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The Effect of Centerline Enrichment for Flexible Low Swirl Burner Flame Stabilization


This study examines the potential for developing a geometrically flexible low swirl burner (LSB) flame stabilization system. Until now, the use of a quarl has been the accepted form of flame stabilization and emissions reduction for the low swirl burner. However, this method is limited by the fixed geometry of the quarl and is relying on the effectiveness at all load conditions. The proposed stabilization method is use of a centerline pilot to induce local fuel enrichment from a small percentage of the load to improve performance. The pilot is expected to help stabilize the flame by ensuring the presence of a locally rich zone to maintain a flame even in leaner conditions without interrupting the central divergent zone. The goal is to have a sufficient fuel enrichment to sustain the stability without generating locally high levels of CO or NOx emissions. The performance was assessed by a direct comparison of the enrichment strategy applied to the sudden expansion case with the quarl at the same overall load conditions. The piloted cases showed evidence of lean blow off limit extension with increase in pilot flow rate. NOx emissions achieved at the leanest points were as low as 3 ppm with the pilot though CO spikes up to 7000 ppm are also observed due to incomplete combustion. Quarl emissions results show a minimum NOx emissions value of 14 ppm while still maintaining low CO emissions. The pilot performance was comparable to the quarl results and proves to be an effective alternative for flame stabilization.

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