Improved Method and Apparatus for Preparing and Applying as Motive Fluid a Mixture of Air and Steam.
Year: 1898

page_text: Date of Application, 19th Aug., 1898
Complete Specification Left, 19th May, 1899-Accepted, 18th Nov., 1899
PROVISIONAL SPECIFICATION.
Improved Method and Apparatus for Preparing and Applying as
Motive Fluid a Mixture of Air and Steam.
I, EDWARD FIELD, of 4, Trafalgar Square, in the County of London, Engineer,
do hereby declare the nature of this invention to be as follows:-
This invention has reference to the preparation of motive fluid consisting of
a mixture of air and steam for which purpose I compress and heat air to the same
or a higher pressure and temperature as or than those of the steam with which
it is to be used then. I mix the air and the steam together, heat the mixture
and use it as motive fluid. I use air as free from moisture as may be conveniently
obtainable and when possible utilize the heat of escaping products of combustion
from the boiler furnace or other heat that would otherwise be wasted for heating
the air and mixture also using such waste heat for preventing condensation in
the apparatus containing the mixture, when being used. For this purpose I
combine and arrange apparatus (which may be actuated either by the engine which
the motive fluid being prepared is intended to work, or otherwise) for compressing
the air, with means for heating it, for adding to it steam from any convenient
source, for heating the mixture of air and steam, and for conducting the motive
fluid thus produced to the engine in which it is to be utilized. As will be evident
in carrying out my invention the several components of the combined or connected
apparatus or system may respectively be variously constructed and arranged.
The air may be compressed by a pump driven from the engine for working
which motive fluid is being prepared, or may be obtained from any suitable
source, the heating apparatus may be in the form of a coil or coils or series
or system of connected pipes, steam from a generator being at a suitable point
introduced into the heating apparatus so as to mix with the fluid therein, the
mixture flowing towards the engine and being gradually heated and expanded
whilst on its way thereto as aforesaid.
According to one arrangement, a good non-condensing high pressure expansion
steam engine is provided with an air pump (which may be driven by the engine)
capable of compressing the required volumes of air to a degree of pressure equal
to the initial pressure in the engine cylinder when running under full load. The
air under pressure is heated in a portion of a suitable heater located in the boiler
flue or flues or in an oven in connection therewith or in a heater that receives
heat from some other source of waste heat, the arrangement being such that
whilst passing through about one fourth (more or less) of the course through the
heater the temperature of the air is raised to or even above that of the steam
in the boiler, after which the air so heated is met by steam, direct from the boiler,
the air and steam become mixed and the mixture passes through the remainder
of the course through the heater or heaters ultimately leaving the heater at a
suitable temperature and pressure and in fit condition for use as motive fluid
to drive an engine.
..
In carrying out my invention definite volumes of air at atmospheric pressure
are, or can be, compressed and forced through a high pressure heater, having such
a capacity and length of "course" as to not only first heat the air which is
preferably admitted alone to the cooler part of the heater but, likewise, after steam
also has been admitted, to intimately mix the air and steam and adequately heat
the volume of mixture before it leaves the hottest part of the heater.

page_text: The steam supply may be always open to the heater, when in use. When
the apparatus is started, steam will occupy the whole of the interior of the heater,
but will be gradually and partially displaced by the entry of the successive
volumes of air at the same pressure and temperature as the steam. The mixture
thus formed can be used with advantage in any non-condensing ordinary engine.
I preferably make the heater of a capacity several times that of the engine
cylinder or cylinders, and it will be understood that in my apparatus I avoid
contact of the air with water and effect the mixture in a part of the apparatus
distinct from that containing the water from which steam is being generated.
The steam and air might enter the cooler end of the heater together and do
comparatively good work. But I prefer the arrangement described, according to
which quantities of air having at atmospheric pressure determined volumes are
compressed to the required working pressure, into the cooler end of the reservoir-
heater located between the steam generator or generators and the engine or engines
to be driven; self regulating admission of steam at working pressure-takes
place according to the requirements of the engine or engines into the reservoir
heater at the point or points indicated, thereby causing successive charges of
mixture to be formed which charges traverse the course of the reservoir-heater
and become thoroughly mixed and heated in their course towards the hottest
part of the heater from which the mixture escapes as required by the engine or
engines the quantity of air remaining constant and that of the steam only being
varied by the cut off as the engines require.
When several engines have to be driven by one central vapour generator a
"self-starting" engine say (Westinghouse) or the like driven by vapour from
the vapour main will supply the air at the pressure required.
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The large vapour main in such cases where practicable may be jacketted
by hot air from the flue.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.
COMPLETE SPECIFICATION.
Improved Method and Apparatus for Preparing and Applying as
Motive Fluid a Mixture of Air and Steam.
I, EDWARD FIELD, of 4, Trafalgar Square, in the County of London, 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:-
This invention has reference to the preparation of motive fluid consisting of a
mixture of air and steam for which purpose I compress and heat air to (or
about) the same or a higher pressure and temperature as or than those of the steam
with which it is to be used, then I mix the air and the steam together, heat the
mixture and use it as motive fluid. I use air as free from moisture as may be
conveniently obtainable and when possible utilize the heat of escaping products
of combustion from the boiler furnace, or other heat that would otherwise be
wasted, for heating the air and mixture, also using such waste heat, if desired,
for preventing condensation in the apparatus containing the mixture, when being
.used.
For this purpose I combine and arrange apparatus (which may be actuated
either by the engine which the motive fluid being prepared is intended to work,
or otherwise) for compressing the air, with means for heating it, for adding to it

