IMPROVEMENTS IN THE MODE OF AND APPARATUS FOR OBTAINING MOTIVE POWER
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by Harry Whiteside Cook at the Office of
the Commissioners of Patents on the 7th December 1876.
HARRY WHITESIDE COOK, of Stondon Massey, in the County of Essex, Gentleman.
"IMPROVEMENTS IN THE MODE OF AND APPARATUS FOR OBTAINING MOTIVE
POWER."
One of the objects and one of the essential features of my Invention of improve-
ments in the mode of and apparatus for obtaining motive power is the use of gases
produced by and remaining over from the combustion of fuel (either alone or
combined with a supplementary supply of air) to work the piston of an engine.
The heating of these gases and air (or, as I shall henceforth call it, of the air) may
be made to produce an increase either of volume or of pressure. In the former case
the arrangement will be as follows:-The fuel placed in a strong closed chamber
supplied with compressed air, and into this chamber air is further forced by means
of a pump or other suitable device. Means are provided either by valves or other-
wise, whereby any given proportion of air may be made to pass through the fuel, so
that the amount of combustion and the mean temperature of the air may be varied
at will. If now the heated air be made to work a piston of the same stroke as the
air pump, and if the air be used expansively so that its mean pressure shall be
equal to that in the air pump, its area must be larger than that of the pump in
proportion to the increase of volume produced by the heat, and this increased area
(which represents the total effect of the heat) represents also the effective power of
the engine after working the air pump. The whole of the heat is thus utilized,
whereas in ordinary steam engines about 30 per cent. escapes up the chimney, and
60 per cent. is wasted in evaporating the water. The present Invention thus secures
a large economy as compared to the steam engine.
In stationary engines (where space is not of importance) the same principle of
expansion may be employed in the following manner:-The fuel (as before) is
contained in an air-tight chamber, and is fed with air by a fan or blower, thereby
producing a certain pressure, and the heated air in passing to the chimney is made
to actuate a windmill working in a closed tube, which indeed may form part of the
chimney itself.
The following is another and commodious form of engine to be worked on the
same principle of expansion, and more especially suited to household purposes and
generally to engines of small power:-The fuel is burnt in an open tube or chimney,

page_text: which supplies the working cylinder with heated gases. This cylinder exhausts
into a coil of pipes, which is surrounded by water, or the exhaust gases are cooled
in any other convenient manner. From the cooler the gases are allowed to pass
into an air pump of capacity equal to that of the cylinder, and by the return stroke
of the pump are expelled into the atmosphere. This arrangement yields an effective
pressure of only 2-3 lbs. per square inch of piston, but it only consumes 1 lbs. of
coal per horse power per hour, and if furnished with a fuel feeder, as before
described, it will only require attention at long intervals.
°
Where obtainable a gas flame may advantageously be employed, as the conden-
sation of the aqueous vapours evolved will increase the power of the engine.
A very simple and economical engine is obtained by my improvements, although
the economy of fuel will not be so great as in the arrangement first mentioned. If
however the windmill be geared so as to run fast, and a previous rotatory motion
be given to the air by properly disposed diaphragms (as in à Fourneyron's turbine) a
windmill working in a tube will transmit about 70 per cent. of the power applied to
it, so that such an engine would consume per horse power much less fuel than is
required by a steam engine. It will thus be evident that in any case the fuel las
to burn in a chamber containing compressed air. In some instances (viz., when
an engine is intended to run a specified time) the chamber may be made large
enough to contain the necessary supply of fuel.
In other cases means have to be provided for introducing the fuel without
allowing the escape of the air. This may be done in various ways, but the simplest
plan is to let the fuel be contained in an upright tube within the air chamber, and
extending above it. At the bottom of this tube is a grating for combustion, so that
the coal sinks in the chamber as it is consumed. This tube is furnished near the
top with two valves or air-tight doors so arranged that either of them can be
opened or closed at will without opening the other; the space between them can
therefore be filled with fuel without letting the air escape, and then the top door or
valve being closed and the bottom one open the fuel will be ready to find its way to
the grate.
Instead of utilizing the increase of volume resulting from the heating of the air
the increase of pressure may be turned to account. In this case the amount of air
introduced by the air pump is limited to the quantity necessary to support combus-
tion, but on the whole this machine will be more cumbersome than the other
arrangement, and a supply of water will be necessary. As however (in some cases)
such an engine may be convenient I will proceed to describe its action.
The coal is burned in an upright tube, as before; there are three closed chambers,
one high-pressure, the second low-pressure, and the third varying. This third
chamber is connected with the other two, and the air in it is treated alternately
with a jet of flame from the furnace, and a jet of water from a pump, and as the
pressure is thus varied it will alternately suck air from the low-pressure, and force
air into the high-pressure chamber, the proper valves being of course supplied to
enable it thus to act as a pump.
The surplus air which is continuously pumped in may be allowed to actuate a
small auxiliary engine as it escapes. When a very large cylinder and a slow piston
movement are employed the first and second chambers may be dispensed with, and
the 3rd chamber connected directly with the cylinder.
It will be observed that I do not make use of regenerators or any similar
contrivance.
By working between a given pair of temperatures it may be mathematically
demonstrated that an engine cannot utilize more than a fixed proportion of the heat
supplied to it, while if worked by the products of combustion a properly constructed
engine will not utilize less than that unpassable limit. It is obvious therefore that
any device for limiting the consumption of fuel diminishes pro tanto the power of
the engine. Indeed, I attribute the practical failure and inability of bot-air engines
to compete with steam, to the prevalent misconception on this fundamental point,
and as it is one great object of this Invention to produce a hot-air engine which

