Process and Apparatus for Igniting the Combustible Charges or Gas Mixtures of Gas and Oil Engines.
Year: 1892

page_text: Date of Application, 30th Nov., 1892
Complete Specification Left, 26th Aug., 1893-Accepted, 25th Nov., 1893
PROVISIONAL SPECIFICATION.
[Communicated from abroad by JOHANN RADEMACHER, Engineer, of 54, Stephan
Strasse, Berlin, in the German Empire.]
Process and Apparatus for Igniting the Combustible Charges or Gas
Mixtures of Gas and Oil Engines.
I, JASPER WETTER, Patent Agent, of 433 Strand, in the County of London, do
hereby declare the nature of this invention to be as follows:
A portion of the combustible mixture of gas or oil with air, conducted into the
cylinder to serve for the next explosion, is separated from the rest and heated (in
a chamber separated from the cylinder) at a low pressure (preferably the lowest
pressure existing in the cylinder), which heating in the case of a four-cycle engine
may take place during the period of compression of the mixture contained in the
cylinder. Shortly before ignition, this separated combustible mixture is rapidly
compressed to the maximum pressure existing in the cylinder, and simultaneously
set in communication with the gaseous mixture contained in the cylinder. By the
rapid compression (without taking off heat) the temperature of this mixture is
raised above the igniting point of the same, the whole of the said mixture ignites
suddenly and starts the combustion of the cylinder mixture, which now
municates with the same.
com-
The compression of the separated mixture may be effected by various means;
for instance by means of a piston or ram controlled from outside.
Or the separated mixture may be contained in a comparatively long tube provided
with a valve, which establishes communication with the compressed cylinder charge
shortly before the moment of ignition, which charge then compresses the mixture
contained in the tube, without any considerable mingling of the two mixtures.
In the case of a four-cycle engine, cold or preheated combustible mixture may
be drawn during the suction period into a tubular chamber heated by the ignitions
or by an external source, by the sucking effect of the working piston, which
mixture is then heated during the compression period, by its contact with the walls
of the said chamber, subsequently, (towards the end of the compression stroke or at
the beginning of the expansion stroke) set in communication with the compressed
cylinder charge, by means of a valve controlled by the working piston or externally
by the engine, whereby the said mixture is compressed and ignited.
In this arrangement, the igniting chamber may be maintained at the required
temperature by closing a valve immediately after the ignition and keeping it closed
until the suction period commences, so that the hot gases of combustion confined in
the said chamber serve to heat the same.
In order to maintain the said igniting chamber at the required temperature, the
speed of the four-cycle engine may be regulated in the following manner :-Either
the valve situated between the said chamber and the cylinder is kept closed, by the
governor during the suction period, in case an explosion does not take place; or
when the load decreases an ignition continues to take place in the igniting chamber,
at every cycle (of four stages), but the power developed by the smallest charge is
scarcely sufficient for keeping the engine in motion.
The tubular igniting chamber may be straight or curved, and is provided with a
valve at each end. The valve which controls the communication between the
cylinder or explosion chamber and the igniting chamber may be operated by the
working piston (as mentioned above), preferably by means of two studs or short

page_text: spindles extending from the face of the piston and adapted to lift the said
valve.
Doted this 30th don of Nawamber 1802
FAIRFAX & WETTER,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Process and Apparatus for Igniting the Combustible Charges or Gas
Mixtures of Gas and Oil Engines.
I, JASPER WETTER, Patent Agent, of 433 Strand, in the County of London, 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 :-
A portion of the combustible mixture of gas or oil with air, which is to be
conducted into the cylinder for the next explosion, (or of another suitable
explosive mixture) is separated from the rest and heated (in a chamber separated
from the cylinder) at a low pressure (preferably the lowest pressure existing
in the cylinder), which heating in the case of a four-cycle engine may take
place during the period of compression of the mixture contained in the cylinder.
