Effects of syngas H۲/CO composition and turbulent intensity on the bluff-body premixed combustion characteristics

The effects of hydrogen content variation in H۲/CO composition with different turbulent intensities were numerically investigated. The GRI۳.۰ reduced mechanism, including ۱۵ species and ۴۶ subreactions with scale-adaptive simulation (SAS) turbulence model and eddy-dissipation concept (EDC) turbulence-chemistry interaction, was utilized in FLUENT. In lean combustion, by increasing hydrogen content, the production of "OH"  radicals is increased, and they consume "CO"  drastically, leading to a high "CO"  consumption rate. In rich combustion, as hydrogen concentration rises, "OH"  and O radicals tend to react with hydrogen instead of "CO"  due to hydrogen’s higher reactivity, decreasing "CO"  the consumption rate. With hydrogen concentration enhancement, the amount of vapor products rises, causing the products’ heat capacity to increase. Then, the produced combustion heat, flame temperature, and produced "NO"  gases are decreased. The maximum flame temperature "NO"  occurs at the equivalence ratios of ۱.۱ and ۰.۹, respectively, from kinetics analysis. Based on the sensitivity analysis, "NO " the production rate is limited by O radicals. At the same time, maximum "NO"  occurs at equivalence ratio one from the CFD result due to the higher residence time caused by the burner geometry. The enhancement of turbulence intensity leads to high residence time, intensifying the flame and resulting in a lower lean blowout limit.

کلیدواژه ها:

Syngas ، Premixed Flames ، Bluff Body ، chemical kinetics ، Lean blowout limit