Combustion Blowoff Effects on the Central Recirculation Zone using various Syngas mixtures in a Tangential Swirl Burner

Lean premixed combustion is one of the most successful technologies for flame control in low NOx systems. The characteristics of these flows its good mixing performance, stability and the low emissions. The potential of using new alternative fuels presents a problem in terms due to heating value changes, flame parameters and reactivity. Bio-renewable processes and industrial systems requiring waste gases are just a few examples. The biggest challenge to fuel-flexibility is the large differences between natural gas and the proposed alternative fuels which causes variations in the stability profiles of the combustion process. In this paper, combustion of CH4/H2/CO mixtures was experimentally and numerically studied to understand the impacts of these fuels on the blowoff process. Atmospheric pressure and ambient temperature were used at moderate swirl number. Various nozzles were used to determine the impact of the blends on the Central Recirculation Zones. Methane content in the fuel was decreased from 50% to 0% (by volume) with the remaining amount split equally between carbon monoxide and hydrogen. The Central Recirculation Zone and its turbulence were numerically characterised using the k-ω turbulence model providing details of the structure close to blowoff. The results show how the strength and size of the recirculation zone are highly influenced by the blend, carbon/hydrogen ratio, nozzle geometry and Re numbers.