Low temperature auto-ignition characteristics of methylcyclohexane/ethanol blend fuels: Ignition delay time measurement and kinetic analysis

New ignition delay times (IDTs) of binary methylcyclohexane (MCH)/ethanol fuels were provided by using a rapid compression machine. Results show that MCH exhibits typical negative temperature coefficient (NTC) regime bounded by two turnover temperatures (T_upper and T_lower). As the ethanol blending ratio increases, IDTs increase, NTC regime shrinks and shifts to the lower temperature. Measured data are then used to validate the most updated kinetic model (Bissoonauth et al. Proc Combust Inst 2018), which well captures the IDT and NTC behavior dependence on the ethanol blending ratio. The kinetic reason for the experimentally observed ignition behavior is that ethanol addition reduces the low temperature heat release and slows down the temperature rise and H₂O₂ decomposition pathway activation. The mole fraction of ROO and QOOH decrease rapidly due to the reduction of MCH initial concentration, and the NTC behavior becomes less apparent consequently. Further comparison among the ignition behavior of the different binary fuels have been conducted to access the effect of ethanol addition on different structure fuels. Results indicate a generalized effect of ethanol addition and the kinetic reason is that the presence of ethanol just simply reduces the hydrocarbon concentration without fuel-to-fuel interactions.