Gas and Petroleum Engines

by H. de Graffigny

Figs. 37, 38.—Sections of the Ragot Petroleum Engine.

By a special arrangement in the carburator all constituents of the petroleum which might foul the cylinder are removed before the oil is allowed to enter the cylinder, and therefore it seldom requires cleaning out. The carburator (Fig. 39) is very ingeniously arranged; it consists of a cast-iron cylinder smooth on the inside, but provided with a spiral rib on its outer surface, and heated by an oil lamp. The spiral rib is itself enclosed by a covering, so that it forms a spiral tube. The petroleum is allowed to enter at the top, and gradually winds its way down, passing over a continually warmer and warmer surface as it approaches the lamp. The more volatile portions of the oil are therefore vaporized first, and the heavier oil passes on and is not vaporized till near the base, where the temperature is high enough to gasify the heavy residue. The air is heated in a jacket surrounding the base of the spiral, and is afterwards mixed with the oil vapour.

Root motor.—These engines work with the ordinary four-cycle, and are interesting because of the double-ignition apparatus. A lateral chamber is attached to the cylinder, communicating with it by an orifice situated at the back end, which is covered when the piston is at the beginning of its stroke. During the compression stroke a portion of the mixture is enclosed in this chamber and separated from the rest of the charge, which is compressed and ignited in the ordinary way. The explosion drives forward the piston, and when it has moved forward some distance it unmasks the above-mentioned orifice, igniting the gas contained in the lateral chamber, and helping to maintain the pressure behind the piston. This addition to the pressure is noticeable in a diagram taken from the cylinder, by sudden rise of pressure. We don’t quite see the utility of this arrangement, which seems to merely complicate matters. The first ignition is effected by a red-hot tube. The Root vaporizer utilizes the heat of the exhaust gases; the air is heated in a spiral coil wound round the tube through which the vaporized oil passes. The two become mixed in a small vessel, and the vaporizer is supplied by a chamber placed directly round the exit of the exhaust gases. Strictly speaking, there is no oil pump, but a plunger in a small auxiliary cylinder serves to direct the flow of oil into the right channels. Admission takes place through an automatic valve. The escape valve is actuated by the same mechanism which drives the piston governing the flow of oil.

Fig. 39.—Carburator of the Ragot Oil Engine.

Koerting-Boulet motor.—In this four-cycle engine we shall only describe the vaporizer and spray-maker. The oil is stored in a reservoir placed about six feet from the ground, and a pipe conducts it into a space between two discs with a valve at the top. This circular space, about half a millimetre in thickness, is traversed by the air which pulverizes the oil; the spray thus formed is vaporized by the high temperature developed by a lamp situated underneath the tube which conducts the carburetted air to the cylinder. In addition, this lamp is used for igniting the gases through a porcelain tube kept at red heat by it. An auxiliary spirit-lamp is used for starting the engine, which takes about fifteen minutes to acquire a sufficiently high temperature.

Knight gas engine.—In his endeavour to completely drive out the products of combustion from the cylinder, Mr. Knight has had recourse to the Griffin cycle and to a double-acting cylinder: we have already discussed the relative merits of this system, and think it is sufficient to point out the greater constancy of speed obtained by it. The vaporizer is placed behind the motor-cylinder, and is separated from it by a steel plate, so that it is maintained at a high temperature; this vaporizer is made of bronze, and is provided with radiating ribs. A pump injects oil into it, and it is also supplied with compressed air by a special pump, which furnishes in addition a jet for producing a blow-pipe flame. This flame white-heats a platinum wire, which ignites the gases. The wire is situated in an opening in the ignition valve; the valve moves forward, and the white-hot wire is brought into contact with the explosive mixture at the right moment. The admission valve is automatic, and situated in the steel plate separating the vaporizer from the cylinder. The other organs of the motor are not of any special interest.

Crossley-Holt oil engine (Fig. 40).—This is practically the same engine which we described in the chapter on gas engines; a vaporizer is added in the oil motor to enable it to work with petroleum.

It consists of a chamber divided into four channels by vertical partitions, and heated by a lamp placed underneath. The flame traverses these channels before reaching the chimney placed at the top. The petroleum is converted into a spray, and drawn off by a jet of air warmed by passing it through a spiral coil placed round the lamp chimney. This jet of air is supplied by a small pump worked by a lever. The oil lamp has no wick, which is rather a novel arrangement: it is supplied by a small pump similar to that which provides the air. Since its first appearance this engine has undergone certain changes which have considerably improved it. Messrs. Crossley Bros. have especially devoted themselves to shortening the length of time necessary to heat and start the engine. Besides this they have paid great attention to simplicity of the working parts.