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October 22nd. You are respectfully requested to contribute.

(Alt rights reserved.)
ADVANCE PROOF~(Subject to rmtion.)
Thl. proof t. «ent to you for discussion only, and on the
•xpress ur.derstandlnathat It Is not to be used for any other
purpose whatever.-(.V« i>„ 40. </ the CunHitmion.)

(iCattAdinit jloc«t« at (&m (ftnflinrew.

INCORPORATED 1887.

TRANSACTIONS.

N.B.-Thl. 8«i,ty, „ , body, does not hold ifelf re.pon,ibl. for th. f„u «>d opinion,
stated in any of its publioations.

THE STEAM ENGINE.

By W. H. Laubib, M. Can. See. C. E.

To be read on Thursdiiy, October 8th, 1891

In tracing up the hi.tory of the steam engine, considered a« a
tramo mechanrnm, we lind that the modern steam engine has
been fully developed within the last 200 years-orsincelhe year
I .90, and Us advance during that time, may be divided into four
stages, 01- periods of 50 years each.

lfi90_FiR8T Stage ok Period— 1740.

As a .ule the great majority of inventions when first intro-
duced to the public are more ,.r less complicated and cumber-
some, the object of subsequent improve.nents bein^ to simplify
and ,-educe the nurr.ber of parts. To this rule tho^Mm engine
torms a striking contrast, it having been first introduced in its
simplest form, each consecutive stage in its history being marked
by an increase in the number of its parts and in the complica-
tion ct Its construction, and a corresponding reduction in the
consumption of steam per horse power.

About the year 1690, Denys Papin invented the Hrst steam
engine, or rather steam cylinder with a piston. When rir.t
introduced, the cylinder performed the functions of steam boiler
steam cylinder, and condenser. It was operated as follows ~-\
^mall quantity ol water was placed at the bottom of cylinder
a hre built beneath it, the steam formed raisins,^ the piston ttl
the top of cylinder, where a latch enga.^od a notch in the piston-
rod holding it up until it was desired that it should drop.

The fire being removed, the steam condensed forming a vacuum
below the piston, the latch being disengaged the piston was
.Inven down by the pressure of the atmosphere, raising a weight
which ha.l been in the mean time attached to a rope from U.e
piston rod over pulleys. This machine made one stroke per
"^Z^':^ . '"'■""^'' '•"'^'"'•'to.l chat a 24" cylinder would raise
,000 lbs., four feet, per minute, or developo nearly one horse
power. I J

A few years after his first invention Pajjin made another im-
poitant invention which increased the efflcioncy of his en-ino bv
using a seperate steam generator, as described at the time, a kind
ot tiro box steam boiler, in which the fire, completely Kirroundetl
by water, made steam so rapidly that his engine could be driven
al the rate of four strokes per minute by the steam supplied
from it. '^

The Papin engine was further improved and developed by
Newcoinen, Bcighton & 8moatoii, producing a combinMtio,, .if
several ol the elementary parts of the modern engine, making it

capable of transmitting^ force directly to the resistance to be
overcome, the object boinj? to make it better adapted to pumping
mincH, &c., the piston being connetlod to the pump by means of
the overhead beam.

During the tirst period of development the steam engine was
used almost entirely as a pumping machine, and might more
properly be considered an atmospherio engine, as steam was
used only to produce a vacuum, the powoi- being supplied by the
pressure of the •ilmosphoreand that on one Mo of piston only.

1740— Second Period— 1790.

The second stage or pei'iod in the devuiopraont of the steam
engine may bo considered enliroly as the work of James Watt
(that stage being marked by more rapid development than any
other). He, among many other important inventions and im-
provements, add,Ml to the engine of the tirst period, the separate
condenser, air-pump, fly-ball governor, crosshoad, guides, par-
allel-motion, rotary-motion, double-action, and non-condenHing,
high-pressure steam engine. With these additions completed, it
embodied nearly all of the cssontial foatuies of the modern
engine. He also discovered the advantages to be derived from
the use of steam expansively, and specihed a cut-oft" at J stroke
as the mOHt ecomomical. This discovery has proved to be most
important in the development of the economical application of
steam, althoiigii shortly after its tirst introduction, it haJ to be
discontinued, owing to the trouble and annoyance Watt exper-
ienced with proprietoi's and their engineers altering the valves.
He intended to rosutoe it at a later period wnen workmen of
greater intelligence and reliability could be found.