Shortly before ignition, this separated combustible mixture is rapidly compressed
to the maximum pressure existing in the cylinder, and simultaneously set in
communication with the gaseous charge contained in the cylinder. By the rapid
compression (without taking off beat), the temperature of this mixture is raised
above the igniting point of the same, the whole of the said mixture ignites suddenly
and starts the combustion of the cylinder charge, which now communicates with
the same.
The separated combustible mixture must, of course, be preheated to such an
extent, that the compression will raise its temperature to or above the igniting
point.
The compression of the separated mixture may be effected by various means;
for instance by means of a piston or ram controlled from outside.
Or the separated mixture may be contained in a comparatively long tube
provided with a valve, which establishes communication with the compressed
cylinder charge, shortly before the moment of ignition, which charge then com-
presses the mixture contained in the tube, without any considerable mingling of the
two mixtures.
Such an igniting device adapted for four cycle engines is represented by the
accompanying drawings.
The power cylinder C contains a power piston K, to the back of which the
inflammable cylinder charge is conducted, and where it explodes. The major
portion of the mixture enters through a separate admission valve, which may be
situated at 9, but is not shown in the drawing, as in some well-known gas and oil
engines. A portion of the inflammable mixture, however, enters the tuber through
the valve a, and thence a small portion may pass through the valve c into the
cylinder C. The valve c is actuated by the engine through a rod t. The tuber is
surrounded by a wider tube R, so as to form between the two tubes an annular
clearance space. The tube R is lined with a bad conductor of heat l. The tube R
has also two openings 1 and 2, capable of being closed.
Supposing that the engine works in a cycle of four operations, and that the
working piston K is in its highest position, ready to commence its suction stroke,
the apparatus will act as follows;
Hot air from a lamp or other source is first conducted through the opening 1
into the tube R where it flows around the tuber and subsequently escapes through
the opening 2. When the tube has been sufficiently heated, the engine is set in
motion.
7"

page_text: During the first down-stroke of the piston K, that is to say, the suction stroke,
inflammable mixture is sucked by the piston, through the inlet valve g of the
cylinder.
During a part of this suction stroke, say towards the end of the same, the
valve c is lifted for a short time by the valve gear of the engine, acting on the rod t.
Consequently the inert gases contained in the tube are drawn off into the cylinder
by the sucking effect of the piston, and inflammable mixture is drawn into the
tuber through the valve a, so as to fill the tube. Immediately afterwards the
valve c is closed by the valve gear and thereby the tuber and its contents separated
from the cylinder. The mixture contained in tube r now is under the same pressure
as the mixture contained in the cylinder. During the subsequent upstroke of the
piston, the mixture contained in the cylinder and consisting of the inflammable
charge diluted with inert residual gases, is compressed, during which time the
valve c remains closed, and the mixture enclosed in the tube r is sufficiently heated
at low pressure by the walls of the said tube.
In the highest position of the piston, or a short time before, that is, at the moment
of the maximum compression of the cylinder mixture, the valve c is opened by the
valve gear. The compressed cylinder mixture now rushes into the tube with
great violence, pushing the highly heated and thin igniting mixture before it and
compressing the same. The temperature of this mixture is thereby raised to the
point of ignition, and the ignition which now takes place is communicated to the
cylinder charge which has followed the mixture, and thereby the desired effect
produced. During the second down motion of the piston the expansion takes place
and power is exerted, and during the second upstroke the gases of combustion
escape through a separate discharge valve, after which the same cycle of operations
repeats itself.
When the engine has thus been set in operation, the heating lamp may be
removed and the two openings closed, the heat generated by the explosions
being, after this, sufficient to maintain the tuber heated to the required
temperature.
As shown in the drawing, the tube r is also, as far as practicable, insulated from
the remaining parts of the engine by a nonconductor of heat.
It has been ascertained by experiment, that explosion may be relied on even if
the tuber be heated to a comparatively low temperature; less than 500° C. are
sufficient, at any rate. The ignition of the charge is in all cases rapid and certain,
which may be easily accounted for by considering that the entire explosive mixture
contained in the tuber attains the temperature required for ignition in all its parts
at the same moment.
