Effects of aspect ratio and initial pressure on asymmetric flame and flame instability of premixed CO/air

Abstract

Syngas is a promising alternative energy carrier with low carbon and pollutants emissions, and CO is the main component. The combustion characteristics of stoichiometric CO/air mixtures with varied initial pressure (0.5–1.5 atm) and aspect ratio (12–40) were examined through experiments in a rectangular closed duct. This experiment simulated the transport and storage conditions of CO to study its combustion characteristics at different aspect ratios and initial pressures. The flame images and overpressure dynamics were captured by high-speed camera and pressure sensor, respectively. Experiment results proved that the increase in aspect ratio had an important effect on flame shape evolution. The tilted flame for low aspect ratios was affected by buoyancy, while flames with high aspect ratios were influenced by competing buoyancy and intrinsic instability. The results showed that the flame morphology and dynamics were enhanced with increasing aspect ratio and initial pressure. The intrinsic instability of premixed CO/air combustion was investigated, and the formation mechanism of tilted flame and twisted flame were comprehensively analyzed. Qualitative distinctions were made between symmetric and asymmetric flame morphology regimes.