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SCIENTIFIC AMERICAN SUPPLEMENT NO. 633




NEW YORK, FEBRUARY 18, 1888.

Scientific American Supplement. Vol. XXV., No. 633.

Scientific American established 1845

Scientific American Supplement, $5 a year.

Scientific American and Supplement, $7 a year.

* * * * *




TABLE OF CONTENTS


I. ARCHITECTURE. - Elements of Architectural Design. - By H.H.
STATHAM. - The commencement of a series of lectures
delivered before the London Society of Arts, giving the line
of development of the different styles and the aspirations
of their originators. 34 illustrations. 10106

II. ASTRONOMY. - A Fivefold Comet. - A curious astronomical
deduction; the probable division of one comet into five by
the disturbing effects of the sun. 1 illustration. 10116

III. BIOGRAPHY. - Linnæus. - By C.S. HALLBERG. - The life and
work of the great botanist, his portrait and birthplace.
2 illustrations. 10114

IV. CHEMISTRY. - An Apparatus for Preparing Sulphurous, Carbonic,
and Phosphoric Anhydrides. - By H.N. WARREN. - A simple
apparatus for this purpose described and illustrated.
1 illustration. 10117

The Arrangement of Atoms in Space in Organic Molecules. - A
review of Prof. JOHANNES WISLICENUS' recent theories
on this abstract subject. 10117

The Isolation of Fluorine. - Note on this last isolation of
an element, with the properties of the gas. 1 illustration. 10117

V. ELECTRICITY. - Observations on Atmospheric Electricity. - By
Prof. L. WEBER. - Abstract of a British Association paper
on this important subject. 10114

The Menges Thermo-Magnetic Generator and Motor. - The direct
conversion of electricity into heat; the generator fully
described. 5 illustrations. 10113

VI. ENGINEERING. - An Investigation into the Internal Stresses
Occurring in Cast Iron and Steel. - By General NICHOLAS
KALAKOUTZKY. - First installment of an elaborate paper,
giving theoretical and experimental examination of this
subject. 2 illustrations. 10105

Hargreaves' Thermo-Motor. - A new caloric engine. - Its
construction, theory, and cylinder diagrams.
6 illustrations. 10104

The Compound Steam Turbine. - A description and discussion
of this motor, in which a series of forty-five turbines are
acted on by the current of steam. 2 illustrations. 10103

VII. MISCELLANEOUS. - Cold Storage for Potatoes. - The application
of artificial cold to preserving potatoes. - Results obtained
in actual experience. - A practical paper by Mr. EDWIN
TAYLOR. 10115

VIII. PHYSICS. - On a Method of Making the Wave Length of Sodium
Light the Actual and Practical Standard of Length. - By ALBERT
A. MICHELSON and EDWARD W. MORLEY. - Description of the
new standard of length and outlines of the practical method for
its determination. - The question of check determinations.
1 illustration. 10115

IX. TECHNOLOGY. - Progress of the Sorghum Sugar Industry. -
Elaborate report on the diffusion process as developed at
the Fort Worth, Kan., station. 2 illustrations. 10110

The Lowe Incandescent Gas Burner. - The well known advanced
type of gas burner described and illustrated. 1
illustration. 10110

* * * * *




THE COMPOUND STEAM TURBINE.


Last year the whole of the lighting of the Newcastle Exhibition was
effected by the agency of seventeen of these motors, of which four were
spare, giving in the aggregate 280 electrical horse power. As the steam
was provided by the authorities of the exhibition, it was good proof to
the public that they had satisfied themselves that the consumption would
not be extravagant, as however favorable might be the terms on which the
manufacturers would be willing to lend their engines, they could
scarcely be sufficiently tempting to compensate for an outrageous
consumption of coal, even in Newcastle. At the time we gave an account
of the result of the test, showing that the steam used was 65 lb. per
electrical horse power, a very satisfactory result, and equal to 43 lb.
per indicated horse power if compared with an ordinary engine driving a
generator through a belt. Recently Mr. Parsons has given an account of
the theory and construction of his motor before the Northeast Coast
Institution, and has quoted 52 lb. of steam per electric horse power as
the best result hitherto attained with a steam pressure of 90 lb. As now
made there are forty-five turbines through which the steam passes in
succession, expanding in each, until it is finally exhausted.

[Illustration: THE COMPOUND STEAM TURBINE.]

