Heat engineering; a text book of applied thermodynamics for engineers and students in technical schools . t the lower end of the figure. Thus modified the DieselCycle took the form shown in Fig. 175, in which adiabatic com-pression in a cylinder of small clearance brings the air from a tob at which the temperature is high enough to ignite oil which isinjected into the cylinder. If the burning progresses at theproper rate the pressure will be kept constant until cut off at c to d adiabatic expansion takes place followed by exhaustfrom d to a and finally to e. The suction stroke from e to
Heat engineering; a text book of applied thermodynamics for engineers and students in technical schools . t the lower end of the figure. Thus modified the DieselCycle took the form shown in Fig. 175, in which adiabatic com-pression in a cylinder of small clearance brings the air from a tob at which the temperature is high enough to ignite oil which isinjected into the cylinder. If the burning progresses at theproper rate the pressure will be kept constant until cut off at c to d adiabatic expansion takes place followed by exhaustfrom d to a and finally to e. The suction stroke from e to a INTERNAL COMBUSTION ENGINES 365 charges the cylinder with air. This is a four-stroke cycle. The efficiency is given by cP(Tc-Tb)-cv(Td-Ta)^73 = — 1 - cP(Tc-Tb) Td-Ta k(Tc-Td)The high theoretical efficiency is due to the high compression. (8) ACTUAL ENGINES The form taken by an actual engine is shown in Fig. represents an engine of the Otto form. In this air is drawninto the cylinder by the outward motion of the piston A throughthe valve B. Gas is admitted by C which is so arranged as to. _J _ Fig. 176.—Ordinary gas engine. 4-cycle. open after B by means of a shoulder formed by a sleeve attachedto the valve stem. These admission valves are opened by thesuction of the piston or they may be opened positively by thevalve gearing. They are closed by the spring D when the pistonreaches the end of its stroke or when the valve mechanism re-leases them. At the end of the expansion stroke the exhaustvalve E is opened by the lever F operated by a cam. Thecam is on a cam shaft, operated by a bevel or spiral gear fromthe crank shaft. The speed of this cam shaft for a four-cycleengine is one-half the speed of the engine shaft. The governor 366 HEAT ENGINEERING operates to throttle the mixture or to prevent gas from enteringas will be explained later. The cylinder K contains a waterjacket L for the purpose of keeping the temperature of the cyl-inder wall low enough for lubrica
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