Experimental and kinetic modeling study of laminar burning velocities of NH3/air, NH3/H2/air, NH3/CO/air and NH3/CH4/air premixed flames

Ammonia (NH3) is a promising energy carrier to store and transport renewable hydrogen (H2) that can be generated using, e.g., wind and solar energy. Direct combustion of NH3 is one of the possible methods to utilize the energy by the end users. To understand the combustion characteristics of NH3 as a fuel, the laminar burning velocities of NH3/air, NH3/H2/air, NH3/CO/air and NH3/CH4/air premixed flames were investigated experimentally using the heat flux method. Measurements are reported for a wide range of equivalence ratios and blending ratios. Kinetic modeling was also performed using available chemical kinetic mechanisms, namely the GRI-Mech 3.0, the Okafor et al. and the San Diego mechanisms. The experimental results for NH3/air flames agree well with the literature data and it is found that blending NH3 with H2 is the most effective manner to increase the burning velocity of NH3 based fuel mixtures. None of the kinetic mechanisms used can accurately predict most of the measured data. Sensitivity and reaction path analyses indicate that the oxidation of NH3 blended with the additive fuels considered can be understood as the parallel oxidation processes of the individual fuels, and that the source of discrepancy between the experimental and modeling results is related to the inaccuracy of the rate parameters of the N-containing reactions. In this regard, the present detailed and reliable experimental data is of special value for model development and validation.