Improvements in Furnace-gas Mixing Devices for Use in Steam Boiler Flues.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in Furnace-gas Mixing Devices for Use in Steam
Boiler Flues.
I, GUILLAUME ARNAUD NUSSBAUM, of 29, Ludgate Hill, in the County of
London, Engineer, do hereby declare the nature of this invention to be as
follows;
This invention has reference to improved constructions of mixing devices for
use in steam boiler flues, such devices being adapted to effectually break up the
streams of hot gases and air flowing through the flues and deflect or bring them
into contact with the walls of the flues.
In one construction each mixing and heating device consists of a metal casting
or forging comprising a sole piece or base shaped at the bottom to fit a flue tube
and provided, with upwardly extending bars that may be of sufficient height to
nearly reach the top of the flue, and which present the appearance of a grid, the
front side of the sole piece and grid bars being preferably curved or bevelled
so as to deflect hot gases and air coming in contact therewith outwards against
the wall of the flue in which the device is placed. These mixing devices may
be each provided with a projecting part to serve as a distance piece so that several
of the devices can be readily placed in a flue and maintained at the proper distance
apart. By rounding or shaping their lower surfaces so as to fit the Hue tube in
which they are used and thus form a good conducting contact therewith, overheat-
ing and rapid destruction of such mixing devices is prevented.
In another construction the mixing and heating device consists of a star-shaped
casting or forging having a solid centre with radial arms, one side of the centre
and arms being inclined or bevelled so as to deflect hot gases coming in contact
therewith sideways.
Such mixing and heating devices can be readily inserted and adjusted in place
to suit varying requirements and be easily removed for cleaning or renewal. They
can be used in the flues or flue tubes of boilers of various constructions.

page_text: manner the same is to be performed to be particularly described and ascertained
in and by the following statement:―
This invention has reference to improved constructions of mixing and heating
devices for use in steam boiler flues, such devices being adapted to effectually
break up and mix the streams of hot gases and air flowing through the flues and
deflect or bring them into contact with the walls of the flues.
In one construction, each mixing and heating device consists of a metal casting
or forging comprising a sole piece or base shaped at the bottom to fit a flue tube
and provided with upwardly extending bars that may be of sufficient height to
nearly reach the top of the flue and which present the appearance of a grid, the
front side of the sole piece and grid bars being preferably curved or bevelled so as
to deflect hot gases and air coming in contact therewith outwards against the wall
of the flue in which the device is placed. These mixing and heating devices may
be each provided with a projecting part to serve as a distance piece so that several
of the devices can be readily placed in a flue and maintained at the proper distance
apart. By rounding or shaping their lower surfaces so as to fit the flue tube in
which they are used and thus form a good conducting contact therewith, overheat-
ing and rapid destruction of such mixing and heating devices is prevented.
In another construction the mixing and heating device consists of a star shaped
casting or forging having a solid centre with radial arms, one side of the centre
and arms being inclined or bevelled so as to deflect hot gases coming in contact
therewith sideways.
Such mixing and heating devices can be readily inserted and adjusted in place
in steam boiler flues to suit varying requirements and can be easily removed for
cleaning or renewal. They can be used in the flues or flue tubes of boilers of
various constructions.
Figs. 1 and 2 of the accompanying illustrative drawings show respectively in
longitudinal section and cross section, a steam boiler furnace flue provided with
mixing and heating devices constructed and arranged according to this invention.
Figs. 3 and 4; Figs. 5 and 6; Figs. 7 and 8; and Figs. 9 and 10 are similar
views to Figs. 1 and 2 respectively, showing various forms which the said devices
may take.
In the arrangement shown in Figs. 1 and 2, each of the mixing and heating
devices comprises a wide heavy metal sole or base piece a made convex at its lower
side to fit against and rest by its own weight upon the bottom of the furnace
flue band provided with a number of upwardly extending metal bars c that extend
more or less across the upper part of the flue and present the appearance of a grid.
The base piece a is made heavy and wide so as to present considerable surface to
the bottom and coolest part of the flue b so that it will rest in close contact there-
with and serve to transinit heat in an efficient manner from the hot gases flowing
through the flue to the water at the opposite side of the wall of the flue, such
construction at the same time preventing overheating and rapid destruction of the
said device. I have found in practice that it is important that the bars c should
not touch the top of the flue as this would cause trouble due to the difference in
expansion of the arms and flue in a direction transverse to the flue, and would
moreover interfere with the ready insertion and removal of the device. The
free ends of the bars should therefore be within an imaginary circle including the
lower convex side of the base piece a. The front side of the base piece a and grid
bars c, that is to say the side against which the hot gases impinge whilst flowing
towards the chimney, are preferably bevelled or inclined so as to deflect the hot
gases coming in contact with them outward against the wall of the flue. In the
arrangement now being described, the front of the base piece a has, for the purpose
mentioned, an upwardly and backwardly inclined surface d, and the grid bars c
have laterally and backwardly inclined surfaces e, the said bars being of triangular
section. The tops of the bars e may also, for a like purpose, be inclined as shown
at f. The several mixing and heating devices are arranged transversely in the
flué b at suitable distances apart. In the case of furnace flues of comparatively

