IMPROVEMENTS IN GENERATING MOTIVE POWER BY THE EMPLOYMENT OF HEATED AIR, STEAM, AN GASPA
Year: 1857

page_text: LETTERS PATENT to Charles Benjamin Normand, of Havre, in the
Empire of France, Engineer, for the Invention of "IMPROVEMENTS IN
GENERATING MOTIVE POWER BY THE EMPLOYMENT OF HEATED AIR, STEAM, AN
GASPA"
Sealed the 9th, October 1857, and dated the 18th April 1857.
PROVISIONAL SPECIFICATION left by the said Charles Benjamin
Normand at the Office of the Commissioners of Patents, with his
Petition, on the 18th April 1857.
1, CHARLES BENJAMIN NORMAND, of Havre, in the Empire of France,
Engineer, do hereby declare the nature of the said Invention for "IMPROVE
MENTS IN GENERATING MOTIVE POWER BY THE EMPLOYMENT OF HEATED AIR, STEAM,
AND GASES," to be as follows:-
The object of my Invention is the economical production of motive power
by engines actuated by gases or vapors expanded by heat at very high
temperatures.
I also propose several improvements for reducing the power absorbed in
the compression of air,and several new arrangements of the parts to constitute
engines suited for various land and marine purposes.
The kind of ongines to which I propose to apply my improvements is
chiefly that into which fresh volumes of atmospheric air are drawn and
compressed by pumps, and after having been heated are made to exert
their effect on the piston of the engine.

page_text: In order to employ, without inconvenience, air or gases at very high tem-
peratures, the cylinder is made of a much greater length than is usual for a
given stroke, and this increased space is filled by two drums, set one on each
side of the piston, and of a length at least equal to that of the stroke. The
diameter of these drums is a little inferior to that of the cylinder, so that
they move without rubbing its interior surface. The hot gases are admitted
at the extremities of the cylinder, and the whole of the fixed and moving sur-
faces against which they exert their force are protected from injurious heat by
a coating of brick, fire clay, or other like substance, or else externally the
cylinder is protected by a cooling body of water. The central part of the
cylinder on which only the packing of the piston works is thus never in
contact with the hot gases, and is, moreover, protected from any inconvenient
transmission of heat by an external cooling, or by the following disposition,
chiefly intended for another object:-A special valve apparatus is set on the
central part of the cylinder, and by it a small supplementary admission is
effected in the annular space round the protecting drums of the piston. This
special admission is supplied only by cool and pure air taken directly from
the pumps, or by steam generated in belts or jackets round the cylinder.
Thus the lubricated surface of the cylinder is not only protected from
injury, induced by the action of the heated air or gases employed in the
cylinder, but also from the destructive effects of the cinders or other
impurities introduced into the cylinder by the heated air or gases.
As the ordinary arrangements of slide or lift valves would be unfit for
distributing the hot working gases, I employ a hollow cylindrical slide valve,
through which water is caused to circulate to maintain the parts cool. The
seats in which it moves, and through which the passages are cut, are also
cooled externally by water, and to the utmost extent possible lined internally
by a coating of fire clay or other such substance, to maintain as much as
possible the temperature of the circulating gases. Instead of the above, I
also propose to employ lift valves, lined to the greatest extent possible with
ceramic substance, and the metallic parts of which are kept in a true shape
by the cooling action of a body of water.
When the engine is to be put in motion, in order to raise the air or gases to
the required high temperatures at which I desire to employ the same, I pass
air into the furnace, to be presently described, and heat it in contact with the
fuel. It is then passed to one of a pair of chambers (which I term heat
transmittors) provided with suitably constructed heat-absorbing surfaces, to
which it is caused to impart the greater portion of its heat before being allowed
to escape into the atmosphere. Fresh air submitted to compression is then

