LES of the Gas-Exchange Process Inside an Internal Combustion Engine Using a High-Order Method

High-order, wall-resolved large eddy simulations (LES) using the spectral element method (SEM) were performed to investigate the gas-exchange process inside a laboratory-scale internal combustion engine (ICE) and study the in-cylinder flow evolution. Using a stabilizing filter, over 30 engine cycles were simulated to generate data for statistical analysis, which demonstrated good agreement in the mean and root mean-squared (rms) phase-averaged velocity fields across three different filter parameter/resolution combinations. The large scale flow motion was characterized during each stage of the engine cycle. Tumble ratio profiles indicate peak values during the intake stroke which decay during compression and are almost non-existent thereafter. The tumble breakdown process is quantified by investigating the evolution of the mean and turbulent kinetic energy over the full cycle, and its effect on the evolution of the momentum and thermal boundary layers is discussed. Algorithmic advances to the computational fluid dynamics (CFD) solver Nek5000, employed in the current study, resulted in significant reduction in the wall-time needed for the simulation of each cycle for mesh resolutions of at least an order of magnitude higher than the current state-of-the-art.