IMPROVEMENTS IN STEAM GENERATORS
Year: 1883

page_text: LETTERS PATENT to Herbert John Allison, of the firm of Allison Brothers,
Patent Agents, of Southampton Buildings, London, for an Invention of
"IMPROVEMENTS IN STEAM GENERATORS" communicated to him from abroad
by Joseph Edwin Culver, Physician, of Jersey City, New Jersey, United
States of America
COMPLETE SPECIFICATION filed by the said Herbert John Allison at the
Office of the Commissioners of Patents on the 11th December 1883.
"
HERBERT JOHN ALLISON, of the firm of Allison Brothers, Patent Agents, of
Southampton Buildings, London, "IMPROVEMENTS IN STEAM GENERATORS
communicated to me from abroad by Joseph Edwin Culver, Physician, of Jersey
City, New Jersey, United States of America.
The object of my invention is to ensure that every successive portion, or particle
of water entering the boiler, shall be heated progressively, that is to say step by
step, until it is finally converted into steam, while calorifacient, or heating gases
from the furnace traverse a thermostatic flue system, the said gases advancing as
they cool and coming into contact with colder and colder flue surfaces until they are
discharged into the atmosphere at a temperature of about 100° Fahrenheit more or
less, as preferred, according to the extent of heating surface employed and the
draught maintained in the apparatus.
In carrying out my invention I employ a shell formed of boiler iron or other
suitable material, by preference of a cylindrical form, enclosing a water-space and
steam-space duly proportioned and furnished with a feed water pipe at the bottom
or lower end, and a steam pipe and safety valve at the top or upper end.
The shell of the boiler contains within the water-space and surroun-led on all sides
by water, a multi-tubular structure, by preference formed of metal, and consisting
of an upper and a lower chamber, connected together by a series of boiler tubes.
Through the outer shell is an entrance to the upper chamber, and an exit or
outlet from the lower chamber is formed or provided. The parts are so formed or
constructed that no leakage shall take place between the multi-tubular structure
and the surrounding space within the shell. The area of the chambers should be
sufficiently less than that of the enclosing shell to allow of free circulation of water
between them; and to the same end, however numerous and closely distributed
the tubes may be they are left out of actual contact. To complete this arrange-
ment, and especially to prevent cushioning of steam upon the fire-plate, water-tubes
across the Blue-chambers and connect the water above then with the water beneath.
The following modification of the plan of construction of the new steam
generator presents some especial advantages. The upper and lower plates of the
1

page_text: flue-chambers, either or both of them, enlarged in diameter sufficiently, may be
riveted to the outer shell of the boiler throughout the entire circumference, so as
absolutely to divide the water-space into separate sections. The several water-
spaces thus formed are then to be connected in a series, only, or chiefly, through
water-tubes crossing the flue-chambers. Constituted thus the boiler is a compound
It includes within one continuous shell several unlike integrant parts, or
segment boilers of dissimilar construction, conjoined consecutively. A thermostatic
flue system traverses the shell from the furnace downward to the far end; and the
flames and fuel gases pass through the several sections of the boiler in succession
and impart heat to the water therein, themselves cooling as they advance.
one.
A thermostatic flue system may be constructed of tubes only or of chambers
suitably connected, or of any suitable combination of chambers and tubes, arranged
within the water-space of the boiler below the water level and, freely inter-
communicating one with another especially at their lowermost parts :-So
connected with the furnace and with the smoke-stack that the smoke shall traverse
them in a downward direction from the furnace to the exit flue:-So inter-
communicating that the descending smoke in every flue and in every branch and
segment thereof shall be left free to descend according as it is cooled and its
gravity is increased, or, to maintain a higher level according as it retains its heat
rarefaction-So that the descending smoke preserves in all the flues at the same
level a uniform temperature, a thermostatic equilibrium not liable to be disturbed
by variable draughts, and that smoke which has cooled the most is at all times
foremost in the descent.
A single flue can not be made thermostatic only as the subdivisional flues
balance each other, each of which so balanced by the other is thermostatic.
I employ a furnace lined with fire brick, soapstone, or other suitable material
jacketed, and by preference of a semi-elliptical shape in transverse section, and
abutting endwise against a secondary combustion chamber so that its archway
coincides in its span with the upper semi-circle of the entrance thereto, at the same
level and continuous therewith.
This furnace is furnished with a large ash-pit, a grate of suitable dimensions,
and ample combustion chamber, a door above the grate for feeding the fuel, and a
door below the grate for removing ashes, and for admitting air, etc.
