Experimental Investigation and Modeling of Early Flame Propagation Stages in Operating Conditions Representative of Modern High Efficiency Spark Ignition Engines 2019-24-0073

The present social context imposes effective reductions of transport greenhouse gases and pollutant emissions. To answer to this demand, car manufacturers adopted technologies such as downsizing, turbocharging, intense in-cylinder aerodynamics and diluted combustion process. In this context, to master mixture ignition is crucial to ensure an efficient heat release. To get to a clearer knowledge about the physics holding early stages of premixed mixture combustion, the PRISME institute in the framework of the French government research project ANR MACDOC generated a consistent experimental database to study ignition and spherical flame propagation processes in a constant volume vessel in laminar and turbulent environment. This allows to have a detailed description of the flame dynamics of an air / isooctane mixture depending on thermochemical properties of the mixture and nature of the diluent (O₂, H₂O, CO₂ and synthetic stoichiometric exhaust gas recirculation), as well as on turbulence intensity and ignition energy. A system simulation model based on the coherent flame model approach was then setup at IFP Energies nouvelles accounting for the influence of the flame stretch, through the integration of a non-linear formulation of the mixture Markstein number, and the flame wrinkling due to turbulence. The model allowed to have a deeper insight in the interpretation of experiments and to dissociate the interacting phenomena holding the combustion process. This modeling improving seems to be a necessary step to model next generation spark ignition engines operating under steady and transient conditions.