Parametric investigation of particulate matter emissions in a gasoline direct injection engine using computational fluid dynamics modelling

The effects of start of injection (SOI) timing, spark ignition (SI) timing and exhaust gas recirculation (EGR) rate on particulate matter (PM) emissions in a gasoline direct injection engine are examined through computational fluid dynamics modelling. Varying SOI timing entails compromising between longer mixing time and lower fuel impingement. Delaying the optimal SOI timing by 20 crank angle degree (CAD) results in a 78% increase in number density and a threefold-increase in mass density. PM control benefits from retarding SI timing which prolongs mixing time and shortens soot residence time. A 10 CAD delay from the SI timing at 25 CAD before top dead centre reduces number density and mass density by 65% and 57%, respectively. EGR renders the in-cylinder condition unfavourable for PM formation despite the overall increase in equivalence ratio. For 10% EGR rate, a drop of 547 K in peak temperature decreases number density by 24%. However, mass density increases by a 1.7 factor due to high particle growth species availability.