ON THE THEORY OF ONE TYPE 



OF AIR-WATER JET (MIST-JET) 



FOR SHIP PROPULSION 



Earl R. Quandt 

 Naval Ship Research and Development Center ' 



Annapolis, Maryland •.•',. 



ABSTRACT "\ •.-:-;•-: .:'j'-' ■• :" '•' 



Vehicles which operate on an air-water interface may use as the thrust 

 medium either phase separately or any mixture of phases. One inher- 

 ently amphibious combination which utilizes a water -augmented air -jet 

 (Mist-Jet) principle has been studied. To analyze this concept, one- 

 dimensional conservation equations for mass, momentum, and energy 

 have been written and solved to define overall propulsive coefficient as 

 well as two-phase nozzle shape and size. It is concluded that the con- 

 cept is practical, provided that reasonably efficient scoops, injectors, 

 and two-phase nozzles can be developed. 



INTRODUCTION 



Among transportation vehicles, ships occupy a unique position in the sense 

 that they operate at the interface between a liquid and a gas of greatly different 

 densities. Because of the availability of either phase for the generation of 

 thrust, it becomes of interest to examine which phase is most suitable for pro- 

 pulsion, and whether some advantages might not also be possible using mixtures 

 of air and water. Certainly, one conceptual advantage of an air-water mixture 

 is the potential for having a thrust medium of widely and continuously variable 

 density. Also, in principle, it should be possible to apply the propulsive power 

 to either fluid or to any mixture, depending upon convenience or the engineering 

 advantages of alternate arrangements. 



Although these considerations are not original, past attempts to apply two- 

 phase propulsion systems to ships have not been notably successful. In 1947, 

 Anderson et al. (1) reported on a study of a hydro-ramjet system powered by 

 compressed air. Although the arrangement was simple in design, propulsive 

 efficiency was too low for practical utilization. Similar conclusions have been 

 reached more recently by Mottard and Shoemaker (2) and by Pierson (3), al- 

 though improved engineering techniques have raised efficiency considerably. 

 Shuster et al. (4) describes comparable German investigations as well as men- 

 tioning work on a pulsating air -water ramjet using expanding combustion air to 

 accelerate the water. Such a scheme is attractive because it permits the fuel 

 energy to work directly on the thrust medium without any intervening machinery. 

 Unfortunately, however, if the hot gas and cold water phases are allowed to mix, 



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