As stated, the tuber continues sufficiently heated, owing to the heat produced
by the explosions. The valve c is open only during part of the suction-stroke of
the piston. By keeping it open for a longer or shorter period, more or less mixture
may be allowed to flow through the tube r, and the tube thereby cooled down to a
greater or less extent. It will thus be seen, that the facility of keeping open the
valve e for a greater or less period of time in itself affords a ready means for
controlling the temperature of the tube r.
Should this means, however, be insufficient to keep the tuber heated to an adequate
temperature (as, whether it is, or not, depends on the extent of the compression
applied), other methods of attaining this object may be resorted to, either singly or
in combination.
In the first place, it is by no means necessary, that the mixture which is conveyed
into the cylinder direct, and the mixture admitted into the tube r, should be alike
in composition, as each may be formed separately and in a different manner; in
which case the explosive mixture may easily be heated beforehand-say, for
example, by the escaping products of combustion, or waste gases, of the engine;
part of such gases being allowed to mix with the explosive mixture, or the mixture
being simply heated by them; or if preferred, the air, which is to form part of
such mixture, may be so heated. In the case of such preliminary heating, the

page_text: tube need not yield as much heat to the explosive mixture, as it would otherwise
have to do, and may consequently more easily be maintained at the required
temperature.
Besides, the proportion of the combustible matter or fuel gas contained in the
mixture may be increased, so that, in burning, the mixture may develop more
intense heat and thus bring the said tube to a higher temperature.
There exists, however, still another very simple and effective method of main-
taining the tuber at the required temperature by successive explosions; and it
consists in closing the valve cimmediately after each explosion. At that moment
the gaseous products of combustion, still contain a very considerable amount of
heat and are still at high pressure. The gases, which are then within the tube r,
are, at this high temperature, confined in the said tuber, by the closing of the
valve c, which is subjected to high external pressure, and remain so confined
during the expansion and exhaust stage. The gases cannot, indeed, leave the tube,
until the valve c re-opens during the subsequent suction-stroke, when a fresh supply
of mixture is drawn into the tube r. In the meantime, however, the said gases
have sufficiently heated the tube r, the extent of such heating being controllable by
keeping the valve c closed for a longer or shorter period of time after each
explosion.
Another method may serve the same purpose as those described above-not,
indeed, by heating the tube r, but by rendering it capable of ensuring ignition,
even while its temperature is comparatively low. In the arrangement shown in
the drawing, explosive mixture is drawn into the tuber by the suction-stroke of the
plunger, while the valve c is open. When this valve is closed, the valve a also
closes automatically, and the explosive mixture confined in the tuber is heated,
during the compression stage, by the walls of that tube. As the mixture cannot
expand, this heating necessarily brings about an increase of pressure, the pressure
rising in proportion, as the heat becomes more intense. Supposing e.g. that the
mixture is heated to about 300° C. (573° abs. temperature); the pressure of the
mixture will rise from 1 atmosphere to 2 atmospheres (absolute pressure). During
subsequent compression to, say, 8 atm. the temperature would therefore,
8\n-1
theoretically, have to rise to
× 573 = 1.493 × 573° 856° (abs. temperature).
-
n
C
C1
In this formula the exponent n =
mixture (to be compressed) at constant pressure, and c¹ the specific heat of the same
gas or gas mixture at constant volume. For atmospheric air n=1.41.
