Improvements in Hot Air Engines.
Year: 1898

page_text: Improvements in Hot Air Engines.
I, FRANZ STOLZE, of 23, Eichen Allee, Berlin-Westend, Germany, Doctor of
Philosophy, do hereby declare the nature of this invention and the manner in which
it is to be performed, to be particularly described and ascertained in and by the
following statement:-
-
My invention relates to certain improvements in hot air engines. Heretofore
the compression and expansion cylinders of hot air engines were made use of to
drive compressed air into the boiler, where it was heated and from whence it was
conducted into the expansion cylinder to therein do its work.
As the compression as well as the heating in the boiler cannot be carried
beyond a certain limit on account of the wear on the machinery, the cylinders and
the pistons had to be made of very large dimensions, with the result that the
friction increased in proportion to the gain in piston surface.
The employment of inner boiler heating, although often, tried, has not been
found as profitable as expected on account of the getting hot of the lubricants,
which absolutely necessitates water cooling and on account of the imperfect
combustion even with liquid and gaseous fuel. Solid fuel, even powdered coal,
cannot be made use of, as all experiments, to do away with the solid particles
in the smoke have met with a negative result.
My new engine has for its object the drawing out of all the caloric power out
of the fuel by doing away with the friction between the working parts and by
making innoxious all solid products of combustion in case solid fuel in the
internal furnace is used.
In order to attain this end, I provide systems of compression and expansion
turbines in place of the ordinary compression and expansion cylinders."
The number of single turbines, making up a system and being mounted
upon the same shaft, varies according to requirements. In front of each working
wheel a rigid guide wheel is arranged. If compressed air now enters into such a
system of turbines the latter will rotate in a sense opposite to the direction of
the lower ends of the turbine blades. If however the shaft is turned by some
means in the same direction as lie the lower ends of the turbine blades, the
system sucks in air through the outer or first turbine.
now
Such a compression turbine system is to be connected with a hot air furnace,
having inner firing; the compressed air is pressed into the furnace, heated and
then conducted to a correspondingly larger system of expansion turbines. The
latter will be rotated and will rotate in its part the compression turbine system
aforesaid. The air having increased in volume by the heating process will
have a certain surplus of energy, which can be made use of in any desirable
manner. The two turbine systems preferably run on the same shaft, when
friction will be done away
with almost entirely. Turbines do not
need to be packed, only the shaft would have to run through a
stuffing box. If however the two turbine systems are mounted upon the same
shaft, no stuffing box is needed and the shaft runs in an airtight casing. A
disk mounted upon the shaft between the two systems of turbines and being also
077

page_text: enclosed by the airtight casing, prevents by the compression of air, exerted by
the centrifugal force on its periphery and which is higher than the compression
within the turbine boxes or casings, any direct interchange of air between the
two turbine casings.
If gaseous or liquid fuel be made use of the combustion may take place directly
within the cylindrical mantle or casing, connecting the mantles or casings of
the turbine systems, thereby obviating the use of a separate furnace. If
however solid fuel is employed a separate furnace is required, within which
the heating space is arranged Pressure air is introduced into this heating
space, so that the oxygen contained in it will combine with a corresponding amount
of coal and form carbon-monoxide, (carbonic oxide gas) which when coming in
contact with the surrounding pressure air will form carbon-dioxide (carbonic
acid). In order to ensure constant combustion the influx of the gases of combus-
tion and of the pressure air into the mixing chamber is regulated in such a
way as to take effect in the same direction. Either one of the air currents will
then act in an aspirating manner upon the other one. The air continuously sup-
ports combustion in the furnace.
Dated this 18th day of Ant 1800
Improvements in Hot Air Engines.
1, FRANZ STOLZE, Professor, of 23, Eichenallee, Westend, near Berlin, Germany,
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 improvements in hot air engines and the object
of my invention is to construct a hot air engine in which most of the defects
appertaining to such engines as hitherto constructed are obviated.
It has hitherto been the practice in the construction and working of hot air
engines to employ compression and expansion cylinders, the former for the
purpose of forcing compressed air into a heating chamber to be there heated and
then to utilize the expanded air in the expansion cylinder.
As neither the compression nor the heating can be carried beyond certain
limits without considerably reducing the durability of parts of the engine it
became necessary to increase the diameters of said cylinders and their pistons.
By such increase and in fact practically proportionately with such increase the
friction of the parts increased, so that the result was really worse rather than
better. Further it has also been often tried to heat the chamber in which the air
is heated from an internally situated furnace or fire-place but hitherto without
great success inasmuch as it has been necessary to employ water jacket or other
means for keeping the lubricant comparatively cool, so as to prevent its being
overheated and further because of the imperfect combustion of the fuel-whether
liquid or gaseous-increasing the friction. Again, the employment of coal dust
which would form one of the cheapest fuels has hitherto been rendered practically
impossible as all attempts to remove the solid particles from the gaseous products
of combustion have been a failure.
These defects are practically entirely obviated by my invention, and my inven-
tion consists in the employment of compression and expansion turbines in place of
the compression and expansion cylinders hitherto employed, the construction,
arrangement and working of the parts being substantially as hereinafter described.