page_text: steam from any convenient source, for heating the mixture of air and steam, and
for conducting the motive fluid thus produced to the engine in which it is to be
utilized. As will be evident in carrying out my invention the several components
of the combined or connected apparatus or system may respectively be variously
constructed and arranged.
The air may be compressed by a pump driven from the engine for working
which motive fluid is being prepared, or it may be obtained from any suitable
source. The heating apparatus may be in the form of a coil or coils or series or
system of connected pipes or chambers, steam from a generator being at a suitable
point introduced into the heating apparatus so as to mix with the fluid therein
the mixture flowing towards the engine and being gradually heated and increased
in volume whilst on its way thereto as aforesaid.
Fig. 1 of the accompanying illustrative drawings shows diagrammatically,
one arrangement of apparatus for carrying out the invention. Fig. 2 is a similar
view to Fig. 1, showing a modified arrangement.
Referring to Fig. 1 of the drawings, 1 represents a non-condensing high-
pressure expansion steam engine which should be of good and economical con-
struction. 2 is an air pump which may, as shown, be driven by the engine 1, or
it may be by any other suitable motor, and is capable of compressing the
required volumes of air to a degree of pressure equal to or above the initial pressure
of the mixture admitted to the engine cylinder when running under full load.
3 and 4 are heating devices shown in the form of bent or sinuous pipes that are
connected together at 5 so as to form a continuous tubular or reservoir heater.
This heater is located within a heating chamber 6 that may form part of the flue of
a steam boiler 7, or be an oven in connection with the boiler flue or that receives
heat from some other source of waste heat. The part 4 of the heater may be
arranged nearer to the source of heat than the part so as to be raised to a higher
temperature than the latter part. The inlet end 8 of the heating device 3 is
connected by a pipe 9 to the air delivery outlet 10 of the air pump 2, and the
outlet end 11 of the heating device 4 is connected by a pipe 12 to the valve
chest 13 of the engine 1, the inlet branch 5 between the two heating devices 3
and 4 being connected to the steam space of the boiler 7 by a steam supply pipe 14
that may be provided with a safety valve 15 and a stop valve 16. The arrangement
is such that whilst passing through the portion 3 of the heater, which may con-
stitute about one fourth (more or less) of the course through the combined heater,
the temperature of the air supplied thereto by the air pump 2 or other appliance
is raised to or even above that of the steam in the boiler, after which the air
so heated is met at the branch 5 by steam direct from the boiler; the air and
steam become mixed, and the mixture passes through the portion 4 of the combined
heater ultimately leaving the same at a suitable temperature and pressure and in
fit condition for use as motive fluid to drive the engine 1.
" course
23
In carrying out my invention definite volumes of air at atmospheric pressure
are, or can be, compressed by the air pump and forced through the high
pressure heater 3-4 which should have such a capacity and length of
as to not only first heat the air, which is preferably admitted alone to the cooler
part 3 of the heater, but, likewise, after steam also has been admitted to the
combined heater, to intimately mix the air and steam and adequately heat the
volume of mixture before it leaves the hottest part of the heater. The steam
supply pipe 14 may be always open to the heater, when the apparatus is in use.
As an example, let it be assumed that the engine 1 is to be worked with motive
fluid at an initial pressure of 120 pounds to the square inch, then the boiler 7 is
worked so as to deliver steam at a pressure of 120 pounds to the square inch to
the reservoir heater 3-4, the temperature of the steam being consequently about
341° F. Under these conditions the air pump 2 is adapted to compress and
deliver air at a pressure of 120 pounds or more to the square inch to the heater 3
wherein its temperature should be raised to the same temperature as the steam
and the mixture of air and steam on its passage through the portion 4 of the

