Performance Criteria of Pulse-Jet Propellers 

 Mj = pQV + T 

 may be determined and accordingly the corresponding momentum velocity 



m^ = V + T/pQ , (58) 



the ideal efficiency, and the basic performance characteristic. 



Further on the volume velocity • 



V2 = Q/^2 (59) 



may be determined, which will in general differ from the momentum velocity, 

 while the conventional procedure implies the equality 



V2 = mj , (60) 



due to the lack of relevant information. 



From the definitions of the various velocities, which may be rendered in the 

 forms 



Vi = Q/Ai = f/Ai J J a> dA dt , (61) 



m. = M./(pQ) = f/0 J J ^2 dA dt , -;- ...-: i ;•' (62) 



' ._ 1/ f A. . ;U oO^.i-'-'Oy: 



or 



2e. = 2Ei/pO = f/Q J J ^' dA dt , 



1/ f A. ^ ' 



the approximate relation 



e^ = 3/2 m^Vi - v? (64) 



may be derived. 



This relation however crude the approximation provides at least a first es- 

 timate of the specific energy at the outlet and consequently of the outflow effi- 

 ciency and the jet efficiency from measured integral values. Theoretical values 

 may be obtained according to the same rule; Schiele, 1967. 



For propellers discharging above the free fluid surface the analysis may be 

 even more refined due to the fact, that the momentum outflow may be deter- 

 mined directly by means of a balance struck by the jet; Fig. 5, In this case it 

 appears reasonable to treat the resistance 



R = M2 - pQV - T (65) 



separately, as the ducting system will in general serve as strut. 



1095 



