Piston and Piston Rings:

The piston transforms the energy of the expanding gasses within mechanical energy. A piston rides inside the cylinder liner or sleeve as displays in above figure.

Pistons are generally made of aluminum or cast iron alloys. To avoid the combustion gasses from bypassing the piston and to keep friction to a minimum, every piston has various metal rings around it, as described through below Figure.

Figure: Piston and Piston Rod

These rings function as the seal among the piston and the cylinder wall and also act to decrease friction through minimizing the contact area among the piston and the cylinder wall. A ring are commonly made of cast iron and coated along with molybdenum or chrome. Most diesel engine pistons have various rings, commonly 2 to 5, along with every ring performing a distinct function. A top ring(s) acts mainly as the pressure seal. The intermediate ring(s) acts as a wiper ring to erased and control the amount of oil film on the cylinder walls. The bottom ring(s) is an oiler ring and ensures in which a supply of lubricating oil is regularly deposited on the cylinder walls.