page_text: In the drawings accompanying this specification I have illustrated diagram-
matically the general constructional principle of my invention. I do not claim
any special construction of the apparatus which is all well known in detail, but
has not to my knowledge been arranged in combination for the specific purpose
hereinafter set forth.
Figure 1 is a diagram of a double set of turbines arranged to work according
to my invention.
Figure 2 is a suitable construction for preventing the flow of air or vapour
under pressure from the one set of turbines to the other along the shaft as here-
inafter explained.
Figures 3 and 4 are diagrams of generating furnaces suitable for supplying gas
in my system
The diagram (Figure 1) shews a set of five turbines within a casing A on a
shaft I. The outlet of the casing A is at C, and the inlet (not shewn) is at the
opposite end of the series of turbines. On the same shaft I is placed a larger
set of turbines within the casing B with inlet E, and outlet at the opposite end.
The two pipes C and E communicate with a heating device of any suitable kind
whereby the temperature of the motor fluid can be raised.
The operation of the apparatus is as follows:-
The shaft I is caused to rotate by any suitable motive power in the direction
of the outer ends of the turbine blades in A. The set of turbines within the
casing A will then aspirate and compress a quantity of air, which is finally
delivered in the compressed state through C to the gas generator or other calorific
medium provided. The gases produced from the generator pass in the heated
state through E into the casing B where their motive force is utilized by the
turbines therein contained. The energy developed in the larger casing B will
obviously exceed the energy required to aspirate the cold air in A, and thus
the apparatus becomes self-driving, and develops energy for motive power or
otherwise.
It will be obvious that if compressed air be allowed to enter B from E the
turbine wheels will be rotated in the direction opposite to that of the outer
ends of the turbine blades.
It is not an essential feature of my device that both sets of turbines be mounted
on the same shaft, but I prefer this construction for the purpose of minimising
friction.
In order to prevent the direct passage of air from A to B without passing
through the gas generator I may make use of the device shewn diagrammatically
in Figure 2, consisting essentially of an annular casing on the hollow tube through
which the said shaft passes, said casing fitting close to a disc on the shaft, which
disc may be grooved or scored in the wellknown manner, to more or less prevent
the flow of air over its surface.
In certain cases I may provide two equally acting expansion, and two equally
acting compression systems, which will be found especially useful if it be desired
to avoid end thrust on the shaft.
If solid fuel be used a special heating chamber is necessary within which the
compressed air is forced and a portion of such air employed to support combus-
tion by combining the oxygen with a quantity of carbon whereby carbonic oxide
is formed which on passing from the heating chamber into the surrounding com-
pressed air is converted into carbonic acid gas.
It may however happen that in consequence of friction between the particles
of fuel considerable re-acting or "back" pressure is produced, which may retard
the motion of the heating gases and air and also to some extent prevent perfect
combustion.
To prevent this two devices of alternative construction are shown in Figs. 3
and 4, whereby the supply of combustible gases and compressed air into the mix-
ing chamber is arranged together in such a manner that they move in the

page_text: same direction and each of the two currents has a tendency to draw with it the
other. Back pressure is by these means avoided.
In Figs. 3 and 4 the letters of reference indicate the following parts: --
a is the furnace; the mixing chamber for the combustible gases and com-
pressed air is the part or place where the combustion of the carbonic oxide
gas occurs: m is a shoot or funnel through which fuel is supplied; m' is a
manhole to enable the hot air chamber to be readily cleaned. is the fire
grate the passage for the compressed air from the compression turbine ;
c the passage for the compressed air into the mixing chamber; is the passage
for the supply of air to the furnace; c and c show the method of introducing
gases and air in parallel directions.
Any suitable motor or means for starting my improved engine may be em-
ployed.
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 —
1. A hot air engine, in which the air is caused to flow continuously from its
entrance to its exit by means of turbines substantially as set forth.
2. A hot air engine having two turbines of unequal sizes fixed on a common
shaft for the purposes and substantially as set forth.
3. A hot air engine such as claimed in Claim 1, in which a common shaft
passes through the casing of two suitably arranged expansion, and compression
turbines or through the casings of two sets or series of such turbines for the
purposes and substantially as set forth.
Dated this 27th day of December 1898.