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.

THE STEAM 1XJECTOR. w being density in pounds per cubic foot, and P pressure in pounds per square foot. [Or if for pressure in pounds per square foot we substi- tute pressure in pounds per square 'inch, and tabe 2‘3 ft. as the fluid head equivalent of 1 Ib. pressure per square inch, then ____________ V = ^/2<7p x 2 3 • • • (ii- «•)] In other words, if steam and water jets issue from a boiler under pressure, then with s denoting the density of the steam and w the density of the water within the boiler, The velocity of steam jet _ / w The velocity of water jet J s If the pipes through wliich the steam and watør jets issue be of the same cross-sectional area, and the discharge in unit time be considered, then Mass of steam dischargeel _ / s . Mass of water discharged J w . „ Momentum of steam i et _ 1 therefore —-------------7-------— — J> Momentum 01 water jet . Kinetic energy of steam jet _ / w and ==-.—-------——c------1— • 1 ~ ' Kinetic energy 01 water jet v § ■ Thus it will be seen that whilst under the conditions aforesaid the momentum of the steam jet is equal to tliat of the water jet, the velocity and kinetic energy of the former jet is to that of the latter as the square root of the density of the water is to the square root of the density of the steam. The density of steam being very mueh less than that of water under the same pressure, its velocity will therefore be greater. Even when the steam jet is mixed with and condensed by a water jet, the velocity and kinetic energy of the resultant jet may be very considerably greater than that of a water jet issuing from the same vessel as the steam jet. It will thus be seen that by utilis- ing the kinetic energy of a jet of steam, a very effeetive