The Bladeless Propeller 



STEADY- FLOW 

 EJECTOR 



ro 





PULSATING- 

 FLOW EJECTOR 



Fig. 1 - Steady-flow and pulsating-flow ejectors 

 (from Ref. 2) 



with greatly reduced interaction lengths (Fig. 2 and Ref. 2). However, their 

 performance normally depends very critically on the timing of the wave proc- 

 esses on which their operation is based. Furthermore, if the primary flow is 

 initially steady, its conversion to nonsteadiness for the purpose of utilizing 

 pressure exchange may be accompanied by losses large enough to offset the en- 

 tire thrust increment that is produced in the augmenter (Ref. 3). 



These drawbacks and difficulties are largely eliminated in a pressure ex- 

 changer whose flow processes admit a frame of reference in which they are 

 steady. This device, which has been variously referred to as the "bladeless" or 

 "pseudob laded" propeller, promises to combine an attractive efficiency with ad- 

 vantages of compactness and simplicity. 



This paper will discuss the principle of operation of the bladeless propeller 

 and briefly review the available theoretical and experimental information that 

 relates to its performance as a thrust augmenter. 



THE PRINCIPLE 



Euler's equation and the definitions of total head // and specific stagnation 

 enthalpy /i° yield for a fluid element, in the absence of body forces. 



and 



M 3p - 7 / • f ■ • u 1 \ 

 -jr- - -^ + u • I (it incompressible) , 



Z)hO 1 Bp „ Ds 1 - 7 ,. . .. , . 

 —prr= — ^+ T -=r- + — u • r (if compressible) , 

 Dt p dt Dt p 



1353 



