Ernest Victor Lallier.

An elementary manual of the steam engine; containing also a chapter on the theory, construction and operation of internal combustion engines for the operating engineer online

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etttK

'Ulnivcreiti^ of Mieconein




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AN ELEMENTARY MANUAL

OF THE

STEAM ENGINE

CONTAINING ALSO

A CHAPTER ON THE THEORY, CONSTRUCTION

AND OPERATION OF INTERNAL

COMBUSTION ENGINES

FOR THE OPERATING ENGINEER



BY

ERNEST V. LALLIER

Instructor of Engineering at the Hebrew Technical Institute^ New York,
N.Y,; Member of the National Association of Stationary Engineers



NEW YORK

D. VAN NOSTRAND COMPANY

25 Park Place

1913



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Copyright, 1913,

BY

D. VAN NOSTRAND COMPANY



Stanbope l^ress

H. GILSON COMPANY
BOSTON, U.S.A.



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188713

SEP 22 m { Ci V? H ^

PREFACE.



The author has for some years been engaged as
an instructor in engineering. He has enjoyed intimate
acquaintance with students and with young men engaged
in the actual operation of steam plants. Many students
of steam engineering, while they may have had excel-
lent training in mathematics and general science, are
yet so inmiature that they do not readily make practical
application of their general knowledge; and the aver-
age operating man, despite his experience, realizes his
lack of adequate grasp of fundamental principles — a
lack which hampers his advancement.

To help both classes of men, teaching them to think
and to reason, they must be taught the subject in a
manner which may supplement their present partial
knowledge.

Great difficulty has been experienced in securing a
textbook fulfilling such requirements. The following
pages have therefore been written with a view to pre-
senting the fundamental principles of the use of steam
and steam engines in an elementary manner. It is
hoped that in thus offering in simple form the results
of an experience gained in active engineering practice,
a satisfactory foundation and guide may be furnished
for further study.



New York, Aug. i, 1913.



I. y. L.



m



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CONTENTS.



Rbciprocatino Stbam Engines Pt^B

The sUde-valve engine a

Principle of operation 5

Details of construction 6

Action of the eccentric and slide valve 13

Effects of lap and lead 17

Reversing link 19

Governors.

Their use and the principle of construction 23

The pendulum governor 37

The centrifugal governor 39

The inertia governor 30

Enoine Calculations.

To calculate the horse power 33

Back pressure 34

Piston speed 37

Thrust on the guides 38

Tangential pressure on crank pin 38

Prony brake 39

Woiic done by steam during formation 43

Saturated steam 43

Superheated steam 43

Heat unit 44

Horse power 47

Expansive working of steam 49

The Indicator.

Indicator cards 58

Description of indicator 69

Planimeter 75

Heat.

Thermometers 83

Units .* 84

Horse power 85

Transfer of heat 86

V



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vi CONTENTS.

Boilers. Fige

Fire-tube boilers 93

Calculations 99

Bursting pressure 102

Safe-working pressure 103

Strength of seams 103

Braces 105

Boiler horse power 109

Water-tube boilers iii

Care and operation of boilers 116

Firing xi8

Water column 121

Steam gage , 123

Furnace grates 125

Chimneys 129

Incrustation and scale 132

Superheated steam 134

Safety valves. 134

Pumps.

Single and duplex 142

Calculations for pumps 150

Injectors 153

Feed-water heaters 156

Corliss Engines.

Simple engines 161

Corliss valves 164

Compound engines 167

Expansions in each cylinder 170

Condensers 171

Pipes and Fittings.

Pipe measurements 174

Use of fittings 175

Valves 179

Steam traps 188

Equation of pipes 191

Flow of steam through pipes 192

Packing 19S

Heat and cold insulators 198



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CONTENTS. vii

Rotary Engines. Puge

Turbines 20a

Vanes 205

De Laval turbine construction 208

De Laval turbine governor 209

Curtis turbine 212

Parsons turbine 214

Internal Combustion Engines.

Gas engines 218

Gas producer 220

The four-part cycle 225

The two-part cycle 229

Operation of the carburetor 231

Igoition 23s

Valve timing 239

Firing order of cylinders 242

Calculation of horse power 244

Ignition wiring diagrams 245

Lubrication.

Friction 248

Oils and greases 251

Lubricating apparatus 253



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Elementary Steam Engineerings

CHAPTER I.

BECIPBOCATING ST£AM ENGINES.

OTEAM ENGINES are divided into various classes
^ according to their uses, as stationary, locomotive,
marine, and portable.

The essential principles are alike in all cases. They
differ only in details due to varying conditions and the
uses to which they are to be put.

An engine may be horizontal, vertical, or a combina-
tion of both. It may have one or more cylinders. It
may be operated condensing or non-condensing, de-
pending on whether the steam, after doing its work in
the cylinder, is allowed to pass to a condensing appa-
ratus or direct to the atmosphere.

