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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90
THE STEAM INJECTOR.
In this case it will be søen that the ratio by wøight of
steam to water is about 1 to 8.
The efficiency of an injector from the point of view of
the ratio of water to steam passing therethrough is affected
by variations in the steam pressure and in the feed-water
temperature.
If tlie pressure of the steam entering an inijector in-
creases wliilst the feed-water temperature remains un-
changed, or if the pressure of the steam remains constiant
whilst the feed-water temperature is increased, the tempera-
ture of the mixture of steam and water is increased. The
vacuum a.t the inlet end of tlie injector where tlie steam
and water first meet is therefore impaired, and results in
a reduction in the quantity of water flowing into the iniector
wliilst maximum weight flow of the steam is maintained
under all normal working conditions.
In the following ta'ble the ratio by weight of water to
steam is given for a typical example when the feecl-water
temperature is constant and the steam pressure is varied:
Tabie vin.
Steam pressure, pounds per square inch absolute 40 65
Pounds of water per pound of steam .......... 28'5 20
90 140 215
17 14 11
The aibove results would be affeoted by variations in
design of t-lie injector, in the lieight oæ lift, or the pressure
head of .feed water, and must only be considered as typical.
If the pressure of the steam and the temperature of the
feed water inc-rease simultaneously, the ratio of water to
steam will deorease more rapidly than if tlie one valne only
were increasing.
The effect of the lieight of suction lift or the pressure
head of the incoming feed water will be appreciated from
the velocity equation for the said water, whioh is
V = 8’025 ^/head in feet;
where V denotes velocity in feet pér second. If the
difference between atmospheric pressure and tlie pressure
at tlie entrance to the combining nozzle be taken as 10 Ibs.