Generators of Mixed Gas and Steam and Utilization of such Mixture in Motor Engines.
Year: 1898

page_text: Date of Application, 16th Mar., 1898-Accepted, 28th May, 1898
COMPLETE SPECIFICATION.
Generators of Mixed Gas and Steam and Utilization of such Mixture
in Motor Engines.
I, ROBERT HENRY SMITH, of Ellerslie, Brunswick Road, Sutton, in the County
of Surrey, and of 63, Victoria Street, Westminster, in the County of London,
Professor of Engineering and Consulting Engineer, do hereby declare the nature
of this invention and in what manner the same is to be performed, to be particu-
larly described and ascertained in and by the following statement:
1
The invention relates to an improved method of and apparatus for the genera-
tion of hot high pressure gaseous or vapourous fluid to be used for driving engines
of any form either reciprocating or rotative in any of the various manners in
which steam or other high pressure vapour air or other gas is used in such engines
without combustion in the cylinder or equivalent working chamber.
The object of the invention is to combine certain advantages obtained separately
in steam and in internal combustion gas and oil engines and to avoid certain
disadvantages inherent in each of these classes of engine.
In gas and oil engines the internal combustion necessitates water-jacket cooling
of the working cylinder and thereby involves wasteful rejection of heat at high
temperature; the intermittency of the combustion hinders the perfect regulation
of the proportion of air to fuel and their perfect intermixture; and the use of
only one stroke out of every four or six strokes as a working stroke makes the bulk
and weight of the engine excessive in proportion to its horse power. These dis-
advantages are avoided by the use of my generator as well as by the use of an
ordinary boiler and steam engine. On the other hand these latter produce large
volumes of highly heated gases which, except for their being dirty and at low
pressure, would be usable as working fluid in the cylinder but are discharged to
the chimney instead, and it has also been found hitherto imposible to avoid the
condensation of a large portion of the steam immediately on its entrance to the
cylinder and before it has done any work on the piston. In using my generator
the whole of the gases are generated by combustion in a steady and continuous
manner under high pressure in a strong vessel apart from the working cylinders,
and are afterwards passed through the working cylinders, in which work may be
done on every piston stroke. These gases are mixed with the steam evaporated in
the same strong vessel and which steam is thus highly superheated and initial
cylinder condensation either entirely prevented or greatly reduced according to
circumstances. The heat given up by the gases for the evaporation of the water
and the superheating of the steam reduces the gas temperature to that degree that
is found compatible with easy and durable piston and cylinder working without
water-jacket cooling. The temperature attained and the degree of steam super-
heating depends upon the pressure maintained and upon the proportion of steam
generated to each pound of fuel burnt and this proportion is capable of regulation.
This proportion depends both upon the area and disposition of the heating surface
in contact with water and upon the difference of temperatures between the hot
gas on the one side and the water on the other side of this heating surface. The
temperature of the water depends upon the pressure maintained and is independent,

