Gas -Turbine Powerplants for Two-Phase Hydropropulsion 



Fig. 3 - Planar hydrojector (Marjet) 



(a) The motion is treated as one dimensional. 



(b) The analysis will concern design performances. 



(c) Water and gas enter the chamber at the same pressure p,; 



(d) The velocity Vi will be expressed by the diffusion coefficient , 



the significance of which is clearly discussed in Ref . [20j. Here </; is a design 

 coefficient which is fixed on the ground of several exigencies (external and in- 

 ternal cavitation, losses, and flow rate). 



(e) The internal pressure drag losses ah^ will be expressed by an 

 overall losses coefficient 



AH, 



^ = 



V.V2g 



(2) 



This is also a design coefficient, meaning that ^ can be considered as a con- 

 stant only when the analysis refers to design performances. 



(f) The two-phase flow is homogeneous. There will be no slip effects 

 between water and gas, that is, water and gas move at same speed. The gas 

 density Pg is negligible in comparison with the water density p^, and the same 

 thing happens for the mass flow rates, that is, the mixing mass ratio e « 1. 



(g) The gas momentum will at the chamber inlet be neglected; this 

 corresponds to the hypothesis of a complete viscous dissipation. The gas en- 

 ergy amount will be taken into account in the form of total enthalpy. 



(h) The gas is perfect and ideal, but its nature will be taken into ac- 

 count by means of different thermodynamic coefficients. 



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