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.

4 ______ THE STEAM INJECTOR. produced by a pressure of 479 Ibs. per square inch.* That is to say, if we neglect all consideration of losses, a steam jet issuing from a boiler under a gauge pressure of 10 Ibs. per square inch would be able (when mixed with and condensed by water) to carry nine times its own weight of water into a boiler under a gauge pressure of nearly 479 Ibs. per square inch. It is hardly necessary to add that it is impossible in practice to obtain anything like this result. The following particulars of a test upon an injector under conditions approaching thos& above set out will show something of the possibilities of the appliance : — Test of an Injector. Steam pressure. Pounds per square inch absolute. Head of feed water. Feet. 2 Temperature of Delivery pressure. Pounds per square inch absolute. Feed water. Delivery water. 25 — Deg. Fah. 60 /3JJ- °C Deg. Fah. 180 &L aC 180 _____ Briefly, an injector may be said to comprise three parts, performing the following functions : — (1) A steam nozzle in which the pressure energy of the steam is converted into kinetic energy. (2) A combining or mixing nozzle in which the steam mixes with and imparts its velocity to the feed water. (3) A delivery nozzle in which the kinetic energy of the water jet issuing from the combining nozzle is con- verted into pressure energy. Fig. 1 is a sectional illustration of an early type Giffard iniector. The steam nozzle is shown at a, the water inlet ______________ ♦ For : Pressure above 5 Ibs. pei- squai-e inch absolute _ velocity2 _ jo . . , . [See formula (ii. a).] 2 <7 X 2’3 = ^ _ 10 148 = 479 Ibs. approximate.