Synergies of Cooled External EGR, Water Injection, Miller Valve Events and Cylinder Deactivation for the Improvement of Fuel Economy on a Turbocharged-GDI Engine; Part 1, Engine Simulation

As CO₂ legislation tightens, the next generation of turbocharged gasoline engines must meet stricter emissions targets combined with increased fuel efficiency standards. Promising technologies under consideration are: Miller Cycle via late intake valve closing (LIVC), low pressure loop cooled exhaust gas recirculation (LPL EGR), port water injection (PWI), and cylinder deactivation (CDA). While these efficiency improving options are well-understood individually, in this study we directly compare them to each other on the same engine at a range of operating conditions and over a range of compression ratios (CR). For this purpose we undertake a comprehensive simulation of the above technology options using a GT-Power model of the engine with a kinetics based knock combustion sub-model to optimize the fuel efficiency, taking into account the total in-cylinder dilution effects, due to internal and external EGR, on the combustion. Based on a carefully designed design of experiments (DOE) our results indicate a potential CO₂ improvement of up to 7% at part load conditions compared to the base engine without the above mentioned technologies while limiting the loss of high load performance using the different technologies in combination.