![]() ![]() After passing through the convergent "combining cone", the mixed fluid is fully condensed, releasing the latent heat of evaporation of the steam which imparts extra velocity to the water. It uses the Venturi effect of a converging-diverging nozzle on a steam jet to convert the pressure energy of the steam to velocity energy, reducing its pressure to below that of the atmosphere, which enables it to entrain a fluid (e.g., water). Injectors exist in many variations, and can have several stages, each repeating the same basic operating principle, to increase their overall effect. The motive fluid induces the secondary fluid to move. The injector consists of a body filled with a secondary fluid, into which a motive fluid is injected. Īfter some initial scepticism resulting from the unfamiliar and superficially paradoxical mode of operation, : 5 the injector became widely adopted for steam locomotives as an alternative to mechanical pumps. The injector was invented by Henri Giffard in early 1850s and patented in 1858, for use on steam locomotives, and patented in the United Kingdom by Sharp, Stewart and Company of Glasgow. An ejector operates on similar principles to create a vacuum feed connection for braking systems etc. ![]() Other types of injector may use other pressurised motive fluids such as air.ĭepending on the application, an injector can also take the form of an eductor-jet pump, a water eductor or an aspirator. When first developed, its operation was intriguing because it seemed paradoxical, almost like perpetual motion, but it was later explained using thermodynamics. It is a fluid-dynamic pump with no moving parts except a valve to control inlet flow.Ī steam injector is a typical application of the principle used to deliver cold water to a boiler against its own pressure, using its own live or exhaust steam, replacing any mechanical pump. A- Steam from boiler, B- Needle valve, C- Needle valve handle, D- Steam and water combine, E- Water feed, F- Combining cone, G- Delivery nozzle and cone, H- delivery chamber and pipe, K- Check valve, L- OverflowĪn injector is a system of ducting and nozzles used to direct the flow of a high-pressure fluid in such a way that a lower pressure fluid is entrained in the jet and carried through a duct to a region of higher pressure.
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