What are the uses of Piston Rings?
- Sealing the combustion/expansion chamber.
- Supporting heat transfer from the piston to the cylinder wall.
- Regulating engine oil consumption
The first question came into mind when I saw the use of piston ring is for sealing the combustion is
" A Piston skirt with a diameter same as the inner diameter of the combustion chamber could have done this? Then why Piston Rings are efficient?"Then I came to the conclusion that using a large surface of the piston to collide with the bore will cause comparitively more friction than collision of piston rings with the bore. But definitely the ring may wear faster. To avoid friction many coatings have been given.
What are the Coating Materials?
- Chromium (CKS] or GDC which are wear resistant peripheral coatings)+
- Nitriding and Nitrocarburizing (Enhancing the performance of piston rings in gasoline engines)
- PVD Coatings
- Thermal Spray Coating (Chiefly for Diesel Engines)
How many Rings will be there in a piston?
It depends. But most of the pistons I have seen has three rings.The First two rings is for the sealing the Compression and the last ring is for controlling which lubricates the Piston Skirt.
How many types of Piston Rings are there?
There are many type of Piston Rings Based on the application for which it is used.
Types of Compression Rings
Types of Scraper Rings
This can be installed in the second groove in passenger car gasoline and passenger car and truck diesel engines, but has been almost entirely replaced by the taper faced Napier ring. It is now occasionally used only in the compressors of air brake systems.
|Taper Faced Napier Ring:|
Like on the taper faced ring, the periphery of this ring is designed with a taper in order to improve oil scraping and quicken running-in. These rings are used on the same applications as Napier rings.
|Taper Faced Closed Gap Scraper Ring::|
On this ring the step runs out at the gap and is designed without an undercut. It seals better against blow by than the Napier and taper faced Napier rings with a continuous step. The applications for this ring are the same as for Napier and taper faced Napier rings.