Near wall effects on the premixed head-on hydrogen/air flame

Abstract

The paper focuses on laminar and turbulent premixed head-on hydrogen/air flames interacting with inert, non-reacting walls. Both adiabatic and isothermal (450K) walls are considered in a counterflow-like, statistically stationary configuration. In the laminar condition, the flame-wall distance and isothermal-wall heat flux are studied under different strain rates. In the turbulent condition, interactions between turbulent, thermal and chemical effects are analyzed via direct numerical simulations. Influences on the flame dynamics due to near wall effects are characterized by conditional statistics on the flame fronts, such as the flame front temperature, thickness and the heat release rate. Compared with the single-step chemistry results, the detailed chemical reaction mechanism brings new and more complicated physics. Because of the differential diffusion between heat and mass, the flame front topology associated with major species changes with the wall boundaries. Accounting for contributions from various reacting species, a newly defined mean flame displacement speed has been proposed to quantify the movement of the turbulent flame zone. Interestingly, the wall heat flux model developed from the single-step chemistry remains applicable even for the detailed chemistry case with good predictability for both laminar and turbulent flames.