Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1892-02-21

but cne-thirty-fifth of its total heat-it
falls to a pressure of but 10 atmospheres.
How can loss so great as this be remedied?
First, by jacketing the cylinder either with
live steam from the boiler, or, preferably,
with steam hotter still from an
auxiliary boiler, or by gas flame.
A second plan is to superheat the
steam, the furnace being modi-
fed for the purpose. The third and best
method of all, usually employed with the
other two, is to use more than one cylinder
for the steam's expansion. In the ordinary
compound engine, which has two cylinders,
the steam is expanded in part in the first
cylinder, and then passes to the second to
be expanded to its utmost limit The triple
expansion engine has three cylinders, be-
tween which the working force of single
charge of steam is divided in the same wav
This seems like an undue multiplication of
machinery, but its operation is gainful,
nevertheless.
Object of Triple Expansion.
The fall of temperature in each cylinder
of triple expansion engine is kept within
one-third the range traversed when full ex-
pansion takes place in o single cylinder.
Thus limited in its cooling, each of the
three cylinders is much more easily kept as
hot as the steam which enters it. Quad
ruple expansion engines have followed
upon triple, but so far they are in much
less demand. Very interesting experiments
have been made with pistons and cylinders
surfaced with non-conductors such as por-
celain, glass and cements, intended to re-
duce the cooling effect Of expansion. Some
practical benefit is very likely to be won in
this direction.
In working multiple expansion engines
there is q mechanical advantage which has
done not little to recommend them. Their
three or four cylinders can be so grouped as
perfectly to equalize the strain on the work.
ing parts, and uniformity of motion is pro-
NOTED at the same time that repairs are
brought to q minimum. With freedom to
run at very high speed, these engines enter
upon q further source of gain. The in
jurious cooling of 8 cylinder by its expand
ing contents requires time, though very
little; if the piston's journey is extremely
rapid, only fracti on of this cooling effect
can be exerted. Economy, Furthermore,
comes with increase in an engines size
this for the reason that while its capacity
augments as the cube of its length or other
dimension, its rubbing surfaces, the areas
at which steam can be hurtfully cooled or
heat wastefully radiated and conducted, in
crease only as the square.
The Most Efficient Known.
Fully to develop its strong points, this
type of engines asks comparatively steady
load, such as that put upon it in textile
mill. Applied to this kind of work re-
Gently erected Corliss triple expansion en-
CINE has shown an efficiency so per cent
greater than that of the very best engine of
the single cylinder class. 1t uses less than
IL pounds of fuel per horse power per
hour. Developing 1000 horse power, it
consumes but !, AS pounds of Pocahontas
coal per hour Its third and last expansion
is performed in two cylinders instead of
one, so as to give perfect balance to the
strains on its shalt.
Though marine and stationary engines in
their best estate are wasteful of the fuel
supplied them, locomotives are more waste
ful still. Wide fluctuations of load, fire.
quent stops, exposure of cylinders all COM
hine to make their losses reach a very high
figure. Compromising has been applied to
locomotives with highly satisfactory re-
suits. Owing, however, to the resistance
which the steam encounters in passing
through two sets of ports, the compound
locomotive is better adapted for slow pas
senger and freight service than for fast ex-
press trains. On the Western New York
and Pennsylvania Railroad last September
the work of two Baldwin locomotives was
carefully compared. The engines we're pre-
cisely alike except that one was simple and
the other compound Ataspeed averaging