Large Eddy Simulation of lifted turbulent flame in cold air using Doubly Conditional Source-term Estimation

Abstract

The present study is focused on Large Eddy Simulation with Doubly Conditional Source-term Estimation (DCSE) applied to a series of lifted turbulent flames in cold air without autoignition. DCSE is formulated for partially-premixed turbulent combustion. Predictions for time-averaged methane concentration and its root mean square (rms), Probability Density Function (PDF), flame width, lift-off height and some qualitative observations are presented and compared with experimental data. The predicted methane concentrations are in good agreement with the experiments. Discrepancies for the rms are observed and several sources of discrepancies are identified. PDF of methane concentration and flammability region are also in good agreement. The lift-off heights are predicted very well. Some edge flame characteristics are visible in the simulated flames. The progress variable scalar dissipation rate model does not have a significant impact on methane concentration predictions, while it has a larger effect on predicted lift-off height and temperature. Inclusion of the non-premixed mode in the closure of the progress variable transport equation has a small effect on the current lift-off height predictions, but has a larger impact on the temperature profiles.