In all cases where mechanical power is developed by
means of such an engine, the essential construction is
that of a piston moving in a cylinder due to a pressure
of steam delivered first on one side and then the other.
This will produce a reciprocating, or forward and back-
ward, motion of the piston, which motion is transformed
into rotary motion by proper mechanical means.

The admission of the steam to either side of the pis-
ton is controlled by valves. The varying types and con-



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2 ELEMENTARY STEAM ENGINEERING.

struction of the valves are largely indicative of the
different types of engines.

Perhaps the simplest and, up to quite recent times,
the most extensively used engines are those of the
slide-valve type, and as the description of this type of
engine will largely serve for all kinds it will be de-
scribed first.

THE SLIDE-VALVE ENGINE.

Referring to Fig. i we have the cylinder A, within
which is the piston B which is moved from one end to
the other by steam entering alternately through the open-
ings CC, the action being regulated by the slide valve D.
The piston rod E passes through the front head of the
cylinder.

The piston is composed of several parts, the piston
proper a, Fig. 2, and the follower &, which is fastened
to the piston by several bolts, leaving an annular ring
space extending completely around the piston.

If the piston were made to fit tightly into the cylinder
there would be no opportunity for the steam to escape,
but the warping of the cylinder walls, expanding un-
evenly, due to variations in temperature, would cause
the piston to bind.

To prevent this, the piston is made slightly smaller
in diameter than the cylinder, and, in order to prevent
leakage, the annular space B, Fig. 2, is filled by piston
rings, the use of which is to prevent the leakage of steam
and yet allow a rapid and free piston movement.

One of the simpler forms of piston rings is shown in
Fig. 3. This consists of a cast-iron ring slightly larger
in diameter than the internal bore of the engine cylin-



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RECIPROCATING STEAM ENGINES.



i



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4 ELEMENTARY STEAM ENGINEERING.




Fig. 2.




(


r


f





Fig. 3



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RECIPROCATING STEAM ENGINES. $

der, turned eccentrically so that one side of the ring
will be thinner than the other. The ring is cut diago-
nally across the thin portion as shown. The cutting re-
duces the length sufficiently that it may be sprung into
place.

In order to prevent leakage through the cut, the
tongue C is placed in the slots provided. The result
of all this is that the piston is free to move, because
the packing r^lg may give and take without binding on
account of any irregularity of the diameter, and it
continues to spring outward as wear takes place, thus
keeping everything steam-tight. On larger engines the
piston rings are sometimes made in sections and pressed
outward by springs inserted between the piston and
the piston ring.

On large pistons where several rings are to be em-
ployed, instead of simply cutting grooves in the piston
and springing the rings into place, a large ring is em-
ployed called the bull ring. This contains grooves on
the edges forming recesses in which the piston rings
proper are placed, while the bull ring is pressed outward
by means of studs and nuts as shown in the partial
section of Fig. 2.

The method of fastening the piston to the piston-rod
is indicated in Fig. 2.

The piston-rod is here shown tapered on the end.
This rod fits a similar tapered opening in the piston.
Both are then drawn tightly together by the nut A.
This is made possible on account of the tapered form.
There is little possibility of shaking loose due to the
vibration incidental to the engine's action, and it is



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6 ELEMENTARY STEAM ENGINEERING.

much more easily machined and fitted than would be
the case if a plain cylindrical joint were used.

Steam is prevented from leaking through the open-
ing in the cylinder head, where the piston-rod passes
out, by means of suitable packing placed in the stuflbig
box P, Fig. I. As will be seen here, the material of
this cylinder head is so formed as to produce a circular
recess around the rod, the lower end of this recess
being cut to an angle of about forty-five degrees. The
collar R, Fig. i, called the gland, fits easily into this
recess. The inner portion of the gland is tapered in a
similar manner to the bottom of the recess. The gland
may be drawn in by means of the studs and nuts S S
shown on either side. When thus held in position the
space P is fiUed with packing. The action of the gland
is to force the packing snugly against the piston-rod,
allowing freedom of movement but maintaining a steam-
tight joint.

The cylinder of the engine is turned sUghtly larger
at each end as shown at F, Fig. i, the object of which
is to allow the piston to over-run at the end of each
stroke. If this were not provided for, the constant
rubbing of the piston would, in time, wear a distinct
shoulder against which it would strike and possibly
cause damage. The cylinder heads are fastened to the
cylinder by means of studs and nuts as shown. The
stud is a short metal bolt threaded at either end and
having a blank space in the center.

