2015 年 57 巻 180 号 p. 134-141
An experimental study was conducted to investigate the patterns of the temperature distribution in a rapid compression machine, inside the cylinder during the auto-ignition process, with a stratified fuel distribution. In this paper, n-heptane was used as the fuel. Carbon dioxide was added in the charge mixture for measuring the temperature distribution using the infrared emission method. The fuel concentration gradient (FCG) was created by injecting the fuel from the bottom part of the cylinder followed by a time delay. The overall equivalence ratio was set to 0.6 and the compression ratio was 10. The relation between the difference of the equivalence ratios at the top and the bottom cylinder sides, ΔØ, and the waiting time from the injection, tw, was investigated in advance. The data obtained showed that the low temperature oxidation process started to occur from the leaner ΔØ region. On the other hand, the hot flame began at the top side with a small ΔØ value, in contrast to the bottom side where the hot flame started with a large ΔØ value. The knock intensity (KI) could be weakened when a proper FCG is applied, but in the cases where the FCG is too steep or inadequate, lower combustion efficiency or a large KI would respectively occur.
