Numerical Simulation of autoignition characteristics of methane/ n-dodecane dual fuel

Numerical simulations were carried out to investigate the autoignition characteristics of methane/n-dodecane dual fuel under the conditions of P =6 atm and T =1100 K. The skeletal mechanism containing 54 species and 269 steps reaction was employed, and the performances of mechanism to cover zero-dimensional homogeneous ignition and laminar flame propagation problems in lean methane-air mixtures were demonstrated. The research results indicate that the combustion processes were divided into the inert mixing phase, the low-temperature chemical reaction phase, and the high-temperature chemical reaction phase. And there are significant competitive relationships between the two fuels during the ignition process, and the autoignition characteristics of n-dodecane in the methane/air mixture are affected by the equivalent ratio of methane. The two-stage ignition characteristics of dual fuel were discovered by direct numerical simulation. The first-stage ignitions are originated from the low-temperature chemical reaction in the richer mixtures. And the second-stage ignitions are caused by the single-stage high-temperature reaction, occurring near the equivalent mixture fraction. Increasing methane equivalent ratio will inhibit the ignition of two stages. It was determined that the elementary reaction CH 4 +OH<=>CH 3 +H 2 O is enhanced due to the addition of methane through sensitivity analysis, resulting in increasing ignition delay times.