Improvements in Steam Generators.
Year: 1894

page_text: Improvements in Steam Generators.
I, LOUIS EDMOND SOLIGNAC, Engineer, Director of La Compagnie de la
Chaudière Mixte, of 22 Rue Richer, Paris France, do hereby declare the nature
of this invention, to be as follows:-
This invention relates to steam generators of the kind in which highly heated
water injected into a heated tube is flashed into steam, the invention consisting
more particularly in the combination and arrangement of the various parts, as will
be hereinafter described.
In a steam generator of this kind, the length of the flashing tube should be as
restricted as possible, otherwise there would be too great a difference in the
evaporative effect at successive parts of the tube, those nearest the jet being
bathed in water, whilst those near the exit evaporate, whereas if the injection be
reduced the latter will only superheat. Now, the great evaporative power
(200 kilos. per square metre) of such steam flashers or generators, entirely depends
upon the fact that their heating surfaces are not, as in ordinary generators,
completely covered with water, which, being a bad conductor of heat impedes the
transmission to the evaporative surface of the calories or units of beat collected at
the heating surface. The thinner the layer of water between the heating and
evaporative surfaces, the more rapid will be the evaporation, which reaches its
maximum when the heating and evaporative surfaces are coincident, as in a heated
tube into which water is injected. Therefore, when a portion of the tube merely
superheats the steam, the surface is but imperfectly utilised inasmuch as superheated
steam only absorbs about one calorie per kilogramme, from which it will be evident
that it is of advantage to limit the length of the tube. When, therefore, it is
required to evaporate a large quantity of water, a number of such steam flashing
tubes should be employed, placed parallel to one another instead of a single one of
greater length.
It is known that in ordinary generators the elasticity of production depends on
the volume of water superheated. I have also found that to avoid overheating it
is only requisite to inject under pressure water at the highest possible temperature
which partly evaporates, moistens the surface of the tube with steam, and thus
ensures the contact of the non-vaporised liquid with the heated surface.
All the above conditions are fulfilled in the generator which I have illustrated in
an elementary manner in the accompanying drawing, Figure 1 being a plan and
Figure 2 a vertical section of the same on line 1-2.
The generator comprises a series of vertical tubes a placed within a furnace and
beated directly therefrom. Into the lower end of each tube projects a nozzle b by
which water is injected in the form of spray, the nozzles 6 being supplied by a
pump d which takes the water from the boiler e and delivers it under pressure
through pipe c, the pump being actuated by a donkey engine supplied with steam
by pipe from the steam space of the boiler e which contains a large supply of
water heated under pressure by the steam generated in the flashing tubes a
which are connected to the boiler by pipes f provided with check valves g allowing
the steam to pass up into the boiler, but preventing the return of water. ; is the
steam pipe of the boiler. A pipe k connects the boiler e and the pipe c for
establishing circulation at starting before any steam is available for working the
donkey engine, a cock on said pipe being closed when the pump is started.

page_text: The advantages claimed for the above described arrangement are:-
1st. Reduced heating surface inasmuch as evaporation is effected by injection
under the most favourable conditions, regard being had to the short length of the
tubes.
2nd. Avoidance of overheating whilst using tubes of large area to promote the
generation of steam and consequently rapid evaporation.
3rd. Elasticity.of production not less than in ordinary boilers, the large body of
water contained in the boiler e serving as a reservoir.
4th. Freedom from risk of accident, as each flashing tube is made independent
by the check valve g, and but a small volume of water is injected at a time.
As the boiler e need not be directly heated by the flames, it may be considered
to be not a boiler but simply as a reservoir and steam chest.
The number and mode of grouping the flashing tubes may be varied according
to the quantity of steam to be produced, said tubes being always independent
either individually or in groups working in parallel under similar evaporative
conditions.
Dated October 25th 1894.
A. M. & WM. CLARK,
53 Chancery Lane, London, Chartered Patent Agents.
I, LOUIS EDMOND SOLIGNAC, Engineer, Director of La Compagnie de la
Chaudière Mixte, of 22, Rue Richer, Paris, France, 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:-
This invention relates to steam generators of the kind in which highly heated
water injected into a heated tube is flashed into steam, the invention consisting more
particularly in novel means of evaporation and a novel method of transmitting the
heat to the volume of water to be evaporated.
In a steam generator of this kind the length of the flashing tube should be as
restricted as possible otherwise there would be too great a difference in the
evaporative effect at successive zones of the tube, those nearest the jet being
covered with water whilst those near the exit vaporize it, whilst on the other hand
if the injection be reduced the latter portions will only superheat. Now the thinner
the layer of water between the heating surface and the plane of evaporation, the
more rapid will be the evaporation, which reaches its maximum when the heating
and evaporative surfaces are coincident as in a heated tube into which water is
injected. Therefore, when a portion of the tnbe merely superheats the steam the
surface is but imperfectly utilized, inasmuch as superheated steam only absorbs
about one balf a calorie per kilogramme, from which it will be evident that it is of
advantage to limit the length of the tube. When, therefore, it is required to
evaporate a large quantity of water a number of such steam flashing tubes should
be employed in parallel instead of a single one of greater length.
In ordinary generators the elasticity of production depends on the volume of
water superheated and I have found that to avoid the overheating of a heated tube
it is only requisite to inject under pressure water superheated to the highest possible
temperature which by partly evaporating moistens the surface of the tube with
steam and thus ensures the contact of the non-vaporized liquid with the heated
surface.
In
The improved steam generator of this invention fulfils all these conditions.
so far as regards the novel means of evaporation the water, instead of circulating