Supported upon the sides of the furnace near its top and built into the walls
thereof, an archi arranged, by preference formed of cast-iron. This arch forms
the dome of the combustion chamber, a brick arch being constructed one or two
inches above the same leaving an open space between the arches for the purpose of
forming an air flue which I prefer to be open at all times at the boiler end of the
archway thereby allowing of the admission of air to the upper flue-chamber or
secondary combustion chamber.
The quantity of air admitted may be regulated by a slide or valve, fitted to the
front of the furnace.
By this means the fire-box receives a properly regulated supply of intensely
heated air arranged to mingle with the flames just at the mouth of the secondary
combustion chamber; and by this means the loss of heat from the top of the furnace
is prevented.
In locomotives or similar boilers the furnace may be enclosed in a water-hood,
and a pipe may serve as the air inlet above the grate.
In order to prevent the escape of heat from outside surfaces, by contact,
radiation or convection, it is preferred that the furnace, boiler, and all appurtenances
be jacketed with any suitable non-conducting material.
In steam boilers of all sizes constructed and arranged according to my invention
as hereinbefore set forth, the maintaining of different temperatures, above and
beneath within the water-space of the boiler, in a descending scale of degrees of
heat from top to bottom, or one end to the other is fully provided for, and promises
to fulfil the problem of rendering available for heating purposes or for motive
energy, nearly all the heat-force developed from the combustion of fuel.

page_text: To accomplish this end in horizontal boilers I annex to the upper or furnace end
an elbow turned vertically upward and to the lower end an elbow extending
downward. The steam dome occupies the upturned elbow.
The lower elbow may be, of any size demanded, it can be dispensed with
altogether without impairing the thermostatic equilibrium of the flue system,
provided the escape flue pass out from the lowermost part of the lower flue-
chamber.
I can form the upturned segment of the boiler, of a size and shape to suit the
requirements presented, and when so formed may constitute in part or wholly a
separate compartment, or annex boiler with its fire-plate, water-space, steam-
space, etc., receiving its water supply from the horizontal segment as hereinafter
explained.
In the elbow boiler the flue-chambers can occupy the angles front and rear, or
can be located elsewhere, if preferred. The front or upper chamber, I use as the
secondary combustion chamber, and it is to be provided with a suitable opening to
admit the flames from the furnace. This opening or flue must be of a sufficiently
sinall diameter so that the passage of the products of combustion shall be slightly
obstructed and deflected in their course to the end that the gases arising from
different parts of the fire shall be thoroughly intermingled, together with the
superadded air, their temperatures equalized, and perfect combustion secured. A
thermostatic equilibrium can not be secured in the flue system if the products of
combustion are allowed an unobstructed passage to the secondary combustion
chamber, as the gases arising from different parts of the fire vary greatly in
temperature, and in case they are not thoroughly intermingled the hottest gases.
will pass through the flues first, leaving the cooler smoke behind.
The flue opening, in order to secure the best results and most perfect combustion,
must connect the furnace and secondary combustion chamber at their uppermost
parts.
The water connection between the horizontal and upright segments of the boiler
can be made chiefly through water-hoods surrounding the chambers, or partly or
wholly through water-tubes crossing the chambers. A system of water-tubes
intercrossing in various directions may connect the opposite sides of the water-hood
and it will contribute efficiently to the generation of steam of high tension and
the tubes will give strength to the combustion chamber.
The water-tubes which cross the flue-chambers may be straight or angular,
curved or spiral as preferred. The water-hoods that surround the chambers consist
of a double hood, an inner and outer plate of boiler iron, strongly riveted and
braced, and having between the plates (which are set an inch or more apart) an
interspace to contain water, that connects laterally with the water-space of the
horizontal segment of the boiler and above with the water-space of the vertical
segment.
I arrange around the circumference of the water-hood Dumerous tubular
communications with the water-space of the annex boiler; or if preferred an
uninterrupted, or continuous confluence throughout the entire circle of their
junction. I provide similar channels between the water-hoods and the water-space
of the horizontal segment of the boiler. The water in the horizontal boiler
maintains a high temperature at the top and relatively a low one at the bottom;
it is evident that the hottest of this water should be sent to the front water-hood,
the water-tubes and the annex boiler; therefore I propose to connect the topmost
part of the furnace end of the horizontal boiler directly to the conjoined
water-hood through a single water-tube; I can regulate the inflow of water
according as it evaporates by a suitable valve placed in this water-tube so as to
maintain a uniform depth of water in the annex boiler.