page_text: "shall be even more compact than existing steam engines I take every means to
enable my engine to usefully consume the maximum possible amount of fuel.
The following is an account of the mode of working this Invention when the
above objects (power and compactness) are more especially in view-In the first
place the compressed air must of course be used at considerable pressure. Now if
from this high pressure the air were expanded down to that of the atmosphere the
engine would be cumbersome, while if not so expanded the air pump would work at
a serious disadvantage, seeing that the same laws which regulate the power obtained
from expansion regulate the resistance of compression. To obviate these difficulties
I expand the air (in the cylinders) to only a moderate extent; I then cool it by
means to be hereafter more particularly described, and allow it to pass to an air
pump of smaller capacity, the capacities of the working cylinder and air pump being
proportionate to the relative real temperature (F+438) in the hot air chamber and
in the condenser. The air pump is thus supplied with cold air at a high pressure,
which it then returns to the heating chamber. In this manner the pressures on the
respective sides of the pistons of the cylinder and of air pump are equal, and the
difference of area represents the effective power.
Both the cylinder and air pump must be jacketed, the one with hot air, and the
other with cold water. The top part of the cylinder jacket is connected with the
hot-air supply pipe, while from the bottom a pipe passes to the lower part of the
hot-air chamber. In this manner the momentum of the air down the hot-air supply
pipe will (when it is cut off from the cylinder) force it through the jacket.
The air for producing combustion is supplied by a separate air pump, the amount
of air admitted to which is regulated by a throttle valve, and the accumulation of
air in the apparatus is allowed to escape through a safety valve on the condenser,
whereby it is made to do its share of work. The machine is also thus rendered self-
acting as regards the maintenance of the chosen relative temperatures in the hot-
air chamber and the condenser.
The heating of the air and the intoduction of fuel are arranged as before
described.
An engine constructed on this principle with 200 lb. original pressure, and working
between 70° and 500° will have an effective pressure of 35 lbs. per square inch of
piston (equal to the average pressure in marine engines), and will consume less than
1 lb. of coal per horse power.
If the engine is to be used at several degrees of expansion a corresponding number
of escape valves must be fitted to the condenser weighted to the different result and
pressures.
Another improvement consists in cooling the exhaust hot air from the cylinder
by making it pass thro' the flues of a small boiler, thereby economizing a certain
amount of heat, but with the more especial object of supplying sufficient moisture
to save the packing from being injured.
The object may be attained in small engines by injecting a certain amount of
water into the hot-air space. This hot-air space may advantageously be partially
filled with fire-brick, thin metal plates, asbestos, or other suitable substance to
ensure that the various streams of gas shall acquire a practically uniform tempera-
ture. In this, as in all heat motors, it is desirable to use gases at the highest
possible temperature, and my last improvement relates to an engine in which (from
its simplicity and absence of moving parts) gases of very high temperature indeed
may be employed. In form this engine resembles a reaction jet, and the jet may
either be applied to the periphery of a wheel to obtain circular motion, or where
locomotion is the object it may be used to obtain a motive force in the desired
direction. It is equally applicable to hot gases, compressed gases, steam, or any
similar source of motive power.
The compressed gas passes into a cone-shaped tube, the mouth of which points in
the direction opposite to that in which motion is desired. The proportions of this
cone depend upon the relative velocities of the efflux of gas due to its compression

page_text: and the intended velocity of the machine at the point where the mouth of the
tube is.
The working of the arrangement is as follows:-On being admitted into the
small end of the tube the first impulse of the gas is to escape by its own momentum
(as in an ordinary reaction jet), but the whole time that it is passing down the
tube lateral expansion is taking place, and the swell of the tube must be so gradual
that this lateral pressure takes effect upon the whole of the inside circle of the tube.
As the gas expands, and its sectional area increases, its velocity will be proportionately
reduced, and the area of the tube at the point of emission should be to the area of
the tube (at the small end) as the velocity of the efflux of the gas due to its
pressure is to the velocity of the motion of the tube. In this way the gas will have
been expanded down to the pressure of the atmosphere, and its velocity (in space)
on leaving the machine will be nil. If then means are taken to maintain the
temperature of the gas during expansion its full effective pressure will be exerted
upon the sides of the tubo, and its momentum will likewise be turned to account.
This machine thus forms a combined pressure and reaction engine.
The inside of the tube may advantageously be slightly rough, as the loss of
momentum due to friction will take the form of useful heat, which will help to
make up the loss of heat by expansion, while the necessary length of the tube will
be proportionately diminished. Where the length of the tube is inconvenient space
may be economized by arranging it in a zig-zag, serpentine, or spiral form. It may
be also observed that the form of the sectional area of the tube is not of importance,
and may be chosen to suit the divers circumstances under which it may be used.