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Abstract

This thesis focuses on the study of natural gas combustion under engine relevant conditions. The work begins with the development of a detailed chemical kinetic mechanism that represents the ignition characteristics of methane with various minor additives over a wider range of operating conditions than previously existing mechanisms. The mechanism includes a NOx submechanism selected from the literature that yields good agreement with experimental data in various methane/air combustion systems. The excessive computational load associated with detailed chemistry is alleviated using a trajectory generated low-dimensional manifold (TGLDM) method. The TGLDMs generated in this work provide a satisfactory approximation of calculation using detailed chemistry in various methane/air reaction systems with a significant reduction of the computational cost. An innovative combustion model for simulating turbulent diffusion flames is presented at the end of this thesis. The model employs the Conditional Source-term Estimation method for the closure of the chemical source term. It obtains production/consumption rates of reaction scalars through TGLDMs generated with the new reaction mechanism. The model was used to simulate ignition and combustion of transient turbulent methane jets under engine-relevant conditions; it has achieved encouraging results in comparison with the experimental data from this work as well as the literature.