Water is almost an absolute nonconductor of beat; neither water or gases
transmit heat from above downwards. In my steam generator this law for the
first time finds a practical application.
Above the upper chamber of the multi-tubular flue system, steam is formed and

page_text: the boiling water is violently agitated; below this chamber the water never boils;
no bubbles rise; there are no interstratic currents; all is motionless, save that the
feed water which is added little by little, uplifts the mass integrally of which it
forms the base.
In the flues like temperatures rest in horizontal planes throughout; but from
top to bottom each plane is a little cooler than the one next above it. The
intensest heat of the furnace is in the upper chamber; and as the combustion
gases descend therefrom through the flue tubes, and the lower chamber, they
impart their heat to the water surrounding them until they reach the escape flue
comparatively cold. In other words the hot gases from the furnace descend
through the flues in contact with colder and colder strata of water successively,
until their temperature at the outflow approximates the temperature of the cold
water at its inflow; and the water entering the water-space at the bottom is
heated as it rises step by step in apposition with warmer and warmer strata of
gases until its temperature near its outflow approximates that of the influent hot
gases from the furnace and it is instantaneously converted into steam.
While the fire is first kindling in the furnace and until the water boils and
steam reaches the working pressure, a sufficient draught can be had by inserting
into the exit flue a smoke pipe about eight feet in height. When the steam is up
the temporary smoke pipe can be removed and thence-forth an exhaust fan, or
blower, or steam ejector may be used to expel the smoke from the escape flue into
the surrounding air. Or, a fan or blower operated by hand or foot can be used
until the steam is up.
For the greater convenience of access to parts within the boiler shell, and to
facilitate the process of cleaning the flues, suitable doors or manholes may be fitted
into the incasement of the chambers. A blow-off cock in the base of each water-
hood, and one in the bottom of the horizontal segment, will enable the engineer to
wash out whatever sediment the water may deposit in the boiler.
: I will now describe the steam ejector also known as the mixing pipe, its
construction and uses.
I provide a suitable gate which tightly closes the larger flue exit from the
boiler.
A steam pipe is made to enter a small discharge flue, the diameter of which is
carefully proportioned to the quantity of gases to be conveyed away from the
lower flue-chamber; this steam pipe extends within the flue centrally coincident
with its long axis, and terminates centrally a few inches from the entrance. The
internal diameter of the steam pipe may be one third to one sixth of that of the
flue it penetrates. The calibre of the flue tapers, or grows smaller, as it approaches
the end of the steam pipe within it. In operation this inner pipe discharges steam
outwardly along the flue it penetrates, which according to its tension creates a
vacuum in the flue behind the steam junction that sweeps the gases from the
furnace onward and mingles with them. This apparatus if rightly adjusted can be
made to yield the most economical of all artificial draughts or can produce a very
powerful one.
When all the steam from the generator passes through the ejector under a
pressure of three or four atmospheres, and the temperature of the fuel gases
discharged there with exceeds somewhat that of the steam, the mixture com-
prehends under a diminished tension all the heat-force developed from the fuel
consumed.
This realizes the highest attainable economy, and has also other advantages as it
can be used for heating purposes or to operate the engines on steam-ships, or
wherever a large supply of low tension steam is worked. In compound engines
it will be found to be less readily condensed by expansion than pure steam of the
same temperature; and will require the atmospheric cylinder, the condenser and
the air pump to be enlarged accordingly. When the mixture is employed to drive
an engine of any kind, I provide a check valve fitted in the flue below the steam
junction to act automatically and prevent reversal of the draught.

page_text: Into the mixing pipe just beyond the steam junction I insert to the bore at an
acute angle to its longitudinal axis a small pipe to convey water preferably from
the lower and colder part of the boiler. The volume of water injected I regulate
by a stop-cock. Throwing a coarse spray it can be made to cool the fuel gases and
to condense the steam in the mixing pipe, the hot water so obtained being returned
to the feed water tank. When the mixture of gases and steam is employed to
drive an engine, if the cylinder becomes heated, a fine spray may temper the gases
and protect the machinery. A similar arrangement of a spray in the exhaust pipe
of a high pressure engine may furnish hot feed water for the boiler.
