Development of Numerical Framework for Research of the Pre-Chamber SI Combustion

A promising strategy for increasing thermal efficiency and decreasing emissions of a spark ignited (SI) internal combustion engine is the application of lean mixtures. The flammability limit of lean mixtures can be increased by using an active pre-chamber containing an injector and a spark plug, resulting in a combustion mode commonly called Turbulent Jet Ignition (TJI). The optimization of the combustion chamber shape and operating parameters for TJI combustion can be a demanding task, since the number of design parameters is significantly increased and is today supported by numerical simulations. In this paper, the process of the development of a numerical framework based on 3D CFD and 1D/0D numerical models that will support the research of the pre-chamber design and optimization of operating parameters will be shown. For 3D CFD modelling the AVL Fire™ code is employed, where the full combustion chamber model with intake and exhaust ports of the experimental engine is prepared. In the pre-experimental phase the 3D CFD model, although not validated due to the absence of experimental results, is used to evaluate initial boundaries in terms of combustion flammability, positions of multiple flame jets and to create verification results of in-cylinder turbulence and combustion required for 0D model tuning. Since there is no commercially available pre-chamber model with multiple jets for the 0D modelling approach, the 0D combustion model of AVL Boost™ was extended to take into account multiple flame propagation in the main chamber. The evaluation of geometry of multiple flame jets was performed with CAD software. The presented numerical framework, once validated with experimental results, can be a useful tool for the definition of optimal pre-chamber geometry and operating parameters.