Mechanical Engineering Ph.D. Dissertation

Abstract

The quest for cleaner, more efficient combustion technology drives the research into understanding the interactions of turbulence, chemical reactions, and ignition processes in internal combustion engines. This work provides a comprehensive investigation into turbulent jet ignition systems, with a focus on the chemical interactions of pre-chamber and main chamber combustion dynamics. A combination of experimental and kinetic modeling techniques has been employed to understand the intricate mechanisms of pre- and main chamber combustion across different fuels.  For the gas-phase study, the jet-stirred reactor (JSR) and rapid compressions machine (RCM) were used to analyze key species profiles and ignition delay times during the fuel combustion under various operating conditions. Based on experimental findings, fuel kinetic models were developed to better account for fuel combustion behavior with the presence of different active species. The surface kinetic mechanism development on the pre-chamber wall included surface characterization techniques, hydrogen temperature-programmed reduction (H₂-TPR), and X-ray diffraction (XRD) experiments. A multi-site detailed H₂ surface kinetic mechanism was developed within the mean-field approximation; this mechanism was assessed and validated against the present and literature experiments. It was subsequently coupled to various gas-phase mechanisms to assess the gas/surface chemistry coupling as a function of wall temperature and other operating parameters.

To summarize: by integrating the development of gas phase and surface kinetic mechanisms, this work provides an in-depth understanding of the intricate interplay among pre- and main chamber combustion behavior in turbulent jet ignition systems. The findings contribute to the advancement of fuel strategies and the optimization of engine design in turbulent jet ignition systems, with the ultimate goal of enhancing efficiency and reducing emissions.

Bio

Wenxian Tag is a Ph.D. candidate in the Mechanical Engineering program in the PSE division, working at the Combustion Chemistry Lab under the supervision of Prof. Mani Sarathy. She holds a B.Sc. degree in Automotive Engineering from Wuhan University of Technology in China and obtained her M.Sc. degree in Mechanical Engineering at University College London, UK. Her research focuses on engine combustion, emissions, kinetic modeling, and materials characterization.