page_text: .
combined heater should be further heated to a suitable extent, say 160° F., or to
a total temperature of about 500° F. When the engine and air pump are started,
steam will occupy the whole of the interior of the reservoir-heater 3-4 and the
engine will make its first few revolutions under the action of steam only. The
steam in the reservoir-heater will however, as the engine continues working, be
gradually and partially displaced by the entry of the successive volumes of air
delivered by the air pump at or about the same pressure and temperature as
the steam, the mixture of air and steam flowing on through the portion 4 of the
heater and thence to the engine which will then be driven by a mixture of steam
and air.
The further heating of the mixture by passing through the portion 4 of the
heater whilst the engine is working, causes the mixture to increase considerably
in volume whilst its pressure is maintained approximately uniform. Air is
admitted in an intermittent manner to the combined heater whilst the air pump
is at work, and steam is admitted from the boiler to the combined heater when
the pressure in the latter falls below the normal pressure due to consumption
of the mixture in the engine. In this way the supply of air and steam under
pressure to the combined heater is self-regulating, the supply of compressed air
depending upon the working of the air pump, and the supply of steam upon the
rate of consumption of the mixture in the engine, both supplies automatically
stopping when the engine and consequently the pump is stopped, and auto-
matically re-commencing when the engine is restarted."
Thus it will be seen that self-regulating admission of steam at working pressure,
into the reservoir heater 3-4, takes place according to the requirements of the
engine or engines, thereby causing successive charges of mixture to be formed,
which charges traverse the course of the reservoir-heater and become thoroughly
mixed and heated in their course through the hottest part of the heater from
which the mixture escapes as required by the engine or engines, the quantity of
air supplied remaining constant and that of the steam only being varied by the
action of the engine cut off as the engine or engines requires or require.
I have found by experiment that by mixing one volume of air having a tem-
perature of about 341° F. and a pressure of about 120 pounds to the square inchi
with 2 volumes of steam at or about the same temperature and pressure and
heating the mixture to a further temperature of about 160° F., or a total tem-
perature of about 500° F., there are obtained volumes of mixture at a pressure
of 120 pounds to the square inch.
A heated mixture of air and steam produced as hereinabove described can be
used with advantage in non-condensing ordinary engines of various kinds.
I preferably make the combined heater 3-4 of a capacity several times that
of the engine cylinder or cylinders to be supplied with the mixture, and it will
be understood that in my apparatus I avoid contact of the air with water and
effect the mixture of air and steam in a part of the apparatus distinct from that
containing the water from which steam is being generated.
The steam and air might enter the cooler end 8 of the heater together and do
comparatively good work, the steam pipe 14 being then extended, as shown in
dotted lines at 14ª, so as to deliver into the inlet end 8 of the part 3 of the heater.
But I prefer the arrangement first herein described, according to which quantities
of air having at atmospheric pressure determined volumes, are compressed to the
required working pressure and alone delivered into the cooler end of the reservoir-
heater 3-4. Non-return valves may be placed on the various pipes when and
where required.
When several engines are to be driven by one steam boiler or battery of steam
boilers having a common main heater, then it is advisable that each engine should
have its own special air pump (of a capacity suited to that engine) in connection
with the main heater. Fig. 2 shows one arrangement of this kind wherein the
combined heater 3-4 is placed in the main heating flue or chamber 6 common
to all the steam boilers, the air pump 2 of each engine being connected by pipes 9
'

page_text: to the inlet end 8 of the portion 3 of the combined heater, and the outlet end 11
of the portion 4 of the combined heater being connected by a pipe 12 to a large
pipe or vapour main 17 common to the several engines 1, so that each combined
engine and pump will serve to effect the supply of air and steam to the combined
heater for producing the mixture necessary for the proper working of such
engine. The large pipe or vapour main 17 in such cases may, where practicable,
be jacketed by hot air passing from the boiler flue 6 through a surrounding
pipe 18.
It is known that when air and steam at or about the same temperature and
pressure are mixed together, an increase in the total volume, at the same pressure,
takes place, but I have discovered that by heating the mixture of air and steam
to a still higher temperature as hereinbefore described, the volume of the mixture
can, whilst maintaining the pressure practically constant, be increased to an
extent which enables the mixture to be used with greater economy in fluid pressure
engines. Other fixed gases, such as products of combustion, might be substituted
for the air.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is:-
1. The herein described method of preparing a mixture of air and steam for
use as motive fluid by compressing and heating air to the same or a higher
pressure and temperature as or than those of the steam with which it is to be
used, mixing the air and steam together, and heating the resulting mixture
to a higher temperature than the original temperature of the steam preparatory
to using it in an engine, as set forth.
2. In the preparation and application of a mixture of air and steam for motive
power purposes as specified in the preceding claim, controlling the admission of
steam to the mixture of air and steam in the manner hereinabove described so
that the further supply of steam is effected in an automatic manner dependent
upon the rate of consumption of the mixture in a motive fluid engine as set
forth.
3. In the preparation and application of a mixture of air and steam for motive
power purposes as specified in Claim 1, supplying a definite quantity of com-
pressed and heated air at each stroke of the engine to the main volume of the
mixture of air and steam, the supply of a further quantity of steam to the said
mixture being effected in an automatic manner when the pressure of the mixture
falls below the normal, substantially as described.
4. For preparing a mixture of air and steam for use as motive fluid as specified
in Claim 1, apparatus comprising air compressing and heating apparatus steam
supply apparatus, and heating and mixing apparatus into which air and steam are
respectively delivered from the air compressing and heating apparatus and steam
supply apparatus and wherein the air and steam are mixed and further heated
preparatory to use, as set forth.
5. For preparing and applying as motive fluid a mixture of air and steam as
herein set forth, apparatus constructed arranged and operating, substantially as
hereinbefore described with reference to the drawings annexed.
For the Applicant,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.