Furthermore, the exhaust steam of high pressure engines can be utilized by my
invention to run the ejector. By this means the caloric derived from the exhaust
steam can be returned to the boiler, and be used in cylinder again and again; in
the mean time the heat in the boiler will become cumulative to such a degree that
in a very short time after starting the engine, the furnace fire can be diminished;
and, even then, there will be a super-abundance of heat which may be capable of
producing steam in excess, but never at any time able to raise it to the working
pressure without aid from the more intense heat of the furnace. The surplus can
be devoted to heating and ventilation.
But that my invention may be fully understood, I will proceed to describe the
same more in detail by the aid of the accompanying drawings which illustrate what
I consider the best means of carrying out my invention.
Referring to the drawings:-
Fig. 1, is a central vertical section of my improved steam generator.
Fig. 2, is a central vertical section of a modification of my invention..
Fig. 3, is a horizontal section taken on the line x, x, Fig. 2..
Fig. 4, is a front elevation.
Fig. 5, is a transverse section taken on the line y, y, Fig. 2.
Fig. 6, is a central vertical section of my improved feed water tank.
Fig. 7, is a central vertical section showing my invention as applied to vertical
boilers.
Similar letters of reference indicate corresponding parts wherever they occur.
A represents a shell formed of boiler iron, or other suitable material, which in the
drawings is shown of a cylindrical form and enclosing a water-space B, and a
steam-space C.
The shell A is provided with a feed-water pipe D, at the bottom or lower end
thereof, and with a steam pipe E and safety valve F at the top or upper end.
The shell A of the boiler contains within the water-space B, and surrounded on
all sides by water a multi-tubular structure G, consisting of an upper chamber G¹
and a lower chamber G, connected together by a series of tubes G³, so arranged
that the whole of the series of tubes G³ shall communicate one with the other
through the medium of the chambers G¹, G².
Through the outer shell A, an entrance A¹ to the upper chamber G₁, is formed
and an exit or outlet, g, from the lower chamber G2, is formed as shown by Figs. 1
and 2. The parts are so constructed that no leakage shall take place between the
multi-tubular structure, G, and the surrounding space within the shell A.
The upper plate g and the lower plate g², of the chambers G', G³, are by
preference joined, or bolted to the shell A at their circumference, so as effectually
to divide the water-space B, into separate sections which are connected together by
water-tubes b.
H is the furnace which is provided with a lining of fire brick, soapstone or
other suitable material which may be enclosed in a water-hood or water-hoods as
shown in Fig. 1; by preference of a semi-elliptical shape in transverse section
and abutting against the boiler shell A in such manner that its archway h, nearly
coincides in its span with the upper semi-circle of the entrance A', to the upper
flue-chamber G', and is continuous therewith.
The furnace H, is provided with an ash-pit H¹, a grate H and a combustion
chamber H. Above the grate H2, a feeding-door H, is provided for the supply

page_text: of fuel, and below the grate H³, a door H for the removal of ashes, and for the
regulation of the draught to the furnace.
In Fig. 2, I show supported upon the sides of the furnace H, near its top and
built into the wall thereof an arch H, by preference formed of cast iron; this
arch H, forms the dome of the combustion chamber H³. Above the arch H, I
construct a brick arch, H7, one, two or more inches above the arch H, thereby
leaving an open space between the arches H and H', for the purpose of forming
an air flue H³, which I prefer to be open at all times for the admission of air
at the boiler end of the said passage or flue H³. When the furnace is enclosed
in a water-hood a pipe H° (see Fig. 1) may serve as an air inlet above tho
grate.
The quantity of air admitted to the flue H³, may be regulated as shown by
a slide or valve H10, fitted to the front of the furnace or by any other suitable
means.
By this means the furnace or fire-box H, receives a properly regulated supply
of intensely heated air arranged to mingle with the flames just at the mouth of
the secondary combustion chamber G¹, and by this means the loss of heat from
the top or upper part of the furnace H, is prevented.
J, J, J2, are a series of tubes intercrossing one another and connecting the
opposite sides of the water-hoods.
To prevent cushioning of steam in the annex boiler K, I arrange a series of
water-pipes J¹ extending across the upper chamber G' and passing through
the fire-plate. g₁ at equal distances apart and terminating flush with its upper
surface.
The upper part of the furnace end of the horizontal section G³ is connected to
the water-hoods by means of a tube b. The inflow of water may be regulated
by a valve placed in the tube b. Similar tubes also connect the other sections.
Above the secondary combustion chamber or section G¹, I construct the annex
boiler K, having the water-space B, and the steam-space C. This boiler may be
strengthened by braces n, n, (Fig. 1), or other suitable means. It is separated
from the rest of the shell by a horizontal partition g¹ beneath it, which also serves
as a fire-plate and as the roof of the secondary combustion chamber or section G¹.
