Acoustically Controlled Combustor NOx

Successful NOx measurements in the end plane of the primary zone of a small tubular gaseous fuelled combustor of conventional gas turbine design, employing acoustic driving of the combustor via the air inlet pipe, have been made at scaled 1/8 load operating conditions. The acoustic drive caused partial blockage of the combustor primary zone air flow which increased the equivalence ratio in the plane of the NOx measurements. The mixing was acoustically augmented which together with the blockage richening significantly changed the combustor mean NOx-mean equivalence ratio characteristic in the end plane of the combustor primary zone. Under lean-conditions at 1/8 load and “with-drive” at 246 Hz mean NOx was reduced indicating that a value of 10ppm (50% reduction) is possible, confirming previous results. Under rich-conditions NOx “with-drive” at 246 Hz might be reduced by 23%, relative to previous results, and even might reach the “no-drive” value of about 25ppm, which was possibly due to acoustic augmentation of the primary zone aerodynamics. The NOx at the combustor exhaust “with-drive” should be even lower than that measured “with-drive” because of normal dilution. Therefore, the technique has the potential to create a low NOx conventional combustor without requiring the complicated design-changes of current industry efforts.