Laminar double flames exist in many combustion configurations involving non-premixed or partially-premixed combustion processes. These flames can exhibit a “double-branched” structure due to local mixing in a non-premixed fuel and oxidizer flows. The dynamics and morphology of double flames in a convective flow could be significantly influenced by buoyancy driven convection such that various strengths of gravitational field may lead to complete different flame behaviors.
In this work, double flames generated at the flow nozzle of a slot burner were investigated using the open source software, OpenFOAM®. A two-dimensional simulation was used to replicate the geometric feature of a slot-burner flame. Conditions of interests include five different gravity levels with and without radiative heat transfer. Through analyzing the spatial distribution of velocity, temperature, heat release rate and species, the difference of double flames at different gravity levels were studied. The results show that higher gravity levels appear to entrain the cool surrounding fluid through buoyancy effects, which is indicated through obvious negative x-velocity region. The heat release rate and OH radical information are used to explain intrinsic behaviors of diffusion flame and premixed fuel-rich branches.