Improvements in Air Engines and other Heat Engines relating to the Mode of Heating the Elastic Fluid Employed therein.
Year: 1887

page_text: Date of Application, 2nd Feb., 1887
Complete Left, 13th Sept., 1887
Complete Accepted, 11th Nov:, 1887
Improvements in Air Engines and other Heat Engines relating to
the Mode of Heating the Elastic Fluid Employed therein.
I, PATRICK JOHN LYNAM of Dundalk in the County of Louth, Ireland, Civil
Engineer and County Surveyor, do hereby declare the nature of this invention to
be as follows:-
This invention relates to a mode of heating the air or other elastic fluid in that
description of motive power engines in which mechanical force is produced by causing
air or other elastic fluid to be expanded by the heat of a furnace, and consists in
heating the air or other elastic fluid through a very large heating surface by means
of a bath of oil or other suitable liquid with a high boiling point (the bath itself being
heated by a furnace), combined with an arrangement to prevent the bath being heated
to an injuriously high temperature.
To prevent the bath being overheated a liquid should be used (such as oil) which
boils at a convenient pressure and temperature and the expansive force of its vapour
(when it exceeds a certain limit to be fixed by convenience) is used to shut a damper
so as to reduce the rate of combustion in the furnace or to cause the superfluous heat
to be expended in boiling away a liquid.
As examples three different ways in which the overheating may be prevented are
shewn in the drawing annexed.
The drawing shews a section of a boiler A A A of any ordinary type such as is
used for steam engines, in which the bath B B is heated, the arrangements to prevent
overheating are shewn at C and D and at E, F is a vessel which contains pipes or
vessels G in which the air or other elastic fluid is heated. The vessel F communicates
with the boiler by means of two pipes H and J, and by means of a force pump K the
hot liquid of the bath is drawn from the boiler through the pipe H, circulated round
the pipes or vessels G in the vessel F and returned to the boiler through the pipe J.
The air or other clastic fluid to be heated coming from the compressing pump or
cold end of the displacer of the air engine enters the pipes or vessels G at I and after
being heated passes away at M to the working cylinder or hot end of the displacer of
the air engine. As the improvement is applicable to any description of air engine,

page_text: the air engine used is not shown on the drawing. N is the chimney of the boiler in
which is a damper 0 0 which is closed, as far as it can conveniently be closed
without actually putting out the fire, by pulling the string at P.
The first arrangement to prevent the bath being overheated is shewn at C. It
consists of a safety valve or pressure reducing valve c¹ communicating on one side
with the space generally called "steam space in the boiler and on the other side
with a small cylinder 2 in which is a piston e³ with a piston rod c¹. The string P
which closes the damper O O is attached to a projection on the piston rod et in such
a manner that when the piston crises the damper OO is closed.
The action of this arrangement is as follows:-When the temperature of the bath
rises until the tension of its vapour exceeds the load on the valve c¹ this valve is
forced open and the vapour ascends into the cylinder c² and forces up the piston c³
and thus the string P being pulled the damper 00 is closed and so the rate of
combustion in the furnace is reduced.
The second arrangement is shewn at I). d¹ is a safety valve or pressure reducing
valve communicating on one side with the "steam space "of the boiler A A A and
on the other side with a vessel 2 in which is a second vessel d³. This second vessel (³
communicates with the atmosphere and contains a suitable liquid, preferably water.
The action of this arrangement is as follows:-When the temperature of the bath
rises until the tension of its vapour is sufficient to overcome the load on the valve d¹,
the valve d' is forced open and the vapour of the bath escapes from the boiler A A A
through the valve d', into the vessel d and is condensed into a liquid state on the
comparatively cold surface of the vessel d³, thereby giving up its latent heat of
vapourisation to the water in d³ which boils away. There should be a small force
pump (not shewn in the drawing) to force back again into the boiler the vapour
which being condensed in the vessel d will fall to the bottom in a liquid state, or if
the load on the valve be very light there may be another valve d' opening down-
wards and held up by a light spring or counterweight, so that the weight of the
liquid in the bottom of the vessel will be sufficient to force open the valve d' and
re-admit the liquid into the boiler. The vessel 3 should be of sufficient capacity and
its heating surface sufficiently large to carry away all the heat received from the
furnace when the engine is at rest.
The boiler should always be fitted with an ordinary safety valve, shewn at E on the
drawing. When the temperature of the bath rises until the tension of its vapour is
sufficiently high the valve E is forced open, the vapour escapes into the atmosphere,
and the bath itself boils away without any further increase of temperature. This is
the simplest and most effective method to prevent the bath being overheated but its
action is very inconvenient as the liquid of the bath is boiled away and lost, and the
vapour which escapes into the atmosphere will be unpleasant and may be dangerous.
It should be loaded more heavily than the valves of the other arrangements, so as
only to come into action when they fail.
All three of these arrangements can conveniently be used together and they may
be placed on the boiler A A A, or on the vessel F or on either of the pipes H or J.
The pipes or vessels G in which the air is heated may be placed in the boiler A A A
instead of in a separate vessel F.
If a liquid be used for the bath which boils at an inconveniently high pressure or
temperature a vessel may be placed in the boiler (or in the vessel F or enclosed in
one of the pipes H or J.) containing a liquid which does boil at a convenient pressure
and temperature. The expansive force of the vapour of this second liquid can then
be used to shut a damper or cause superfluous heat to be expended in boiling away
a liquid, and so to control the temperature of the bath.
As the difference in temperature (on which the rate of transfer of heat depends)
between the bath and the air to be heated will always be much less than the difference
in temperature between the bath and the furnace the heating surface of the pipes or
vessels G in which the air is heated must be larger than the heating surface of the
boiler A A A in at least the same proportion. The heating surface often consists of
the end of the working cylinder or displacer of the air engine, so that the air is

