Abstract
This research investigates the impact of syngas, hydrogen-enriched syngas (H/C ratio), and nitrogen (N(2)) diluent on the combustion characteristics of NH(3)/air mixtures in a constant volume vessel. Pressure peak (p (max)), combustion duration time (t (c)), maximum rate of pressure rise (dp/dt)(max), and laminar burning velocity (S (L)) were obtained at an initial pressure p (0) = 3 bar, a temperature T = 300 K, and at various equivalence ratios ϕ = 0.8-1.3. The results indicate that increasing the syngas proportion and/or H/C ratio could enhance p (max), (dp/dt)(max), S (L), and shorten t (c). The reverse is true for the dilution of N(2) to the NH(3)/syngas mixtures. The maximum value of S (L) of NH(3)/syngas/air mixture is nearly at ϕ = 1.1 for all cases in which S (L) varies from 7.5 to 22 cm/s, increasing by 1.25 to 3.7-fold as compared to its values of NH(3) flame. Using Mei-Mech, the sensitive analysis shows the most dominant reactions for S (L) of the stoichiometric NH(3)/syngas/air mixtures, including (R1): H + O(2) = O + OH, (R15): H + O(2) (+M) = HO(2) (+M), (R76): NH(2) + NH = N(2)H(3), and (R94): NH(2) + NH = N(2)H(2) + H, where R1 and R15 exhibit the highest positive and negative sensitivity coefficients, respectively. Notably, in the case of H/C ratio effect, the net reaction rate of (R3): H(2) + OH = H(2)O + H significantly increases, whereas it is less or negligible for the remaining reactions.