a change of 

 previous propulsors or a completely new design; it can be seen as a device 

 similar to the afterburner of a turbojet engine, both on thermodynamical and 

 on performance point of view. 



For all the powerplants a gas turbine was considered as the basic engine, 

 whose behavior was suitably idealized. The gas turbine therefore will supply 

 high-temperature high-pressure gas or mechanical power, or both, to the pro- 

 pulsor, as shown in the diagrams. 



The fundamental powerplant configurations which have been analyzed are: 



(i) a gas-turbine cycle provided by single or double combustion; 



(ii) a turbine with three possible points for gas extraction: just be- 

 fore the turbine, at a suitable point during the turbine expansion, and just after 

 the afterburner. The powerplant shown in Fig. (22d) or (25d) is the most gen- 

 eral one, because cases (a), (b), and (c) can be obtained by regulation of 

 scheme (d). 



(iii) The gas for the ejector can be supplied by the secondary cycle 

 of a bypass turbine or of a driven compressor (Figs. 23 and 26), with or with- 

 out secondary combustion. 



The thermodynamical cycles are represented in Figs. (27a and 27b). The con- 

 straints the powerplant must satisfy are: 



(a) hydromechanical constraint, represented by the equality of the 

 turbine net power and the pump or propeller power; 



(b) gas-dynamical constraints, represented by the equality of the gas- 

 extraction pressure, the chamber pressure, and the overall gas flow-rate 

 continuity. 



1134 