When the steam enters from the boiler through the
main steam pipe H, it occupies a space I, called the
steam chest; from the steam chest it enters the cylin-



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RBCIPROCATING STEAM ENGINES. 7

der through the ports CC. The position of the slide
valve D determines in which direction the steam shall
enter. When the slide valve is in the position shown
in Fig. i| steam from the steam chest will enter the
port C and force the piston to the other end of the
cylinder. The steam from the previous stroke which
is filling the cylinder on the opposite side of the piston
must have some means of getting out. It passes
through the port C^ under the slide valve D, and out
through the central exhaust port J, to the air. During
the next stroke the conditions will be reversed. The
valve will have moved far enough over to cover port C
and uncover port C Steam will now enter from the
steam chest through the port C^ forcing the piston
towards the left, while the steam from the previous
stroke will escape through C, under the valve D, to J.
Steam which has not been used for developing power
fs called LIVE STEAM. Steam which has done its work
and been allowed to escape is called EXHAUST STEAM.
As it is necessary to prevent condensation, as far as
possible, the engine cylinder is often enclosed with a
covering of wood called lagging; in this way an air
chamber is formed around the cylinder in which there
can be no movement of air, and as air at rest is a
non-conductor of heat, it prevents, to a great extent,
condensation of the steam in the cylinder.
' At the outer end of the piston-rod is the cross-head N.
The object of this is to guide the end of the rod and to
take up the strain due to the angularity of the con-
necting rod K. The cross-head consists of an iron
block into which the end of the piston-rod is fastened



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8



ELEMENTARY STEAM ENGINEERING.



by threads or by means of a tapered joint and a wedge
pin. The cross-head is kept in position by guides
forming a part of the engine frame, and placed one
above and one below the cross-head in the direction in
which it receives the strain.




Fig. 4-



In order to prevent undue wear, the cross-head does
not bear directly upon the guides, but a space between
the two is fiUed by pieces of metal, called slippers, aa.
Fig. 4, their bearing surfaces being composed of Bab-
bitt or other anti-friction metal. These slippers are
adjustable for wear so that they may be slightly tight-
ened when necessary, in order to prevent the cross-head
from running so loose as to be shaky, and yet not so
tight as to prevent freedom of motion.

The cross-head pin T, Fig. i, passes through one end



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RECIPROCATING STEAM ENGINES. 9

*

of the connecting rod E. The other end of the con-
necting rod rests on the crank pin U, which is fastened
to the crank L. The opposite end of the crank is
firmly fixed upon the crank shaft M.

The ends of the connecting rod F, Fig. 5, are made
square. The strap B is fastened in place by a gib and



Fig. 5.

cotter leaving a space which is filled by two gun-metal
blocks CC, called the brasses. These are tightened to
the required amount by means of the wedge-shaped
pin D, which, upon being driven down, draws in the
strap B, tightening the brasses CC upon each other.
When first made the brasses do not quite touch; but
after having been adjusted for wear a number of times
the edges may come in contact at E. It is then neces-
sary to take them out and file off the edges in order to
allow for drawing them still closer together. Adjusting
the brasses at the ends of the connecting rod may in
time produce a change in the original center distance of
the two ends. It is then necessary to insert thin pieces



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lo ELEMENTARY STEAM ENGINEERING.

of metal between the ends of the connecting rod and
the brass at F in order to restore the original length.
These thin pieces of metal are called shims. A change
in the center distance of the connecting rod would make
no material difference in the operation of the engine
were it not for the fact that a shortening of this rod would
cause the piston to come a little closer to the front
head of the engine at each stroke and in time would
so reduce the clearance space as to cause the piston
to strike the head, when serious damage would result.

The crank pin is usually shrunk into its place in the
crank. This is done by turning the pin slightly larger
than the hole in which it is to go, about one one-hun-
dredth of an inch larger for each inch of diameter. The
crank is then heated and the resulting expansion enables
the pin to be slipped easily into position. As the crank
cools its contraction causes it to grip the pin firmly.

When the piston is at the end of its stroke a line
drawn through the center of the piston-rod would also
pass through the centers of the cross-head, crank pin
and shaft. The engine is then said to be on dead
center and no matter how much pressure might be
exerted on the piston there would be no tendency for
it to move. When the crank has moved around to an
angle of ninety degrees from the dead-center line, the
point of maximum power is reached.

As the crank passes the dead centers at two points
during each revolution, some means must be employed
to help the engine over these points where little or no
turning power is derived from the piston. A wheel
with a heavy rim, called the FLY-WHEEL, placed on the



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RECIPROCATING STEAM ENGINES. il

crank shaft, serves this purpose, for during that portion
of the s^oke when the greatest power is developed, a
part of it is used in setting this wheel in motion. Dur-
ing the weakest portion of the stroke the momentum of
the heavy fly-wheel restores some of this stored power
to the shaft, thus helping to produce a regular and con-
tinuous motion.

