Sealing refers to sealing the gas, in order to prevent the leakage of gas from combustion chamber into the crankcase, control the amount of gas leakage to a minimum, and improve thermal efficiency. Because leakage of the gas will not only make the engine power decline, but also lead to the oil deterioration.
Adjusting oil is to scrape the surplus lubricating oil on cylinder wall, and at the same time to make a thin oil film so as to guarantee normal lubrication of cylinder, piston and piston ring. In modern high speed engine, special attention has been paid to the effect of controlling of oil film of piston ring.
The heat conduction is to conduct the heat from the piston to the cylinder sleeve through the piston ring, that is, to receive the cooling effect by the piston ring.