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 CO2opposing multiple jets on the thermoacoustic instability and NOxemissions in a lean-premixed model combustor.The feasibility was verified from three variables:the CO2jet flow rate,hole numbers,and hole diameters of the nozzles.Results indicate that the control effect of thermoacoustic instability and NOxemissions show a reverse trend with the increase of open area ratio on the whole,and the optimal jet flow rate range is 1-4 L/min with CO2opposing multiple jets.In this flow rate range,the amplitude and frequency of the dynamic pressure and heat release signals CH*basically decrease as the CO2flow 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%.NOxemissions 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 CO2opposing multiple jets.This research achieved the synchronous control of thermoacoustic instability and NOxemissions,which could be a design reference for constructing a safer and cleaner combustor.