The Steam Engine Familiarly Explained and Illustrated: With an historical sketch of its invention and progressive improvement; its applications to navigation and railways; with plain axioms for railway speculatorsLardner, Dionysius
History
The Steam Engine Familiarly Explained and Illustrated: With an historical sketch of its invention and progressive improvement; its applications to navigation and railways; with plain axioms for railway speculators
Lardner, Dionysius
Steam-engines -- Early works to 1850
It appears therefore from this reasoning, that when the direct force
of steam of greater pressure than the atmosphere is used without
condensation, the total mechanical effect is always less than that
produced by the condensation of atmospheric steam without expansion;
but that the greater the pressure under which the steam is produced,
the less will be the difference between these effects. In general, the
proportion of the mechanical effect of high-pressure steam to the
effect produced by the condensation of atmospheric steam, will be as
the number of atmospheres expressing the pressure of the steam to the
same number increased by one. Thus, if steam be produced under the
pressure of six atmospheres, the proportion of its effect to that of
the condensation of atmospheric steam will be as six to seven.
(133.) Another method of applying the power of steam mechanically is,
to combine its direct action with condensation but without expansion.
The piston being, as before, loaded with one ton, the evaporation of
the water will raise it through six perpendicular inches, and the
result so far will be equivalent to a ton raised half a foot; but if
the piston-rod be supposed also to act by a chain or cord over a
wheel, so as to pull a weight up, the steam which has just raised the
ton weight through six inches, may be condensed, and the piston will
descend with a force of one ton into the vacuum thus produced, and
another ton may be thus raised through half a foot. The total
mechanical power thus yielded by the steam, adding to its direct
action its effect by condensation, will then be one ton raised through
one foot, being an effect exactly equal to that obtained by the
condensation of atmospheric steam.
If the piston be loaded with two tons, its direct action will, as we
have shown, raise these two tons through four inches, which is
equivalent to two thirds of a ton raised a foot. By condensing this
steam a ton weight may be raised in the same manner, by the descent
of the piston through a third of a foot, which is equivalent to the
third of a ton raised through one foot.
By pursuing like reasoning, it will appear that, if the direct force
of high-pressure steam be combined with the indirect force produced by
its condensation, the total mechanical effect will be precisely equal
to the mechanical effect by the mere condensation of atmospheric
steam.
(134.) In applying the principle of expansion to the direct action of
high-pressure steam, advantages are gained analogous to those already
explained with reference to the method of condensation.
Public-domain text, read in full here on John Shaqi.
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