USE OF RINGS & SIGNIFICANCE OF GAPSometimes the best solutions are deceptively simple. Take, for example, sealing the combustion chamber in an internal combustion engine. Extreme temperatures mean pretty significant expansion rates when it comes to moving components within an engine and the exacting tolerances required to make that engine work properly. It gets worse when you mix metals that have different expansion rates, which is exactly what happens when you have an aluminum piston traveling inside a cast-iron cylinder bore. Leave enough tolerance between the piston and cylinder when it's hot, and it will never seal well enough to even start when it's cold. Tighten up the tolerances enough to achieve a cold start, and the engine tears itself apart from the inside out before you can even get the car on the track.
The top ring is the most important. It provides the seal that is used to create compression, hold the burning-and rapidly expanding-air/fuel mixture in the combustion chamber on the power stroke, and push the burnt remains of combustion out of the chamber to complete the process. The second ring is a bit of a backup; whatever compression slips past the first ring, the second ring helps to contain. The third ring is commonly referred to as the oil ring. It is actually two scraper rings assembled with a corrugated spacer ring between them. The oil ring's job is to scrape excess oil off the cylinder walls so that it doesn't mix with the air/fuel charge.
IN SHORT
RINGS DO NOT ALLOW THE COMPRESSED MATERIAL TO BY-PASS
AND GAP DO NOT ALLOW THE RING TO STICK..........BY RESEARCH ENGINEER JITESH
