Water- Jet Propulsion for High-Speed Surface Ships 



VII. TESTS ON THE 50 KNOT SOGREAH PROPULSION UNIT 



SFJP TYPE IN THE CEAT (Centre d'Essais Aeronautique 

 de Toulouse) HIGH-SPEED TOWING TANK 



After completion of tests carried out on the internal circuit, 

 using the test rig already described, and on the external circuit in 

 the tunnel, we designed and constructed a 800 kw prototype unit for 

 complete testing in the CEAT high-speed towing tank. Impeller 

 diameter is 0,772 m for the prototype compared with 0,268 for 

 the impeller of the model while the ratio of power consumed under 

 cruising conditions was 800/7 Kw for the two types of test. 



The graph 8 shows the comparison of efficiency obtained on the 

 test rig for the scale model and in the tank for the prototype. 



Curve 1 represents the net efficiency obtained with the 0, 772 

 diameter prototype. This efficiency takes account of the nacelle drag. 



Curve 3 is derived from curve 1 by subtracting the external 

 drag losses of the nacelle and therefore represents the gross ef- 

 ficiency as defined above. 



Curve 2 represents gross efficiency obtained with the scale 

 model, diameter 0, 268 m. Comparison of curves 2 and 3 shows 

 that the variation of efficiency with the thrust coefficient is properly 

 predicted from the model. The difference in efficiency between model 

 and prototype is of order of magnitude which can be anticipated from 

 scale effect consideration. 



Figure 9 shows the net thrust Tn versus V characteristics - 

 the limiting curves are those derived from the model test results. 



The points represent the results obtained to date on the 0, 772 m 

 prototype with operation near to the diagram limits. 



The test program will be continued for even closer approach to 

 the operating limits. It must be noted here that the drag losses are 

 likely to be reduced if the trailing edge profile of the nozzle is mo- 

 dified which will help to improve overall efficiency. 



The following characteristic parameters may be noted from 

 both figures : 



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