Abstract
Intermediate species formed in the low temperature heat release (LTR) of autoignition were evaluated in test engines by crank angle resolved in-cylinder sampling and exhaust gas analysis with FT-IR at hot ignition suppressed conditions. PRF (iso-octane/n-heptane) and NTF (toluene/n-heptane) were used as the fuels. The LTR fuel consumption decreases with increasing iso-octane content in PRF, whereas the effect of toluene in NTF is weaker. Formaldehyde generation yield increases with increasing iso-octane content in PRF but the opposite trend was found in NTF. The chain reaction mechanism of LTR accounts for the observations; i.e., the chain carrier OH reproduced by n-heptane is consumed by iso-octane, toluene and intermediates such as formaldehyde. Reaction pathways for product species characteristic to each fuel component are also discussed.
