메탄 스월 화염에서 산화제 조성 변화에 따른 질소산화물 저감 특성 연구 = Investigation of Nitrogen Oxides Reduction Characteristics in Methane Swirl Flames under Varying Oxidizer Compositions

다국어 초록 (Multilingual Abstract)

Emissions of nitrogen oxides (NOx) from high-temperature combustion remain a major concern because thermal NOx formation increases sharply with temperature. This study proposes a nitrogen-dilution-based oxidizer composition control strategy inspired by membrane air separation, in which the nitrogen fraction is increased and oxygen concentration reduced without burner modification or active control. Experiments were conducted using a premixed methane-air swirl burner at atmospheric pressure under three oxidizer conditions, and NOx emissions were evaluated as EINOx. Flame structure was analyzed using CH* chemiluminescence imaging with inverse Abel transform to estimate flame volume and residence time. Under constant fuel flow, nitrogen dilution reduced NOx by up to 45% in concentration and 26% in EINOx due to reduced oxygen concentration and lower adiabatic flame temperature. Overall, the results demonstrate the effectiveness of oxidizer composition control as a practical NOx reduction strategy.