Improved Means for Inducing Draught in Boiler Furnaces, Fire Places and the like, and for Producing a Vacuum and Raising Fluids.
Year: 1897

page_text: Date of Application, 13th Oct., 1897
Complete Specification Left, 7th July, 1898-Accepted, 13th Aug., 1898
PROVISIONAL SPECIFICATION.
Improved Means for Inducing Draught in Boiler Furnaces, Fire
Places and the like, and for Producing a Vacuum and Raising
Fluids.
I, LOUIS EMILE PRAT, of 95, Boulevard Beaumarchais, Paris, in the Republic
of France, Engineer, do hereby declare the nature of this invention to be as
follows:-
"
The draught promoting process which forms the object of this invention is
based upon the use of air injected, not in a chimney or stack, but in a special
apparatus which I have termed a pressure transformer" by reason of its capa-
bility of transforming or converting the pressure of the air supplied thereto into
a depression or lowered pressure i.e., of reducing the pressure of such air; this
apparatus moreover having a great power of suction while producing a high
mechanical yield, although its size is comparatively small.
These improved draught promoting means are characterized by the considerable
extent of such draught. Thus each apparatus being designed to produce a depres-
sion of from 80 to 100 m/m of water, when the ash box is closed and from 15
to 25 m/m when the latter is opened, there results for the steam boiler a variation
of vacuum which may become quadruple, whereas in ordinary chimneys or stacks
such variation scarcely reaches a few millimetres of water. Now this is a very
important point, for when the grate is loaded with coal, the passage of the gases
is further impeded and the volume of air diminishes, whence follows smoke and
incomplete combustion unless the pressure is reduced at the same moment and it
will be understood that an ideal draught should be that resulting from a con-
tinuous exhaustion the reducing power of which increases with the resistance.
This draught is represented by the formula Te=QH wherein Te represents the con-
stant operation, Q the volume of the gases exhausted and H the reduction of
pressure produced. This equation shows at one glance that if the volume Q has
a tendency to diminish on account of an increase in height of the fuel on the
grate, the pressure reduction H must likewise increase, since Tc remains con-
stant and under the action of this suction the air gains full access to the fuel and
burns the same, conversely with full fires, the draught H decreases when the
volume of the exhausted air has a tendency to increase too much and the fire
slackens.
This kind of draught is thus contrary to that of a chimney the reducing power
of which depends on the temperature of the gases of combustion and on their
volume and would rather tend to decrease, in consequence of the cooling produced
by the loading of fresh fuel, than to increase. In fact a chimney produces an
exhausting effect varying scarcely by a few millimetres of water whether the ash
boxes are closed or not, it is therefore an apparatus producing a constant exhaus-
tion, while the fire places or furnaces would require on the contrary a variable
depression which should be produced by an exhaustion with a constant yield.
The object of my process for promoting draught is to obtain such a result, and