The theoretical efficiency of a motor of this kind is arrived at by Mr.
Parsons in the following manner:

The efflux of steam flowing from a vessel at 15.6 lb. per square inch
absolute pressure through an orifice into another vessel at 15 lb.
pressure absolute is 366 ft. per second, the drop of pressure of 0.6 lb.
corresponding to a diminution of volume of 4 per cent. in the opposite
direction. The whole 45 turbines are so proportioned that each one,
starting from the steam inlet, has 4 per cent. more blade area or
capacity than that preceding it. Taking the pressure at the exhaust end
to be 15 lb. absolute, that at the inlet end will be 69 lb. above the
atmosphere. The steam enters from the steam pipe at 69 lb. pressure, and
in passing through the first turbine it falls 2.65 lb. in pressure, its
velocity due to the fall being 386 ft. per second, and its increase of
volume 3.85 per cent. of its original volume. It then passes through the
second turbine, losing 2.55 lb. in pressure, and gaining 3.85 per cent.
in volume, and so on until it reaches the last turbine, when its
pressure is 15.6 lb. before entering, and 15 lb. on leaving. The
velocity due to the last drop is 366 ft. per second. The velocity of the
wheels at 9,200 revolutions per minute is 150 ft. per second, or 39.9
per cent. of the mean velocity due to the head throughout the turbines.
Comparing this velocity with the results of a series of experiments made
by Mr. James B. Francis on a Tremont turbine at Lowell, Mass., it
appears that there should be an efficiency of 72 per cent. if the
blades be equally well shaped in the steam as in the water turbine, and
that the clearances be kept small and the steam dry. Further, as each
turbine discharges without check into the next, the residual energy
after leaving the blades is not lost as it is in the case of the water
turbine, but continues into the next guide blades, and is wholly
utilized there. This gain should be equal to 3 to 5 per cent.

As each turbine of the set is assumed to give 72.5 per cent. efficiency,
the total number may be assumed to give the same result, or, in other
words, over 72 per cent. of the power derived from using the steam in a
perfect engine, without losses due to condensation, clearances,
friction, and such like. A perfect engine working with 90 lb. boiler
pressure, and exhausting into the atmosphere, would consume 20.5 lb. of
steam per hour for each horse power. A motor giving 70 per cent.
efficiency would, therefore, require 29.29 lb. of steam per horse power
per hour. The best results hitherto attained have been 52 lb. of steam
per hour per electrical horse power, as stated above, but it is
anticipated that higher results will be attained shortly. Whether that
be so or not, the motor has many advantages to recommend it, and among
these is the increased life of the lamps due to the uniform rotation of
the dynamo. At the Phoenix Mills, Newcastle, an installation of 159
Edison-Swan lamps has been running, on an average, eleven hours a day
for two years past, yet in that time only 94 lamps have failed, the
remaining 65 being in good condition after 6,500 hours' service. Now,
if the lamps had only lasted 1,000 hours on the average, as is commonly
assumed, the renewals would have amounted to double the year's cost of
fuel, as at present consumed.

The present construction of the motor and dynamo is shown in the
figures.

[Illustration: Fig. 1 though 6]

Fig. 2 shows the arrangement of 90 complete turbines, 45 lying on each
side of the central steam inlet. The guide blades, R, are cut on the
internal periphery of brass rings, which are afterward cut in halves and
held in the top and bottom halves of the cylinder by feathers. The
moving blades, S, are cut on the periphery of brass rings, which are
afterward threaded and feathered on to the steel shaft, and retained
there by the end rings, which form nuts screwed on to the spindle. The
whole of this spindle with its rings rotate together in bearings, shown
in enlarged section, Fig. 3. Steam entering at the pipe, O, flows all
round the spindle and passes along right and left, first through the
guide blades, R, by which it is thrown on to the moving blades, S, then
back on to the next guide blades, and so on through the whole series on
each hand, and escapes by the passages, P, at each end of the cylinder
connected to the exhaust pipe at the back of cylinder. The bearings,
Fig. 3, consist of a brass bush, on which is threaded an arrangement of
washers, each successive washer alternately fitting to the bush and the
block, while being alternately 1/32 smaller than the block outside and
1/32 larger than the bush in the hole. One broad washer at the end holds
the bearings central. These washers are pressed together by a spiral
spring, N, and nut, and, by friction against each other, steady or damp
any vibration in the spindle that may be set up by want of balance or
other cause at the high rate of speed that is necessary for economical
working.

