Piston rings and their functions.

A piston ring is a seal that surrounds the piston as it moves inside an engine's cylinder wall. Piston rings serve three basic functions: provide a gas-tight seal between the combustion chamber and the crankcase; transfer heat from the piston to cooled cylinder wall; and control oil consumption.

Usually, there are three piston rings for each piston: 

01. The top ring is the top compression ring acts as the primary seal between the piston and the cylinder wall.

 

02. The middle ring acts as a secondary seal between the piston & cylinder wall to help transfer heat to the cylinder wall and assure that no gas escapes from combustion chamber .

03. The bottom the oil control ring is the final ring made up of two smaller rings with a sort of spring separating them. This spring presses the ring against the cylinder wall to protect extra oil consumption.

Why backfire occure in gas engine ?

A backfire is an explosion produced by a running internal combustion engine that occurs in the air intake or exhaust system. Backfire may cause an objectionable popping noise with possible loss of power and forward motion.

A backfire can occur  in the intake manifold, carburetor, or air filter of an internal combustion engine when the intake valves are not shut prior to fuel combustion.

Also a backfire can occur in exhaust system when the engine runs leaner or if there is less time for the fuel to burn in the combustion chamber, there is a tendency for incomplete combustion. The result of a misfire or incomplete combustion is that unburned fuel delivered to the exhaust manifold where they may ignite. Another backfire situation occurs when the engine is running rich with excess fuel and there is incomplete combustion with similar results.

Common causes of backfires are:

1. Poor or unregulated engine timing is often a cause of backfires in both intake and exhaust system.
2. Improper wiring in the ignition can also lead to timing issues and backfires.
3. Low fuel pressure, clogged fuel filters, and weak fuel pumps (Turbocharger pressure) could cause a severe lean air-to-fuel ratio during fuel injection and cause backfire.

We faced backfire problem in our gas generator engine with big pop sound and air filter breakage. So backfire occurred fuel intake system due to lack of improper intake valve timing or intake valves may stick due to carbon deposits in the valve guides or valve seats may be uneven for which valves were not close properly. 

For which it is necessary to clean all carbon deposited in cylinder head and grinding valve seats to make evenness to seat valves properly.

Also may check total electrical systems which are related to engine ignition system like spark plugs, ignition harnesses, ignition modules etc.