1790_Third Pbriod— 1840.

The distinguishing feature of the thii-d period was the intro-
ducing of the compound, or two-cylinder engine. Although the
lirst compound engine was invented in 1781, by Jonathan Horn-
blowcr, it was not a success, owing to the steam i)ressure used at
that time being so low that uo advantage was gained by the
device.

In 1804 the Hornblower compound engine was again intro-
duced by Arthur Woolf, and, by using steam at a higher pressure,
and expanding it from six to nine volumes, a very great advan-
tage was gained over the Wiitt and other engines of that time.
Other engineers followed in Woolf V footsteps, designing moditi-
cationn of the compound engine, so that by the end of the thin)
period which we have considei'od, the compound had become a
standard engine.

1840— Fourth Period— 1890.

The most important features in the development of the eco-
nomical use of steam during the fourth period, or that of the
immediate past, has been the invention and introduction of the
automatic engine, and the system of expansion (in two cylinders
during the former period) being carried to three oi' four cylinder.-.

The fli-st automatic engine was invented by George II. Coriis~,
about the year IH.iO. An aljustable drop cut-off had boon in
vented ten years earlier by F. E. Sickeis, but Corliss was the firsi
to attach the governor directly to the cut-otf i.iechanism, and, \>y
so doing, I'egulato the speed of the engine by adjusting the point
of cutoff, and also using titoam in the "ylinder at nearly boiler
pressure up to that point.

To form an idea of the advantages of modern steam practise as
compared wilh thai of the earlier stages of its use, and to note
tlie advance made during the lour ditferent stages that wc have
considered, wo will have to assume an avei'age indicator card
from x;ach period from the inform.ation we. hnvo, and, by annliz-
ing each, form a compaiison.

For that purpose we will assume a atoam cylinder of 13f" dia-
meter, or a net area of 144 squuro inches in ench, and for the first
period a guage pressure of 1 lb. or 16 Iba absolute— i.e.

Oabd No. 1.

Allowing 1 lb. to raise weight of piston, rod, etc., and that a
vacuum be produced equal to a M. E. P. of 7 lbs. below the
atmospheric line, and allowing a piston truv ol of 100 f9et per
minute, the power developed will be 144 X 100 X 7 = 100,800
:- 33000 = 305 horse power, and the theoretical consumption of
steum will be 100 cubic feet per minute or 6,000 cubic feet per
hour, and as steam at l« lbs. absolute weighs •0411 per cubic
foot, then 6000 X 0411 = 246-6 lbs. of steam per hour, and as
we have found that the power developed will be 305 H. P. then
2466 — 3-05 = 8085 lbs. of steam per hour per H. P, as the
consumption for Ihe first period.

For the second period with same cylinder area we will assume
200 feet of piston travel. (Steam at this period was used above
atmospheric pre,s8uro, and double acting.)

Cahd No. 2.

For this card wc will assume a steam p;es8ure of 15 lbs and a
terminal of 26 lbs. absolute, a M. ii. P. of 224 lbs., the power
developed will bo 144 X 224 X 200 ~- 33000 = 195 H. P. and
the amount of steam consumed will be 200 cubic feet per minute
or 12,000 cubic feet per hour and as steem at the terminal
pressure, viz. : 26 absolute, weighs 0650 per cubic foot then
12000 X '0650 = 780 lbs. per hour, this divided by 19-5 = 40
lbs. of water per hour per H. P. for the second period, or about
one-half of that required to develop ■ horse power 50 years
earlier.

For the third period a still higher steam pressure was used
and expansion carried to 6 and 9 volumes. '

Cabd No 3.

For this cai-d we will assume, sitme eylin.ler area, 400 feet
piston travel 40 lbs. steam pressure expanded 7^ volumes and a
M. E. P. of 16 lbs., the power developed will be 144 x 4"0 X 16
4- 33000 = 27-93 H. P. and the steam consumption measured
from terminal of !) lbs. will he 400 X 60 = 24000 X -0239 ~
27-93 — 20-5 lbs. of steam per hour per horse power, or about
one-half of the cost of same power during second period and one-
fourth of cost of same power during first period.

