The Bladeless Propeller 



7.0 



6.0 



5.0 







4.0 



3.0 



2.0 



10 



A,/A, 



20 



30 



Fig. 16 - Static performance of two- 

 phase bladeless propeller, Grumman 

 steam-water tests 



EXPERIMENTAL RESULTS 



The first experiments on a bladeless propeller were conducted by this 

 writer in 1952, using an unshrouded model with a large afterbody. The tests 

 (air-to-air) were conducted in a free jet simulating a forward speed of 300 

 ft/sec. Thrust augmentation ratios as high as 1.2 were measured, but the re- 

 sults were considered inconclusive because it could not be ascertained whether 

 the apparent increase of thrust was not in part a decrease of drag such as might 

 be caused by delayed flow separation on the afterbody. Following some work on 

 pumping applications, thrust augmentation experiments were resumed at R.P.I. 

 by Vennos in 1959 (Ref. 16). These experiments were conducted on a variety of 

 water-water models, the most successful of which had zero coning angle, a spin 

 angle of 35° (Fig. 17), a secondary-to-primary area ratio of 37.6, and a shroud 

 length-to-diameter ratio of about 1. Two of the test points are shown in Fig. 9. 

 Not shown are the test points corresponding to the highest augmentation ratios 

 measured in these experiments, because they were obtained under test conditions 



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