When an engine is running so that a person standing
at tlie cylinder end of it sees the crank pin move up and
away from him it is said to be over-running; when the
crank pin moves in the opposite direction the engine is
said to be under-running.

When an engine is over-running the pressure on
the piston, transmitted through the crank shaft to the
crank pin and doing the work, tends to produce a
downward pressure at the cross-head during the first
part of the revolution. During the second part of the
revolution the piston is pulling the crank pin towards
the cylinder and a similar downward pressure is again
exerted. If the engine were under-running the pres-
sure on the cross-head would be in an upward direc-
tion, for similar reasons; thus, in the case of a sta-
tionary engine designed to run only in one direction,
slides on both sides of the cross-head are not abso-
lutely essential, but as conditions may occasionally re-
quire that the direction of operation of the engine be
changed, and as the presence of both guides tends to
stiffen and steady the engine frame, it is advisable
that they be used. In case of marine, locomotive,
hoisting, or similar engines, in which the direction of
operation must frequently be changed, the guides on



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12 ELEMENTARY STEAM ENGINEERING.

both sides of the cross-head are a self-evident necessity.
As the slide valve controls the admission of the steam
which operates the piston, which, in turn, by means of
a crank, changes its reciprocating movement into rotary
motion at the main shaft, it is evident that some defi-
nite relation must exist between the movement of the
piston and the slide valve. These are mechanically
connected more or less directly according to conditions
presented in the design of the engine. It is apparent
that if a small crank were attached to the main shaft
and this in turn connected to the slide valve, this second
crank could be placed in such a position, relative to
the main crank of the engine, that it would operate the
slide valve and cause it to open and close at such times
as would be required for the proper admission of steam.
The building of such a crank, however, would make the
engine commercially expensive and in some instances
seriously weaken the shaft.

The same purpose is served in a far better way by
the use of the eccentric.

QUESnOXS.

1. What is a steam engine?

2. Name the principal parts of a slide-valve engine.

3. Describe the piston.

4. Describe the cylinder of a slide-valve engine.

5. How are the cylinder heads fastened ?

6. How is the piston made steam-tight?

7. How is steam prevented from leaking where the piston and
valve rods pass out of the cylinder and steam chest ?

8. How does the steam reach the cylinder from the supply pipe ?

9. What is the cross-head and its use?

10. Sketch one end of the connecting rod.

11. What are the dead centers?

12. On which guide does the cross-head pressure occur?



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CHAPTER n.
ACTION OF THE ECCENTRIC.

Imagine a pulley fitted on a shaft with a center hole
concentric with its outer surface. When the shaft and
pulley are rotated every point touched by the circum-
ference of the pulley will at all times be the same dis-
tance from the center of the shaft.

In the eccentric, Fig. 6, the opening for the shaft



is drilled out of center in the pulley, and it may be
readily seen that, as the shaft rotates, a point indicated
by the arrow will, at some part of the revolution, be
quite close to the shaft and at another at a distance
away from it, represented by the larger radius of the
eccentric.
The arrow, if its point were kept pressing against the

13



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14



ELEMENTARY STEAM ENGINEERmG.



circumference of the eccentric, would have a movement
equal to the diflference, a, between the shorter and the
longer radius.

This principle is taken advantage of in engine con-
struction for operating the slide valve. The eccentric,
Fig. 7, consists of a disc having a shaft hole drilled out




Fig. 7.

of the center, and a groove turned in its edge. In this
groove is fastened the eccentric strap C, the two halves
of which are fastened together by bolts at DD. The
strap is free to swing easily in the groove and prevented
from sliding off at the sides by the raised edges. When
the eccentric is revolved by the turning of the main
engine shaft, the eccentric rod E receives a movement
similar to that of the arrow in the previous illustration.

The eccentric rod is sometimes directiy connected to
the valve rod O, Fig. i, shown passing through the
walls of the steam chest, leakage being prevented by
a stuflbig box similar in construction to that described
in connection with the piston rod.

On other engines it is necessary to interpose a rocker
arm F, Fig. 8. In this case the rocker arm F, pivoted at



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ACTION OF THE ECCENTRIC.



15



6 to some suitable point of the engine frame, is also
pivoted to the eccentric rod, as shown, and receives
movement from it, which movement is imparted to



:^



=fi



\^




Fig. 8.

the valve rod, at its upper end, and through this to the
slide valve itself.

The distance from the center of the hole in the eccen-
tric to the true center of the eccentric disc is called the
raditis of the throw* The throw of the eccentric is
equal to twice this radius or the diameter of a circle


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Online LibraryErnest Victor LallierAn elementary manual of the steam engine; containing also a chapter on the theory, construction and operation of internal combustion engines for the operating engineer → online text (page 1 of 17)