Effect of Swirl on the Flame Dynamics and Pollutant Emissions in an Ultra-Lean Non-Premixed Model Gas Turbine Burner

ABSTRACTThe effect of varying swirl strength on the isothermal flowfield, flame dynamics, and pollutant emissions in a novel, unconfined and non-premixed swirl burner at atmospheric conditions was investigated using optical and laser diagnostic methods. The burner (IIST-GS1), operated with methane as fuel, produced stable ultra-lean flames at the two geometric swirl numbers investigated, S = 1.59 and 2.81. In both cases, the burner exhibited two flame stabilization zones with varying θglob, the bluffbody stabilized and swirl stabilized, with a transition region separating the two zones. Comparison of two-dimensional (2D) flowfield plots with OH* images revealed that the size of the two stabilization zones and, hence, the heat release distributions depended on the swirling strengths. Higher swirl strengths in S = 2.81 enhanced the reverse flow of burned gases towards the burner exit thereby aiding in the flame stabilization. Also, the increased mixing between the fuel, air, and burned gases for S = 2.81 re...