Quandt 



Although the water augmented air jet may be somewhat less efficient than 

 the all-water systems, this is not of great significance for smaller ships be- 

 cause these tend to be more sensitive to machinery weight than fuel weight (10). 

 Perhaps one of the more critical application problems for any of the ship pro- 

 pulsion systems appears to be satisfactory passage through the low speed hump 

 condition. For a Mist-Jet design, this consideration is made more or less sig- 

 nificant depending upon desired top speed capability because of the availability 

 of the air-only thrust at all speeds. Additionally, as mentioned earlier, water 

 augmented air jets have the inherent amphibious capability and furthermore may 

 also have sufficient air flow to augment lift fans at the hump condition so that 

 not as great a horizontal thrust need be supplied. 



CONCLUSIONS 



The significant conclusions of this analytical and experimental investigation 

 of two-phase air-water ship propulsion systems are: 



(i) There exist analytical techniques for predicting performance of the 

 two -phase components with first-order confidence. 



(ii) These analyses are being improved through more detailed descrip- 

 tions as well as by comparison with selected experimental data. 



(iii) Overall propulsion coefficients of 50% are predictable for high- 

 speed ship applications of water-augmented air-jets. 



(iv) This efficiency is achievable with a bulky but light propulsion 

 plant. 



(v) Air-water jets are inherently amphibious, and also offer certain 

 design flexibilities for craft using air-support concepts. 



ACKNOWLEDGMENTS 



The work reported herein has been sponsored by the Independent Explora- 

 tory Development program of the Naval Ship Research and Development Center. 

 Additionally, the author particularly wishes to acknowledge John H. Garrett, 

 Rolf K. Muench, and Allen E. Ford for their efforts on this program and for 

 their work in performing some of the computations for this paper. 



NOMENCLATURE 



Symbol Description Units 



A Flow area in nozzle ft^ 



A^ Flow area in water scoop ft-^ 



Aq Flow area in free stream ft^ 



1076 