For the fourth and last period of steam engine practice we have
in many instances a steam pressure of 200 lbs., also cylinder steam
jacketed with superheated steam, and other refinements that tend
to reduce steam consumption.

Cabd No. 4.

For this period we will assume a steam pressure of 150 lbs
expanded 20 volumes, a M. E. P. of 31 lbs. referred to sam'e
cylinder area as in other cards, viz. 14t inches and a piston travel
of 800 ft., this will develope 108 horse power, and the steam con-
sumption will be abcut 10 lbs. per hour per horse power.

In reviewing these four periods we have in the first, steam used
at a little over atmosphere pressure, without expansion, a piston
travel of 100 ft. per minute, a power developed of 3.05 H. P.. at
a cost of 80 lbs. of steam per hour per H. P.

In the second period we have steam at 15 lbs. .ibovo atmos-
phere, without expansion, a piston travel of 200 it. pur minute
a power develoi)ed of l<t5 II. P., with a steam consumption of 40
lbs. pei- hour per II. P.

In the third period, we have steam at 40 lbs. above atmosphere,
expanded to 7J volumes, a piston travel of 400 ft a minute, a
power dcvclopea of 2793 II. P., with a steam comsumption of 20
lbs. per hour per H. P.

And in the fourth period we have steam at a pressore of IBO
lbs. above atmosphere, expanded to 20 volumoM, a piston travel of
800 ft. per minute and a power develop*! of 108 H.P., with a
a ateam consumption of 10 lbs. per hour per horse power.

Cyi~ An«A.

Piston tr'vel.

Steam P.

Power.
306

Theoretical
Consumption

lit.... 144

100

80 lbs.

L'nd... ''

200

106

40 "

Srd... "

40O

28-0

20 "

4th.... "

800

160

108. U

10 "

From the^e figures we find that the tendency through all the
different periods, has beun increased stoam pressure, and higher
ratio of expansion or hi,%'h initial and low terminal, i.e., theoretic-
ally the higher the initial and the lower the terminal, the greater
the economy. But practice has estnblishol it to be a fact thrt
the higher tho initial and the lower the terminal, or the greater
the ratio of expansion in a single cylinder, tho greater the loss
both by clearance iind condensation.

Clearance in tho space between the piston and valve face when
:in engine is on it« centre (including area of ports, passages, etc.)
which has to bo tilled with steam each stroke before the piston
moves forward, and is computed by the percentage its volume
bears to the area of piston raullipliod by the length of its stroke.
This percentage varies from 2 p.c. in long stroke engines to 15
!ind even 20 p.c. in short stvoko engines.

The loss by clearance is quite a serious one where expansion is
carried to extremes in a single cylinder and also in short stroke
engines, where it forms a high percentage of the volume of
cylinder.

If we take as an illustration a condensing engine card, with
steam pressure 80 lbs., expanded 20 volumes without loss by
clearance, we get a mean etlective pressure of 15 lbs.

(^'aed No. 6.

Then expand the same volume of steam in a cylinder of s;imo
area, but with 5 per oeiil. clearance, we tind that the card shows
the steam to have been cut otf at the time the engine was on its
centre; we' got the same expansion line and same terminal, but
the area is minus the initial pressure, or a mean average pro-
sure of 10.5 lbs. instead of 15 lbs., as in the first instance, repre-
senting a loss of 30 per cent, in power.

Than, again, if the same pressure, viz., 80 lbs., be expanded 10
volumes, the loss is reduced to 16.66 per cent.; expanded 5
volumes, the loss is reduced to 0.76 per cent., and if only ex-
panded 3 volumes, the loss is reduced to about 7 per cent.

Therefore the greater the i-atio of expansion in a sin_y;lo
cylinder the greater the loss by clearance, and the less the ex
pansion in a cylinder the less the percentage of loss by clearance.
The loss by clearance may be .educed to u (certain extent, but
not entirely- overcome by coiupression or cushion.

( 'ONDENSATION.

