Numerical modeling of premixed combustion of Li-ion battery thermal runaway gases : Study of flame acceleration by a normal shock in an obstacle-laden channel

Li-ion battery safety is a critical concern due to the risk of fire and explosion. During thermal runaway, flammable gases are released from the cells, potentially accumulating as a reactive mixture in relatively large confined spaces, such as garages or Battery Energy Storage System (BESS) containers. To model the combustion process and its consequences at this scale, a simulation code (Europlexus) with simplified physical modeling will be used. The simplification necessitates closure models for local flame speed, which in turn depends on the specific chemical mixture, local pressure and temperature, and turbulence characteristics. The methodology involves revisiting existing correlations—previously developed for H 2 /air premixed combustion in the Europlexus code—and adapting them for application to the complex mixtures produced during battery thermal runaway. This includes: (a) developing a correlation for the dependence of laminar flame velocity on local pressure and temperature using the Cantera code with a specific mechanism representative to mixtures from Li-ion battery thermal runaway, and (b) verifying the flame-turbulence correlation by comparing its effects with results from a 2D fully resolved reactive compressible code Dryads. The study examines the interaction between a premixed flame and a shock wave in a 2D semi-confined channel, where obstacles are placed downstream to further accelerate the flame — after its initial interaction with the shock — and enhance vortex generation. A comparison of the large-scale simulation model with the high-fidelity reference solver demonstrates good agreement in the predicted flame speeds.