page_text: admitted to the heated chamber, and passing over the heat-absorbingsurfaces
it will take up heat therefrom. This fresh but highly-heated air next passes
to the cylinder of the engine, where it exerts its expansive force on the piston
and then escapes to the furnace. Here it is brought into contact with the
fuel, and its temperature being raised, it is conducted to the transmittors and
there deprived of its heat, after which it is discharged into the atmosphere.
Thus it will be understood that when the engine is once fairly set in action the
furnace will be fed with unburnt air from the working cylinder, and that air
when heated will be used as the medium for imparting heat to the next
succeeding supply of air admitted to the cylinder. The heating chambers
or heat transmittors consist of two long metallic cases, connected at their
extremities, and provided with openings and valves, by which the currents
of feed and exhaust are alternately exchanged at the required intervals.
These valves are constructed after the improved plan described to prevent
the ill effects of heat on their durability and tightness.
The heat-absorbing and transferring surfaces of the transmitters may be
made of wire gauze or thin metal plates, or they may consist of thin tiles
of fire clay, porcelain, glass, or other vitreous or ceramic substance. In
order both to prevent the loss of heat and maintain the resisting parts at
a low temperature, a lining of fire brick is disposed throughout the interior
surface of the transmitters, and to maintain more certainly an equilibrium
of temperature in all the parts, the whole apparatus is set in a tank of water
boiling under atmospheric or higher pressure.
Hitherto in working air engines the action of the furnace for restoring
the quantity of heat expended in the production of power and by radiation
has been applied to the compressed feed air. My proposed engine might
also be worked in the same order, the heating of the air being as above
effected by immediate contact with the burning fuel.
Instead of disposing the fuel on a grate, as in furnaces generally, I lay it
on the sole of the furnace, and cause the air which is to support the ignition
and impart heat to the transmittors to traverse over the fuel. This furnace,
which is lined with fire brick, is made long and broad, and a space is left
behind the bridge for the deposit of most part of the cinders carried away
by the current of air. What impurities it might still contain are further
separated by a sieve of platinum, wire gauze, or a veil of asbestos cloth.
But instead of applying the furnace heat direct to the compressed air, I
prefer to effect it indirectly by heating the exhaust from the cylinder, as
before explained. When air is compressed in the ordinary force pump, the
expenditure of
power is much increased by the rise of temperature attending

page_text: the reduction of volume. To diminish this increase of resistance I propose
to divide the work of compression into successive operations in pumps of
decreasing sizes, in a manner inversely similar to that of Woolf's steam
engines, and causing the air to undergo a thorough cooling at each inter-
inediate stage of pressure. And further, I propose to effect a continuous
and immediate cooling of the air in one and the same pump by means of
minute metallic surfaces, which fill the space where the compression is
effected, and are cooled by a body of water surmounting the piston, and
renewed in order to maintain a low temperature of the parts.
Part of the improvements above described as applicable to hot air engines
might also be employed in the class of motors in which the impelling fluid is
a mixture of heated air and steam, whether the heating of the air and
vaporization have been effected by conduction through metallic surfaces, or
by direct contact of the air with the fuel and of the hot gases with the water.
The various means described for distributing and employing hot air in
engines can also be employed in using a mixture of air and steam at high
Lemperatures. I propose, moreover, for this class of engines an improved
generator, in which the heating of the air and vaporization are effected by
the direct action of the fire.
A strong shell of plate iron, shaped as a high-pressure cylindrical boiler,
is set horizontally. It is divided at about the half of its length to a tight
partition, rising to about two-thirds of its height. One of the compartments
forms properly the furnace, and is lined with fire bricks. The fuel either
lies on a grate or on the sole of the brick lining, the compressed air being
in this case introduced by narrow lateral apertures, and made to impinge
on the ignited mass. The other part of the generator is filled with water
to about one-third of the diameter, the space above serving as a passage for
the hot air and gases from the furnace to the engine. An agitating wheel,
mounted on a horizontal shaft, serves to bring the required quantity of
water into contact with the stream of hot gases, by which it is immediately
converted into vapor.
This arrangement for producing a mixture of heated air and steam presents
great safety compared with former proposed and tried arrangements. The
sudden throw of water into the fire itself being possible, a great part of
the cylinders and impurities will also be retained on the wet surfaces of the
agitator before being finally sieved, as before described. Highly-heated
motive fluids might also be obtained by mixing together steam generated
in ordinary boilers with hot gases proceeding from combustion in a closed
furnace under pressure.

