Page:Model steam turbines; how to design and build them (IA modelsteamturbin00harrrich).pdf/29

Rh spread laterally as at A, fig. 12, and the velocity would be about 1400 feet only, and would not be increased even if the nozzle were discharging into a perfect vacuum; but by providing a taper extension piece, the discharge is as sketch B, and the energy developed is much greater. The following table

Fig. 12.--Difference between Simple Orifice and Taper Nozzle.

gives the weights of steam passed through a De Laval nozzle having a throat area of 1 square inch, and also shows the increased area required at the discharge end, atmospheric pressure in the turbine casing being assumed. The taper of the flaring end should be 1 in 12, which, with the throat and discharge dimensions, fixes the length of the nozzle.