Fig. 40.—Crossley-Holt Petroleum Engine.
Trusty oil engine.—This motor was devised by Mr. Knight, and is constructed by Messrs. Weyman and Hitchcock. There is no spray-maker, the liquid oil being directly converted into vapour. The vaporizer is heated by the waste gas from the cylinder, and the oil falls drop by drop on to the hot metal walls and becomes vaporized. The engine is of the ordinary four-cycle type, the most noticeable feature being the governing arrangement; a governor of the inertia pattern regulating the admission valve and the oil-pump. If the speed becomes too great the action of the governor on the valves ceases, and oil is no longer supplied to the vaporizer from the pump and the admission valve remains closed. Ignition is obtained by a red-hot tube heated by an oil lamp; a layer of asbestos on the outside prevents the tube from cooling, and keeps the tube at a high temperature. It takes twenty minutes before the vaporizer becomes sufficiently heated to enable a start to be made, and the cylinder is very liable to become fouled by tarry products from the oil. These serious disadvantages are scarcely neutralized by the variety and small quantity of oils which the engine will burn. An engine of this type with two cylinders consumed in certain trials only half-a-pint of oil, which speaks for itself.
Griffin oil engine (Figs. 41, 42).—Yet another Otto cycle engine provided with a pump reservoir and vaporizer. The latter is hidden in the bed-plate, and is heated by the gases from the exhaust. The pump is driven by an eccentric on the main shaft, and compresses the air to about 8 lbs. on the square inch in a reservoir also situated in the bed-plate. The compressed air passes from this chamber into a needle pulverizer, along with a quantity of oil which it has gathered in a small ante-chamber. This pulverized oil arrives in the vaporizer at the same moment as the air for the explosive mixture. A portion of the vaporized oil and air is used for the lamp, which red-heats the ignition tube. At starting, a small quantity of air is compressed in a hand pump, and in ten minutes the vaporizer is hot enough to gasify the oil. The Griffin engine is very economical, and only uses about a pint of petroleum per horse-power hour.
Figs. 41, 42.—Griffin Oil Engine.
Niel petroleum engine.—In these motors, the general arrangement of whose parts is similar to that of the gas engines constructed by the same firm, the principal part is the vaporizer. It consists of a small cast-iron chamber, provided with radiating ribs in its interior so as to increase the surface; the petroleum, coming from a reservoir placed at a height of about six feet, passes through a regulating valve, and is dispersed in fine drops over the surface of the radiating ribs; the vaporization is consequently very steady. An automatic valve allows air to pass into this chamber from the outside, forming an explosive mixture with the vaporized oil. A special tube coming from the reservoir supplies a lamp with oil for heating the ignition tube and also the vaporizer at the same time. A methylated spirit lamp is used for warming them up to the right temperature before starting the engine. The governor acts on both the admission and the exhaust, and the supply of oil is indirectly regulated by the closing of the exhaust valve. The whole mechanism is ingenious, giving excellent results; the speed is very constant, and the consumption of oil is within wide limits proportional to the demand for power. About a pound of oil is consumed per horse-power hour, including that necessary for the lamp.
Two patterns of this engine are built, one vertical and the other horizontal. In the latter, called the Atlas engine, the consumption per hour is slightly greater. The governor is also different. The compression in the cylinder rises to about two atmospheres, and the quantity of water necessary for the water jacket varies from seven to ten gallons per horse-power hour, according to the size of the motor.
CHAPTER VI
GAS GENERATING PLANT
We have so far followed, step by step, the various improvements undergone by internal furnace engines, from their first practical realization thirty-seven years ago by M. Lenoir. This improvement has continually tended, as one might naturally expect, to cheapen the cost of the motors themselves, and lessen the cost of the fuel consumption so that they might successfully compete against the steam engine, over which they have many advantages. As a rule, coal gas is pretty expensive, in some particular districts ruling as high as 4s. or 5s. per 1000 cubic feet. This price would be prohibitive were it not for the extreme economy which has been obtained in gas engines by such devices as compression and the lengthening out of the combustion. Inventors have sought to still further lessen the cost of power by replacing the expensive coal gas by other gases of lower illuminating power, produced by special gas plants attached to the engine, and which can be used in places where there is no coal gas laid on. Other engines have been devised, as we have already shown, which get over the difficulty by consuming petroleum oil or distillates of same, such as benzoline and other light hydrocarbons.