INJECTOR, a mechanism for feeding water into a steam boiler while it is in operation, through the force of its own steam. The ac tion of this device is based on that principle of hydrodynamics in virtue of which the velocity of a moving body of water or other liquid may be transmuted into pressure, and vice-versa, by proper arrangements of conduits and apertures.
In the injector a jet of steam, issuing from the boiler at a velocity of from 1,500 to 3,500 feet per second (depending upon the boiler pressure), is passed through A conical nozzle, indicated in the diagram by the letter A; from which it passes into another cone-shaped tube B. The open space 0 around the cone A is connected freely with the water-supply pipe D. This space may be filled with water by gravity from a reservoir above its level; or the action of she injector may be so arranged that through the exhausting of the air in B and 0 by the let of. steam a vacuum is produced and water may be thus °sucked° up from a well below, if the lift is not more than 15 to 18 feet. The rush of steam through the conical °combining tube° B drags along with it a conical shell of water lying next the walls of B and encasing a cone shaped body of steam in its centre. As the moving steam . and water are choked at the apex of B, the 'steam is compressed, in part condensed and in part absorbed by the water, which takes up its velocity to a lqrge, degree and rushes into the apex of the conical tube C. Here the flare of the cone is in the opposite direction and as the column of water moves forward into this tube its velocity lessens as the tube grows larger, and is resolved iron pressure, which presently becomes greater than the steam pressure in the..boiler by which the check valve V is kept closed. The valve V then opens and permits the water in C to flow through. At this instant the vatying pressures throughout the injector come to an equilibrium, based on the condition of that pressure at which the water flows freely from the injector into the boiler — and that condition continues indefinitely as long as the steam pressure in the boiler remains uniform. Previous to the establishing of the steady flow, that is, before sufficient pressure obtains, steam and water es cape into the casing space S and make their way out through the overflow valve F, which is notmally held closed by a spring. When the
flew into the boiler is established the overflow ceases.
The injector for any particular boiler is re quired to be of certain dimensions to suit the pressure of steam with which it must work. However, there are adjustments which may be made to cover the variations to be expected in the normal use of the boiler in question. Thus, steam issuing at the boiler pressure of 6.' pounds may be made by the proper configura tion of the conical tubes of the injector to exert a pressure of 90 pounds at the check valve into the boiler. While this pressure is too high for the feeding in of a normal supply of water — that required to replace the water which the boiler evaporates into steam from hour to hour — the pressure in the injector may be modified to a degree by the needle valve N in the steam supply pipe, and the dis charge of the injector into the boiler regulated to a nicety.
The injector works well with water of a moderate temperature, that is, about 75°- with water above 110° it will not work at all.
The injectors most in use are of the non automatic type, although the automatic sorts are coming more and more into favor. There are also some forms with two injector tubes working into the one discharge chamber which feedlifte boiler. This latteris preferable where.the injector is operated with-the ex haust steam (of high-pressure engines) which requires a larger steam supply and a larger area in the steam orilices to do the work.
The accompanying diagram is intended only to show clearly the principles on which the injector is able to perform its duty. For a study of the adaptations of these principles the reader is referred to