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.

PRINCIPLES OF THE INJECTOR. 9 i per square inch, and the head equivalent of 1 Ib. pressure per square inch as 2'3 ft., then, if the water is on the same level ais the injector, the velocity of the1 water entering the injector is obtained as follows: — V = 8-025 710 x = 38’5 ft. per second. If the water is supplied under a head of 5 ft. its velocity is V = 8'025 710 x 2-r+ 5 = 42'5 ft. per second. When the water is lifted through a height of 5 ft. the velocity of inflow to the injector is V = 8-025 710 x 2-3 - 5 V 34 ft. per second. A reduction in the velocity cÆ the entering feed water naturally results in a reduction in the velocity of the æm- bined »team and water jet, but the effect is pnacticaUy inappreciable far small variations of lift. The velocity losses due to impact of the rapidly-onoving steam upon the water will, however, greatly increase as the water velocity diminåshes. . . „ Two effeots follow from a variation in the ratio oi water to steam passing through an injector, jiamøly, variations in the delivery temperature, and a variation in- tlie over- pressure or excess of pressur© of the delivery jet in relation to that of the steam enttering the injector. The smaller the ratio of water to steam (within the working limits or range of the injector), the higher the delivery temperature and pressure. Under ordinary conditions the maximum delivery pressure obtainable in a live-steam injectoi is con- siderably in excess of the pressure of thø steam entering the injector. Thus, with steam at 60 Ibs. pressure, the maximum delivery pressure may be a'bout 75 Ibs.; at 80 Ibs., about 100 Ibs.; and 150 Ibs., about 175 Ibs., and so on.* It is alwa.ys possible, therefore, when the injector * These amounts depeud entirely upon the feed-water temperature, height of -lift, and other conditions.