page_text: heated inside the cylinder or displacer, but not nearly sufficient heating surface can
be obtained in this way. The air must be heated in a separate vessel so that it is
heated before it enters the working cylinder or hot end of the displacer.
I prefer to use oils or fats such as stearin for the bath, but any substance may be
used which is liquid at a convenient pressure and temperature and which has no
injurious chemical effect.
The advantages claimed are :-
First. That as the temperature of the boiler plates exposed to the furnace can
never much exceed the temperature of the bath, while the temperature of the bath is
under control, the evils of excessively high temperatures are avoided and the boiler
may be expected to last nearly if not quite as long as an ordinary steam boiler, while
at the same time by means of a very large heating surface between the bath and the
air, the air can be effectually heated.
Second. The air being heated by means of a hot bath in an enclosed vessel (not
simply the end of the working cylinder or displacer), the area of heating surface
between the bath and the air or other elastic fluid can be increased as much as may
be required to render it effective, so that any required quantity of heat can be
transferred to the air or other working fluid without danger of overheating.
Dated this 2nd day of February 1887
CARPMAEL & Co.,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in Air Engines and other Heat Engines relating to
the Mode of Heating the Elastic Fluid Employed therein.
I, PATRICK JOHN LYNAM, of Dundalk in the County of Louth, Ireland, Civil
Engineer and County Surveyor, 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 a mode of heating the air or other elastic fluid in that
description of motive power engines in which mechanical force is produced by causing
air or other elastic fluid to be expanded by the heat of a furnace, and consists in
heating the air or other elastic fluid through a very large heating surface by means of
a bath of oil or other suitable liquid with a high boiling point (the bath itself being
heated by a furnace) combined with an arrangement to prevent the bath being heated
to an injuriously high temperature.
To prevent the bath being overheated a liquid should be used (such as oil) which
boils at a convenient pressure and temperature and the expansive force of its vapour
(when it exceeds a certain limit to be fixed by convenience) is used to shut a damper
so as to reduce the rate of combustion in the furnace or to cause the superfluous heat
to be expended in boiling away a liquid.
As examples three different ways in which the overheating may be prevented are
shown in the drawing left with the provisional specification.
The drawing shows a section of a boiler A A A of any ordinary type such as is used
for steam engines, in which the bath B B is heated, the arrangements to prevent
overheating are shown at C and D and at E, F is a vessel which contains pipes or
vessels G in which the air or other elastic fluid is heated. The vessel F communicates
with the boiler by means of two pipes H and J, and by means of a force pump K the
hot liquid of the bath is drawn from the boiler through the pipe H, circulated round
the pipes or vessels G in the vessel F and returned to the boiler through the pipe J.
The air or other elastic fluid to be heated coming from the compressing pump or cold
end of the displacer of the air engine enters the pipes or vessels G at L and after
being heated passes away at M to the working cylinder or hot end of the displacer of
the air engine. As the improvement is applicable to any description of air engine,
the air engine used is not shown on the drawing. N is the chimney of the boiler in
which is a damper OO which is closed, as far as it can conveniently be closed without
actually putting out the fire, by pulling the string at P or in other convenient
way.
The first arrangement to prevent the bath being overheated is shown at C. It
consists of a safety valve or pressure reducing valve e¹ communicating on one side
with the space generally called "steam space, in the boiler and on the other side
with a small cylinder c² in which is a piston c³ with a piston rod c. The string P
which closes the damper 00 is shown to be attached to a projection on the piston

