LES Prediction of the Ignition Probability Map for a Model Aeronautical Spray Burner

This study presents the computation of the ignition probability map of a model gas turbine, investigated experimentally at CORIA laboratory, using Large Eddy Simulation (LES). The simulations leverage the recently proposed TFM-AMR-I model, which is based on the Thickened Flame Model (TFM) formalism and enables a full flame resolution (i.e. no thickening) of the flame kernel in the initial instants of ignition. LES simulations of ignition are performed for 14 spatial points distributed in the combustion chamber, with 6 repetitions for each in order to obtain a reasonable estimate of ignition probabilities. Probabilities are adequately predicted for most of the selected points, with a typical error of 30 \(\%\). Nevertheless, the ignition probability is largely over-estimated at two locations where the mean diameter of liquid droplets is shown to be under-predicted, which may lead to too easy ignitions. Parametric variations show a satisfying robustness of the proposed approach with the two following key highlights: (i) the initial full flame resolution made possible by TFM-AMR-I is necessary, as an abrupt initial thickening leads to an artificial extinction; (ii) a correction of the over-sensitivity of the thickened flame to stretch, recently proposed in the literature, is necessary to predict ignition accurately.