Reduced kinetics of NH3/n-heptane: Model analysis and a new small mechanism for engine applications

Abstract

A compact reduced mechanism covering a wide range of conditions is developed for use in simulations of NH3/n-heptane combustion in engines. Reduction targets were selected after reviewing available experimental studies of NH3 combustion in engines. Ignition, flames and oxidation of NH3/n-heptane mixtures were targeted. Particularly, mixtures with very low molar percentage of n-heptane which are important for the applications were considered. They have been observed to have a distinct ignition behavior. Target quantities also included pollutants with a goal to account for two possible mechanisms of N2O formation in engines, discussed in literature. The reduced mechanism of this study was developed with ant colony reduction method. It consists of 57 species and 159 reactions, and its range of applicability is 10–100 atm pressure and 0–100 % NH3 in the fuel mixture. The performance of the mechanism was found comparable to larger models from literature. Importance of carbon–nitrogen interactions, influence of key reactions in the NH3 subset and effect of CO on N2O formation were analyzed and discussed in terms of the predictive ability of the reduced mechanism of the present study and those available from literature.