Numerical investigation on the laminar combustion characteristics of primary reference fuel: the effects of elevated temperatures and pressures

Abstract

The one-dimensional premixed laminar freely propagating flame was used to numerically simulate the laminar combustion characteristics of primary reference fuel (PRF). The equivalence ratios are set as 0.7–1.5 at initial temperatures of 298, 358, and 403 K, initial pressures of 1, 2, and 5 atm. Laminar burning velocity (LBV), adiabatic flame temperature (AFT) and mole fractions of H, CO, CO2, C2H4 at Φ = 1.0 are investigated. Meanwhile, temperature sensitivity, rate of production (ROP) and reaction pathway are analyzed. The results show that LBV and AFT decrease with n-heptane doping ratios increasing. With the increase of initial temperatures, the LBV and AFT increase. With the increase of initial pressures, the LBV decreases, while AFT increases slightly. Through temperature sensitivity analysis, it can be found that R1 H + O2 ⇔ O + OH and R97 OH + CO⇔ H + CO2 are main exothermic reactions. R12 H + OH + M ⇔ H2O + M and R56 H + CH3(+M) ⇔ CH4(+M) are major endothermic reactions. n-Heptane is decomposed into C2H4 and C2H3, and iso-octane is decomposed into CH3, CH3O, and CH2O. These small molecule species are further oxidized to generate HCO, which is finally changed into CO2.