Combustion and Nitrogen Oxide Behaviors of Ammonia/Methane–Air Premixed Flames in a Model Gas Turbine Combustor: Model Validation and Numerical Investigation

Abstract This research presents a numerical analysis of the combustion and nitrogen oxide (NOx) emission characteristics of premixed ammonia/methane (NH3/CH4) swirl flames in a gas turbine combustor, aimed at supporting clean energy applications. Simulations were conducted at equivalence ratios of φ = 1.0 and 1.2 at varying ammonia doping ratios (NH3 by vol%) of 20%, 30%, 40%, and 50%. A detailed chemical mechanism consisting of 957 reactions and 128 species was integrated into a flamelet-generated manifold framework. The model validation showed strong agreement in temperature and species fields. The results show that increasing ammonia content leads to a reduction in the peak flame temperature, carbon monoxide, and carbon dioxide (CO2) emissions. For a 20% NH3 blend, the peak temperature reached 2206 K at φ = 1.0 and decreased to 2129 K at φ = 1.2. For a 50% NH3 mixture, peak temperatures were 2171 K and 2084 K, respectively. Increasing the ammonia fraction from 20% to 40% resulted in a CO2 reduction of 14.06% at φ = 1.0 and 18.05% at φ = 1.2. NOx emissions rose by 8.0% when ammonia content increased from 20% to 30% at φ = 1.0, but further increasing NH3 to 50% led to a 20% reduction. Overall, the highest NOx emissions were consistently observed at 30% NH3 and φ = 1.0.