Effects of radial fuel staging on the emission and stability of swirl micromix syngas flames

In Integrated Gasification Combined Cycle (IGCC) systems, the combustion of syngas may potentially lead to combustion instability and excessive NO_x emissions. The technique of micromix combustion with radial staging offers innovative solutions to this problem. The present work examines the effects of radial fuel staging on a swirl micromix flame by integrating experiments with numerical simulations to investigate how the staging ratio influences flame stability and emissions. The results indicate that increasing the staging ratio results in a more concentrated heat release intensity. When the staging ratio is greater than 1.0 at low flow rates, the outer flame’s OH* intensity and stability significantly decrease. As the staging ratio increases, the pressure in the combustion chamber gradually rises. Meanwhile, the vibration frequency and intensity of high-frequency pressure decrease. The flame can be attributed to three main zones: the inner recirculation zone, the outer recirculation zone, and the flame overlap zone. These zones exhibit frequencies of approximately 220 Hz, 430 Hz, and 1000 Hz, respectively. As the staging ratio increases, NO_x emissions increase, while CO emissions remain nearly constant. Novelty and significance statement: Micromix combustion technology represents an emerging solution for achieving low nitrogen oxide combustion in syngas gas turbines. In micromix combustion technology, the introduction of fuel staging strategies shows potential for further mitigating thermoacoustic coupling risks in micromix flames. However, the influence mechanisms of fuel staging on micromix flame heat release, combustor pressure oscillations, and pollutant emissions remain unclear. In this study, an integrated approach combining experimental and numerical simulation methods was employed. For the first time, experimental measurements were conducted to obtain the pressure oscillations, static/dynamic structural characteristics, and NO_x/CO emission evolution patterns of syngas micromix flames under radial fuel staging configurations, complemented by numerical simulations to analyze low-pollutant emission mechanisms. This research will contribute to the application of fuel staging technology in micromix combustion systems, enabling better realization of stable low-NO_x combustion for hydrogen-containing fuels.