page_text: To obtain highly-superheated steam without mixture of air, so that it can
be used with a condensor, I cause ordinary steam to travel alternately through
one of two passages filled with heat-absorbing and transferring surfaces,the
other set of surfaces in the adjoining chamber being by this time heated by
the hot gases from a furnace, these apertures being alternately exchanged
at the required intervals. This last mode of working sufficiontly shows that
the first-described improvements are also applicable to engines working by
pure steam highly surcharged with heat.
In the various arrangements proposed, where a closed furnace working
under pressure has to be employed, the long continuous working of the
engines when required may be effected by dividing tho generating apparatus
and disconnecting successively the separate parts for feeding and cleaning
the fires.
The fuel can also be supplied to one and the same furnace by the known
employment of a closed hopper or intermediate supply vessel. Such con
tinuous feeding 1 propose to facilitate or even perform entirely by the use
of coal tar, which by its liquid nature can be fed continuously under
pressure by suitable pumps.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Charles Benjamin Normand in the Great Seal Patent
Office on the 17th October 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
BENJAMIN NORMAND, of Havre, in the Empire of France, Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eighteenth day of April, in the year of our Lord
One thousand eight hundred and fifty-seven, in the twentieth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Charles Benjamin Normand, Her special license that I, the said
Charles Benjamin Normand, my executors, administrators, and assigns, or
such others as I, the said Charles Benjamin Normand, my executors, admi-
nistrators, and assigns, should at any time agree with, and no others, from
time to time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle of Man,

page_text: an Invention for "IMPROVEMENTS IN GENERATING MOTIVE POWER BY THE EMPLOY-
MENT OF HEATED AIR, STEAM, AND GASES," upon the condition (amongst others)
that I, the said Charles Benjamin Normand, by an instrument in writing
under my hand and seal, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Charles Benjamin Normand, do hereby
declare the nature of my said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement, reference being had to the Drawing hereunto annexed,
and to the letters and figures marked thereon (that is to say):-
The object of my Invention is the more economical production of motive
power by the employment of compressed air or steam, or a mixture of both,
expanded by heat at very high temperatures.
The advantages to be derived in working at such high temperatures are
well known in theory, but even at the comparatively moderate temperatures
at which it has been attempted to work air or surcharged steam the
following difficulties have hitherto prevented their employment :-
First, the rapid oxidation and destruction of the parts through which the
heating of the air or steain is effected.
Second, the drying and destruction of the rubbing surfaces, and the
leakage caused by the alterations in the shape of those parts of the engines
with which the hot gases come in contact.
Third, when the heating of the air or steam is effected by immediate
contact with the fuel in closed furnaces, the introduction of cinders and
other impurities into the engine causing a still more certain and rapid
corrosion of the rubbing parts of the engine.
The improvements which I propose to introduce have for their object the
removal of these hitherto insuperable difficulties, and the enabling of engines
to work without detriment to the moving parts and packing at the highest
temperatures which the gases resulting from combustion attain.
The kind of engines, to which I propose to apply my improvements is, chiefly
that in which volumes of atmospheric air are employed, the same being drawn
from the atmosphere and compressed by pumps, and after having been
heated to a high temperature are made to exert their effect on the piston
of the engine.
Figures 1, 2, and 3 represent the cylinder piston and working valve of my

