Ring flutter
As ring flutter an unwanted vibration in the axial direction of the is compression ring starting from the ring gap referred to, which under unfavorable circumstances in internal combustion engines occurs. This is caused by insufficient gas pressure on the inside of the ring. The consequences are, on the one hand, a lower engine output and, on the other hand, a possible ring break with further, usually considerable damage to the engine.
In two situations, the gas pressure may not be sufficient to press the ring against the cylinder surface with the necessary force:
- If at the combustion dead center the resultant of gas and friction forces is smaller than the inertia force of the ring. The ring lifts off the lower flank of the groove and thus the gas pressure on the inner surface of the ring is reduced. The ring now lifts off the running surface and gas can enter the crankshaft housing from the combustion chamber ( blowby ).
- In addition, high engine speeds promote ring flutter. The gas cannot advance fast enough into the groove space behind the ring and the same effect occurs as at the combustion dead center.
Various methods have proven effective to avoid ring flutter. Since the flutter originates from the ring ends, the ring at the ring joint can be pressed against the running surface with a higher force than the rest of the circumference with an asymmetrical pretensioning force. Lighter rings reduce the inertia force and move the flutter to a higher speed range. In order to guarantee the gas pressure on the inner surface, there are radial bores in the piston, which also ensure access to the rear groove space when the ring is in contact with the upper flank. Sealing the ring joint has not proven itself in series due to the high manufacturing costs.
Footnotes
- ↑ Piston Damage: Findings, Causes and Remedies
- ^ Franz Pischinger: Internal combustion engines , lecture reprint, Volume 1, self-published, Aachen, October 1995, p. 248
- ↑ Piston rings for engines and compressors ( Memento of the original dated May 8, 2014 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , PDF (0.6 MB)