page_text: experience teaches that it is superior as regards its operation to equivalent orifices
however diversified which may produce either the exhaustion of a large volume
of air at low pressure or that of a small volume of air at high pressure.
In order to render my invention more fully understood I have shown, by way of
example, in the accompanying drawings my new pressure reducing apparatus.
Figs. 1 and 2 show my pressure reducing device fitted inside a brick chimney
stack. Fig. 3 shows the same applied to a metallic flue or funnel (boat, locomo-
tive, workshop). Figs. 4, 5, 6 and 7 show modifications of the arrangement
shown in the above figures.
As shown in Fig. 3 my apparatus consists chiefly of a bell or hood A forming
an inwardly convergent connection acting as a flue. A bell or hood B likewise
metallic like the first forming an inwardly converging connection superposed to
the first, so as to leave between the two a free space or interval for the injected
fluid to run out. A casing cowl or tube C surrounding the two preceding cowls
or tubes and communicating with the air generator, this air being supplied
through the conduit 1). A cylindrical flue pipe E having a sufficient length to
allow for the diffusion of the injected fluid. A conical connection F tapering
inwardly acting as a diffusing device and designed to reduce the pressure of the
mixture of the injected with the drawn fluid.
The apparatus comprises as shown no regulating device, as the dimensions of
the various parts are calculated with precision.
The result is great simplicity in the construction without impairing the
strength and durability of the apparatus.
It may be preferable in some cases to use a central injection as shown very
clearly in Fig. 5. In this case the apparatus is still simpler and consists of a
hood or flue H, a nozzle G, a chamber E and a diffuser F. In either arrange-
ment such as above described, the apparatus comprises moreover; a centrifugal
fan V placed outwardly of the chimney stack or funnel or of the flue for the gases
of combustion (Figs. 1, 2 and 5). An air conduit provided with a butterfly
valve m (Fig. 5) and with a device n for actuating the furnace door which is
within reach of the stoker for the purpose of regulating the fan supply accord-
ing to the draught required. A pressure reducing device arranged in the brick
chimney such as K in Figs. 1 and 2, HEF and AEF (Figs. 3 and 5).
Figure 1 shows the arrangement of the pressure reducing device placed inside
a stack made of brickwork and Fig. 2 shows the manner of constructing the whole
or a part of this pressure reducing device in brickwork.
Figures 6 and 7 illustrate the manner of arranging the pressure reducing device
inside a sheet iron or brick chimney with annular dampers a and b allowing
natural draught to have its sway when these parts are open.
Figure 5 refers to a chimney which is enlarged at the bottom to allow natural
draught notwithstanding the pressure reducing device located therein.
Figure 4 refers to the general case when the pressure reducing device communi-
cates with the flue either through the conduit T when the fan acts in the central
injector or through the conduit S when the fan acts in the annular injector T.
In this case, the pressure reducing device only acts as a chimney, its upper end
becoming uniformly larger or is surmounted by a cylindrical connection as shown
in Fig. 4.
The advantages of this new draught promoting process are as follows-
1. The partial suppression of stacks and their foundations such as used for
works.
2. A more economical combustion of the fuel by reason of the kind of draught
having a constant yield.
3. Almost perfect combustion of smoke with well stoked fires.
4. The preservation of the furnaces of steam boilers and the preventing of the
inrush of cold air during the loading and cleaning of fire places or furnaces.
I do not intend to restrict the use of my pressure reducing device for promoting

page_text: the draught in furnaces, as I may utilize it in various manners, as an apparatus
capable of producing a vacuum or of drawing up any suitable fluid, being supplied
likewise with any suitable fluid such as air, steam and the like; the apparatus
being then arranged as shown in Fig. 4 wherein the draught may be produced by
the fluid running out or escaping through the central injector S or through the
annular injector T.
I may moreover construct my pressure reducing device of any suitable material.
Improved Means for Inducing Draught in Boiler Furnaces, \Fire
Places and the like, and for Producing a Vacuum and Raising
Fluids.
I, LOUIS EMILE PRAT, of 95, Boulevard Beaumarchais, Paris, in the Republic
of France, Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
+6
The draught promoting process which forms the object of this invention is
based upon the use of air injected, not in a chimney or stack, but in a special
apparatus which I have termed a pressure transformer" by reason of its capa-
bility of transforming or converting the pressure of the air supplied thereto into
a depression or lowered pressure, i.e. of reducing the pressure of such air; this
apparatus moreover having a great power of suction while producing a high
mechanical yield, although its size is comparatively small.
These improved draught promoting means are characterized by the considerable
extent of such draught. Thus each apparatus being designed to produce a depres-
sion of from 80 to 100 m/m of water, when the ash box is closed and from 15
to 25 m/m when the latter is opened, there results for the steam boiler a variation
of vacuum which may become quadruple, whereas in ordinary chimneys or stacks
such variation scarcely reaches a few millimetres of water. Now this is a very
important point, for when the grate is loaded with coals, the passage of the gases
is further impeded and the volume of air diminishes, when follows smoke and
incomplete combustion unless the pressure is reduced at the same moment and it
will be understood that an ideal draught should be that resulting from a con-
tinuous exhaustion the reducing power of which increases with the resistance.
This draught is represented by the formula Te=QH wherein Te represents the con-
stant operation, Q the volume of the gases exhausted and H the reduction of
pressure produced. This equation shows at one glance that if the volume Q has
a tendency to diminish on account of an increase in height of the fuel on the
grate, the pressure reduction H must likewise increase, since Tc remains con-
stant and under the action of this suction the air gains full access to the fuel and
burns the same, conversely with full fires, the draught H decreases when the
volume of the exhausted air has a tendency to increase too much and the fire
slackens.
This kind of draught is thus contrary to that of a chimney the reducing power
of which depends on the temperature of the gases of combustion and on their
volume and would rather tend to decrease, in consequence of the cooling produced

