The engine works on the ordinary Otto cycle. To start it, air compressed in a separate vessel is injected into the cylinder. The piston flies out, and on its return squeezes the air to about 500 lbs. to the square inch, thus rendering it incandescent.[11] Just as the piston begins to move out again a valve in the cylinder-head opens, and a jet of pulverised oil is squirted in by air compressed to 100 lbs. per square inch more than the pressure in the cylinder. The vapour, meeting the hot air, burns, but comparatively slowly: the pressure in the cylinder during the stroke decreasing much more gradually than in other engines. Governing is effected by regulation of the amount of oil admitted into the cylinder.
In spite of its high compression this engine runs with very little vibration. The writer saw a penny stand unmoved on its edge on the top of a cylinder in which the piston was reciprocating 500 times a minute!
ENGINES WORKED BY PRODUCER-GAS
These engines are worked by a special gas generated in an apparatus called a "producer." If air is forced through incandescent carbon in a closed furnace its oxygen unites with the carbon and forms carbonic acid gas, known chemically as CO2, because every molecule of the gas contains one atom of carbon and two of oxygen. This gas, being the product of combustion, cannot burn (i.e. combine with more oxygen), but as it passes up through the glowing coke, coal, or other fuel, it absorbs another carbon atom into every molecule, and we have C2O2, or 2 CO, which we know as carbon monoxide. This gas may be seen burning on the top of an open fire with a very pale blue flame, as it once more combines with oxygen to form carbonic acid gas.
The carbon monoxide is valuable as a heating agent, and when mixed with air forms an explosive mixture.
If along with the air sent into our furnace there goes a proportion of steam, further chemical action results. The oxygen of the steam combines with carbon to form carbon monoxide, and sets free the hydrogen. The latter gas, when it combines with oxygen in combustion, causes intense heat; so that if from the furnace we can draw off carbon monoxide and hydrogen, we shall be able to get a mixture which during combustion will set up great heat in the cylinder of an engine.
In 1878 Mr. Emerson Dowson invented an apparatus for manufacturing a gas suitable for power plant, the gas being known as Producer or Poor Gas, the last term referring to its poorness in hydrogen as compared with coal and other gases. While the hydrogen is a desirable ingredient in an explosive charge, it must not form a large proportion, since under compression it renders the mixture in which it takes part dangerously combustible, and liable to spontaneous ignition before the piston has finished the compression stroke. Water-gas, very rich in hydrogen, and made by a very similar process, is therefore not suitable for internal combustion engines.
There are many types of producers, but they fall under two main heads, i.e. the pressure and the suction.