page_text: improved air engine, Fig. 1 being a vertical longitudinal section of the
same; Fig. 2, a sectional plan view, taken in the line 1, 2, of Fig. 1; and
Fig. 3, a cross section, taken in the line 5, 4, of the same Figure.
In order to employ without inconvenience air or gases at very high
temperatures even when heated by direct contact with the fuel (which method
I sometimes propose to adopt), the cylinder A is made of a much greater
length than is usual for a given stroke, and this increased space is filled by two
drums B, B, set, one on each side of the piston P, and each of a length at
least equal to that of the stroke. The diameter of these drums is a little
inferior to that of the cylinder, so that they move without rubbing its interior
surface. The hot gases are admitted at the extremities of the cylinder by the
openings C. C. To prevent the injurious effect of the heat, the whole of the
fixed or moving surfaces on which the gases exert their force are protected
internally by a coating D, D, of fire-clay brick, or other like indestructible
substance, or else they are coated externally by a body of water contained in
the belts or jackets E, and boiling under pressure. This protection, repre-
sented in the Drawing as effected in a compound manner, might be done solely
by one of the two modes described, either by the exterior cooling water or by
the internal covering of clay, &c. The central part of the cylinder, over which
only the packing ring P of the piston works, is, by reason of the peculiar con-
struction of the piston, never in contact with the hot. motive gases. And the
further to secure this result, a special valve apparatus F is sot in the central
part of the cylinder, by which a small supplementary admission of air or
gaseous fluid is effected through two annular passages G, G, in the narrow
space between the protecting drums and the cylinder. This special admission
is supplied only by cool and pure air taken directly from the pumps, or by
steam generated entirely or partially in the jackets round the cylinder. No
exhaust takes place through this apparatus. At the same time that the main
bulk of hot working gases is being introduced at either end of the cylinder, a
stream of pure and comparatively cool fluid is kept issuing round the protecting
drums. Thus the lubricated surface of the cylinder is not only protected from
any inconvenient transinission of heat, but also from any access of cinders or
other impurities contained in the main working gases. For the protection
of the piston rod the stuffing box His removed to a distance from the cylinder
cover. Pure steam or air is admitted in the narrow space between the pipe I
and the rod J, which is, moreover, hollow, and with water circulating inside..
As the ordinary arrangement of slide or lift valves would be unfit for dis-
tributing very hot gases, I employ a hollow cylindrical slide valve K, through

page_text: which water is made to circulate, to keep the rubbing parts cool, aud allow
a certain amount of lubrication. The cylindrical seats L in which the
passages are cut, and the pipes M and N which convey and emit the hot
gases, are also cooled externally by water, and to the furthest extent possible
lined inside by a coating of fire clay, or other such substance, in order to
maintain the temperature of the hot gases.
Instead of the above-described valve gear, I also propose to employ the
arrangement of lift valves shewn in Fig. 4. O is the opening to the
cylinder; Q, the induction; and R, the exhaust valve. The whole of the
valve casing with the exception of the seats is lined internally with fire
clay, and the valves Q and R cooled by a surmounting body of water.
In Fig. 11 I have shewn a different arrangement of cylinder and piston,
which effects a saving in the weight and the space occupied by the engine.
The piston S is a hollow plunger. The hemp or metallic packing T is
attached to the cylinder, and presses on the surface of the piston S, which
is longer than the stroke, and turned true and smooth throughout its length.
The introduction of protecting steam or pure air takes place in the annular
passages U, U.
In the above-mentioned Drawings I have not represented any of the
complementary parts of the engine requisite for applying its alternate
recilinear motion to the working of pumps, &c., or to the continuous rotation
of a shaft. The framing guides, connecting rod, shaft, &c., will be disposed
according to circumstances, and require no description. The cylinder repre-
sented as fixed, horizontal, and double-acting could, if required, be cou-
structed vertical, inclined, or vibrating, and the action of the working gases
might take place only on one side of the piston.
I will now describe my improvements relating to the heating of the air
to be used in my improved motive power engine.
Figures 5 and 6 represent an improved form of furnace for effecting this
object, Fig. 5 being a vertical longitudinal section, and Fig. 6 a cross section,
taken in the line 1, 2, of Fig. 5. This furnace consists of a tight outer casing
of sheet iron, of a thickness corresponding to the pressure which it is
required to sustain. The metal casing is lined with bricks or fire clay.
Instead of this the iron casing might be made double, forming a water space
between the plates, the steam generated therein being employed in the engine
either separately or intermixed with the hot air. The fuel is not laid on a
grate, as generally done, but it is spread over the sole A, A, of the furnace,
and the compressed air is admitted through the sides by the openings B, B.

