8. An oil engine is a form of internal-combustion engine especially adapted to the use of kerosene and the heavier petroleum products. The oil engine differs from the gas engine in some particulars that will be explained later.
9. An alcohol engine is one especially adapted for using alcohol as fuel, differing from the gasoline engine chiefly in the means whereby the fuel is gasified.
10. The charge is a mixture of fuel and air taken in at one stroke of the engine. It varies according to the conditions of operation, and may sometimes be sufficient to fill the cylinder completely at atmospheric pressure, while at other times it may be reduced. The proportions of gas and air may also vary from time to time.
11. The exhaust gases—sometimes called the exhaust—are the waste products of combustion that are expelled from the engine after having performed the work required of it.
12. The compression space is a portion of the cylinder into which the piston does not enter, and into which the charge is compressed previous to ignition. It is sometimes called the clearance, or combustion, space.
CONVERSION OF HEAT INTO WORK
13. It has been shown that heat may be made to do work by being
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applied to the outside of a cylinder containing a gas such as air, as shown in Fig. 3. If, instead of
heating the confined gas by means of a flame on the outside of a cylinder, a stream of some combustible gas is introduced, as in Fig. 4, through a hole in the bottom of the cylinder, allowing it to burn as it enters, a large amount of heat