The loss by condensation is due to the variation in the tem-
|)orature of steam during expansion. If steam at 80 lbs. gauge
pressure, or 95 abs dute, be expanded 20 volumes, tho initial tem-
perature would bo 324 degrees Fahrenhiet and the terminal
about 160 degrees.

During expansion, as the temperature of tlie steam falls, the
temperature of the metal of the cylinder tails in proportion, so
that when the boiler pressure is again admitted to the cylinder it
takes a certain proportion of the steam admitted to raise the
temperature of the suri'ounding metal to the initial temperature;
the greater the ratio of expansicm the greatei- the variation in
temperature in the I'yiinder, and the greate" the proportion of

8tf«m required to raiHe that temperature; the Ibhb the expansion
in a cylinder tfjii Jesn tlie variation of temperature, and the Ip-w
Hteani will be condenned in raining tiiat ten.perature each Btroke ;
or the smaller the volume of^team admitted to the cylinder each
stroke the greater will the percentage "of loss by condensation "
bear to that volume, and, on the other hand, the greater the
volume of steam admitted to the cylinder each stroke the Ibbh
will the percentage "of loss by condensation" bear to that volume.
From experiments carried out these losses have been com-
puted approximately for unjiicketed single cylinder engines with
low percentage of cleariince as follows, viz. :—

Expunsiono. I'owor Loss.

56 p. f. 45 p. c.

«5 " 35 '•

7B " 26 "

80 " 20 "

2 85 " 15 "

With 5 per cent, added for condensing engines,
Another seiious objection to high ratios of expansion in a
single cylinder, is the very great variation in the working strains
throughout the stroke. For example, if wo expand 80 lbs. steam
pressure to 20 volumes in a single cylinder Condensing Engine,
we have a pressure of 92 ILs. por ^q^urc inch of piston at the
beginning of the stroke, 1 .75 lb. at the ..nd of the stroke, and a
M. E. P. ot 15 Ibn., and us the strength of un engine in all its
woiking parts must bo in proportion to the greatest pressure to
which it is subjected, then the weight of the working parts must
be entirely out of proportion to the power actually developed, and
the t\y wheel especially must be very much heavier than that re-
quired in an engine whoi'e steam is expanded from ,! to 5 volumes.
The theoretical gain by expansion in a condensing engine is
approximately as follows, taking 80 lbs. gauge pressui'e without
expansion as a basis.

Expanded to 20 volumes. To por cent.
10 - ti5
" 6 " (10 "

" 'a " 50 ■'

" 2 " 40 "

" Ik " -'()

To obtain the economical advantages resulting from high ratios
of expansion, and Mt the same time avoid the enormous losses
attending its expu,.. ion in a single cylinder, is the object oi the
introduction of the compound. Triple and (iuadruple'expansion
engines. For example, in a compound engine with low pressure
cylinder four time, the area of high pressure, l(i expansions may
be .,blaiiie.l with four expansions in each cylinder. In this way
the high pressure cylinder works with steam between limit« of
tempeiature, such as occasion compaiatively small lo.sses by con-
densation, and the low pressure cylinder works between the
temperature of the exhaust from high pressure and that of the
c.iidenser; these temperatures not varying very widely the loss
by c..nden.sati(m is correspondingly small. Another great ad van-
tage of the compound over that of the single cylindiii- engine
(expanding steam to the same number of volumes), is the botte,.
distribution of the work throughout the stroke, admitting of the
working parts being made much lighter in proportion to the
actual power develojjed.

Ii would almost apjjear as if the economical limit in expansion
had been reached, as by our example for the last period, the
theoretic consumption lor 150 lbs. expanded 20 volumes, was 10
lbs. of water per hour per II. P., whereas, if we raise the pre-sure
to 200 lbs. and expand :i0 volumes, the gain is only abtit 5
per cent. ; if raised to 400 lbs. and expanded 40 volumes, the gain
IS about 20 percent.; and if to 800 lbs. expanded 40 volumes
about 25 per cent. '

But to counteract this apparent gain, we have increased coal
consumption in raising the water to the temperature duo to the
increase of pressure, and also increased losses by condensation in
using steam ut that temperature.