Effects of the cold wall boundary on the flame structure and flame speed in premixed turbulent combustion

The near-wall flame structure is analyzed based on the direct numerical simulation (DNS) data of a statistically stationary counterflow-like flame-wall interaction (FWI) configuration. According to the relative orientation between the flame normal and the wall normal, a flame element can be either head-on or entrained. Within the quenching zone of FWI, the flame elements are more likely to be entrained, while the head-on flame elements are more likely to appear beyond the influence zone. The flame in the quenching zone thickens considerably which has implications on the variation of the displacement speed of different progress variable isosurfaces. To characterize the dynamics of the local flame elements, a local mean density-weighted displacement speed across the flame front is introduced and investigated. Moreover, the scalar dissipation rates conditional on non-dimensional temperature and progress variable are found to be considerably different in the quenching zone because of significant differences in the distributions of progress variable and non-dimensional temperature in the near-wall region. (c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.