Abstract
This paper was aimed at clarifying the ring collapse phenomena through the experimental study. The oil film thickness and fluttering of second ring with taper face were measured in the operating engine under various engine speeds. The measurement of second land pressure also carried out. As the results, It is found out that the oil film thickness of second ring greatly increases just after compression top dead center and that the larger blow-by gas flow through the second ring at the same time during high engine speed range. It is because of the ring collapse allowing the second ring loses the contact with the liner wall.
