%0 Journal Article
%T Fundamental analysis on auto
%A Hiroshi Miyagawa
%A Koichi Nakata
%A Makoto Koike
%A Mitsuaki Ohtomo
%A Nozomi Yokoo
%A Tetsunori Suzuoki
%J International Journal of Engine Research
%@ 2041-3149
%D 2019
%R 10.1177/1468087417751240
%X This article presents a study of the mechanism that the lubricant oil droplet initiates low-speed pre-ignition in highly boosted downsized gasoline engines. Low-speed pre-ignition is a phenomenon that the fuel¨Cair mixture ignites before the spark timing, leading to flame propagation that results in a heavy knock. The ignition of lubricant oil droplets is thought to be one possible mechanism for low-speed pre-ignition. However, the oil droplet ignition conditions are not yet well understood. First, the conditions under which a single oil droplet initiates the combustion of a fuel¨Cair mixture were investigated using a rapid compression and expansion machine. When an initial droplet temperature was above 250£¿¡ãC, the vaporized oil ignited before the gasoline¨Cair mixture, in which case the combustion of the gasoline¨Cair mixture around the droplet was initiated. The numerical results showed that the oil droplet temperature increases above 250£¿¡ãC if the droplet is heated by burned gas remaining in the combustion chamber from the previous cycle. A direct-injection single-cylinder research engine was operated under the condition that no residual gas exists in the combustion chamber. In this case, no low-speed pre-ignition occurred even if gross indicated that mean effective pressure was 2.5£¿MPa. These results indicate that an oil droplet does not cause low-speed pre-ignition if any droplet flies into the combustion chamber unless it remains in the chamber over the exhaust stroke
%K Spark ignition
%K pre-ignition
%K low-speed pre-ignition
%K internal combustion engine
%K lubricant oil
%U https://journals.sagepub.com/doi/full/10.1177/1468087417751240