page_text: rod in such a manner that when the piston crises the damper 00 is closed the
movement of the piston rod might however be caused to act upon the damper in other
convenient ways.
The action of this arrangement is as follows; when the temperature of the bath rises
until the tension of its vapour exceeds the load on the valve c¹ this valve is forced
open and the vapour ascends into the cylinder e² and forces up the piston c and thus
the string P being pulled the damper Ŏ O is closed and so the rate of combustion in
the furnace is reduced.
The second arrangement is shown at D. is a safety valve or pressure reducing
valve communicating on one side with the "steam space of the boiler A A A and on
the other side with a vessel 2 in which is a second vessel d³. This second vessel d³
communicates with the atmosphere and contains a suitable liquid, preferably
water.
The action of this arrangement is as follows; when the temperature of the bath
rises until the tension of its vapour is sufficient to overcome the load on the valve d'
the valve d' is forced open and the vapour of the bath escapes from the boiler A A A
through the valve d' into the vessel d and is condensed into a liquid state on the
comparatively cold surface of the vessel, thereby giving up its latent heat of
vapourisation to the water in which boils away. There should be a small force
pump (not shown in the drawing) to force back again into the boiler the vapour
which being condensed in the vessel d' will fall to the bottom in a liquid state, or if
the load on the valve d' be very light there may be another valve d opening down-
wards and held up by a light spring or counterweight, so that the weight of the liquid
in the bottom of the vessel d will be sufficient to force open the valve d and re-admit
the liquid into the boiler. The vessel 3 should be of sufficient capacity and its
heating surface sufficiently large to carry away all the heat received from the furnace
when the engine is at rest.
The boiler should always be fitted with an ordinary safety valve, shown at E on the
drawing. When the temperature of the bath rises until the tension of its vapour is
sufficiently high the valve E is forced open, the vapour escapes into the atmosphere,
and the bath itself boils away without any further increase of temperature. This is
the simplest and most effective method to prevent the bath being overheated but its
action is very inconvenient as the liquid of the bath is boiled away and lost, and the
which
vapour escapes into the atmosphere will be unpleasant and inay be dangerous.
It should be loaded more heavily than the valves of the other arrangements, so as only
to come into action when they fail.
All three of the arrangements can conveniently be used together and they may be
placed on the boiler A A A, or on the vessel F or on either of the pipes H or J. The
pipes or vessels G in which the air is heated may be placed in the boiler A A A
instead of in a separate vessel F.
If a liquid be used for the bath which boils at an inconveniently high pressure or
temperature a vessel may be placed in the boiler (or in the vessel For enclosed in
one of the pipes H or J) containing a liquid which does boil at a convenient
pressure and temperature. The expansive force of the vapour of this second liquid
5 can then be used to shut a damper or cause superfluous heat to be expended in
boiling away a liquid, and so to control the temperature of the bath.
As the difference in temperature (on which the rate of transfer of heat depends)
between the bath and the air to be heated will always be much less than the
difference in temperature between the bath and the furnace the heating surface of
0 the pipes or vessels G in which the air is heated must be larger than the heating
surface of the boiler A A A in at least the same proportion. The heating surface
often consists of the end of the working cylinder or displacer of the air engine, so
that the air is heated inside the cylinder or displacer, but not nearly sufficient heating
surface can be obtained in this way. The air must be heated in a separate vessel
5 so that it is heated before it enters the working cylinder or hot end of the
displacer.
substance may
I prefer to use oils or fats such as stearine for the bath, but
any

page_text: be used which is liquid at a convenient pressure and temperature and which has
no injurious chemical effect.
The advantages claimed are:-
First. That as the temperature of the boiler plates exposed to the furnace can
never much exceed the temperature of the bath, while the temperature of the bath
is under control, the evils of excessively high temperatures are avoided and the
boiler may be expected to last nearly if not quite as long as an ordinary steam
boiler, while at the same time by means of a very large heating surface between
the bath and the air, the air can be effectually heated.
Second. The air being heated by means of a hot bath in an enclosed vessel (not
simply the end of the working cylinder or displacer) the area of heating surface
between the bath and the air or other elastic fluid can be increased as much as may
be required to render it effective, so that any required quantity of heat can be
transferred to the air or other working fluid without danger of overheating.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what I
claim is :-
First. In motive power engines known as hot air engines in which mechanical
power is obtained by causing air or other elastic fluid to be expanded by the heat
of a furnace, the use of a bath of oil or other suitable liquid with a high boiling
point through which all the heat utilised from the furnace is passed before being
transferred to the air or other elastic fluid, combined with the regulation of the
temperature of the bath so as never to exceed a convonient limit by using the expan-
sive force of its vapour (or the expansive force of the vapour of a liquid immersed in
it) to close a damper so as to reduce the rate of combustion in the furnace or to
cause the superfluous heat to be expended in boiling away a liquid.
Second. In motive power engines known as hot air engines the use of an enclosed
vessel in which the air or other elastic fluid is heated by a bath of oil or other
suitable liquid having a high boiling point before it enters the working cylinder or
hot end of the displacer of the air engine, combined with the arrangements berein
described to prevent the air being heated to an injuriously high temperature.
Third. In hot air engines in which the air is heated by a bath of hot liquid, the
arrangement substantially as described and illustrated at C on the drawing to
prevent the bath being overheated by using the expansive force of its vapour (or the
expansive force of the vapour of a liquid immersed in it) when such expansive
force exceeds a convenient amount to close a damper by pulling a string or by
other convenient means to reduce the rate of combustion in the furnace.
Fourth. In hot air engines in which the air is heated by a bath of hot liquid,
the arrangement substantially as described and illustrated at D on the drawing for
controlling the temperature of the bath by using the expansive force of its vapour
(or the expansive force of the vapour of a liquid immersed in it) when such expan-
sive force exceeds a convenient limit to cause superfluous heat to be expended in
boiling away a liquid, without wasting the liquid bath.
L 1
S