page_text: through tubes either filling them as in ordinary boilers or by successive injections
as in steam flashers, is injected in a novel condition which may be thus defined :-It
-water-at-a-temperature-pear-the-point of evaporation be drawn into a pump it forms
a mixture of water and steam, the temperature of which rises if the mixture be
compressed to a higher pressure, and if the mixture thus compressed be then
suddenly expanded there is formed a kind of impalpable mist composed of infinitely
small molecules of water each enclosed in an atmosphere of steam which it has
formed. The atmosphere which thus envelopes the aqueous molecules opposes
their reunion into drops of appreciable size and so maintains permanent the divided
state. If water in this condition be introduced into a tube heated externally the
evaporation of the aqueous molecules is very rapidly effected, without possibility of
overheating since the liquid can not assume the spheroidal state; the permanence
of the divided condition being thus ensured the mist is converted into steam which
becomes drier and drier as it progresses through the heated tube. It is upon this
new principle of evaporation that this invention is based.
The second point with regard to the novel mode of transmitting the units of heat
collected at the heating surface, to the mass of water consists in effecting the
transfer of heat by means of steam instead of by direct contact of the water with
the heating surface as has been usual hitherto. In this new apparatus the water
instead of abstracting the heat by contact with the heating surface is allowed to
remain stagnant and without circulation and it is heated by a current of steam
which leaves the flashing tubes in a dry state and condenses in the mass of water so
as to produce steam by spontaneous evaporation as in fireless locomotives.
The invention is illustrated diagrammatically in the drawing accompanying my
Provisional Specification Figure 1 showing a vertical section of the boiler and a
horizontal section of the steam flashing tubes and Figure 2 a vertical section (on
line 1-2) (Figure 1) of the steam flashing tubes and furnace.
The generator comprises a series of tubes a placed within a furnace and heated
directly therefrom. Into the end of each tube projects a nozzle b by which water
is injected in the form of spray, the nozzles b being supplied by a pump d which
takes the water from the boiler e and delivers it under pressure through pipe c.
The pump is actuated by a donkey-engine h supplied with steam by pipe from the
steam space of the boiler e which contains a large supply of water heated under
pressure by the steam generated in the flashing tubes a which are connected to
the boiler by pipes provided with check valves g allowing the steam to enter the
lower part of the boiler and pass up through the water therein but preventing the
return of water. j is the steam pipe from the boiler to the engine to be driven.
A pipe connects the boiler e to the pipe c for establishing a circulation at starting
before any steam is available for working the donkey-engine, a cock on said pipe
being closed when the pump is started.
The operation of the apparatus is as follows:-The pump d takes from the
boiler e water heated by the steam generated in the flashing tubes to the temperature
corresponding to the pressure and by the effect of the vacuum produced by the
pump piston a certain quantity of steam is formed. When this mixture of water
and steam is compressed by the pump its temperature rises correspondingly with the
pressure, the compression being due to the contraction of the nozzles leading into
the flashing tubes. On emerging from the nozzles and thus passing from one
pressure to a lower pressure, (the flashing tube being at the same pressure as the
boiler and the pump having compressed water taken from the boiler) the water
becomes atomized and assumes the condition herein before indicated, the mist in its
progress through the flashing tube becoming drier and drier until finally it is by
steam alone that the check valves g are lifted. The steam on entering the boiler e
condenses and restores the heat units carried off by evaporation and by the
admission of cold water. The steam for working is produced in the boiler e by
spontaneous evaporation of the water as in fireless locomotives. As the check
valves g prevent any return of the water to the flashing tubes the projection of
large quantities of water into the furnace cannot possibly occur.
:

page_text: Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to he performed, I declare that what
1 claim is :-
:-
1st. The herein described method of producing steam which consists in injecting
a mixture of compressed steam and water by means of a pump, through a
contracted nozzle into a tube exposed to the direct heat of the furnace, as
specified.
2nd. The herein described method of producing the mixture of steam and water
which consists in drawing the water from a boiler in which the water is contained
at a temperature corresponding to its pressure, and of avoiding loss of heat during
the operation of compression, until the moment when the mixture is injected into
the flashing tube and the water becomes atomized and converted into the mixture
of water and steam in the form of mist required for the operation of the generator
described.
3rd. The herein described steam generator comprising a number of flasher tubes a
directly heated by the furnace, in combination with a boiler e containing water
under pressure heated by the steam generated in the flashing tubes, and a pump d
injecting the water into the flasher tubes under the conditions and for the purpose
herein specified.
Dated this 11th dox of Tul, 1805
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.