Experimental Investigations of the Lean Blowout Limit of Different Syngas Mixtures in an Atmospheric, Premixed, Variable-Swirl Burner

An atmospheric, variable-swirl combustor was used to study the influence of syngas composition on the lean blowout (LBO) limit under various flow conditions created at different swirl numbers. The fuels used in the experiments consisted of generic mixtures of CO, H-2, and CH4. The results were compared to those for CH4 at the same swirl numbers. The effect of dilution on the LBO limit was studied by adding N-2 to the syngas mixture. The swirl number was varied by changing the ratio of axial/tangential flow through the combustor inlet and was determined using laser Doppler anemometry (LDA). A perfectly stirred reactor (PSR) model was used to test whether the experimental results could be explained by changes in chemical kinetics. The experiments showed that increasing the swirl number reduced the LBO equivalence ratio for a given fuel composition. At a certain swirl number, increasing the H-2/CO molar ratio of a binary mixture decreased the LBO equivalence ratio significantly. The addition of CH4 to a binary mixture shifted the LBO limit to higher equivalence ratios. N-2 dilution increased the LBO equivalence ratio of the syngas mixture; however, the impact was relatively small. The PSR model was able to predict the effect of adding CH4 reasonably well, but it underestimated the effect of the H-2/CO molar ratio on the LBO limit.