Effect of CO2 Opposing Multiple Jets on Thermoacoustic Instability and NOx Emissions in a Lean-Premixed Model Combustor

This paper experimentally studied the effect of CO2 opposing multiple jets on the thermoacoustic instability and NOx emissions in a lean-premixed model combustor. The feasibility was verified from three variables: the CO2 jet flow rate, hole numbers, and hole diameters of the nozzles. Results indicate that the control effect of thermoacoustic instability and NOx emissions show a reverse trend with the increase of open area ratio on the whole, and the optimal jet flow rate range is 1ȃ1 L/min with CO2 opposing multiple jets. In this flow rate range, the amplitude and frequency of the dynamic pressure and heat release signals CH* basically decrease as the CO2 flow rate increases, which avoids high-frequency and high-amplitude thermoacoustic instability. The amplitude-damped ratio of dynamic pressure and CH* can reach as high as 98.75% and 93.64% with an optimal open area ratio of 3.72%. NOx emissions also decrease as the jet flow rate increases, and the maximum suppression ratio can reach 68.14%. Besides, the flame shape changes from a steep inverted “V” to a more flat “M”, and the flame length will become shorter with CO2 opposing multiple jets. This research achieved the synchronous control of thermoacoustic instability and NOx emissions, which could be a design reference for constructing a safer and cleaner combustor.