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.
Forfatter: V. A. B. Hughes
År: 1912
Forlag: The Technical Publishing Company Limited
Sted: London
Sider: 145
UDK: 621.176
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32
THE STEAM INJECTOB.
CHAPTER IV.
The Delivery Nozzle.
The jet of water which leaves the combining or mixing
nozzle of an injector is travelling at a high velocity—a
velocity higher than that with which a water jet would
issne from the boiler being fed—but merely to direct the
high velocity jet against the water within the boiler would
be- a very inefficient niethod of utilising that jet, for the
latter would strik© the mass of water in the boiler with
great violence, and its energy be to a large extent dissi-
pated in the form of eddies. This effect would be increased
in proportion to the increase in the velocities of tlie water
tending to enter and that tending to leave the boiler.
The object which mast be had in view in the treatment
of the jet leaving tlie combining nozzle is to reduce its
velocity and increase its pressure till the latter exceeds
that within the boiler being fed. Such object is attained
by causing the jet leaving the ponverging combining nozzle
to pass through a diverging delivery nozzle.
The diverging nozzle has received a de-gree of attention,
apart altogether from its connection with the subject of
injectors, on account of the faet that by its aid the quantity
of water discharged through an orifice in a given time can
be increased, the theoretical rate of increase being in tlie
ratio of the cross-sectional area at the diverging nozzle
mouth or outlet to the cross-sectional area at the diverging
nozzle throat, if the jet is able to fill the diverging nozzle
completely. Many investigations have been made on the
best form or taper of nozzle to give a maximum rate of
delivery from a tank or vessel being emptied.
In connection with injectors, it will be readily underst ood
that the water passing through the delivery nozzle mnst
completely fill the latter, due to the pressure against which
delivery is being effectecl resisting the free flow through
the nozzle, and that if said nozzle be cut through at several
points the same weight of water will pass each section