Direct Numerical Simulation Study of Lean Hydrogen/Air Premixed Combustion

Turbulence-chemistry interaction is known to play a vital role in changing the characteristics of a flame surface. It changes evolution, propagation, annihilation, local extinction characteristics of the flame front. This study seeks to understand how turbulence interaction affects flame surface geometry and propagation of turbulent premixed H₂/Air flames in a three-dimensional configuration. 3D Direct Numerical Simulation (DNS) study of premixed turbulent H₂/Air flames has been carried out using an inflow–outflow configuration at moderate Reynolds number (Re) with a fairly detailed chemistry. The simulations are conducted at different parametric conditions in conjunction with differential diffusion (non-uniform Lewis number) effects. The topology of the flame surface is interpreted in terms of its propagation and statistics. Statistics related to the flame surface area and the correlations between the curvature and the gradient of temperature are obtained from the computed fields. It is found that the displacement speed increases with the negative mean curvature, while it correlates well for high turbulent cases and scattered for low turbulent cases. It is also observed that the diffusion effects become more dominant for deciding the flame structure when the mean flow is lower (low Re case). Further, the unsteady effects of tangential strain rate, curvature on flame propagation, and heat release rate are also investigated. Later, effects of prominent species and radicals are described to correlate the production of the maximum heat release rate in the lower temperature regions.