Large eddy simulation of turbulent premixed-flame in engine by using the renormalization group theory and the multi-level formulation.

Large-eddy simulation of a turbulent premixed flame in an engine is performed in a wide range of operating conditions such as engine speed, airfuel ratio, and ignition timing. A numerical method for estimating supergrid fluctuations of physical quantities and the space-averaged quantities accurately is proposed. As the subgrid estimations, the Yakhot-Orszag turbulence model based on the renormalization group theory and a flamesheet model are employed. For some variations of the operating conditions, obtained computational data agree well with experimental data on turbulence intensity and pressure history. It is also shown that the developed numerical model has the potential of calculating the cyclic variations of flow and combustion. An important understanding on the physical situation in conventional 4-valve engines, is obtained from the present study, which is that laminar regions may exist at the low engine speeds.