The Last Word in Submarine Engines.—Having tried out both steam and gasoline engines for submarine work and both having been found wanting, further experiments were made in engine building.
Now, since it was known that the chief fault of the gasoline engine lay in the fuel it used and not in the engine itself, inventors worked hard to make an engine that would burn a fuel so much heavier and less volatile than gasoline that all danger from vapor would be done away with.
Many engines were built along this line, but all failed until Diesel (pronounced Dé-sel), a German inventor, found a way to make an engine that would burn a heavy oil. The Diesel engine is now used in every submarine that is built, nearly; and for this reason I want you to understand exactly how it is made and how it works.
How the Diesel Engine Works.—The Diesel engine works on the same general principle as the gasoline engine—that is, by the explosion of a fuel mixture in the cylinders—but it is different from the gasoline engine in the way in which the fuel is admitted into the cylinder and fired.
In the Diesel engine, a rough diagram of which is shown in [Fig. 32], there are two valves in the head of the cylinder, one of which lets in the heavy fuel mixture and the other one admits compressed air to the cylinder. The exhaust valve is at the bottom of the cylinder, and the lower part of the cylinder is built to form an air compressor.
FIG. 32. A TWO-CYCLE DIESEL ENGINE.
The way it works is like this:
(a) When the compressed air valve opens, the compressed air is forced into the cylinder and this drives the piston down when the valve closes.