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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124
THE STEAM INJECTOR.
Questions.
(1) Define an injector, and describe the essential parts
of same, giving particulars of their functions.
(2) The pressure of the steam entering the steam nozzlo
of a live-steam injector is 200 Ibs. per square inch absolute,
and the pressure at the delivery end of said nozzle is 5 Ibs.
per square inch absolute (vaouum. of 20 in.). Describe and
illustrate with rough diagrams the nature of the pressure
drop in and beyond tlie nozzle if tlie latter is of («) con-
vergent and (b) divergent form. What shape do you
recoinmend for the inlet to the nozzle throat, and what
taper for the outlet from said throat? What is the effect
of having the degree of clivergence of the outlet too great?
(3) Derive a formula for calculating the ratio of areas
of a steam nozzle throat and mouth to provide for any
desired pressure drop between said points, and calculate
the -said ratio for steam of a boiler pressure of 150 Ibs.
per square inch absolute discharging into a vacuuni of
28 in. (1 11). per square inch absolute pressure). Can you
give any simple approximate formula for obtaining said
ratio of areas?
(4) What form of nozzle do you recommend to obtain the
greatest velocity of discharge of steam? What is the
effect of («) under and (&) over expanding the steam upon
its velocity of discharge? At what point of a steam nozzle
does tlie greatest wear take placc?
(5) Describe and illustrate by a sketch an arrangement of
separate concentric lifting and forcing steam nozzles for
an injector. What special overflow arrangement is
necessary for this arrangement of nozzles? Describe and
illustrate a form of valve for controlling both the lifter
and forcer in an effeetive manner.
(G) Describe tlie funetion of an injector combining nozzle,
and set out tlie cbief factors which enter into the deter-
mination of the design or shape and length bf the nozzle.
What is considered a suitable length of combining nozzle
(compared with the diameter of the delivery nozzle throat)
for a hot-water injector?