Evaluation of NOx Emission Characteristics with Respect to Residual Ammonia Concentration in Ammonia Cracked Fuel

This study investigates the effect of residual ammonia on NO_x formation in combustors using cracked ammonia fuel. Simulations were conducted under gas turbine-relevant conditions, including pressures of 1–25 bar, residence times of 2–10 ms, and equivalence ratios (ϕ) from 0.5 to 0.8. Residual NH₃ concentrations ranged from 10 to 10,000 ppm. Nine chemical kinetic mechanisms were compared. Results showed that low NH₃ concentrations led to pressure-driven NO_x increase via the thermal–NO pathway, while high NH₃ suppressed NO_x formation due to enhanced radical recombination. A crossover point (2000–5000 ppm) was identified, marking the transition between dominant NO formation mechanisms. These findings inform strategies for NO_x mitigation in gas turbines using cracked ammonia. These findings offer a fundamental information for optimizing residual ammonia control in gas turbines using ammonia cracked fuels.