Measurements and large eddy simulations of turbulent premixed flame kernel growth

Abstract

A combined experimental and large eddy simulation (LES) study of flame kernel growth in isotropic, homogenous turbulence has been carried out. LES calculations using the combustion methodology of Weller were compared with experimental measurements from a fan-stirred bomb for iso-octane and propane air mixtures at various turbulence intensities and pressures. For the purpose of model validation, the mean radius evolution was compared with experimental measurements, obtained from Schlieren photographs. Initially, a small laminar flame kernel was produced that burned at an increasing rate as it grew and was wrinkled by the turbulent flow field. It was also observed that at atmospheric pressure propaneair flames demonstrated less variability between experimental realizations than did iso-octane air flames High-variability combustion events were associated with the convection of the flame kernel away from the spark plug during ignition. Good agreement between experiments and calculations was obtaiend for the full range of conditions investigated in this study, and the LES results were able to reproduce some of the observed variability between experimental realizations as a result of turbulent interactions with the small kernel during ignition. These results provided further validation of the combustion model, though the simple ignitiion treatment did not reproduce the full range of ignition variability due to strain sensitivity.