CARBURETTED AIR ENGINE
If cold air be saturated with the vapour of volatile spirits such
as gasoline, or distillates of petroleum of about ·65 mean specific
gravity, an explosive mixture is formed with similar properties to that
produced by coal gas mixed with air. This carburetted air can be used
as fuel for heat engines of the explosive type. About twenty different
methods of carburating air are in existence, some of which are more
practical than others. We shall proceed to describe the best known of
these.
_Mille carburetted gas._—In this system air is drawn into a reservoir
containing a petroleum spirit by the volatilization and fall of the
petroleum vapour, this vapour being heavier than air. The reservoir
is placed on a higher level, and an indiarubber tube connected to its
base leads the explosive mixture to the cylinder. The success of this
arrangement encouraged inventors to perfect it. One of the earliest
carburators by Lafroque was provided with a tiny hot-air engine, which
helped to obtain a more perfect saturation of the air with the volatile
spirit. In the Eclipse motors, and also in the Phœbus motors of Pluyer
and Muller of Birmingham, the air and spirit vapour are mixed by an
injector. The vapour is first obtained by heating the liquid spirit in
a small still; it then passes by a fine nozzle across a space drawing
air with it after the manner of the Giffard injector. The explosive
mixture thus obtained passes into a reservoir.
_Faignot apparatus._—The air is drawn in by a revolving pump and forced
into a vessel, divided into several compartments, one above the other,
separated by porous partitions and containing gasoline; several taps or
valves cause the compartments to be alternately opened or closed, so
that the mixture can always be drawn off rich in hydrocarbon vapour.
This apparatus appeared in 1885 at the Antwerp Exhibition, and supplied
a Bénier motor with carburetted air. It is suitable for lighting
villages, country houses, etc., in fact, any places where coal gas is
not laid on. The apparatus has been imitated by Polack of Hamburg and
others.
_Lenoir carburetted air motor._—Carburators for producing fuel for
motive power have been carefully studied during the last ten years
by reason of the rapidly extended use of gas motors. One of the
most ingenious is due to M. Lenoir, constructed for a special motor
designed by himself and constructed by Messrs. Rouart _frères_. This
carburator consists of a horizontal cylinder rotated by a pinion wheel,
and performing five or six revolutions a minute. Vertical perforated
partitions divide the cylinder internally into several compartments,
and the interior wall of the cylinder has attached to it a number of
small buckets which draw up the spirit like a water-wheel, and pour it
out again when they reach the summit of their path. The air and vapour
are thus thoroughly mixed, and pass from thence into the cylinder.
Motors supplied by such carburators have been used for agricultural
operations, and also for driving small pleasure vessels, the cost of
maintenance per horse-power hour being about 2½_d._
_Schrab carburator._—The idea of this apparatus is quite original.
The jacket for cooling the motive cylinder is filled not with water
but with the hydrocarbon to be vaporized. From thence it passes
at a temperature of about 180° F. into a carburator containing
several compartments, and through which pass part of the products of
combustion; these gases passing through the already boiling liquid
hydrocarbon become saturated with its vapour, but require admixture
with air before they are capable of being exploded. The inventor
states that the waste gases only take up 1/16 part of that which pure
air would in passing through the hot liquid fuel, and thus explains
the extraordinary economy of fuel which is obtained by these motors,
only 1/16th of a litre of gasoline being necessary to produce one
horse-power hour. This is a very remarkable result, and if it is
correct places this combined plant in the foremost rank of carburetted
air engines.
_Meyer carburator._—This apparatus has the advantage of allowing
heavier and cheaper oils to be used, at the same time completely
volatilizing them. The heavy hydrocarbons are allowed to fall drop by
drop into a steel chamber about eight centimetres diameter and four
centimetres in height, heated by a flame. The vapour is produced at
a high pressure, and escapes through a fine nozzle at high speed
drawing the necessary air with it. Entering a reservoir this explosive
mixture is prevented from returning by a check-valve. The apparatus
is so arranged, that when the pressure in the reservoir has reached
a certain point, the flame heating the vaporizer is turned down and
prevents further explosive mixture being formed. The apparatus is
therefore self-regulating, the supply of carburetted air being always
proportional to the demand.
_Delamare carburator._—M. Delamare-Deboutteville has devised a very
compact carburator for use with his Simplex motor. Gasoline is
contained in an upper vessel, from which it flows in a fine stream
from a tap on to a horse-hair brush, and is there met by a similar
stream of warm water coming from the water jacket of the cylinder. The
heat obtained from this source tends to vaporize the hydrocarbon, and
the two liquids fall together into a closed vessel. The gasoline rids
itself of its impurities and floats on the surface of the water, which
is withdrawn from underneath it by a siphon. The hydrocarbon vapour
produced during the fall, and afterwards by the heat of the substratum
of water, passes by a check-valve to the motor. It is found that the
cleansing effect of the water renders the cylinder much less liable to
become fouled by tarry products.
_Lothhammer carburator._—Experience has shown that vapour of petroleum
when mixed with air soon separates out; the vaporizer must therefore be
placed as close to the engine as possible. In this motor it has been
the aim of the inventor to obtain an exceedingly perfect mixture of the
explosive gases. In order to do this the air enters the vaporizer near
its base, and passes through it in a number of exceedingly fine streams
of bubbles. The petroleum spirit is at the same time heated by a flame,
and the result is a very close mixture of the gases. The inventor
claims that he thereby obtains much more complete combustion.
