A comparative study of directly injected, spark ignition engine performance and emissions with natural gas, gasoline and charge dilution

This paper presents an experimental study of a 4-cylinder, downsized and boosted, spark ignition engine fuelled by either directly injected compressed natural gas (DI CNG) or gasoline (GDI). Three different charge preparation strategies are investigated for both fuels: stoichiometric operation without external dilution, with exhaust recirculation (EGR) lean burn. The performance the optimized DI CNG is first shown to be comparable that baseline GDI at conditions, exhibiting potential matching peak torque lower speeds substantial fuel economy benefits. impact dilution on then examined EGR Between these two strategies, burn demonstrates higher brake thermal efficiency than equivalent levels. Similar tests performed fuelling results compared those CNG, showing strategy’s influence specific. engine-out total CO2 emissions utilizing all three modes assessed over range operating conditions. consistently GDI, though final choice combustion strategy requires consideration aftertreatment system.