Flame structures of a syngas swirl-stabilized diffusion flame in a model combustor were measured using the OH-PLIF method under different fuel and air swirl intensity.The flame operated under atmospheric pressure with air and a typical low heating-value syngas with a composition of 28.5% CO,22.5% H2 and 49% N2 at a thermal power of 34 kW.Results indicate that increasing the air swirl intensity with the same fuel,swirl intensity flame structures showed little difference except a small reduction of flame length;but also,with the same air swirl intensity,fuel swirl intensity showed great influence on flame shape,length and reaction zone distribution.Therefore,compared with air swirl intensity,fuel swirl intensity appeared a key effect on the flame structure for the model combustor.Instantaneous OH-PLIF images showed that three distinct typical structures with an obvious difference of reaction zone distribution were found at low swirl intensity,while a much compacter flame structure with a single,stable and uniform reaction zone distribution was found at large fuel-air swirl intensity.It means that larger swirl intensity leads to efficient,stable combustion of the syngas diffusion flame.
