Combustion of ethanol-air mixtures in closed vessel comparison of simulation with the use of RANS and LES method

Large Eddies Simulation method (LES) has become a powerful computational tool with application to turbulent flows. It links classical Reynolds Averaged Navier-Stokes (RANS) approach and Direct Numerical Simulation (DNS). This modeling approach computes the large eddies explicitly in a time-dependent simulation using the filtered Navier-Stokes equations. LES resolves the large flow scales that depend directly on the geometry where small scales are modeled by the sub-grid-scale models. LES is expected to improve the description of the aerodynamic and combustion processes in Internal Combustion Engines. With LES it is possible to resolve the essential part of the flow energy, yielding reliable results. Proper predictions depend on the quality of sub-grid-scale (SGS) models. In this paper the computational analysis is compared with experimental results in constant volume chamber. In that way there is a possibility to see the difference in results of initial flame kernel development and laminar flame speed. The calculations were made for two different combustion models. This allows to compare the experimental and simulation results for RANS (Fire ECFM combustion model) and LES (Fire) method and make further improvement in LES combustion model for application in full engine simulation.