Experimental study on combustion stability of a gas turbine model combustor under oxygen-lean conditions

Flue gas recirculation has emerged as a promising low-NOx emission technology in advanced gas turbines, while the slower oxidation rate induced by the low oxygen content could potentially cause combustion instability. We conducted an experimental investigation in a single-nozzle swirl combustor to examine the impact of oxygen content, inlet flow rate as well as temperature on combustion instability under oxygen-lean conditions. The results show that reducing oxygen content from 23.3% to 21% leads to reduced amplitudes of pressure pulsation and exothermic pulsation, indicating improved combustion stability. However, further reduction in oxygen content to 18.6% causes a decrease in the combustion reaction rate, resulting in an increase in the amplitude of pressure pulsation. As the oxygen content drops to below 18.6%, the exothermic intensity decreases, which results in a decrease in the amplitude of pressure pulsation. Besides, under oxygen-lean conditions, increasing the inlet temperature is conducive to reducing the amplitude of pressure pulsation and enhancing combustion stability. Additionally, as the incoming flow rate increases from 7.4 to 9.9 m/s, the refined fuel atomization and improved uniformity of oil-gas mixing contributed to decreased pressure pulsation amplitude. Nonetheless, when the incoming flow rate further increases to 12 m/s, the amplitude of exothermic and pressure pulsation increases.