Development of a reduced chemical kinetic mechanism for ammonia combustion using species-based global sensitivity analysis

The increasing demands on efficiency and accuracy for numerical studies are urgently driving the development of chemical kinetic mechanisms with reliable prediction performance and compact size. In this work, a reduced kinetic mechanism was developed to comprehensively predict the combustion characteristics of ammonia. First, the performances of a series of detailed ammonia mechanisms were evaluated based on the average error function between mechanism predictions and experimental data from various typical reactors. The Han Mech., Mei Mech., and Zhang Mech. were identified to best predict the ignition delay time, laminar flame speed, and concentration profiles under a wide range of operating conditions, respectively. Then, the species-based path sensitivity analysis and global sensitivity analysis were utilized to identify the importance of species in these three selected detailed kinetic mechanisms on specific targets. The redundant species are eliminated until the relative errors between the predicted results using the interim reduced mechanisms and the detailed mechanisms exceed 10%. Finally, by merging and optimizing the three interim reduced mechanisms, a new reduced model was developed, which consists of 25 species and 174 reactions. Extensive validations against experimental data in shock tubes, premixed laminar flames, and jet-stirred reactors over broad operating conditions show satisfactory agreements, thereby substantiating the good practicability of the developed mechanism.