This seminar will deal with the work accomplished during my PhD at CERFACS sponsored by Renault.

Cycle-to-cycle variations (CCV) in Internal Combustion (IC) engines need to be controlled since they can cause an unwanted increase of fuel consumption, significant increase in pollutants emissions, and reduce vehicle driveability.

Large-Eddy Simulation (LES) seems to be an appropriate tool for studying and predicting this unstationary phenomenon, due to its capability of solving the time-resolved Navier-Stokes equations. However, LES applied to piston engines are not numerous in the literature due to the lack of experimental data to validate the numerical results. To tackle this issue, the SGEMAC project (funded by the French research agency) has been set up to acquire experimental data on a 4-valve, mono-cylinder IC engine fueled by gaseous propane tailored for LES validation. The experimental database includes numerous operating points and diagnostics, such as Particle Image Velocimetry (PIV), pressure transducers, chemiluminescence, and OH planar laser-induced fluorescence (PLIF) for flame visualization.

LES has been conducted with the AVBP solver on more than 100 consecutive cycles. The seminar will focus on:

• Presentation of the LES methodology which has been set up to simulate the SGEMAC bench: simulation domain, meshing strategy with full tetrahedron elements, moving mesh techniques, and modeling of flame arrestors.
• Validation of the LES methodology on a motored operating point: comparison of flow field to PIV measurements.
• Extension of the methodology for fired operating points and comparison with the experiments on a stable operating point (low CCV) and an unstable one with high CCV.
• Analysis of the physical phenomena responsible for high CCV.