Piston rings are an important part of the engine, providing a seal to the combustion chamber to prevent gases and combustion products passing the piston to the crankcase.
Functions
> Seal combustion chamber and avoid blow past
> Conduct heat away from the piston to the cylinder liner.
Types Of Piston rings
Piston rings are classified according to the function and use.
Compression ring or Pressure ring – The purpose of this piston ring is to prevent blow-by. They should provide an effective seal of the combustion chamber space. Top piston rings are compression rings.
Wiper rings or Napier Ring- Its the back up for compression ring, installed just below the compression ring. It act help to stop any leakage of compressed gases and clean the liner surface for the excess oil
Scraper or Oil Control ring – They are rings which eliminate the possible ingress of oil into the combustion chamber. They are fitted lowermost of the rings on the skirt in trunk type pistons. Distributes oil on the cylinder liner preventing the oil passing upwards into the combustion chamber. These rings are normally found on trunk piston engines ( 4-stroke engines).
Material
Piston rings are made of cast Iron. Alloys and coatings are provided, as per the type of the ring as the functionality of these rings. The most common form of alloying cast irons are Grey Cast Iron, Nodular chromium, molybdenum, Carbidic malleable Cast Iron etc
You Can Answer Following Questions
> Types of Piston rings in marine diesel engine (Imp)
> Function of Oil scrapper ring (V.Imp)
> Which piston ring is at the top & order
> Function of compression ring