Comparison of Chemical Mechanisms for Simulation of Hydrogen/Ammonia Combustion*

Ammonia and hydrogen are two fuels with the potential to enable future carbon emission-free combustion systems. Due to complex chemical pathways, chemical mechanisms describing the combustion of ammonia/hydrogen mixtures are often inaccurate. While simulations of combustion systems have the potential to accelerate the transition to a carbon-free future, they rely on accurate chemical mechanisms thereby motivating the need to assess existing mechanisms for accuracy. In this work, several existing chemical mechanisms describing hydrogen/ammonia combustion are assessed. Both premixed and non-premixed flames are considered and evaluated by comparing simulation results against existing experimental data. Premixed flame accuracy is assessed based on flame speeds from one-dimensional freely propagating flames, while non-premixed flame accuracy is assessed based on extinction strains of counterflow flames. For both configurations, sensitivity and reaction path flux analyses are performed to better understand the behavior and differences of the various chemical mechanisms investigated. From the aggregate of these analyses, recommendations for the most accurate mechanisms are drawn.