_Tenting motor._—M. Tenting has arranged his gas engine, which we
have already described on page 57, for use also as an oil engine. The
carburator is composed of three superposed vessels, through each of
which the oil flows in turn. The upper vessel acts as a reservoir and
will hold a day’s consumption of oil, and the lower one is traversed
by the exhaust pipe, which supplies the heat necessary to obtain the
change of state of the oil from liquid to gas. Although this carburator
is rather crude it gives a very fair practical result.
_Durand carburetted air engine_ (Fig. 27).—M. Durand has set himself to
produce a motor which should work equally well with gas or petroleum,
and which should require a minimum of attention at the same time,
keeping in view such points as regularity of speed, rigidity, economy
of space, and above all low price. This ideal he has, however, failed
to reach, although his engine has many good points. He fails chiefly
because the mechanism is too complicated. The motor works with an
Otto cycle, and the ignition is by an electric spark generated by a
small magneto machine. The regulation of the speed is obtained by
throttling the admission, and the air is drawn through a tube heated
by the waste gases; this arrangement allows a slight economy to be
effected. The carburator is automatic, consisting of a closed cylinder
placed vertically over the motor cylinder. Within it is placed the
oil fuel, and also a spongy mass of cork which soaks up the heavier
impurities found in the oil, and thereby allows cheaper oils to be
used. Air is drawn through the spongy mass, becoming carburetted in the
process; these gases are mixed with a further quantity of pure air in a
distributing chamber before entering the cylinder.
[Illustration: FIG. 27.—Durand Carburetted Air Motor.]
Such a Durand motor sins only by the number of its parts, the
inconvenience of which is noticeable not only by the amount of
lubrication they require, but also by their rapid deterioration.
_Daimler motor._—This motor, constructed by Panhard and Levassor, has
become especially famous for its application to power-driven road
vehicles. It gained nearly all the best prizes in the automobile
races organised in 1894 between Paris and Rouen, and again in 1895
between Paris and Bordeaux. MM. Panhard and Levassor also construct
their motors as fixed engines, but except for slight modifications,
the mechanism is the same in both; we shall therefore describe the
automobile type.
There are two single-acting cylinders working on the same crank-shaft.
A central valve allows compressed air to be admitted which completely
drives out the products of combustion. The admission and exhaust
valves are enclosed in a chest also containing the incandescent tube
which ignites the mixture. The governor on the crank-shaft prevents
the exhaust gases from escaping when the normal speed is exceeded. The
gases remaining in the cylinder prevent a fresh charge from entering,
and during the next revolution no explosion takes place. The whole
mechanism of the engine, together with the fly-wheels, are enclosed
in an air-tight case communicating with the outside air by a valve
opening inwards. The pistons during the backward stroke draw in air
through this valve and compress it during the forward stroke; this
forms the supply of compressed air for the explosive mixture. The
carburetted air is obtained by the suction of heated air through oil
placed in a vaporizing vessel. The motor cylinder is kept cool by a
stream of water, which is itself cooled by travelling through a long
annular pipe which runs completely round the carriage. The heat which
it has absorbed from the cylinder is rapidly extracted from it by the
circulation of the air on both the inside and outside of the tube.
_Brouhot gas and carburetted air engine._—The firm of Brouhot of
Vierzon construct an engine capable of working either by coal, gas,
or petroleum, and which has been especially designed for agricultural
operations. The general appearance of the engine is of the usual type;
the cylinder projects over the bed-plate and is cooled by a water
jacket. The explosive mixture is ignited by an electric spark produced
from a battery of cells whose charge lasts from 120 to 130 hours, or by
a small magneto machine driven by the motor itself. When working with
petroleum a carburator is attached filled with a very volatile mineral
spirit. The air is carburetted by being sucked through it directly into
the cylinder. A second vessel is provided, which serves as a reservoir
for oil feeding the carburator automatically, and keeping the oil in
it at a constant level. The whole machine, though not presenting any
novel features, is strongly constructed and thoroughly suitable for the
work it has to perform.
_Carburetted air motors for horseless carriages._—Although not to such
a great extent in England, self-propelled vehicles have within the last
two years come rapidly into favour on the Continent, and the success
which has attended them has caused inventors and makers to concentrate
their efforts on building the motors as light and as practicable as
possible, as much for purposes of locomotion as for a host of other
uses. We have already spoken of the Daimler motor, which is used to
drive several different types of motor cars; we will now speak of more
recent developments in the same direction. Among many of the same
character, the most noticeable is the high-speed motor of MM. de Dion
and Bouton, who have applied them with great success to the propulsion
of tricycles (Fig. 28).
[Illustration: FIG. 28.—De Dion Motor Tricycle.]
The cooling is effected by radiating cast-iron ribs offering a
considerable surface to the air. The ignition is obtained by an
induction coil and accumulator with a contact mechanism, invented by
Captain de Place. The rotation of the crank-shaft is transmitted to the
wheel-shaft of the tricycle by a reduction gear.
Among other motors we must mention the benzoline engines for
self-propelled vehicles of Lepape, Gautier, the Gladiateur tricycles
and quadricycles constructed by the Société des Voitures sans Chevaux;
also the exceedingly light motors of the Kane-Pennington type; and
lastly, the voiturette-tandem of M. Leon Bollée, some of whose vehicles
have shown a remarkable speed with a very small consumption of fuel.
A few monstrosities have also appeared in the shape of a five-cylinder
motor driving a bicycle called the “bicyclette Soleil Millet,” and
a heavy and complicated mechanism by Wolfmüller, also driving a
bicycle and using petroleum. These motors have not, however, obtained
any success, nor will they at a future date, by reason of their
complication and weight. It is almost unnecessary to state, that any
of the above types may be equally well used for driving a dynamo and
producing electric energy or light.