NH2* Chemiluminescence in Premixed NH3/H2/N2-Air Flames

Ammonia (NH3) is a promising fuel source for future gas turbines as it produces zero carbon dioxide (CO2) emissions. However, pure NH3 has low chemical reactivity, increased NOx emissions, and unstable combustion. Given these drawbacks, premixed NH3, hydrogen (H2), and nitrogen (N2) blends, which produce combustion properties similar to methane (CH4), can be used. Before the widespread use of NH3 blends for transportation or power generation, experimental data are needed to validate combustion models. The present work focuses on a fuel blend comprised of 40% NH3, 45% H2, and 15% N2 by volume, which can be obtained from the partial cracking of NH3. Amino radical (NH2) diagnostics can provide information on NOx consumption and flame propagation. In this work, NH2* chemiluminescence was detected in NH3/H2/N2-air flames stabilized on a premixed Bunsen jet burner mounted on a McKenna flat-flame burner acting as a pilot flame. NH2* chemiluminescence was also detected in a fuel blend of NH3/H2/N2 mixed with different O2/N2 concentrations in a Bunsen jet burner without a pilot flame. The O2-enriched flames showed a positive correlation between NH2* and O2 concentration. Experimental data as a function of Φ was compared to Cantera 0D simulations of NH2 concentrations. NH2* signals were also recorded at various heights at Φ=1.2 and varying O2/N2 concentrations, and the signal increased from 0 mm to 4 mm but decreased above 4 mm. The NH2* measurements presented here give insight into NH2 production in various flame environments to provide experimental data for validating NH3 combustion models.