A novel transient turbulent jet flame for studying turbulent combustion

This paper introduces a new class of transient turbulent flames as a new benchmark case for studying turbulent combustion. It also brings together the latest high-speed laser imaging experiments with large-eddy simulation (LES)/probability density function (PDF) to advance the calculations of transient processes in the newly introduced test cases. The otherwise steady jet flames are subjected to a pulse of inflow velocity such that the flow experiences sequentially increased local extinction, the formation of upper and lower burning regions separated by a blown-off section, re-ignition and reconnection of the separated flame regions, and then the returning of the flame to statistical stationarity. The base test cases considered here are Sydney University's turbulent methane piloted flames L, B and M. The LES/PDF model predicts the flame's dynamic response to the velocity pulse qualitatively, with the extinction limit predicted accurately compared to the measurement. This paper reports the first LES/PDF calculations of these flames which have narrow reaction zones compared to Sandia's partially premixed flames, D, E and F. The statistically-transient jet flame introduced here provides a new benchmark for studying the effects of turbulence-chemistry interaction. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.