![]() If the injector cannot initially overcome boiler pressure, the overflow allows the injector to continue to draw water and steam. Overflow Īn overflow is required for excess steam or water to discharge, especially during starting. It differs from the non-lifting type mainly in the relative dimensions of the nozzles. ![]() fluid lying below the level of the injector. The lifting injector can operate with negative inlet fluid pressure i.e. The non-lifting Nathan 4000 injector used on the Southern Pacific 4294 could push 12,000 US gallons (45,000 L) per hour at 250 psi (17 bar). The steam-cone minimal orifice diameter is kept larger than the combining cone minimal diameter. In a non-lifting injector, positive inlet fluid pressure is needed e.g. Other key properties of an injector include the fluid inlet pressure requirements i.e. The compression ratio of the injector, P 2 / P 1 (in kg/h) of motive fluid. Key design parameters įluid feed rate and operating pressure range are the key parameters of an injector, and vacuum pressure and evacuation rate are the key parameters for an ejector.Ĭompression ratio and the entrainment ratio may also be defined: The entrained suction fluid may be a gas, a liquid, a slurry, or a dust-laden gas stream. The motive fluid may be a liquid, steam or any other gas. Injectors are therefore typically over 98% energy-efficient overall they are also simple compared to the many moving parts in a feed pump. Most of the heat energy in the condensed steam is returned to the boiler, increasing the thermal efficiency of the process. The condensate mixture then enters a divergent "delivery cone" which slows the jet, converting kinetic energy back into static pressure energy above the pressure of the boiler enabling its feed through a non-return valve. 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. ![]()
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