Two-stroke Engines
In two-stroke gasoline engines, the crankcase is sealed and is used as a pressurization chamber for the fuel/air mixture. As the piston rises, it pushes out exhaust gases and produces a partial vacuum in the crankcase which aspirates fuel and air. As the piston travels downward, the fuel/air charge is pushed from the crankcase and into the cylinder.
Unlike four-stroke gasoline engines, the crankcase does not contain engine oil because it handles the fuel/air mixture. Instead, oil is mixed in with the fuel, and the mixture provides lubrication for the cylinder walls, crankshaft and connecting rod bearings.
A majority of ships today use two stroke diesel engines, where the crankcase is completely separated from the cylinders. Unlike smaller engines, they usually have a separate tank below the crankcase as an oil holding tank (sump tank).
Read more about this topic: Crankcase
Famous quotes containing the word engines:
“America is like one of those old-fashioned six-cylinder truck engines that can be missing two sparkplugs and have a broken flywheel and have a crankshaft that’s 5000 millimeters off fitting properly, and two bad ball-bearings, and still runs. We’re in that kind of situation. We can have substantial parts of the population committing suicide, and still run and look fairly good.”
—Thomas McGuane (b. 1939)