page_text: By this arrangement the air will not carry away so great a portion of the
ashes as if it passed vertically through a mass of fuel lying upon fire bars.
A bridge C divides the furnace into two parts, and fuel is introduced in the
first only, the other serving for the deposit of the greater portion of the ashes
carried over by the current of air. A further separation is effected by a
screen or veil of platinum, wire, or asbestos cloth D laid across the exit
opening to the engine.
It will be easily understood that from the above I anticipate only tho
separation of the coarser part of the impurities contained in the hot air, the
ininor particles retained floating as if in the air will be rendered innocuous by
the already described improvements to the ongine.
In order to turn to useful effect the greater part of the heat still retained
in the exhaust air from the working cylinder, I make use of an apparatus
previously employed, but in which I introduce several alterations. This: appa
ratus, which I term "the heat transmitter," (its object being to transfer the
heat contained in the exhaust to the current of compressed air,) is represented
in Figures 7 and 8. It consists of two long metallic cases E, E¹, connected
together at their extremities, and provided with openings and valves F, F¹, by
which the currents of exhaust and compressed feed air are admitted to and
discharged alternately from each chamber, and the continuity of the flow of
each current is thus maintained. The chambers E, E, are filled with exten-
sive heat absorbing surfaces G, which may consist of metal plates, wire, gauze,
or thin tiles of fire clay, porcelain, glass, or other vitreous or ceramic substance.
The exhaust air derived from the working cylinder of the engine is admitted
through the valve F, and flows along the chamber E, where, meeting with the
metallic or other heat-absorbing surfaces, which decrcase gradually in tem-
perature towards the further end of the chamber E, it gives up the greater
part of its heat to the absorbing surfaces before escaping to the atmosphere.
Whilst this action is going on, the compressed air from the feed pumps is
introduced from the reservoir I into the valve box H, and flows through the
chamber E' (which has been previously heated) by the passago through it of
the exhaust air. The fresh air meeting heated surfaces increasing in tempera-
ture gradually towards the discharging end of the chamber E',takes up the
heat held by those surfaces, and attains in its traverse a temperature little
inferior to that of the exhaust when leaving the cylinder. If such action
were continued for a certain time without alteration one of the chambers and
set of transmitting surfaces would be raised through its whole length to the
temperature of the exhaust, whilst the other set would be in a corresponding
way reduced to that of the compressed air current, and the required inter-

page_text: change of heat would no longer take place. The slide valves at each end of
the heat transmitters are therefore moved simultaneously at regular and suffi-
ciently short intervals; the set of surfaces which had been gradually heated by
the exhaust is submitted to the curront of feed air, and that which had been
cooled under this last actiou now receives a fresh supply of heat. In order
to maintain the shell or case of the heat transmitters at a low and uniform
temperature, so that no alterations of shape can take place in the valve seats
which require lubrication, the whole apparatus is set in a tank of water boil-
ing under atmospheric or greater pressure. To lessen the loss of heat, a
lining of fire brick is disposed throughout the interior surface of the trans-
mitters, and the valve box H' at the hot end thereof is also lined with fire
brick. When the change in the direction of the air currents takes place, by
the simultaneous motion of the valves F and F at the opposite ends of the
transmitters, the passages are all closed for a moment. In order, therefore,
to maintain the continuous flow of the compressed air and the exhaust, the
valve box H is provided with a weighted valve K, communicating by a branch
pipe L with the exit pipe M of the heated air. Whenever, therefore, the
pressure of the air in the valve box H is increased by the closing of the
passages governed by the valves F and F', the valve K will rise and restoro
the required communication between the reservoir I and the furnace.
As a further improvement in the working of air engines, instead of leading
the compressed feed air directly into the furnace to be heated, I conduct the
exhaust air from the cylinders to the furnace, and restore to it the amount of
heat which it lost in the engine by expansion and radiation, after which I
introduce it into the transmitters to heat the metallic or other surfaces con-
tained therein for the purposes above explained. In this manner the tempera-
ture of the transmitting surfaces is brought to such a point, that the
compressed air in passing through the transmitter from the pumps on its way
to the engine will receive at once the heat required without going through
the furnace. This mode of action does not lessen the consumption of fuel,
the same supply of heat being required in both cases; but it possesses the
advantage, that the fire has not to be maintained and fed under a considerable
pressure, and that the hot air supplied to the cylinder not having been in
contact with the fuel, will only carry to the engine the small amount of ashes
which it may have gathered from the heat-transmitting surfaces. When air
is compressed in an ordinary force pump, the expenditure of power to work
the pump is much increased by the rise of temperature, attending the reduc-
tion of the volume of air over that which would be required were the
temperature to remain constant. To diminish this resistance I propose to

