Waterjet Propulsion 



Moreover, if we define as internal efficiency the ratio between the ideal and 

 the real head of the pump, the total propulsive efficiency assumes the following 

 general expression: .. .^ ^, ,, 



'T ~ 'ideal 'internal 'pump 'external , ; .:. ' - 



where, for the free jet, 



2 



^i = 1 + r ' -. .■ ■ .- --:.-..;-.■ -^ - ; 



- 1 



^( 1 + K ) + (Kj - 1) + Zk/3. + 2! 



V. 



while for the jet on wake. 



T] - con s t an t 



2(T-X.) 

 1i = —2 



'''"' ~ r^d + KJ + (K,-X2) + 2/Si^ ^2^' ""' " ''' 



2 



'0 



In the above equations we have assumed /.:'>.■ , .;,i. 



Ap = B • Q and T - Tg = A^ • e + Ap • e + i p Aj Vq^ Cp 



and we use the following symbols: 

 Vq = design speed 

 V. = speed at the inlet 

 V^ = speed at the nozzle, rel. Vq 



r = V /V„ 



u 



K. = free-stream head loss coefficient, rel. V^ 

 K = outlet head loss coefficient, rel. V 



u ' u 



IK = sum of suction duct head loss coefficient, rel. v. 



' 1 



1055 



