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.

COMPOUND INJECTORS. 117 CHAPTER X. Compound Injectors. In our discussion of the steam nozzle we referred to that arrangement of lifting and forcing steam nozzles in which the incoming water jet is caused to move with a high velocity before it is acted on by tlie forcing steam jet. In compound injectors, two steam nozzles—-termed lift- ing and forcing nozzles—are employed. The watei' jet is given a high velocity by the lifting nozzle, such velocity being then converted into pressure in a diverging nozzle, and again reconverted into velocity at the entrance to the combining nozzle of the forcing portion. A compound injector is simply two injectors, the one—termed tlie forcer—receiving the delivery of the other termed the lifter. A compound injector is illustratecl at fig. 66. Tlæ lift- ing portion' comprises a steam nozzle a, a watei’ inlet b, and a combining delivery nozzle c. The jet issuing from the latter nozzle passes to the inlet end of the combining delivery nozzle d of the forcing portion, wliere.it is acted on by the steam jet from the forcing steam nozzle e. The steam valves g and h of the steam nozzles are operated by a cross bar i from a rod j connected to the hånd lever k, which also operates the overflow valve m by means of a connecting link and eccentric. To start the injector the hånd lever k is pulled towards the left in the illustratecl example, and first opens the overflow valve m and at the same time moves the bar i to open the steam valves. As, however, tlie area of the forcing steam valve h is larger than that of the lifter valve g, the steam holds the former valve upon its seat and the latter valve is opened. When water appears at the overflow, the lever k is given a further movement to the left, which closes the overflow valve m and opens the forcing steam valve h. Delivery is then cffected into the boiler being fed. The lifting portion of the compound injector is designed on thø lines of an ejector; that is to say, tlie effective