page_text: divide the work of compression into two or three successive operations, using
pumps of decreasing capacities, in a manner inversely similar to the action
of steam in Woolf's double cylinder engines, and I cause the air to undergo
a thorough cooling at each intermediate stage of pressure. The heat evolved
in the first compression will thus be absorbed before the next takes place,
and the volumes and proportionate expenditure of power of the second and
third pump will be reduced in a corresponding proportion. The action of
the resistance will also be rendered less irregular.
Figures 9 and 10 represent an illustration of the said improvement; Fig. 9
being a longitudinal vertical section in the axis of the first or larger pump,
and Fig. 10 a cross section in the line 1, 2, of Fig. 9. The two pumps are
represented as cast together, and having their rods issuing in parallel lines
from the same end, as if to be moved simultaneously from the same cross
head; the air is first drawn by the large pump A, and compressed in the.
reservoir B, which it enters through the opening C. This reservoir is filled
through a certain portion of its length by a faggot of wire gauze or thin
branches of wood D,. over which cold water drops in a continuous shower.
The air descending through these cooling surfaces parts entirely with the
heat it had acquired during the first compression. It is then drawn through
the opening E by the second pump F, of smaller capacity, which brings it to
the final required pressure, or delivers it to a new set of cooling and com-
pressing apparatus.
Fig. 12 shows, in vertical section, an arrangement by which a continuous
cooling of the air during compression, a great economy of power is effected.
The upper part of the compressing cylinder is filled with thin vertical plates
of metal G, set at a small distance from each other. The piston H is
surmounted by a body of water 1, which at each stroke is caused to fill
entirely the spaces between the plates G and expel the air by the valve J.
By this arrangement the mass of air divided during compression in a quantity
of narrow spaces will surrender continuously the heat evolved, and the power
absorbed will be reduced to a minimum; the water over the piston is renewed
in any convenient manner to prevent an undue rise of temperature.
The improvements above described as applied to air engines (for working at
very high temperatures for rendering applicable the heat of the exhaust and
reducing the
power absorbed in the compression of the air) might also be
employed in that class of motors in which the impelling fluid is a mixture of
heated air and steam, whether the heating of the air and vaporization aro
effected in the ordinary manner, by conduction through metallic plates, or

