CFD modeling of combustion of a natural gas Light-Duty Engine

A CFD methodology to model natural gas Light-Duty SI (Spark-Ignition) engines is here proposed. The ignition stage is modeled by means of a simplified Eulerian spherical kernel approach (deposition model). Then, the fully turbulent flame propagation is reproduced by the Coherent Flamelet Model (CFM), where turbulence effects are taken into account by considering the flame surface density evolution. The laminar to turbulent flame transition is managed by the CFM model and it is assumed to occur when the flame radius reaches a fraction of the integral length scale. This methodology was validated with experimental data of in-cylinder pressure and heat release rate at different loads and speeds.