Wilson gas-producer.—The generator is broader than it is high, and it is possible to use in it all sorts of cheap coal and coke. A window is provided, so that the attendant can see if the fuel is sticking and not settling down properly. The air is blown into the centre of the hearth by a steam injector at a low pressure of about two inches of water or less. Stoking is effected by turning spiral grate bars which rid the fire of clinkers and ashes. The air is heated by waste gases from the motor, a process which gives a slight gain in economy.
Longsden process.—We have mentioned that water gas generated by various processes has been used for lighting towns in America on the incandescent system. The drawback of the system is the exceedingly poisonous nature of carbon monoxide even when very dilute, and it is all the more dangerous because it is odourless. Many accidents have in consequence occurred, some of them terminating fatally. Mr. Longsden has attempted to produce a gas entirely free from carbon monoxide, so as to avoid this difficulty. He first attempted to rid water gas of the monoxide, but not being able to find a cheap enough solvent for it he tried other means. His present process consists of adding a sodium salt to the carbon in the generator. The gas produced has then the following composition:—
| Hydrogen | 62·2 | volumes |
| Carbonic acid gas | 26·4 | ” |
| Carbon monoxide | 1·2 | ” |
| Hydrocarbons | 6·5 | ” |
| Nitrogen | 2·2 | ” |
| Oxygen | 1·5 | ” |
| —— | ||
| 100 | ” |
This very rich gas, which might easily be ridded of its carbonic acid by passing it through lime, is very suitable for supplying motive power through the medium of the gas engine.
Gayon and Métais process.—This process, which, as far as we know, has not been put into practice, was intended by its inventors to diminish the price of coal gas. Instead of allowing coke to be deposited in the gas retorts, as it usually is, and selling it as a bye-product, their intention was to use it there and then for the production of water gas, which was to be mixed with the coal gas and increase its heat of combustion, while diminishing its cost of production. One ton of coal would produce 450 cubic metres of gas instead of 300; the idea has, however, never been put into practical shape.
CHAPTER VII
ENGINES FOR USE WITH POOR GASES
Simplex motor (Fig. 45).—Although this motor works equally well with coal gas and oil, we have put off the description of it until now because it has become associated particularly with the production of poor gases, and by their help forms one of the most formidable rivals of the steam engine.
The Simplex was invented in 1884 by MM. Edouard Delamare-Deboutteville and Léon Malandin. In appearance it is of the usual four-cycle type. A lateral shaft transmits the rotation of the crank-shaft to a small crank which actuates the sliding valve. This sliding valve forms one of the principal features of the engine, and consists of a sliding iron plate pierced with two holes, one oblique regulating the ignition, and the other straight forming the admission valve. The piston having completed its first forward stroke comes back to compress the explosive mixture, and the sliding valve having advanced puts it in communication with a chamber containing two metallic points, between which a continuous stream of electric sparks is made to flow. After the explosion this cavity and the passage leading to it are filled with burnt gas, which must be driven out to prevent a miss-fire at the next stroke. This is effected by a small purging hole, through which they are driven by a fresh charge entering the cylinder.
In earlier patterns of this engine an ingenious air governor was used, but it has now been replaced by a fresh arrangement of a different pattern. This governor (Figs. 46 and 47) consists of a double pendulum, which takes up a vertical position because of the lower ball, seen in the illustration, being the heaviest. The whole pendulum is pivoted on a fixed bearing. The variation in the speed is obtained by a weighted knife blade acting on the gas-valve. The sliding valve is provided with a knife blade square at one end and pointed at the other, which catches in a notch on the pendulum, and is held by it in position so that the square end hits the end of the gas-valve and admits gas. If, however, the speed of the engine be too great the sliding valve carries its knife blade forward too soon and it does not catch in the notch, with the result that no gas is admitted as the square end is too low. The speed of the engine, therefore, tends to remain adjusted to the rate of vibration of the pendulum, which is a fixed quantity. A self-starting arrangement is provided by stopping the engine half-way back along the compression stroke, so that it is only necessary to pass an electric spark across for an explosion to occur and give it the necessary starting impetus.