Role of Boundary Emissivity on Radiation-Induced Uncertainty in Laminar Flames of Methane/Air and Ammonia/Air Mixtures

Accurate radiation modeling is essential for the correspondingly accurate assessment of the resolved and global properties of laminar flames, such as the propagation speeds, species profiles, and the kinetics information derived based on such information. The present study highlights the importance of radiation from the gaseous medium as well as the boundary emissivity on the uncertainties in the prediction of such properties. Results show that, in addition to the expected influence of bulk radiation transfer, there also exists substantially increased flame speed uncertainty with higher surface emissivity, especially at the hot boundary; that radiation induced uncertainty varies non-monotonically with pressure; and that low strain-rate stagnation flames exhibit large uncertainties induced by radiation and boundary emissivity. Furthermore, speciation of burner-stabilized premixed flat flames is subjected to large uncertainties due to radiation of the active radicals such as H and OH. These findings suggest the need of accounting the role of radiation and surface emissivity in flame studies, especially in the extraction of kinetics information from experiments.