IMPROVEMENTS IN AND CONNECTED WITH STEAM-BOILER AND OTHER FURNACES
Year: 1883

page_text: LETTERS PATENT to John Elliot, Junior, and Thomas Allison Cunningham
both of Dalbeattie in the County of Kirkcudbright, North Britain for an
Invention of IMPROVEMENTS IN AND CONNECTED WITH STEAM-BOILER AND
OTHER FURNACES
"
PROVISIONAL SPECIFICATION left by the said John Elliot, Junior, and
Thomas Allison Cunningham at the Office of the Commissioners of Patents
on the 28th May 1883.
"
JOHN ELLIOT, Junior, and THOMAS ALLISON CUNNINGHAM, both of Dalbeattie
in the County of Kirkcudbright, North Britain, IMPROVEMENTS IN
CONNECTED WITH STEAM-BOILER AND OTHER FURNACES
"
AND
This Invention has for its object to economise fuel in steam-boiler and other
furnaces; and it consists principally in supplying the air required for the com-
bustion of the fuel, in a compressed and heated state, and in such a manner as to
cause a vigorous circulation of the fire gases by making a portion of them pass
again over, through, or in contact with the burning fuel.
The Invention is applicable to various kinds of steam boilers and furnaces; and
in general extremely simple apparatus is required for carrying it out. In the case
of an ordinary type of marine boiler with internal furnaces having tubes above
them through which the fire gases return from the back or inner end to a smoke
box at the front, a vertical return pipe is placed in the smoke box above each
furnace, the upper end of the pipe being above the tubes and being formed with
an open flared or funnel-like mouth, whilst the bottom end communicates with
the furnace. A small pipe is arranged to extend from above into the return pipe
and a jet of compressed and heated air is forced in through this small pipe and has
the effect of drawing in and forcing down the larger pipe a portion of the fire gases
which have passed through the tubes and are (in existing boilers) on their way
to the chimney or uptake funnel. The air introduced by the small pipe is com-
pressed and forced in by means of a pump and becomes heated in consequence of
its compression; it may also be additionally heated by being passed through pipes
or casings or regenerative chambers heated by the fire gases prior to the ultimate
ID C31

