| The low-velocity regime of filtration combustion in an inert packed bed of 3 mm diameter alumina pellets was studied experimentally and numerically for mixtures of air or oxygen-enriched air for two types of fuel: a hydrocarbon (methane), and a non-hydrocarbon (hydrogen sulfide) from ultra-lean to ultra-rich at a single filtration velocity (30 cm/s). Intrinsic properties of the filtration combustion waves, temperature, wave velocity, as well as products of combustion, were measured and comparatively analyzed. A comprehensive numerical simulation using the GRI 3.0 kinetic mechanism was carried for methane/air as well as the oxygen enrichment and depletion cases.; For methane/oxidizer combustion, it was found that on the average, temperature is suppressed by 20 K with successive increase of the oxygen content in the oxidizer (OCO). At any OCO, it was found the flames produce minimal amount of pollutants such as oxides of nitrogen and carbon monoxide in the ultra-lean regime of combustion. For ultra-rich mixtures, significant amount of the methane was converted to hydrogen and carbon monoxide in the partial oxidation regime with minor amounts of higher hydrocarbon such as acetylene and ethylene.; In hydrogen sulfide/air combustion, it was found that the lean and ultra-lean regime produces a fair amount of sulfuric acid along with sulfur dioxide while the ultra-rich region converts most of the fuel to hydrogen (20% maximum) and molecular sulfur (50% at maximum). |
