Effects of different preheated CO2/O2 jet in cross-flow on combustion instability and emissions in a lean-premixed combustor

Abstract

To reveal the suppression mechanism of thermoacoustic instability flames under CO2/O2 jet in cross flow. Experiments on the effects of different preheated CO2/O2 jet in cross-flow (JICF) on combustion instability and NOx emissions in a lean-premixed combustor were conducted in a model gas turbine combustor. Two variables of the JICF were investigated—the flow rate and the temperature. Results indicate that combustion instability and NOx emissions could be suppressed when the JICF flow rate increases from 1 to 5 L/min. The average pressure amplitude decreases from 18.6 Pa to 1.6 Pa, and the average NOx emission decreases from 26.4 ppm to 12.1 ppm. But the average pressures amplitude and NOx emissions increase as the JICF temperature grows up. The sound pressure and the flame heat release rate exhibits different mode-shifting characteristics. The oscillation frequency of the sound pressure almost unchanged under JICF injection. However, the oscillation frequency of the heat release rate jumps from 95 Hz to 275 Hz under different JICF temperatures. As the CO2/O2 JICF flow rate arrived 3 L/min, the oscillation frequency of flame heat release rate jumps from 85 Hz to 265 Hz. The color of the flame fronts and roots were changed by the JICF injection. The average length of flame under CO2/O2 JICF cases is shorter than the N2/O2 JICF cases. There are three different modes of flames when the CO2/O2 JICF flow rate varies, and two different modes of flames when the CO2/O2 JICF temperature varies. This article explored the joint effects of different CO2/O2 or N2/O2 JICF on combustion instability and NOx emissions, which could be instructive to the designing of safely and clean combustors in industrial gas turbines.