Pallabazzer 



low weight of the propulsive system (about 50% less than a water jet's propul- 

 sive weight), simplicity, easy maintenance, higher efficiency, and less powerful 

 turbine. Its disadvantage is the lower thrust obtainable which in turn needs 

 larger propulsors and therefore higher external drag. However the efficiency 

 advantage can allow an operating range where the thrust ineffectiveness could 

 be minimized and the lower propulsive weight allows a moderate increase in 

 drag. On the other hand, until now the hydrojector appears to be the only pro- 

 pulsive device which does not fall at the highest speed as the water jet does both 

 for propulsive and for cavitation reasons. 



NOMENCLATURE 



A local cross section (m-^) 

 Ag part of A occupied by gas 

 Ajj ' part of A occupied by water 

 A^ nozzle critical (throat) cross section (m^) 

 Bj, B^, B3 fxinctions defined by Eq. (19') 



c velocity of sound, for the two-phase mixture (m/s) 

 Cg the same, for gas 



the same, for water 



specific heat at constant pressure, for air (kcal/kg °K) 

 Cpg Cp, for gas, (mean in the H.P. turbine) 

 c^g Cp, gas (L.P. turbine) 



-H 



pa 



"pm *^p' inean air-gas at the principal burner Bl 



=pm '^p' ^^^^ air-gas at the afterburner B2 



Cg thrust coefficient [Eq. (26)] 



g gravity acceleration (m/s^) 



Hj fuel heat of combustion (kcal/kg) 



h gas total enthalpy (kcal/kg) 



H pump head (m) 



j mechanical equivalent of heat (=426.9 kcal/kg m) 



1164 



