DNS of spherically expanding turbulent premixed flames of pressurized lean methane/air mixtures in homogeneous isotropic turbulence

Turbulent premixed flames expanding in a vessel are a canonical flame configuration of practical interest. The confined geometry, well-defined characteristics of homogeneous isotropic turbulence, and symmetry of the statistics allow for detailed studies of the interplay between turbulence and flame propagation. In this work, we report recent results on the direct numerical simulation of turbulent premixed flames propagating in a lean mixture of methane and air at 4 bar and preheated at 800 K. The turbulent flow is such that 70 < Reλ < 90, 2 < u'/Sf < 10, and l/δth ≈ 5, resulting in δth between 5-10. The flame is found to propagate at the laminar flame speed and the increase in burning rate is mostly due to the increase in the flame surface. Simulations are repeated for two different flow conditions and statistics of the flow field, burning rate, and turbulent flame speed are obtained and discussed. This work is a first step towards a comprehensive characterization of turbulent premixed flames over a wide range of turbulence conditions.