The bearings are oiled by a small screw propeller, I, attached to the
shaft. The oil in the drain pipes, D and F, and the oil tank, D, lies at
a lower level than the screw, but the suction of the fan, K, raises it
up into the stand pipe, H, over and around the screw, which gripes it
and circulates it along the pipes to the bearings. The course of the oil
is as follows: The oil is forced by the propeller, I, and oils the
bearing, A. The greater part passes along the pipe, E, to the end
bearing, C; some after oiling the bearing, C, drains back by the pipe,
F, to the reservoir, D; the remaining oil passes along through the
armature spindle, oils the bearings, B, and drains into the reservoir,
D, from which the oil is again drawn along the pipe, G, into the stand
pipe, H, by the suction of the fan, K. The suction of the fan is also
connected to the diaphragm, L, and forms, with it and the spring, M, the
principal part of the governor which actuates the throttle valve, V.
Fig. 4 is the electrical control governor, which will be further
described in connection with the dynamo. It acts directly upon the
controlling diaphragm, L, by admitting or closing a large access of air
to it, and thus exercises a controlling influence upon it.

The dynamo which forms the other portion of the electric generator, Fig.
1, is coupled to the motor spindle by a square tube coupling fitted on
to the square spindle ends. The armature is of the drum type. The body
is built up of thin iron disks threaded on to the spindle and insulated
from each other by tracing paper. This iron body is turned up and
grooves milled out to receive the conducting wires. For pressures of 60
to 80 volts there are fifteen convolutions of wire, or 30 grooves. The
wire starting at b, Fig. 6, is led a quarter of a turn spirally, c,
round the cylindrical portion, a, then passing along a groove
longitudinally is again led a quarter turn spirally, d, round the
cylindrical portion, a, then through the end washer, and back
similarly a quarter turn, e, then led along the diametrically opposite
groove, and lastly a little over a quarter turn, f, back to g, where
it is coupled to the next convolution. The commutator is formed of rings
of sections. Each section is formed of short lengths. Each length is
dovetailed and interlocked between conical steel rings. The whole is
insulated with asbestos, and, when screwed up by the end nut, forms,
with the steel bush, a compact whole. There are fifteen sections in the
commutator, and each coupling is connected to a section. The whole
armature is bound externally from end to end with brass or pianoforte
steel wire. The magnets are of soft cast iron and of the horseshoe type.
They are shunt-wound only.

On the top of the magnet yoke is the electrical control governor, Fig.
4. It consists of one moving spindle on which are keyed a small soft
iron bar, and also a double finger, T. There is also a spiral spring, X,
attached at one end to the spindle, and at the other to an adjustable
top head and clamping nut, Y. The double finger, T, covers or opens a
small hole in the face, U, communicating by the pipe, W, to the
diaphragm, L. The action of the magnet yoke is to attract the needle
toward the poles of the magnet, while by turning the head the spiral
spring, X, is brought into tension to resist and balance this force, and
can be set and adjusted to any degree of tension. The double finger, T,
turns with the needle, and, by more or less covering the small air inlet
hole, U, it regulates the access of air to the regulating diaphragm, L.
The second finger is for safety in case the brushes get thrown off, or
the magnet circuit be broken, in which case the machine would otherwise
gain a considerable increase of speed before the diaphragm would act. In
these cases, however, the needle ceases to be attracted, falls back, and
the safety finger closes the air inlet hole.

There is no resistance to the free movement of this regulator. A
fraction of a volt increase or decrease of potential produces a
considerable movement of the finger, sufficient to govern the steam
pressure, and in ordinary work it is found possible to maintain the
potential within one volt of the standard at all loads within the
capacity of the machine, excepting only a slight momentary variation
when a large portion of the load is switched on or off.

The resistance of the armature from brush to brush is only 0.0032 ohm,
the resistance of the field magnets is only 17.7 ohms, while the normal
output of the dynamo is 200 amperes at 80 volts. This, excluding other
losses, gives an efficiency of 97 per cent. The other losses are due to
eddy currents throughout the armature, magnetic retardation, and bearing
friction. They have been carefully measured. By separately exciting the
field magnets from another dynamo, and observing the increased steam
pressure required to maintain the speed constant, the corresponding
power was afterward calculated in watts.