;c being the specific heat of the gas or gas
If the valve a be allowed to remain open during compression (i.e. during the
preparatory heating stage), or be opened towards the close of the compression
period, so that the contents of the tube may come into contact with the external
air, or are placed in communication with the chamber from which the supply of
mixture has been taken, the pressure, to which the mixture will be submitted at the
close of the heating stage, will not be higher than at the outset, while the temperature
will be the same as though the valve a had remained closed. Now, just before the
explosion, this valve a is closed, and the valve c is opened instead. The pressure
of the explosive mixture will consequently rise in the same proportion, as the
pressure of the mixture in the cylinder, viz. from 1 atmosphere to 8 atmospheres, as
before while the resulting rise of temperature will be:
;
81-1
n
(8\n]
x 573 =
12
n
×
n-
12
x 573856
n-1
=
856 x 1.224
22

page_text: that where this method is adopted, i.e. the valve a left open during the preparatory
or initial heating process, the temperature of the tuber may be lower, than it
would have to be if the said valve a were closed during that period. To keep the
valve a open during the initial heating of the explosive mixture, as stated, and
while compression takes place in the cylinder-the main valve gear of the engine,
or, if preferred, any other suitable device may be employed.
By applying either or all of these methods to the working of engines of the class
herein referred to, the desired result may be easily attained, i.e. the explosive
chamber or tuber may be maintained at the requisite temperature, without any
special provision being necessary for heating the same. It may be mentioned,
however, that in some cases it may be advantageous to "start" the explosive
chamber by means of an external source of heat, say the exhaust gases from the
engine, or a special lamp or burner.
It should furthermore be observed, that as the heat imparted by the explosions
to the tube or chamber r of the same engine, at a varying pressure, must vary also,
it may be necessary under certain circumstances to change the method employed
for keeping the tube r sufficiently heated, according to the amount of pressure, to
which the engine is subjected for the time being,-the heating effect being intensified
or reduced, as the case may be, which may be done by means of the valve gear and
with the assistance of the governor.
As regards the special arrangement involved in the performance of the process of
ignition of explosive charges in gas engines, herein described, it may be stated that
the valves above mentioned may be replaced by other equivalent devices, such as
slide valves &c. The introduction of the explosive mixture into the chamber r may
be effected by pressure, instead of by direct suction; or mixture may be derived
from the cylinder itself, and conveyed into the tube or chamber in any convenient
manner.
r
In conclusion, it may be mentioned, that the improved process and apparatus
described are applicable not only to four-cycle engines herein specially referred to,
but to any gas engines working with compression of the explosive charge, it being
merely necessary, to vary the details of the arrangement, so as to suit different
circumstances.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is ;-
1. The process for igniting the combustible charge of gas and oil engines working
with compression of the combustible mixture, which consists in preheating a portion
of the inflammable mixture at a low pressure, either before or after its arrival in a
separate igniting chamber, raising the pressure of this igniting mixture shortly
before the moment of ignition, and simultaneously establishing communication with
the contents of the cylinder, so that the temperature produced by the compression
of the separated igniting mixture reaches at least to the igniting point, and the
ignition thus produced is communicated to the cylinder charge, substantially as
described.
2. An appliance for performing the above described igniting process in the case
of four-cycle motors, chiefly comprising a tubular chamber r and valve mechanism,
the said chamber being heated by the ignitions or by an external source, and
connected with a supply of combustible mixture and with the working cylinder, and
the valve mechanism being operated in such a manner, that during the suction
period cold or preheated ignitable mixture is drawn in by the working piston, and
subsequently heated on the walls of the said chamber during the compression period,
and that, towards the end of the compression stroke or at the beginning of the
expansion stroke, this heated mixture is set in communication with the compressed
cylinder charge by means of an automatic valve c (or equivalent device), whereby
the contents of the chamber r are compressed and ignited, substantially as
described.

page_text: 3. In an igniting apparatus of the type specified by Clause 2, the partial or
combined use of the following means for maintaining the tube r at the temperature
required for sure ignition, without otherwise supplying external heat, during the
working of the engine;
a, preliminary heating of the igniting mixture before it enters the tube r;
b, an igniting mixture richer in fuel than the cylinder charge;
c, closing the valve e immediately after ignition, and keeping it closed until
the suction period, in order to heat the chamber as much as possible by
the hot gases of combustion contained in the same;
d, keeping the valve a open during the period of the compression in the
cylinder, or towards the end of the said period, in order to reduce as much
as possible the temperature necessary for ignition in the tube r;
substantially as described."
Dated this 25th dox of August 1892