INJECTOR, GIFFARD'S, is now in general use for feeding water into steam-boilers, particularly locomotive boilers. Feed-pumps are difficult to keep in order when driven at high speed. The very rapid action of the valves severely tries their durability. In tire case of locomotives, inconvenience was often occasioned by tire fact that their feed-pumps acted only when they were running; and thus, if an engine happened to stand still for any length of time, the water occasionally got too low in the boiler. The. injector acts equally well whether the engine is running or at rest..
The diagram fig. 1 will give an idea of the essential parts of the injector. A. is the, steam-boiler, B hieing the water-level, CDF a pipe into which steam is admitted: this Pipe terminates in a cone DF, which is inclosed in a larger cone IIH. In the cone DF, the pointed plug E can be raised or lowered so as to increase or diminish the areaof the ......m............ aperture at its lower end P. G is a pipe conlinuni * eating with the water-cistern, and admitting water: into the extetaial cone IIH. K is a pipe communi- _ _ _ _ eating with the boiler ,ruder the water-level. On open _ G t _ _, I. lug communications between the boiler and this i apparatus, it might be. expected that steam would, rush out at F. and water at li, both currents meet ' big with great force, and escaping into the atmosphere between the two openings. Paradoxical as it may - , appear, the outflowing stream of water at K, although 1 it is actually flowing under a greater pressure than the . - --== -----_---.. I- -:'--2-Z----1 Of steam escaping at F, clue to the head of ""7-=- ! ' . ',.., 7 ',f water arising from the difference of level between the - -- lo,;4. aperture at K and the water-level at is overpowered, a t and driven back into the boiler; and not only is the - _ _ _.
' - - -- _ _ -_----- outflowing current of steam at F able to drive back .
- - - - - ' the stream of water trying -to escape at K, but the H torrent of steam drags with it a large quantity of_ _ water with which it collies into contact as it is passing :V". through the cone HH. This water finds its way into
_ . the cone Hit, through the pipe G, from the tender- - or cistern, and constitutes the feed-water. The steam - - - - - - ____-_----- rushing from the aperture at 1' will necessarily be _ _ __ -_-_-_ __ _-_ condensed by the cold water with which it conies into contact in the cone HH. The explanation offered of iii. -,.- the action of this apparatus is as follows. The open Faa. 1. ing at' F, through which the steam escapes, has nearly twice the area of the opening into which the water is to be forced at K. The opening in the cone HH is also larger than the aperture at K, and it appears that the mechanical power contained in the flow of steam from F is, as it were, transformed from a large area to a smaller, with a corre- fi .
sponding increase in its intensity. This diminution of its volume 11 ; , arises from its condensation by the cold water through which it has 1;111, y to rush in the cone MI. We get thus the mechanical power due '`-f I to a column of large area concentrated into a small area, with a cor responding increase in its velocity, and to this increase of velocity is due the fact that a current issuing at FH will enter at K, in spite of the . , counter-pressure at K The injector for feeding boilers is rather an 1 expensive apparatus, in consequence of the number of adjustable parts required to be provided. Variations in the pressure of steam ---=-- require alterations in the area of the steam-passage, and in the distances between the months of the conical openings for the outflow and inflow of steam and Fig. 2 shows in section a simple form of injector for raising water. s Steam issuing from the pipe S, into the vessel WR, will draw the water through the pipe T, and force it up through the narrow neck FIG. 2 below R., to a height of about one foot for every pound of pressure per square inch. It is doubtful if those injectors can work so economically, as regards expenditure of steam, as ordinary slow-moving pumps: but they possess many con veniences and advantages, which are bringing them into use.