The commercial efficiency of this dynamo, after allowing for all losses,
is a little over 90 per cent. In the larger sizes it rises to 94 per
cent. Assuming the compound steam turbine to give a return of 70 per
cent. of the total mechanical energy of the steam, and the dynamos to
convert 90 per cent of this into electrical output, gives a resulting
efficiency of 63 per cent. As steam at 90 lb. pressure above the
atmosphere will with a perfect non-condensing engine give a horse power
for every 20.5 lb. of steam consumed per hour, it follows that an
electrical generator of 63 per cent. efficiency will consume 32.5 lb. of
steam for every electrical horse power per hour.

Again, with steam at 150 lb. pressure above the atmosphere, a generator
of the same efficiency would consume only 22.2 lb. of steam per
electrical horse power per hour.

The results so far actually obtained are a consumption of 52 lb. per
hour of steam for each electrical horse power with a steam pressure of
90 lb. above the atmosphere. - _Engineering._

* * * * *




HARGREAVES' THERMO-MOTOR.


From the researches and investigations of Carnot, Joule, Rankine,
Clausius, and Sir William Thomson, the science of thermo-dynamics has
not only been brought into existence, but fully matured. We learn from
it that whereas in the steam engine, on account of the limited range of
temperature in the working cylinder and the rapid conduction of steam
during condensation, no combination of cylinders can materially affect
its present efficiency, internally fired engines, such as gas and
caloric engines - being, as it were, less fettered - can have their
already high efficiency increased by simply overcoming mechanical
difficulties. To this fact is no doubt due the recent remarkable
development of gas and caloric engines. The first caloric or hot air
engine was invented by Sir George Cayley in 1807, and in 1827 Dr. Robert
Stirling, a Scotch minister, took out his first patent for a hot air
engine, which was the foundation of many subsequent machines, and by the
invention of the regenerator he converted what was practically a
scientific toy into an efficient machine.

One of the most ardent workers in this field at the present time is Mr.
James Hargreaves, of Widnes, who, with a thorough theoretical knowledge
of the subject has, after many years of patient perseverance, over come
many of the mechanical difficulties, and designed the engine of which
the above is an illustration.

The sectional elevation, shown in Fig. 1, is an expanded view of the
machine, shown thus to enable the action of the machine to be more
clearly understood; the relative position of the different parts, as
actually made, is shown in the side elevation (Fig. 4). The principal
working parts of the machine are the combustion chamber, D, which is of
the form shown, lined with fire brick, and having an entrance, with the
door screwed down like a manhole lid; the working cylinder, A,
surrounded by the water casing, K; the piston, B, with a water lining,
and coupled to the end of the working beam by a parallel motion, the
beam being supported by two rocking columns, Z, as in engines of the
"grasshopper" type; the air compressor, C, coupled directly to the
piston of the working cylinder; the injection pump, F, for supplying the
fuel - creosote or coal tar - to the combustion chamber; the regenerator
E; the receiver and separator, V Y; the feed and exhaust valves, M.

[Illustration: Fig. 1 - SECTIONAL ELEVATION - HARGREAVES' THERMO-MOTOR.]

[Illustration: Fig. 2.]

The action of the machine is as follows: Assuming the engine to be in
condition for starting, the sides of the combustion chamber, D, are red
hot, the chamber charged with air, and the spray of creosote, injected
by the pump, F, is ignited; the expansion of the gases produced by the
combustion acts upon the bottom of the piston, B, forcing it to the top
of the cylinder, and thus, by intermediate mechanism, causing the crank
shaft to revolve. By the same stroke a charge of air is forced by the
compressor, C, into the receiver through the pipe, R. The cylinder is,
of course, single acting, and on the down stroke of the piston, B - which
falls by its own weight and the momentum of the fly wheel - the exhaust
gases are forced through the regenerator, E, which absorbs most of their
heat; they then pass through the exhaust valve, placed immediately under
the feed valve, M, along the pipe, Q, up through the pipes, T, fitted
into the receiver, V, down the pipes, T, fitted into the saturator, Y,
and out of the funnel fixed to the bottom of Y.

[Illustration: Fig 3.]

[Illustration: Fig. 4.]

