Stabilization and Emission Characteristics of Gliding Arc-Assisted NH₃/CH₄/Air Premixed Flames in a Swirl Combustor

Abstract

This paper investigates the effects of gliding arc (GA) discharge on the stabilization and emission characteristics of premixed NH3/CH4/air swirl flames under various ammonia contents, flow rates, and global equivalence ratios. First, the lean blowout (LBO) limits are measured. We find that although blending CH4 extends the LBO limit of the ammonia flame to 0.6–0.8, the GA discharge further remarkably extends it to 0.3–0.4. Then, the flow and flame structures are visualized by simultaneous OH planar laser-induced fluorescence and particle imaging velocimetry measurements. The results reveal that the discharge increases the OH radical concentration and expands the inner recirculation zone, leading to improved flame stability. Second, the NO x emissions are investigated over a wide range of global equivalence ratios and ammonia contents. It is seen that the GA discharge slightly increases the NO x emission by less than 7% at low NH3 contents (<0.6), which can be attributed to the thermal and OH-involved reaction pathway of NO x formation. However, as the NH3 content further increases (which is accompanied by the rapid growth of the NO x emission), the GA discharge effectively reduces the NO x emission by up to 30%. This effect might be due to the more intensive NO x -consuming reactions by plasma-induced NH2 radicals at a higher ammonia content, which is confirmed by the strengthened NH2* chemiluminescence under GA discharge conditions. Finally, a chemical reactor network analysis gives reasonable NO x predictions without GA discharge and highlights the NO x -reduction effects of NH2 radicals under high ammonia contents.

Effects of H2O Dilution on NOx Emissions of Methane-Added Ammonia Oxidation

“…Ariemma et al indicated that the increased OH production due to CH 4 oxidation consumes NH 2 radicals, which inhibits the DeNO x process. To mitigate high NO x emissions from NH 3 /CH 4 combustion, various combustion technologies have been adopted, including gliding arc-assisted combustion, , rich-lean combustion, , pressurized combustion, and flameless combustion. , In many studies, a small percentage of NH 3 is adopted as the fuel-N source. , As the NH 3 proportion increases, the concentrations of OH, N, and HNO radicals are altered, thereby influencing NO x formation characteristics. Zhang et al and Filipe Ramos et al both noted that the NO x emissions reach the peak value when the volume fraction of NH 3 in the fuel ( V NH 3 ) equals 0.5.…”

“…Ariemma et al 36 indicated that the increased OH production due to CH 4 oxidation consumes NH 2 radicals, which inhibits the DeNO x process. To mitigate high NO x emissions from NH 3 /CH 4 combustion, various combustion technologies have been adopted, including gliding arc-assisted combustion, 37,38 rich-lean combustion, 39,40 pressurized combustion, 41 and flameless combustion. 42,43 In many studies, a small percentage of NH 3 is adopted as the fuel-N source.…”