Influences of Temperature and Equivalence Ratio to Auto-ignition Promotion by Additives

Abstract

The ignition timing of homogeneous charge compression ignition (HCCI) combustion engines is the important factor which should be controlled. In this study, the influences of the adding reaction intermediates to auto-ignition delay time were evaluated, by using a constant volume combustion simulation with detailed chemical reaction models of n-heptane and isooctane. The influences were evaluated for the initial temperature 600K-1050K and φ =0.3, 0.5 and 1.0, for n-heptaneair mixture and isooctane-air mixture. For both mixtures, the lower the initial temperature becomes, the larger the effect of additives on the ignition promotion becomes. Especially in the temperature range that is lower enough than negative temperature coefficient region, this effect becomes maximum. In addition, this feature is remarkable in lean mixture. Therefore, it is appropriate to supply additives at the temperature which is dominated by low temperature oxidation reaction, in order to control the auto-ignition timing of HCCI combustion.