This study investigates the effect of fuel ignitability (Octane Number) on combustion characteristics in a Two-stroke engine using visualization and pressure analysis. The objective is to determine if the octane number, a standard anti-knock index for spark ignition engine, holds significance in a Two-stroke engine with high residual gas content. Experiments with Primary Reference Fuels (PRF 20, 50, 90) showed that lower octane fuels increase both knock frequency and intensity. Image analysis revealed that this correlated with a faster apparent flame propagation speed after autoignition. Furthermore, PRF 20 showed an earlier and higher rate of pressure rise compared to PRF 50, influencing knock severity. These findings confirm that octane rating trends are relevant even in Two-stroke engines.
Kato et al. (Wed,) studied this question.