The charge of air for supplying the combustion chamber is forced by the
compressor, C, through the pipe, R, _outside_ the tubes, T, in the
chambers, V and Y, along the pipe, P, through the feed valve, M, and the
regenerator, E, into the combustion chamber. In its passage from the
compressor, it first picks up the residual heat of the exhaust gases in
the tubes, T, and finally the heat absorbed by the regenerator, E, thus
entering the combustion chamber in a highly heated state. Having
described generally the passage of the air from the compressor to the
working cylinder, and back again to the funnel, we will now describe the
details. The working cylinder, A, is fitted into the casting which forms
the water casing, K, a space being left between the bottom of the
cylinder and the casing, which is filled with a non-conducting mixture
of asbestos to protect it from the heat of combustion; the bottom of the
piston, B, has a similar protection, and the regenerator has a lining
of the same mixture, to prevent any heat from escaping through the
casting which holds it. The water in the casing, K, and in the piston,
B, is supplied by a small pump, G, which forces the water through the
pipe, P4, into the telescopic pipe, L either into the piston, B, or
through the pipe, P6, into the casing, K - the bottom of the casing
being connected by the pipe, P10, with the auxiliary boiler, W. The
steam generated in the casing, K, is carried to the boiler, W, by the
pipe, P3, and from the boiler it passes along the pipe, P2,
through the valve, A2, into the chamber, V, thus giving up its heat
to the incoming air, with which it mixes. The vapor gradually condenses
at the bottom of the vessel, Y, and the water so formed is drawn by the
pump, J, along the suction pipe, P9, and forced through the pipe,
P8, back to the chamber, Y, through the valve, A1, and in the form
of spray plays on the tubes, T, and absorbing any residual heat. The
heat generated by compression in the cylinder, C, is absorbed by a spray
of water from the pump, H, the vapor being carried along with the air
through the pipe, R, to the chamber, Y, where it is separated, and
falling to the bottom is circulated, as just described, by the pump, J.
X is a small auxiliary air compressor, to obtain the necessary
compression to start the engine, and is worked from the boiler, W. In
future engines this compressor will be superseded by a specially
designed injector, which will produce the necessary pressure at a
considerable reduction in cost. When once the engine is started, the
fire of the auxiliary boiler can, of course, be drawn, as the main
engine afterward makes its own steam. The regenerator, E, has circular
ends of fire clay perforated, the body being filled with fire clay
spirals of the shape clearly shown in elevation in Fig. 2. The injector
valve for the creosote is shown to a larger scale in Fig. 3. This valve
has, however, been since considerably modified and improved. The feed
and exhaust valves, M, are actuated by cams keyed to a countershaft
driven by bevel wheels from the main shaft. The creosote pump, F, is
also worked by a cam on the same shaft, but the pumps, G H J, are worked
by eccentrics. A stop valve, N, is fixed to the supply pipe, P, under
which is place a back pressure valve to retain the pressure in the
combustion chamber. The engine is regulated by an ordinary Porter
governor actuating the throttle valve, O. An engine, as described, has
been constructed by Messrs. Adair & Co., engineers, Waterloo Road,
Liverpool, and has been running most satisfactorily for several weeks,
the results being clearly shown by the indicator diagrams (Figs. 5 and
6). The results obtained by this motor are very remarkable, and are a
long way in advance of any previous performance, as only a little over ½
lb. of fuel is used per i.h.p. per hour. It may be mentioned that the
temperature of the combustion chamber is calculated to be about
2,500°F., and that of the exhaust gases does not exceed
180°F. - _Industries._

[Illustration: Diagram from cylinder - 25 in. diam, 18 in. stroke.
I.H.P., 63. Scale, 1/30 in. Mean pressure, 28.2 lb. FIG. 5.]

[Illustration: Diagram from air pump - 15 in. diam., 18 in. stroke.
I.H.P., 23. Scale, 1/30 in - Mean pressure, 28.5 lb. FIG. 6.

DIAGRAMS FROM CYLINDER AND AIR PUMP.

Net indicated horse power, 40; revolutions per minute, 100; coal tar
consumed per hour, 20.5 lb.; coal tar per I.H.P. per hour, 0.512 lb.]

* * * * *




AN INVESTIGATION INTO THE INTERNAL STRESSES OCCURRING IN CAST IRON
AND STEEL.


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Online LibraryVariousScientific American Supplement, No. 633, February 18, 1888 → online text (page 1 of 10)