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.

48 THE STEAM INJECTOB. the combining nozzle and the production of a vacuum in the feed supuly pipe prevented. If an injector is unable to rapidly clear itself uf steam when re-starting, so as to allow of the production of a vacuum in tlie feed-water pipe witliout reducing the steam supply, it is a non-automatic appliance. In 1871 it was proposed to provide an additional over- flow outlet at a point in the combining nozzle where the latter is of large diameter. The arrangement is illustrated at fig. 24, a indicating the usual overflow aperture between Fig. 24. the combining and delivery nozzles, and & the additional aperture. There is a valve c upon the overflow pipe from the injector. It is of the utmost importance in the consideration of the overflow arrangements of any particular injector to have an accurate knowledge of the pressure conditions at the various points in the combining nozzle where said arrange- ments are to be pro vided. For example, in all injectors a high degree of vacuum exists during the normal working of the appliance at the point where the steam and water first meet (i.e., at the mouth or inlet end of the combining nozzle), due to the rapid condensation of the steam. The intensity of such vacuum gradually diminishes as the jet approaches tlie delivery nozzle, due to the increase both in the tempera-