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.

38 THE STEAM INJECTOR. and 4, causing loss in velocity and probably grooving of the nozzle. The angle of clivergence of the walls of conical delivery nozzles is usually abo ut 5 deg. At the moutli or exit the nozzle is rouuded, as shown in fig. 20. Fig. 21 shows a design of delivery nozzle as forind in some injectors, the upper portion of the figure giving velocity and pressure curves for the nozzle. It will be seen that the pressure curve is of very even form. Makers are not in agreeme-nt as to the best length and form of nozzle to employ to effect the requirecl conversion of kinetic into pressure energy. The length of the delivery nozzle varies in different injectors from 10 to 16 times the diameter of the nozzle throat. Fig. 19. The correct proportioning of a diverging nozzle, to re- dtioe the velocity of the jet passing theivthrough. to a certain amount, depends upon the velocity of the jet as it enters the nozzle. In the case illustrated at fig. 17, where a velocity curve has been plotted for an initial velocity of 100 ft. per second, the final velocity is 5 ft. per second; but when the cntering jet travels at 200 ft. per second the final velocity is 10 ft. per second. It would appear, there- fore, tliat different designs of nozzle should be employed for high and low jet velocities in order to obtain the most efficient action; otherwise if the nozzle be designed for a low velocity jet, and a high velocity jet be employed, the latter will leave the delivery nozzle with an unnecessarily large amount of its kinetic energy unconverted into pres- sure energy. The point is, however, of more importance from a theoretical than from a practical standpoint, as