. Agricultural engineering; a text book for students of secondary schools of agriculture, colleges offering a general course in the subject and the general reader. Agricultural engineering. FARM MOTORS 351. be about one part of gas or fuel vapor to four parts of air. The same authority gives one part of fuel vapor to fourteen parts of air as being the leanest mixture that will burn. It is to be remembered in this connection that of every one hundred parts of air only 23 parts are oxygen; and it is the oxygen that supports combustion. The largest constitu- ent of air, nitrogen, composes about 7
. Agricultural engineering; a text book for students of secondary schools of agriculture, colleges offering a general course in the subject and the general reader. Agricultural engineering. FARM MOTORS 351. be about one part of gas or fuel vapor to four parts of air. The same authority gives one part of fuel vapor to fourteen parts of air as being the leanest mixture that will burn. It is to be remembered in this connection that of every one hundred parts of air only 23 parts are oxygen; and it is the oxygen that supports combustion. The largest constitu- ent of air, nitrogen, composes about 77 parts of the one hundred. Nitrogen is entirely inert, and in the gasoline engine cylinder it occu- pies space which would be more desir- ably filled with gasoline and oxygen. In changing from a liquid to a vapor, the fuel is increased in volume some 600 to 1000 times. This means that the ratio of the volume of liquid fuel used to that of air must vary from 1 to 8,000 up to about 1 to 16,000. From this we see why the carburetor of the gasoline engine is such a sensitive affair. Not only must the ratio of fuel to air be quite constant, but the difficulties encountered are magnified by the fact that the mixing must take place between colorless gases and " sight unseen" inside the engine cylinder. The gas engineer must resort to tests that will show the condition of the mixture. If the mixture can be adjusted until it will burn, then the adjustment for the proper mixture is easy. A too rich mix- ture is indicated by black smoke from the exhaust; and one too lean, by a sharp, prolonged exhaust, indicating a slowly burning mixture. The smoke of a too rich mixture is black, while that caused by too much lubricating oil is blue. When the engine is provided with a hit-or-miss governor, the needle or supply valve should be adjusted to require the least number of explosions necessary to furnish a given Fig. 223. An au- tomatic carburetor, shown in section, which supplies addi-
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectagricul, bookyear1919