page_text: by the loading of fresh fuel, then to increase. In fact a chimney produces an
exhausting effect varying scarcely by a few millimetres of water whether the ash
boxes are closed or not, it is therefore an apparatus producing a constant exhaus-
tion, while the fire places or furnaces would require on the contrary a variable
depression which should be produced by an exhaustion with a constant yield.
The object of my process for promoting draught is to obtain such a result, and
experience teaches that it is superior as regards its operation to equivalent orifices
however diversified which may produce either the exhaustion of a large volume
of air at low pressure or that of a small volume of air at high pressure.
In order to render my invention more fully understood I have shown, by way of
example, in the drawings filed with the Provisional Specification, my new pressure
reducing apparatus. Figs. 1 and 2 show my pressure reducing device fitted inside
a brick chimney stack. Fig. 3 shows the same applied to a metallic flue or funnel
(boat, locomotive, workshop).
Figs. 4, 5, 6 and 7 show modifications of the arrangement shown in the above
figures.
As shown in Fig. 3 my apparatus consists chiefly of:-
A bell or hood A forming an inwardly convergent connection acting as a flue.
A bell or hood B likewise metallic like the first forming an inwardly converg-
ing connection superposed to the first, so as to leave between the two a free space
or interval for the injected fluid to run out.
A casing cowl or tube C surrounding the two preceding cowls or tubes and
communicating with the air generator, this air being supplied through the con-
duit D;
A cylindrical flue pipe E having a sufficient length to allow for the diffusion of
the injected fluid.
A conical connection F tapering inwardly acting as a diffusing device and
designed to reduce the pressure of the mixture of the injected with the drawn
fluid.
The apparatus comprises as shown no regulating device, as the dimensions of
the various parts are calculated with precision.
The result is great simplicity in the construction without impairing the
strength and durability of the apparatus.
It may be preferable in some cases to use a central injection as shown very
clearly in Fig. 5. In this case the apparatus is still simpler and consists of a
hood or flue H, a nozzle G, a chamber E and a diffusor F. In either arrange-
ment such as above described, the apparatus comprises moreover: a centrifugal
fan V placed outwardly of the chimney, stack or funnel or of the flue for the gases
of combustion (Figs. 1, 2 and 5). An air conduit provided with a butterfly
valve m (Fig. 5) and with a device n for actuating the furnace door which is
within reach of the stoker for the purpose of regulating the fan supply accord-
ing to the draught required. A pressure reducing device arranged in the brick
chimney such as K in Figs. 1 and 2, HEF and AEF (Figs. 3 and 5).
Fig. 1 shows the arrangement of the pressure reducing device placed inside a
stack made of brickwork and Fig. 2 shows the manner of constructing the whole
or a part of this pressure reducing device in brickwork. Figs. 6 and 7 illustrate
the manner of arranging the pressure reducing device inside a sheet iron or brick
chimney with annular dampers a and b allowing natural draught to have its sway
when these parts are open.
Fig. 5 refers to a chimney which is enlarged at the bottom to allow natural
draught notwithstanding the pressure reducing device located therein.
Fig. 4 refers to the general case when the pressure reducing device communi
cates with the flue either through the conduit T when the fan acts in the central
injector or through the conduit S when the fan acts in the annular injector T
In this case, the pressure reducing device only acts as a chimney, its upper end
becoming uniformly larger or is surmounted by a cylindrical connection as shown
in Fig. 4.

page_text: The advantages of this new draught promoting process are as follows:-
1. The partial suppression of stacks and their foundations such as used for
works.
2. A more economical combustion of the fuel by reason of the kind of draught
having a constant yield.
3. Almost perfect combustion of smoke with well stoked fires..
4. The preservation of the furnaces of steam boilers and the preventing of the
inrush of cold air during the loading and cleaning of fire places or furnaces.
I do not intend to restrict the use of my pressure reducing device for promoting
the draught in furnaces, as I may utilize it in various manners, as an apparatus
capable of producing a vacuum or of drawing up any suitable fluid, being supplied
likewise with any suitable fluid such as air, steam and the like; the apparatus
being then arranged as shown in Fig. 4 wherein the draught may be produced by
the fluid running out or escaping through the central injector S or through the
annular injector T.
I may moreover construct my pressure reducing device of any suitable material.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, declare that what
I claim is:-
1. The process for continuously promoting by mechanical means the draught in
chimneys, furnaces and the like substantially as herein described.
2. The apparatus for carrying out the promotion of draught in chimneys, com-
prising the devices herein before described which devices may be utilized without
an external casing or may be placed in a brickwork or sheet metal stack substan-
tially as herein described and shown.
Dated thin fith low of Lul.. 1908
CRUIKSHANK & FAIRWEATHER,
Chartered Patent Agents, 62, Saint Vincent Street, Glasgow,
Agents for the Applicant.