Impact of K-H Instability on NO x Emissions in N 2 O Thermal Decomposition Using Premixed CH 4 Co-Flow Flames and Electric Furnace

This study systematically investigates the formation of NO x in the thermal decomposition of N 2 O, focusing on the impact of Kelvin–Helmholtz (K-H) instability in combustion environments. Using premixed CH 4 co-flow flames and an electric furnace as distinct heat sources, we explored NO x emission dynamics under varying conditions, including reaction temperature, residence time, and N 2 O dilution rates ( X N2O ). Our findings demonstrate that diluting N 2 O around a premixed flame increases flame length and decreases flame propagation velocity, inducing K-H instability. This instability was quantitatively characterized using Richardson and Strouhal numbers, highlighting N 2 O’s role in augmenting oxygen supply within the flame and significantly altering flame dynamics. The study reveals that higher X N2O consistently led to increased NO formation independently of nozzle exit velocity ( u jet ) or co-flow rate, emphasizing the influence of N 2 O concentration on NO production. In scenarios without K-H instability, particularly at lower u jet , an exponential rise in NO 2 formation rates was observed, due to the reduced residence time of N 2 O near the flame surface, limiting pyrolysis effectiveness. Conversely, at higher u jet where K-H instability occurs, the formation rate of NO 2 drastically decreased. This suggests that K-H instability is crucial in optimizing N 2 O decomposition for minimal NO x production.