On Explosion Limits of Ammonia–Oxygen Mixtures with Hydrogen Addition: Sensitivity and Nonmonotonicity
Cheng Zhou, Wenkai Liang, Zheng Chen
Abstract
We investigate numerically the ammonia–hydrogen–oxygen explosion limits, showing that the addition of a trace amount of hydrogen to ammonia–oxygen mixtures can qualitatively modify the explosion limits from the monotonic case to the nonmonotonic case, with multiple turning points including being Z-shaped which is characteristic of hydrogen–oxygen explosions. Furthermore, as the hydrogen concentration increases, (1) the first limit moves toward lower temperature conditions; (2) the second limit also shifts toward lower temperature conditions when the hydrogen addition is less than 10% of the ammonia–hydrogen fuel, but it moves in the opposite direction with higher additions; and (3) the third limit is minimally affected. Sensitivity analysis shows that at different pressures, the dominant reactions change with hydrogen addition. The present results facilitate understanding of the kinetic interaction between hydrogen and ammonia and are of practical relevance to the safe handling of ammonia–hydrogen fuels.