NOZZLES 



279 



The issuing jet now possesses high velocity and its store of energy is 

 almost entirely in the kinetic form. 



Theoretically, if pointed vertically upwards, and if no energy losses 

 were experienced, the height of the jet would be the same as that of the 

 free surface of the supply reservoir, or that corresponding to the pressure 

 head inside the nozzle. The various frictional resistances, however, 

 reduce the nozzle pressure and the issuing velocity, after which the 

 resistance of the air and that due to the impact of falling particles of 

 water tend to retard the upward motion of the rising particles, so that 

 the height to which the jet rises is considerably less than that given by 



v z 

 h = 5, v being the velocity of efflux. 



*9 



The following results are deduced from experiments carried out by 

 J. T. Fanning 1 with ordinary converging fire nozzles and with a stream 

 slightly inclined to the vertical, so that the effect of the falling particles 

 would not be so great as with a vertical stream. 



Forms of Nozzle. These are usually of circular section and may either 

 converge uniformly to a short parallel neck at the orifice (Fig. 126a), or 







FIG. 126. 



have a convergence which becomes more gradual as the outlet is 

 approached (Fig. 126/;). 



1 Engineering News, July 14, 1892 T 



