OH* Chemiluminescence in Non-premixed Industrial Natural Gas/hydrogen Flames under Air-fuel and Oxy-fuel Conditions: Kinetic Modeling and Experimental Validation

The application of OH* chemiluminescence diagnostics is becoming increasingly prevalent in the combustion characterization of hydrogen. As the current literature is lacking a systematic study of OH* chemiluminescence in non-premixed turbulent natural gas (NG) and hydrogen (H2 ) flames, the present work was designed to address this research gap. Therefore, extensive experiments were performed on a semi-industrial burner operating at 50–100 kW in NG/H2–Air/O2 combustion modes, which were complemented by comprehensive numerical simulations, including 1D laminar counterflow diffusion flamelet calculations and full 3D CFD simulations of the semi-industrial furnace setup. In this way, an OH* chemistry model is presented that accurately predicts the global reaction zone characteristics and their difference between CH4 and H2 in air-fired and oxygen-fired flames. The comprehensive numerical approach, in conjunction with the subsequent study of different operating conditions, yielded novel insights into both combustion modeling and the underlying thermochemical phenomena, providing an essential contribution to the transition of the thermal energy sector towards hydrogen as an alternative carbon-free fuel.