Combustion and pollutant characteristics of IC engines fueled with hydrogen and diesel/ hydrogen mixtures using 3D computations with detailed chemical kinetics

In order to develop design guidelines for optimum operations of internal combustion engines fueled with alternative fuels, a comprehensive understanding combustion behavior and the pollutant formation inside the cylinder are needed. The first part of this thesis aimed to numerically study the engine performance and in-cylinder pollutant formation in a spark ignition engine fueled with hydrogen. Advanced simulations were performed using multi- dimensional software AVL FIRE coupled with CHEMKIN. The detailed chemical reactions with 29 steps of hydrogen oxidation with additional nitrogen oxidation reactions were also employed. Formation rates of nitrogen oxides (NO x) within the engine were accurately predicted using the extended Zeldovich mechanism with parameters adjusted for a carbon-free fuel. The computational results were first validated against experimental results with different equivalence ratios and then employed to examine a spark-ignition engine fueled with hydrogen under different operating conditions. Strategies that could have significant effects on the engine performance and emissions, such as exhaust gas recirculation (EGR) and ignition timing were also investigated. Furthermore, the maximization of engine power and minimization of NOx emissions were considered as conflicting objectives for preliminary optimization. Finally, a skeletal reaction mechanism was developed to include the reaction kinetics of diesel and hydrogen fuel mixtures to investigate in-cylinder combustion processes of such a dual fuel compression-ignition engine. The model was then employed to examine the effects of exhaust gas recirculation (EGR) and N2 dilution on NOx emissions.