page_text: whether the same are performed by direct contact of the air with the fuel and
of the hot gases from combustion with the water to be vaporized.
Ipropose, moreover, for this class of engines an improvedgenerator or furnace
where the combustion and vaporization are to be effected. This apparatus is
represented in vortical longitudinal section at Fig. 13, and in cross section at
Fig. 14. It consists of a strong cylindrical shell of plate iron, sethorizontally,
and divided at about the middle of its length by a partition K, rising to about
two-thirds of its diameter; the compartment L forms properly the furnace, and
is lined completely with fire brick. The fuel either lies over a grate or on the
sole of the brick lining, the compressed air being in this case introduced by
lateral apertures M,and made to impinge on the ignited mass. The other part
N of the generator is filled with water to about one half of the height of the
partition K, the space above serving as an exit passage for the hot air and
gases from the furnace to the engine. An agitating apparatus, consisting of
a number of plates or bars O, carried by radial arms affixed to an horizontal
rotating shaft P, serves to bring in contact with the stream of hot gases the
amount of water required to be converted into steam. It will be easily under-
stood that if a great extent of wet surfaces is so presented to the hot air the
resulting mixture of gases and steam will be at a temperature little exceeding
that of ordinary steam of the same pressure; if, on the contrary, the motion
of the agitator is entirely stopped, the gases from combustion will pass with-
out being cooled and intermixed with steam. It follows, that by properly
adjusting the rotatory speed of the agitating wheel any desired proportion
of vaporization and cooling will be easily and efficiently secured.
This arrangement of generator also presents great safety compared with
former proposed or tried arrangements, no throw of water on the fire and
consequent sudden rush of steam or probable production of explosive gases
being possible; also a great part of the cinders will be retained on the wet
surfaces and discharged into the water, from which they can be withdrawn
by the usual blow off.
Highly-heated motive fluids might also be obtained by mixing together
steam generated in ordinary boilers with hot gases proceeding from combustion
in a closed furnace under pressure.
To obtain highly-superheated steam with scarcely any mixture of air, so
that it can be more easily used with a condenser, I employ an arrangement of
heat-absorbing and transferring surfaces, similar to that described with refer-
ence to Figures 7 and 8, and used for heating compressed air. The two
chambers containing the heat-absorbing surfaces I charge alternately with

page_text: heat, by passing into the chambers air heated in a furnace working under
ordinary atmospheric pressure. When thus. heated,..I..cause. ordinary
steam to travel over the heated surfaces, and thereby absorb the heat
which they have received.
This last mode of working sufficiently shows that the first-described
improvements are also applicable to engines working by pure steam highly
surcharged with heat.
In the various arrangements which I have proposed, where a closed
furnace working under pressure is employed, the long continuous working
of the engines when required may be effected by dividing the generating
apparatus and disconnecting successively the separate parts for feeding
and cleaning the fires. The fuel can also be supplied to one and the same
furnace by the known employment of a closed hopper and intermediate
supply vessel. Such continuous feeding I propose to facilitate and even
perform entirely by the use of coal tar, which by reason of its liquid nature
can be fed continuously under pressure by suitable pumps. Fig. 13 shews
an application of such feeding by the openings Q in the roof of the furnace.
Having now set forth the nature of my Invention of "Improvements in
Generating Motive Power by the Employment of Heated Air, Steam, and
Gases," and explained the different modes of carrying the same into effect.
I wish it to be understood that under the above in part recited Letters
Patent I claim,-
First, the means herein described for preventing the access of dust and
radiation of the heat of the gases used in air engines to the pistons and
rubbing parts of the cylinders of such engines.
Second, protecting those parts of the engine which are subject to the
action of the heated gases from the injurious effects of high temperatures, by
lining the same with fire clay or other like indestructible material, or by
the use of water jackets, as above set forth.
Third, constructing furnaces, as above described, for heating air under
pressure in contact with the ignited fuel.
Fourth, employing the exhaust air from the engine (after passing it
through a furnace) as the medium for heating compressed air to be supplied
to the engine in connection with heat-absorbing and transmitting surfaces.
Fifth, the construction of heat transmitters, as described with reference
to Figures 7 and 8.
Sixth, the employment of such heat transmitters for superheating steam,
as explained.
Seventh, economizing the power required to compress the air to be used

page_text: in air engines, by dividing the work between two or more pumps of
decreasing capacities and cooling the air at the intermediate stages, or,by,
effecting a continuous cooling during compression in one and the same
pump, as described.
Eighth, the arrangement of closed furnaces, 'described with reference to
Figures 13 and 14, for heating air and generating steam simultaneously.
And, lastly, I claim feeding furnaces which burn under pressure with
coal tar as a fuel.
In witness whereof, 1, the said Charles Benjamin Normand, have here-
unto set my hand and seal, the Seventeenth day of October, in the
year of our Lord One thousand eight hundred and fifty-seven.
:
Witness,
J. W. MOFFATT,
☐ 66, Chancery Lane.
C. B. NORMAND. (L.B.)