Experimental and Numerical Study on the Effects of N2 and NH3 in NH3/Syngas/Air Laminar Premixed Flame

Blending syngas with ammonia (NH3) effectively overcomes the high minimum ignition energy and low laminar burning velocity (SL) of NH3, facilitating the realistic application of NH3 as a fuel for gas turbines. Thus, the present study combines experiments and numerical simulations to investigate the impacts of diluent N2 (0–60%) and NH3 (25–50%) on NH3/syngas/air flames. The analysis suggests that increasing N2 and NH3 content, respectively, results in a decrease in the SL of the mixture. At Φ = 1.0, as the N2 content increases from 0 to 60%, the SL of the mixture decreases from 80.1 to 28.3 cm/s. The SL decreases from 80.1 to 36.4 cm/s as the NH3 content increases from 25 to 50%. The increase in N2 content decreases the maximum mole fractions of H, OH, and O radicals, and the net reaction rates of chain reactions also decrease. The net reaction rate of H + O2 = O + OH at ZN2 = 60% decreases by 85.8% compared to 0.018 (mol/cm3 s) at ZN2 = 0% at Φ = 1.0. As NH3 content increases, the impact of chain reactions associated with the NH3 reaction mechanism on the combustion process becomes more pronounced. With the increase in NH3 content, the ratio of chemical effect to physical effect initially increases and then decreases, reaching a maximum value of 25.4% around ZNH3 = 30%. This value is much less than 1, indicating an overall inhibitory effect. The analysis of reaction pathways and NO emissions suggests that the presence of N2 reduces NH3 consumption, which in turn reduces NO generation. The increase in NH3 content promotes the conversion of N2O to N2, simultaneously reducing NO emissions.