page_text: or nearly wholly so, of the amount of superheat in the steam, while the temperature
of the gas in the furnace depends mainly upon the proportion of air to oil or other
fuel injected. For normal working the air injected is to a small extent only in
excess of the chemical equivalent required for complete combustion of the fuel,
and the area and disposition of the normal heating surface is designed to give the
desired degree of superheat with the furnace temperature so arising and with the
desired normal pressure. If it be desired to vary the degree of superheat from
the normal degree this may be done either by altering the proportion of air to fuel
injected or by altering the water level and thus altering the area of the heating
surface.
Another advantage of this mode of generating working fluid for engines consists
in the equality of the pressures upon the water and furnace sides of the heating
surface plates. This equality of pressures permits the use of very thin plates
which facilitates the conduction of heat through them and thus increases their
heating efficiency per square foot making the size of the generator per horse power
smaller. It also permits the use of metals for these plates of high thermal con-
ductivity such as copper or brass without necessitating any increase of thickness
as compared with that needed for metals such as steel which has higher tensive
strength and lower thermal conductivity. The equality of pressures also makes
simpler and cheaper the provision of tightness against leakage of the joints of
the heating surface and other plates forming the water space. It also results in
very great freedom of the heating surface plates to expand and contract with
variation of temperature because these plates need be jointed to the rest of the
generator only at the lower end of the water space and may be left entirely uncon-
nected at their upper parts. These advantages form some of the reasons for
adopting this design of generator and the attainment of these advantages by means
of this design constitutes part of my invention.
In the accompanying drawing Fig. 1 is a sectional elevation of one form of the
generator and shows fully its construction. A A is a steel or iron cylinder flanged
at its upper and lower ends. BB is a cast steel or iron cover or dome. C is the
supply pipe leading the high pressure mixture of gas and steam to the engine.
D) is a mounting for the attachment of one or two safety valves. E is a mounting
for pressure gauge, whistle &c. F is an aperture left open during the warming
up of the generator at starting but closed by a screw down valve as soon as the
internal pressure begins to be raised.
GG is a thin brass or copper cylindrical partition between the hot gas space H H
and the water and steam space which lies between G and A. This brass or copper
partition is exposed to equal pressures on both sides. It may therefore be made
very thin. This, besides making the weight small and the workmanship inexpen-
sive, gives also high heating surface efficiency. The partition is entirely free
from mechanical restraint except at one end and is therefore entirely free to expand
and contract with variation of temperature.
KK is a thin brass or copper partition dividing the water spuce into an outer
cooler part containing water alone and an inner hotter part containing water and
steam and promoting circulation. LL is the water feed pipe. MM is a baffle plate
which as the steam rises from the water space throws it inwards and downwards to
mix with the hot gases rising in H H. Upon A A above the level of the top
of K K are attached the usual water gauges. Both G G and K K or either of
them may be corrugated either longitudinally or circumferentially in order to
increase the heating surface efficiency.
NN, the base of the generator, is of cast steel but may be also a steel or iron
forging. To it are attached A and G by bolted and rivetted joints. It carries
the firebrick combustion chamber lining OO built up in segments and capped by
the fire-brick perforated crown P P. QQ is a fire brick cover to the gun metal
burner R R. QQ burns away rapidly and can be removed and replaced by a
fresh cover by drawing the split steel ring on which it rests. The burner contains
an outer reservoir for benzoline to be burnt at starting in order to warm up the

page_text: generator during which time the aperture F is kept open and when also the burner
is kept a small distance below its normal position so as to allow the entrance of
air round its outer edge to burn the benzoline. The burner is afterwards screwed
tight against the conical seat on the lower surface of N N by nuts S S through
the intermediation of the bridge beam T T and the block U U. When the nuts
are only slightly slackened the block U U can be slung to one side round the hinge
pin on which it is set and then the burner as also its firebrick cover Q Q can be
dropped below the lower edge of N N and withdrawn sidewise.
Pipe supplies of high pressure air and petroleum or other oil fuel or gaseous fuel
are brought into the bridge T T. These are led by annular passages through U
and the lower part of the burner up to the combustion nozzle where the air and
oil jets are made to impinge on each other and upon gunmetal baffle surfaces.
The drawing shows a small sized generator, A A being 16 inches in diameter by
4 ft. length. In large sizes the dome and base plate B B and N N are not cast but
are boiler plate structures.
The air is supplied from a high pressure reservoir fed by one or more air pumps.
The air is filtered on its way to the suction valves of the pump. Such filtering is
unnecessary if gaseous fuel be used unless the air be unusually dirty and it is
useless if solid powdered fuel be used. In the latter case the mixture of gas and
steam should be filtered of ash dust on its way from the generator to the engine.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is:-
(1) The burning of fuel, preferably oil but also gaseous and finely powdered
solid fuel, in a steady and continuous manner under high pressure in one part of
a strong vessel which contains water in another part.
(2) The evaporation of the water by conduction of the heat of the products of
combustion through a metal partition which has equal pressures on either side,
which can therefore be made very thin, and which therefore has high efficiency
as a heating surface.
(3) The superheating of the steam and the cooling of the gaseous products of
combustion down to the temperature of the superheated steam by the actual
intermixture of the steam and the hot gases.
(4) The use of such mixture of steam and hot gas as the working fluid in any
form of engine not an internal combustion engine.
(5) The adjustment of the proportion of steam produced to fuel burned so as
to superheat the steam sufficiently to prevent entirely or for the most part initial
condensation and so as to cool the gas sufficiently to prevent burning of the
cylinder and piston surfaces without water-jacket cooling and to permit easy
efficient lubrication of the piston motion.
(6) The combination of the parts of the generator to effect the operations
mentioned in Claims 1, 2, 3, and 5 substantially as hereinbefore described and
illustrated.