Detonation properties and nitrogen oxide production in ammonia-hydrogen-air mixtures

Ammonia is a promising compound for chemical storage of renewable energy produced from non -continuous sources. However, the low reactivity of ammonia requires to use ammonia-hydrogen blends as a fuel for combustion applications. The present study corresponds to a first numerical assessment of the potential of ammonia-hydrogen-air mixtures as reactive mixtures for detonation engine applications. Both ideal and curved detonation models were employed to calculate the detonation properties, entropy production, and NOx production for mixtures with varying amounts of ammonia and hydrogen under a wide range of initial thermodynamics conditions. Interestingly, our calculations show that the entropy production and the amount of nitrogen oxides produced at the Chapman-Jouguet state respectively decreases and increases with the proportion of hydrogen in the ammonia-hydrogen blend. These aspects could have a great impact on engine efficiency and air pollution and should be considered with care. Our results also demonstrate that only mixtures with relatively low amounts of ammonia, i.e., X NH3 lower than 0.25 of the fuel blend, can be employed for detonation engine applications.