Page:Popular Science Monthly Volume 91.djvu/700

 684

��Popular Science Monthly

���tanks and fed to the cylinders. Compressed air has been experimented with more or less successfully. But that does not seem to be economical. Why not liquid air, or, better still, liquid oxygen? Four-fifths of the air that we breathe is composed of nitrogen which serves the very useful pur- pose of diluting the oxygen that we really need and preventing us from literally burn- ing up. Since an engine is an inanimate piece of machinery which can be con- structed to meet certain operating condi- tions, there seems no reason why liquefied oxygen could not be used effective- ly. And so, I have designed the machinery which is disclosed in the accompanying il- lustrations and which, I am sure, will drive a sub- marine under Water at high speed and for long distances.

An engine is driven by heat, converted into mechanical en- ergy. Liquid oxygen is very cold. When it vaporizes and be- comes a gas again it absorbs heat, or energy, from theheatingagent, which combines

in this case sea water and other means. To make the most of our liquid oxygen, then, this stored energy ought to be used for propelling the vessel. Hence, in the de- sign which I here present, the gas given off by the liquefied oxygen is fed to an expan- sion engine, which is an engine very much like a steam engine in principle, the differ- ence being that a compressed gas is the motive agent instead of steam. It is evi- dent that after the oxygen has expended its energy in driving the piston of that expansion engine, it is just as fit to breathe as it ever was before. In other words, it can be fed to the internal combustion engines of the submarine to be mixed with fuel as if it had never been utilized in the ex- pansion engine at all. This is what I have done. The result is that the me-

��liguid oxygen in coil

heated by used cooling water

��chanical energy stored up in the liquid oxygen serves to supply additional power for driving the vessel and the oxygen itself to furnish the medium without which there can be no combustion. The captions ap- pearing beneath the illustrations describe the actual invention in such detail that it is unnecessary to dwell further upon its construction here.

I have said that the exhaust gases of an engine when discharged into the water appear as bubbles on the surface and not only betray the presence of the craft but indicate the exact course. In order to dispose of these gases, I discharge them through an exhaust device of special type. They are sifted through millions of small holes. After that they strike the pro- peller, by which they are beaten up with the sea water. Since these exhaust gases are com- posed chiefly of steam and carbon dioxide, they will be entirely ab- sorbed by the sea water after hav- ing been thus mi- nutely sub- divided. No be- traying wake will be visible.

Compressed air in strong, steel tanks, could no doubt be used to drive the engines of a submarine under water. Indeed, the experiments which have been made with what is known as the Neff system, described some time ago in the pages of the Popular Science Monthly, have been encouraging. Officers of the navy have criticised the use of compressed air because of the wake. My objection to the system is chiefly to the nitrogen contained in the compressed air. Nitrogen is not easily absorbed by sea water ; it resists combination with all elements. The whole difficulty of avoiding a wake is more easily solved, to my mind, by utilizing pure liquid oxygen. Moreover, no matter how highly air may be compressed in tanks, a liquefied gas is even more compact.

��oxygen « heated by Jea water

��Diluting the Oxygen with .Hot Exhaust Gases

Before it can be fed to the explosion engine after having been exhausted from the expansion engine, the oxygen must be diluted; otherwise it would simply destroy the explosion engine. Hence, the oxygen after it leaves the expansion engine passes into a tank where it is mixed with a certain quantity of the hot exhaust gases (dried carbon dioxide and steam) from the explosion engine. That quantity is carefully measured by a meter pump and forced through a pipe into the mixing tank as here shown. A certain amount of fuel (oil or gasoline) is forced through a carbureter and supplied to the mixing tank

�� �