Achieving diesel-like efficiency on a high Stroke-to-Bore ratio DISI engine under stoichiometric operation
This work developed and demonstrates pathways to achieve diesel-like, high-efficiency engine operation from spark ignition (SI) combustion at stoichiometric operation with 3-way catalyst compatibility. A high stroke-to-bore (S/B) engine design (1.5:1) with cooled exhaust gas recirculation (EGR) and high compression ratio were used to improve engine efficiency by up to 30% compared with a production turbocharged gasoline direct injection (GDI) SI engine. To achieve the efficiency goals, engine experiments were coupled with computational fluid dynamics (CFD) simulations to guide the experiments to extend the stability and operable limits of high-dilution, high-efficiency SI combustion. The effects of EGR and late intake valve closing are investigated in this work on their effect on Pressure-Temperature history and their effect on efficiency improvement and knock.