Chemical Kinetic Modeling of the Autoignition Properties of Ammonia at Low–Intermediate Temperature and High Pressure using a Newly Proposed Reaction Mechanism
Anand Singh, Subhankar Mohapatra, Raghu Boyapati, Ayman M. Elbaz, Sukanta Kumar Dash, William L. Roberts, V. Mahendra Reddy
Abstract
Global emissions can be significantly reduced with the use of zero-carbon emission fuels. Ammonia is now at the center of attention because of its promise as a carbon-free energy fuel. So, a detailed study on ammonia’s combustion and emission characteristics is necessary, especially at low–intermediate temperature and high-pressure conditions. Very few reaction models are available for low–intermediate-temperature ammonia chemistry, and most of them could not show reasonable agreement with the experimental conditions. In the present work, a new ammonia oxidation reaction model has been proposed by referring to the previous available literature for low–intermediate temperature and high-pressure ammonia oxidation chemistry, and also a comprehensive chemical kinetic modeling for the autoignition characteristics and NOx emissions is performed for an ammonia/air mixture using the newly proposed mechanism. The newly proposed ammonia reaction model consists of 32 species and 259 reactions. The proposed mechanism has also been tested by performing the computational fluid dynamics (CFD) modeling for a premixed NH3/air mixture in a microflow reactor with varying wall temperature at equivalence ratios of 0.8, 1, and 1.2, and the model validation has been carried out by comparing the mole fraction profiles of species NH3, O2, and H2O with the available experimental results. The proposed reaction model was able to predict the formation of steady weak flames of the NH3/air premixed mixture within the computational domain. An excellent agreement is observed between the computational and experimental results for autoignition properties and CFD model validation using the newly proposed reaction model.