Perpustakaan Digital ITB

Ammonia is a promising carbon-free fuel for power generation, but its low reactivity presents significant combustion stability challenges. This research investigates the stability limits, flame structure, and nitrogen oxide (????????) emissions of swirl-premixed, partially cracked ammonia-air flames, emulated as ????????3?????2?????2 mixtures, under conditions relevant to gas turbines. The study was conducted in a swirl-stabilized combustor at atmospheric pressure, systematically varying the ammonia fuel fraction (????????????3), equivalence ratio, geometric swirl number (????????=0.5?1.2), and Reynolds number (????????=5,000?20,000). Results demonstrate that increasing ????????????3 suppresses flashback, transitioning the upper stability limit to a rich blowout boundary and significantly expanding the operational window; at ????????=10,000 and ????????=1.2, the stable equivalence ratio range (????????) expanded from approximately ?????????0.43 at ????????????3=0.6 to ?????????1.87 at ????????????3=0.7. Critically, increasing the Reynolds number to 20,000 enhances flashback resistance, shifting this transition to a lower, more reactive fuel fraction of ????????????3=0.55 for ????????=1.2. ???????? emissions exhibited a non-monotonic trend with ????????, decreasing as ???????? increased from 10,000 to 20,000 due to reduced residence time. At ????????=20,000, ???????? emissions for fuel-rich condition, ????>1.1, consistently produced ???????? emission <100 ????????????, indicating an optimal regime for practical application. These findings indicate that high-Reynolds-number, fuel-rich operation with tailored fuel composition and swirl intensity is a viable strategy for achieving stable, low-emission ammonia combustion.