THE NUMERICAL GENERATION OF AN IGNITION MAP BY MEANS OF A TURBULENT FLAME SPEED CLOSURE APPROACH FOR THE CONFIGURATION OF A JET FLAME

摘要

This paper presents a numerical investigation of ignition phenomena in turbulent partially premixed methane/air flames under standard conditions for the configuration of a jet flame. In this work, a Turbulent Flame Speed Closure model (TFC) is applied in conjunction with an ignition delay module extension. The flame kernel propagation and consequent establishment or extinction of the flame are examined and subsequently compared to the experimental findings. A sensitivity analysis with respect to the spark ignition position and the prescribed boundary conditions is accomplished. An ignition map is inferred from the results and matched with the ignition probability map obtained in the experiments. In addition, the expansion speed and the lift-off height of the flame are analyzed. Generally, a very satisfying agreement is achieved in regions in which the mixing is the dominant factor. Discrepancies in the prediction occur in the far downstream area, where long ignition delay times impede a successful transition of the spark to a full flame.