Experimental and Numerical Study on the Effects of N2and NH3in 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 NH3as 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 N2and NH3content, respectively, results in a decrease in the SLof the mixture. At Φ = 1.0, as the N2content increases from 0 to 60%, the SLof the mixture decreases from 80.1 to 28.3 cm/s. The SLdecreases from 80.1 to 36.4 cm/s as the NH3content increases from 25 to 50%. The increase in N2content 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/cm3s) at ZN2= 0% at Φ = 1.0. As NH3content increases, the impact of chain reactions associated with the NH3reaction mechanism on the combustion process becomes more pronounced. With the increase in NH3content, 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 N2reduces NH3consumption, which in turn reduces NO generation. The increase in NH3content promotes the conversion of N2O to N2, simultaneously reducing NO emissions.