Experimental research on using CO2-Ar microjets to control liquid fuel combustion instability and pollutant emission

Combustion instability has become an obstacle to the development of modern gas turbines. In this study, four categories of jet tubes inject CO2-Ar mixture to the flame root at different total injection volume flow rates and mixing ratios. These jets do not change the dominant combustion instability frequency, yet the large flow rate jets can significantly weaken the pressure and the heat addition oscillations. The tube type or the CO2-Ar volume fraction in the jets has no apparent influence on the control efficacy. When the total jet volume flowrate reaches 10 L/min, the maximum amplitude reduction ratio of pulsating pressure and CH* chemiluminescence intensity is 90% and 89%, respectively. Meanwhile, the jets caused a significant drop in the flame temperature, and the NOx emission was reduced by at least 35%. However, the side effect of the jets is that the flame is on the verge of blowing out, and the CO emission increases sharply. The higher the volume fraction of CO2 in the jets, the more likely it is to generate CO. Designers need to compromise the impact of jets on the safety and cleanliness of the combustors.