Large Eddy Simulation of Lifted Non-Premixed Jet Flames Using 2-Scalar Flamelet Model

In this paper we introduce the LES of lifted non-premixed jet flames based on two-scalar flamelet modeling. The flamelet G-equation for premixed combustion and the conserved scalar equation for non-premixed combustion are combined to express partially premixed flame propagation. In order to close filtered G-equation, the subgrid burning velocity model is proposed based on the concept that small triple flamelet are projected into unburnt gas from the flame-base of the lifted non-premixed flame. The calculation results are shown that wrinkling lifted flames are simulated and the difference of the lift-off height and the flame-shape with the variation of the co-flowing velocity is predicted. It is also confirmed that the conditional axial velocity near the flame base which is thought to relate the condition of the flame stabilization is on the order of two–three times of the laminar burning velocity, which agrees well with the experimental data. We hope that this method will be useful to investigate the flame stabilizing mechanism or flame controls of practical non-premixed jet flames.