Three-dimensional geometrical effects on the near-wall quenching of turbulent premixed flame

Abstract

The three-dimensional geometric structure of near-wall flame and its effect on the near-wall flame quenching characteristics have been investigated using direct numerical simulation data of a V-shaped H-air flame in turbulent channel flow. The principal curvatures of the flame are calculated to categorize various flame structures. Additionally, the quenching status of the near-wall flame is evaluated based on a local fuel consumption speed, derived by integrating the fuel reaction rate across the local flame element. The results show that, there is a significant change in the statistical characteristics of the flame’s structure as it approaches the wall: flat flames predominate in the far-wall region, while cylindrical-shaped flames are more prevalent in the near-wall regions which align with the buffer layer and linear sublayer of the corresponding non-reacting turbulent boundary layer. A notable transition is observed from a turbulence-driven to a wall-driven influence on the flame’s geometric structure within the buffer layer. Meanwhile, the spherical and cylindrical flames convex towards the burned side, which are initially characterized by high reactivity in the far-wall area, exhibit a significant reduction in reaction rate within buffer layer. This leads to a shift in the general relationship between flame curvature and reactivity from a positive to a negative correlation. Furthermore, it has been found that the flame gets near-wall quenched mostly with a cylindrical surface. And, the flame elements convex towards the burned gas exhibit longer quenching distances and lower levels of wall heat flux compared to those with other geometric structures. The current results underscore the impact of flame’s geometric structure on its near-wall quenching characteristics. Future work will focus on investigating these findings in near-wall combustion under various turbulent conditions and different wall-bounded combustion configurations.