Insights into the Nonlinear Dynamic Features of Mesoscale Combustor Flames

This study investigates mesoscale flame dynamics through nonlinear time series analysis from a dynamical systems perspective. A mesoscale flame is stabilized within a slender quartz combustor tube with a diameter comparable to the flame's quenching distance. Experiments employ premixed methane-air mixtures, with equivalence ratio and Reynolds number as control parameters. Key diagnostics include acoustic pressure measurements, OH* chemiluminescence, and high-speed flame imaging. Four distinct flame regimes are identified: stable flames (SF), flames with repetitive extinction and ignition (FREI), propagating flames (PF), and combined flames (CF), each exhibiting unique dynamical behaviors. Wavelet scalograms, phase space reconstructions, and recurrence plots elucidate interactions between competing time scales across these regimes. Pressure fluctuations and OH* chemiluminescence signals reveal regime-specific topological features, which are contrasted with classical models from the literature. These dynamics emerge from the coupling of transport and reaction time scales—including convection, diffusion, chemical kinetics, and acoustic interactions—whose relative contributions vary with flame regime and operating conditions.