page_text: escape or discharge of these gases by the chimney or uptake funnel. The action of
the air jet causes the fire gases to pass more rapidly through the tubes, which
renders them more effective in generating steam and at the same time keeps the
tubes cleaner; and complete ignition of any combustible portions of the gases or of
suspended carbonaceous particles which may escape combustion when first passing
through the tubes, is insured by the air jet, added to which an increased heat is
maintained in the furnace. By these means a great economy of fuel is effected
and steam boilers for a given power may be considerably reduced in size. The
return pipe or pipes through which the fire gases are made to return to the furnace
may be constructed to pass through the water of the boiler so as to be available as
additional heating surface. The ordinary inlets for air into the furnace above or
below the grate or at other parts are closed; and the air forced in with the fire
gases is led into the furnace either by one inlet or by two or more branches. Thus
some of the mixed air and gases may be led in above the grate and some below it;
and if found desirable some may be led by a branch pipe to the bridge or inner
end of the furnace.
In some kinds of furnaces the return passage for a portion of the gases may be
a flue formed in or lined with brick, the air jet being applied so as to propel the
gases along such return passage.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Elliot, Junior, and Thomas Allison Cunningham in the
Great Seal Patent Office on the 26th November 1883.
JOHN ELLIOT Junior, and THOMAS ALLISON CUNNINGHAM, both of Dalbeattie,
in the County of Kirkcudbright, North Britain IMPROVEMENTS IN AND
CONNECTED WITH STEAM-BOILER AND OTHER FURNACES
"
"
Our said Invention has for its object to economise fuel in steam-boiler and other
furnaces; and it consists principally in supplying the air required for the
combustion of the fuel, in a compressed and heated state, and in such a manner
as to cause a vigorous circulation of the fire gases by making a portion of them
pass again over, through, or in contact with the burning fuel.
Our Invention is applicable to various kinds of steam boilers and furnaces; and
in general extremely simple apparatus is required for carrying it out. On the
accompanying sheet of explanatory drawings we have shown one modification of
apparatus as applied to an ordinary type of marine boiler. This boiler which is
shown in front elevation in figure 1 and in vertical section in figure, 2, has internal
furnaces, 8, with a combustion chamber, 4, at the back, and with tubes, 5, above
the furnaces through which tubes the fire gases return from the back or inner end
to a smoke box, 6, at the front. There are two furnaces and two smoke-box
doors, 7, and one of these doors is shown open in figure, 1. Above each furnace
there is placed in the smoke box, 6, a vertical return pipe, 8, the upper end of
each pipe being above the tubes, 5, and being formed with an open flared or
funnel-like mouth, 9, whilst the bottom end communicates with the interior of the
furnace. A small pipe, 10, is arranged to extend from above into and down the
return pipe, 8, and a jet of compressed and heated air is forced in through this
small pipe, 10, and issuing through a small bole in a nozzle or thimble, 11, at the
lower end, has the effect of drawing in and forcing down the larger pipe, 8, a
portion of the fire gases which have passed through the tubes, 5, and are (in
existing boilers) on their way to the chimney or uptake funnel, 12. The air
introduced by the small pipe, 10, is compressed and forced in by means of a pump,
and becomes heated in consequence of its compression; it may also be additionally
heated by being passed through coiled pipes, 13, in the uptake, 12, or through
casings or regenerative chambers heated by the fire gases prior to the ultimate
escape or discharge of these gases by the chimney or uptake funnel.
The action of the air jet causes the fire gases to pass more rapidly through the
tubes, 5, which renders them more effective in generating steam and at the same
time keeps the tubes cleaner; and complete ignition of any combustible portions
of the gases or of suspended carbonaceous particles which may escape combustion
when first passing through the tubes is insured by the air jet, added to which
an increased heat is maintained in the furnace. By these means a great economy
of fuel is effected and steam boilers for a given power may be considerably reduced
in size.
The return pipe or pipes, 8, through which the fire gases are made to return to
the furnace may be constructed to pass through the water of the boiler so as to be
available as additional heating surface. The ordinary inlets for air into the
furnace above the grate are closed; and the air forced in with the fire gases is led
into the furnace either by one inlet or by two or more branches in each case.
some of the mixed air and gases may be led in above the grate and some below
it; and if found desirable some may be led by a branch pipe to the bridge or
inner end of the furnace. When led in below the grate the ash pit may be closed.
Thus

page_text: .
The quantity of air supplied may be varied when desirable by altering the speed
of the pump or apparatus by means of which it is forced through the small
pipes, 10; or air may be forced uniformly through those pipes, and additional
supplies may, if required, be drawn in by the action of the jets. For this purpose
there is connected to each large return pipe, 8, an air pipe, 14, having an inlet
mouth, 15, for air and a valve, 16,. for regulating the amount admitted in that way,
and when the valve, 16, is open the sucking action of the downward current in the
pipe, 8, will cause air to enter by the pipe, 14, and mix with the descending fire
gases.
In some kinds of furnaces the return passage for a portion of the gases may be
a flue formed in or lined with brick, the air jet being applied so as to propel the
gases along such return passage.
Having thus particularly described our said Invention and the manner of
performing the same we have to state that we do not restrict ourselves to the
precise details herein described or delineated but that what we believe to be novel
and original and claim as the Invention secured to us by and in terms of the
hereinbefore in part recited Letters Patent is:
1. The employing, in or in connection with a steam-boiler or other furnace, of
one or more jets of compressed and heated air in a manner to cause a return or
circulation of a portion of the fire gases through a passage or passages leading them
again over, through, or in contact with the burning fuel, substantially as and for
the purposes herein before described.
2. The addition to a tubular boiler of a return pipe (8) having extending into it
a pipe (10) leading in a jet of compressed and heated air, so as to cause a portion
of the fire gases after they have passed through the tubes (5) to pass again over,
through, or in contact with the fuel and through the tubes (5) substantially as and
for the purposes herein before described.
In Witness whereof we the said John Elliot Junior and Thomas Allison
Cunningham, have hereunto set our hands and seals this twenty-third day of
November in the year of our Lord One thousand eight hundred and eighty-three.
JOHN ELLIOT JUB.
(L.S.)