Abstract
Generally, soot emission is increased in smaller-size bore diesel engine than larger one because spray-impingement on cavity wall is more significant. From 1st. report to 3rd. report, required conditions to maintain emission similarity for different sized engines have been verified to improve soot-NOx tradeoff in a small bore engine. In this report, effects of bore size and injection conditions on heat transfer coefficient are clarified experimentally and theoretically from a viewpoint of fuel efficiency. Furthermore, the relation between fuel efficiency and engine size are correlated quantitatively based on new equation of heat transfer coefficient.
