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.

17 __________________________ THE STEAM NOZZLE. A steam control valve such as d, fig. 13, is provided for the steam supplies to the lifter and forcer wlien the injector is to lift its feed water. The first opening movement of said valve allows steam to pass to the annular “ lifter ” a, whilst further movement allows steam also to pass to tlie “ forcer ” b. The aforesaid arrangement of double steam nozzles is more powerful for lifting purposes than a single steam nozzle, though the latter is sufficient for most services. Velocity of Discharge of Steam. The general formula for obtaining the ideal or theor&ti- cal velocity of discharge of steam from an orifice in a vessel is as follows : — V = J 2 g■ U__________________(iii.) where V dønotes velocity in feet per second, g acceleration due to gravity, and U the net amount of work performed by unit weight of steam during admission to the discharg- ing means at constant pressure, expansion to the exhaust pressure, and discharge at that pressure. If the expansion is adiabatic, then U will be i-epresented by the- whole of the available heat energ-y or heat units between the temperatures of saturation corresponding to the initial and final steam pressures (or the admission and exhaust pressures) multiplied by the dynamical equivalent of a heat unit. That is, U = j I”Heat supplied up to _ Heat rejectedl L point of expansion at discharge J a J { (^ 4- - (t2 + x2L„) } .... (v.) where J indicates Joule’s dynamical equivalent of a heat unit = 778 foot-lbs. per B.T.U. Equation (iii.) can be expanded to include (v.) when it bqcomes ____________________________ v J 2 g J + xY Lx - £2 - x2 L2) • • • (vi.) where tx and t2, xx and a?2, L2 and L2 indicate the thermo- metric temperatures, dryness fractions, and latent heats of 3 si