Control of Thermoacoustic Oscillations and NOx Emissions by Bias Jets in the Form of Corner Tangential Slots

Abstract

ABSTRACT Corner tangential and bias combustion technology have significant advantages in optimizing combustion and pollutant emissions. This paper combined the corner tangential, bias combustion and jet technology for the first time to control thermoacoustic oscillations and pollutant NOx emissions synchronously. The control feasibility was examined by three variables: widths of corner tangential slots, bias jets ratios, and jet flow rates. Results indicate that the widths of corner tangential slots and bias jets ratios significantly affect the suppression effectiveness of thermoacoustic oscillations and NOx emissions. The synchronous control effectiveness with larger widths of corner tangential slots and smaller bias jets ratios is better than that with smaller widths of corner tangential slots and larger bias jets ratios. The maximum damping ratio of dynamic pressure and CH* can achieve 90.1% and 82%, respectively. The dynamic pressure drops from 39.2 Pa to 3.9 Pa and CH* reduces from 0.006 arb.units to 0.001 arb.units. A lower oscillations frequency will form by the bias jets, which avoids the occurrence of high-frequency and high-amplitude thermoacoustic self-excited oscillations. Besides, the NOx emissions drop from 26.2 ppm to 13.9 ppm reaching a maximum reduction of 12.3 ppm. Meanwhile, a slimmer flame root and flatter flame front are triggered. Two flame modes are summarized as Model A and Model B. This research realized an efficient simultaneous control of thermoacoustic oscillations and pollutant NOx emissions, which could be a helpful guideline for designing lean premixed flames.