Effect of Equivalence Ratio on the Performance and Emission Characteristics of a Dual-Fuel HCCI Engine with Swirl

This study examines the performance and emissions of a dual-fuel HCCI engine using an 85% n-dodecane and 15% ethanol blend. The ECFM-3Z compression combustion model in STAR-CD is employed to analyze the engine's behavior and emissions at varying equivalence ratios. The findings reveal that increasing the equivalence ratio from 0.5 to 0.65 raises in-cylinder pressure and temperatures due to enhanced heat release, but further increases may decrease pressure. Ethanol offsets temperature rise and reduces peak temperatures. Higher equivalence ratios generally lead to increased CO emissions but decreased CO2 emissions. Although NOx emissions typically rise with higher ratios, this study shows a decrease due to ethanol's cooling effect. Piston work initially declines but increases after combustion initiation. Soot emissions decrease with higher equivalence ratios. Velocity magnitude and turbulent kinetic energy are crucial for efficient combustion. An equivalence ratio of 0.65 is optimal for reducing NOx emissions by 84.21% at the expense of a little amount of piston work.