page_text: small cross section, such as the flue or smoke tubes of boilers of the locomotive
and marine types, the said devices may be maintained at the desired distance apart
by distance pieces located between them. The distance pieces may conveniently
be in one piece with one another and constitute a bar that is separate from the
devices but is adapted to be engaged therewith. In Figs. 1 and 2, there is employed
a bar y that extends through a hole in the base piece a of each device and is
formed at intervals with notches i to receive and fit over parts of the several base
pieces a. The rear end of the bar may be secured to a metal cross bar the ends
of which are adapted to fit the flue a. By means of this bar the several devices
can be readily and simultaneously pushed into or withdrawn from the flue tabe
and when in the tube can be maintained at the required distance apart.
Figs. 3 and 4 show a construction of mixing and heating device similar to that
shown in Figs. 1 and 2 but wherein the grid bars c extend upwardly towards the
top of the flue and are each inclined to a vertical plane passing through the centre
of the flue so that the hot gases flowing between them will be directed to one side
of the flue. By using several of such devices with the grid bars of one inclined
side-ways in an opposite direction to those of the next, the hot gases flowing
through the flue can have a zig-zag direction imparted to them.
In Figs. 5 and 6, the mixing and heating device consists of a metal base piece a
with a number of radial bars e extending from a solid centre piece j, the front side
of the arms and centre piece being inclined as before.
Figs. 7 and 8 show an arrangement somewhat like that shown in Figs. 5 and 6
but wherein the bars c are made flat and wide and arranged to form screw-like
blades or vanes whereby a circular motion will be imparted to the hot gases flowing
past and between them.
In Figs.
and 10 each of the mixing and heating devices comprises a metal
base piece a and a grid like series of connected vertical and horizontal bars c each
of which is or may be of hollow or vee section, the vertical and horizontal bars
of one device being arranged opposite the spaces between the vertical and hori-
zontal bars of the next adjacent devices. In the case of furnace flues of large size
such as those of Lancashire & Cornish boilers, the said gas mixing, heating and
retarding devices will be of such large size and weight that they will need to be
put in place and removed separately, a bar such as in Figs. 1 and 2 being then
dispensed with. In such cases also each of the said devices may be made in two
or more parts to facilitate its being inserted in place and withdrawn.
Mixing and heating devices constructed and arranged as described, effect an
intimate mixture of the hot gases and air flowing through a steam boiler flue so
as to effect complete combustion of the gases; they deflect the heated gases against
the sides and top of the wall of the flue, so as to give up a large portion of their
heat thereto; and they also serve to transmit heat from the gases to the bottom
of the flue wall. The said devices when aranged in the flue as described, also serve
to divide up the flue into a series of combustion chambers separated by highly
heated transveise divisions, whereby a more uniform temperature can be main-
tained throughout the length of the furnace flue than usual and unequal expansion
of the fiue, due to unequal temperatures at different parts thereof, be thereby
greatly diminished. The said devices also tend to steady and check the flow of hot
gases through the flue and so prevent undue cooling of the flue by admission of
cooler air on opening the fire doors, and also to check down draught, and by
their use the gases can be considerably reduced in temperature before they are
finally allowed to escape into the chimney.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that I do not
broadly claim the use of metal plates arranged transversely to and at intervals
within a steam boiler flue but what I do claim is:
1. A mixing and heating device for a steam boiler flue, comprising a wide heavy
base piece having a convex lower side adapted to rest upon and bear closely against

page_text: the bottom of the flue and a number of bars adapted to extend across the upper
part of the flue, substantially as described and shown for the purpose specified.
2. A mixing and heating device for a steam boiler flue, comprising a wide
heavy base piece having a convex lower side adapted to rest upon and bear closely
against the bottom of the flue and a number of upwardly extending grid-like bars
adapted to extend across the upper part of the flue, substantially as described and
shown for the purposes specified.
3. A mixing and heating device for a steam boiler flue, comprising a wide heavy
metal base piece having a convex lower surface and an upwardly inclined front
surface and a number of metal bars extending from the top of and integral with
the said base piece and having inclined front surfaces, substantially as herein
described.
4. The improved mixing and heating devices for steam boiler flues, constructed
and operating substantially as hereinbefore described with reference to and shown
in Figs. 1 and 2; in Figs. 3 and 4; in Figs. 5 and 6; in Figs. 7 and 8; and in
Figs. 9 and 10 of the drawings annexed.
nber 1899.
For the Applicant,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Chartered Patent Agent.