The Steam Injector
A theoretical and practical treatise on the design and operation of injectors and on the flow of fluids through and the design of nozzles.

98 ______________________________ THE STEAM INJECTOB. difference between atmospheric pressure and tlie pressure within the injector) is : ______ V = 7 2 = J 2 x 32-2 (2 + 12 x 2-3) = 44 ft. per second. [One pound pressure per square inch is taken as equal to a water head of 2’3 ft.] The steam nozzle throat area is now obtained thus— . _ C (a?2 u-i) 1 s “ B x V' _ 4 (-956 x 8-1) 13-3 x 1469 = 00158 square foot. The velocity imparted to the water is obtained as follows : Momentum Momentum _ Momentum of of steam + of water ~ delivery jet 1 x 2606 + 13-3 x 44 = 3191 ; therefore velocity of delivery jet = 223 ft. per second. This would give the delivery nozzle throat area as— __________4j<_143 d ” 13 3 x 624 x 223 = ‘00031 square foot. We thus find that the ratio of areas of steam nozzle throat to delivery nozzle throat is about 5’1 to 1. In actual practioe, for the conditians statecl, the said ratio would be about 3 to 1. We have already shown that the delivery jet of an injector only represents the expenditure of a very small portion of the heat energy of the steam which is available for imparting velocity to said jet. In the example oaloulated the delivery jet, instead of having- a velocity of 223 ft. per second, would probably have a velocity of about 136 ft. per second,—that is, about 25 per cent more