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Chemical kinetic mechanism of compression ignition with PRF (iso-octane/ n-heptane) and NTF (toluene/ n-heptane) is investigated according to crank angle resolved in-cylinder sampling experiments. Profiles of two-stage consumption of fuel components in accordance with the timings of heat releases have been obtained. As well, production and consumption of intermediate species were observed. It was found that toluene consumption at the first stage is considerably less than that of n-heptane, whereas iso-octane consumption is comparable to that of n-heptane, which is accounted for by the smaller rate constant of toluene with OH. N-heptane and iso-octane are considered to produce formaldehyde; however, toluene has no or little contribution.

Intermediate species formed in the cool ignition stage of autoignition were evaluated by exhaust gas analysis with FT-IR in a test engine at hot ignition suppressed conditions. PRF (iso-octane/n-heptane) and NTF (toluene/n-heptane) were used as the fuels. The fuel consumption rate decreases with increasing iso-octane content in PRF and toluene content in NTF. HCHO generation rate increases with increasing iso-octane content in PRF but the opposite trend was found in NTF. These tendencies correspond to the difference in the detail reaction mechanism for PRF and NTF oxidation.