Laminar flame speed and explosion characteristics of ammonia/dimethyl ether blends with hydrogen addition under elevated pressure

A growing interest is being paid to mixing ammonia (NH 3 ) with dimethyl ether (DME) as a potential alternative fuel , in which H 2 may be cracked from NH 3 in the mixture under specific conditions. In this study, the laminar flame speeds ( S L ) and explosion characteristics of NH 3 /DME blends (blend ratios of 40/60 and 20/80) with H 2 addition of 0 %–40 % at various initial pressures ( P u = 0.1–0.5 MPa) and equivalence ratios ( ϕ = 0.7–1.7) were investigated based on a constant-volume combustion approach. The results show that S L of NH 3 /DME blends increases with adding H 2 , while the elevated initial pressure presents a negative influence. The pressure power exponent β of NH 3 /DME blends with H 2 addition presents a similar non-monotonic behavior to that without H 2 addition as equivalence ratio increases. This is because both the main chain-reactions affecting S L and β of NH 3 /DME blends have a minor change with H 2 addition. Although H 2 addition does not change the tendency of β , it can increase the corresponding equivalence ratios of minimal β for fuel-rich. This can be explained through three key CH 3 consumption reactions. That is, H 2 addition enhances the inhibitory ability of CH 3 + H(+M) = CH 4 (+M) on S L of ϕ = 1.5 compared to that of ϕ = 1.0 and 1.4, and weakens the promotion effect of CH 3 + HO 2 CH 3 O + OH and CH 3 + OH CH 2 (S) + H 2 O on S L at ϕ = 1.5. Furthermore, due to the positive correlation between S L and explosion pressure and the negative correlation between S L and explosion time, adding H 2 can also improve the explosion intensities of NH 3 /DME blends. •H 2 addition can enhance the combustion/explosion intensities of NH 3 /DME blends. • β of NH 3 /DME/H 2 blends presents a non-monotonic trend as ϕ increases. • Main chain-reactions affecting S L and β have a minor change with H 2 addition. • H 2 addition rises the corresponding equivalence ratio of minimal β for fuel-rich. • The changes of β in rich fuel are related to three key CH 3 consumption reactions.