Bulletin . gettingthem in, treating them right while in and getting theburnt gases out, doing it as often as may be necessary,as fast or slow as may be necessary, and as much asmay be necessary. There must also be some elementof control, so that if much work is required of the enginemuch work will be done on the piston by the use of muchmixture, while if little work is required by the engineonly little mixture \yill be used. Now, all complicatedmechanisms that are seen about gas engines are there forjust these things, as well as perhaps a few others, such aslubrication, cooling of the hot wall
Bulletin . gettingthem in, treating them right while in and getting theburnt gases out, doing it as often as may be necessary,as fast or slow as may be necessary, and as much asmay be necessary. There must also be some elementof control, so that if much work is required of the enginemuch work will be done on the piston by the use of muchmixture, while if little work is required by the engineonly little mixture \yill be used. Now, all complicatedmechanisms that are seen about gas engines are there forjust these things, as well as perhaps a few others, such aslubrication, cooling of the hot walls to preyent them twist-ing out of shape and to preyent the oil from burning up,but not much more. It is hard to believe that there is notmuch more than this when studying a large gas engine. The drawing in of the mixture occupies the whole ofthe suction or charo-inu stroke. Under the influence ofthe flywheel the piston returns compressing the mixturewith all the yalves closed. Near the end of this compres-. Fkukk 1. >i()n stioke ignilion lakes jihicc witli a rc-sultant pressurerise. This is followed by the expansion ot the gases, allyalves still remaining closed. Toward the end ot tliisexpansion stroke the exhaust \al\e is open, and the gasesbegin to rush out. The piston then returns, expelling therest of the burnt gases or nearl\- all of them through yalxe which is open : ot course some burnt gases must be left behind, as much as can till the explosionchamber. This is the succession of processes occupyingfour strokes, given the name four-cycle engine. In structural detail some of the mechanism is shown inFigure i for one of these four-cycle engines. Here itappears that the piston has webs under its head to strengthenit. It has rings around part of it, so formed as to preventthe high pressure gases leaking out. There is water allaround the cylinder and around the valve chambers. Thevalves are shown with springs to close them and to keepthem closed all the time
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Keywords: ., bookcentury1900, bookdecade1, massachusettsinstituteoftechnology