It is fitted with a safety valve F, steam pipe E, and also with suitable water cocks,
guages, etc. (not shown). This annex boiler may be of any required form.
M is a steam ejector or mixing pipe which is provided with a gate or valve m
which controls a flue or passage m¹ leading to the boiler.
A steam pipe E connected at one end with the steam-space of the annex boiler
is conducted into a small discharge flue m² the calibre of which tapers or grows
smaller at m' until passes the end of the steam pipe E. The pipe E is formed
of a diameter is proportion to the quantity of gases desired to be carried away
from the lower chamber G2. The pipe E is arranged centrally within the flue m²
in position to cause a current of steam to be driven along the flue m² thereby
creating a vacuum in the flue m¹ thus sweeping the products of combustion and
gases from the furnace H, onward and mingling with them.
In the vertical portion of the pipe M I arrange a check valve m which is so
constructed as to prevent the draught being reversed when the mixture is
employed to drive an engine or otherwise encounter resistance. m' is a small
pipe the upper end of which is inserted into the mixing pipe or ejector M at an
acute angle as represented in Figs. 1 and 2. The pipe m at its lower end is
connected with the water-space of the boiler by preference at its lower and coolest
end, as shown in the drawings.
The volume of water from the pipe m' is regulated by a stop-cock m³. The
spray of cold water issuing from the pipe m' is employed to cool the fuel gases
and also to condense the steam in the mixing pipe.
The hot water thus obtained is returned to the feed water tank by a suitable
pipe.
M' is a large flue exit from the bottom of the lower chamber G³, connecting

page_text: with a suitable smoke pipe or chimney as desired. When the ejector or mixing
pipe M is used this flue exit is tightly closed by a damper m³.
Having thus described my invention, what I claim and desire to secure by
Letters Patent is :-
1. The combination in a steam generator of a thermostatic flue system, a feed
water inlet, sectional water-spaces and their connections, and an annex boiler
with its steam dome substantially as shown and set forth.
2. The combination in a steam generator of a furnace, a secondary combustion
chamber, a thermostatic flue systein, and an annex boiler substantially as and for
the purpose set forth.
3. The combination in a steam generator of a thermostatic flue system,
secondary combustion chamber, a system of water-tubes crossing said. chamber,
and an annex boiler the whole being arranged to operate substantially as shown
and described.
4. The combination in a steam generator of a thermostatic flue system, a
secondary combustion chamber, an annex boiler and an air-inlet pipe adapted to
heat and discharge a current of air into the entrance of the secondary combustion
chamber, the whole being arranged to operate substantially as shown and
described.
5. The combination in a steam generator of a thermostatic flue system, a
secondary combustion chamber, an annex boiler having a fire-plate g¹, and a series
of water pipes J¹, adapted to prevent the cushioning of steam in the annex boiler,
substantially as shown and described.
6. The combination in a steam generator of a thermostatic flue system with
water-hoods enveloping the flue-chambers, the several water-spaces being connected
with each other by water-tubes, as and for the purpose described.
7. The thermostatic flue system described and shown consisting of two or more
chambers connected by multi-tubular flues, the chambers containing numerous
crossed and interspaced water-tubes, substantially as and for the purpose set
forth.
8. The thermostatic flue system described and shown consisting of two or more
chambers connected by multi-tubular flues, each chamber being enclosed in a
separate water-hood and containing numerous crossed and interspaced water-tubes
substantially as described and shown.
9. A boiler shell constructed with two elbows, the one nearest the furnace
extending upwards and adapted to contain a secondary combustion chamber and
an annex boiler with its steam dome; the other being the rear end of the shell
prolonged downward, and adapted to contain a lower chamber enclosed in its
water-hood and to receive the feed water-inlet pipe, and smoke-exit flues,
substantially as and for the purpose set forth.
10. In combination with a thermostatic steam generator a spray ejector
adapted to operate as described and temper the products of combustion employed
as a source of motive power substantially as and for the purpose set forth.
11. In combination with a thermostatic steam generator the spray ejector m' in
combination with a smoke and steam mixing pipe M substantially as and for the
purpose set forth.
In witness whereof, I, the said Herbert John Allison, have hereunto set my
hand and seal, this eleventh day of December in the year of our Lord one
thousand eight hundred and eighty-three.
HERRERT T ALLISON (LS)