Analysis of Flame Onset and Propagation for the Flame Speed Closure Turbulent Combustion Model in Constant-Volume Vessels

Abstract

Computational simulations of the kernel growth resulting from a spark discharge in fuel-air mixtures have been carried out in many works to date by different groups, under both laminar and turbulent conditions. Within the Reynolds-Averaged Navier-Stokes (RANS) context, most turbulent combustion models in current and widespread use lack thorough testing and validation in a seemingly simple, though extremely valuable setup. Namely, a fan-stirred vessel with well-defined turbulence statistics, in which a spherical flame grows as it burns fresh mixture after a spark is discharged. A notable exception is the Flame Speed Closure (FSC) Model, which has been extensively employed to predict explosions under a wide range of conditions. The main focus of the present work is to examine a weak point associated to the model through the application of Computational Fluid Dynamics (CFD) for simulating turbulent combustion in constant-volume vessels, specifically the difficulty in producing successful ignitions using standard ignition models. A modification to circumvent the referred issue is proposed and assessed.