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.

THE D ELIVERY NOZZLE. 43 On the subject of the losses in diverging nozzles through which water is flowing, Professor A. H. Gibson, D.Sc., has conducted an extended series of experiments, the results of which are given in an article entitled “ The Conversion of Kinetic to Pressure Energy in the Fiow of Water through Passages having Divergent Boutidaries,” which appeared in Engineering of February 16th, 1912. The most important portion of such article, so far as the injector is concerned, is given below, by the kind permission of the proprietors of the above-mentioned journal. The article also deals with trumpet-shaped pipes or nozzles, and it was fouud in this case tbat the most efficient nozzles were those in which the loss of head per unit length of the passage was constant. Compound pipes or passages are also dealt with. Referriug to uniformly tapering pipes, the writer states : “It would naturally be supposed that by enlarging the section gradually, shock and -consequent eddy formation and loss of energy would be reduced, and to determine the extent to which this conclusion is justified a series of experi- ments on uniformly tapering pipes was carried out. Some of these were of circular cross-section, others were square, and others rectangular, with one pair of sides parallel. The ratio of final to initial areas ranged between 2'25 to 1 and 9 to 1, the larger diameters being 3 in., while the larger end of the square and rectangular pipes had the same area as the circular pipes. The mean results of these experiments are shown in figs. 22 and 23, from which the foHowing conclusions are to be drawn :— (a) In a circular pipe, with uniformly diverging boundaries, the loss of head, expressed, hs a percentage of - v.i)1 4- 2 g, varies somewhat with the mean diameter of the pipe, and with the ratio of final to initial area, as well as with the angle (9, between its opposite faces. For values of 0 between 6 deg. and 35 deg. the differences are comparatively small, and the loss of head is given fairly accurately by— Loss = 0-011 Ø1-22 feet, 2 <7 where t) is measured in degrees.