Performance Criteria of Pulse-Jet Propellers 



All the component efficiencies will in general be functions of the ideal effi- 

 ciency. The problem in any particular case is to evaluate the mean mass- 

 specific quantities displayed in the energy diagram (Fig. 4) as far as possible 

 and determine the various ratios and efficiencies according to their appropriate 

 definitions. 



m|/2 •> 



^ 



-0 



m?/2 



STATION 2 20 10 1 



Fig. 4 - Specific energy diagram 



FREE-RUNNING PROPELLERS 



4.1 Conventional Procedures 



The first case to be considered is a free -running propulsion device advanc- 

 ing in an otherwise undisturbed fluid with constant speed V . The volume, mo- 

 mentum, and energy velocities at the inlet section of the boundary of the system 

 in this case are by convention 



and 



Vj = V , 



nil = V , 

 r, = V , 



respectively, and the inflow efficiency is therefore 



^INF = 1 • 



(49) 

 (50) 



(51) 

 (52) 



The inflow section of the fluid boundary may be imagined as a large surface 

 around the propeller leaving an appropriate hole for its jet to pass. Due to the 

 convention adopted, no further details have to be specified. 



Provided now that the mean thrust and power of the propeller are meas- 

 ured, how far may we proceed in the evaluation of the performance criteria 



1093 



