Numerical modeling of pollutant emissions in practical combustion systems using detailed chemical kinetics

Pollutant emissions from combustion systems are a major area of concern with today’s energy needs. Numerical simulations have helped with the design of clean and efficient combustion strategies over the years. However, with the emergence of new fuels and combustion modes, it is necessary to improve the computational models. In this research, improved NOx and soot models are developed which uses detailed chemical kinetics in order to simulate the combustion phenomenon. These models are coupled with Computational Fluid Dynamics (CFD) to predict the NOx and soot emissions in practical combustion systems. In the first part of the dissertation, a reduced chemical reaction mechanism is developed for modeling the combustion of biomass-derived gas (i.e., producer gas or synthesis gas). The mechanism reduction is performed on a well-validated comprehensive mechanism that was designed to simulate the combustion of natural gas constituents and NOx emissions. The reaction mechanism also includes species and reactions related to the combustion of ammonia, which is an important component in the producer gas. Combustion experiments of a pilot-scale burner are simulated using the developed mechanism, and the model is able to predict the NOx emission levels resulting from different feedstocks under a wide range of operating conditions. Detailed analyses of the simulation results are performed in order to determine the NOx generating regions in the flame and reaction pathways leading to formation and destruction of NOx. Further, new burner designs are evaluated using the model in order to select the best design for reduced NOx emissions.