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.

NOZZLE DIMENSIONS. 99 than the velocity equivalent of 80 l'bs. per square inch above latmospheric pressure—the pressure at the delivery nozzle throat being oonsidered as atmosplieoic, and in the delivery pipe as 95 Ibs. absolute, or 5 Ibs. above boiler pressure. If we øonsider that the velocity of the incoming water was 25 per cent less th.a.n that calculated above, say about 33 ft. per second, then the actual effective velocity re- quired in the steam to giv© a delivery velocity of 136 ft. pei’ second would be about 1,506 ft. per second. The calculated area øf the delivery nozzle throat would be:—- , 4 x 14-3 '' 13-3 x 62-4 x 136 = '0005067 square foot, which gives a ratio of steaun nozzle throat area to delivery nozzle throat area of 3’1 to 1, which is near to that adopted in practice A point about which experimental data is lacking is the density of the jet as it passes the delivery nozzle throat. It is known from experiments that a quantity of air is mixed with the water, but it is not known as to whether the steam is all condensed in the combdnino- nozzle. This knowledge would enable us to give a more acourate figure for density in the formula for area of delivery nozzle throat. The above method has been set out in full, but it involves several cumbersome calculations. The determination of the steam nozzle throat area can b© effected quite readily by the applikation of Napier’s formula: — W — P * 70 ’ . W x 70 A = -------. or P The amount of steam used per second in the injector was —— Ibs. and the pressure (/>) was 90 Ibs. per square inch; 13*3