Deliverables

It is well known that low reactivity of ammonia (NH₃) is enhanced when blended with hydrogen (H₂). This blending could affect the interactions between ammonia-based flames and walls. In the present study, the side-wall quenching (SWQ) of two-dimensional (2-D) premixed laminar ammonia/hydrogen/air flames is examined using detailed chemistry and the mixture-averaged transport model. Six test cases are designed to assess the SWQ characteristics of such flames by systematically varying the equivalence ratio from 0.6 to 1.2 and the blending ratio (molar ratio of hydrogen to ammonia/hydrogen in the mixture) from 0.35 to 0.45 under a fixed wall temperature of 500 K at atmospheric pressure. The results show that the quenching distance (maximum wall heat flux) decreases (increases) as the equivalence ratio and the blending ratio increase. In addition, the results indicate that, for the same fuel mixture, the ratio of the quenching Peclet number for the SWQ to the corresponding value for the head-on quenching (HOQ) is in the range of 1.2 to 1.35. The results reveal that the N₂ pathway is the dominant mechanism of NO formation near the wall at the quenching region. Within this pathway, R76 (NH₂ + NO ⇔ N₂ + H₂O) is the leading reaction converting NO to N₂. Furthermore, the significant role of R85 (NH + NO ⇔ N₂O + H) in converting NO to N₂O is highlighted near the wall. Moreover, the contribution of radical recombination reactions to the total heat release rate is highlighted near the wall, and their significant reactions are identified. These reactions get more prominent as the equivalence ratio and the blending ratio increase.