Date of Award


Publication Type


Degree Name



Mechanical, Automotive, and Materials Engineering


Catalytic converter, Emission regulations, High efficiency engine, Internal combustion engine, Three-way catalyst


X. Chen


M. Zheng




The push for environmental protection and sustainability has led to strict emission regulations for automotive manufacturers as evident in EURO VII and 2026 EPA requirements set to take effect in the coming years. The modern gasoline spark ignition (SI) engine typically employs various in-cylinder emission reduction techniques along with an exhaust after-treatment system to comply with emission standards. The three-way catalyst (TWC) is wholly responsible for removing the engine-out emissions including hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx). The main objective of this thesis is to investigate the impact of extensive exhaust gas recirculation (EGR) on the performance of the TWC to meet upcoming EURO VII and 2026 EPA emission requirements. Relevant engine-out exhaust conditions were selected from a gasoline engine operating with varying ratios of EGR which were then replicated on a heated aftertreatment flow bench containing a TWC. The results indicate that higher ratios of EGR allow for greater H2 yield from increased availability of HC at the cost of elevated CO slip. The formation of NH3 and N2O is ultimately suppressed from decreased engine-out NOx emissions with the application of EGR. Increased NOx conversion efficiencies are also realized at higher rates of EGR from the decrease of engine-out NOx combined with higher concentrations of NOx reducing reactants, however, at the cost of increased HC and CO slip. Finally, the results indicate that the reduction in exhaust gas temperature from EGR is not significant enough to hinder the performance of the TWC.