Lower flammability limits of NH3/H2 mixtures under different initial temperatures and initial pressures.

• LFLs of NH 3 , H 2 and NH 3 /H 2 are investigated under different conditions. • Prediction models of NH 3 , H 2 and NH 3 /H 2 mixtures LFL are established. • OH radicals in elementary reactions are crucial to the effect of LFL. In this paper, the lower flammability limits (LFLs) of NH 3 /H 2 mixtures under different initial pressures (50–250 kPa) and initial temperatures (20–100 °C) are experimentally and numerically investigated. The LFLs of ammonia and hydrogen are reduced by the increase of the initial temperature, and the reduction of ammonia LFL is greater than that of hydrogen. An increase in initial pressure decreases the LFL of ammonia but increases the LFL of hydrogen. The LFL of the NH 3 /H 2 mixture is reduced by the increase of H 2 , which is consistent with Le Chatelier's Law. When H 2 reaches 10%, the LFL trend of the mixture with the initial temperature and initial pressure is similar to that of hydrogen. The LFL prediction models of NH 3 , H 2 and NH 3 /H 2 mixtures under different initial temperatures and initial pressures are established. The changes of OH radicals in elementary reactions are crucial to the effect of LFL. Except for H + O 2 = O + OH and 2OH = O + H 2 O, the main OH ROP of NH 3 is NO 2 + H = NO + OH, NH 2 + OH = NH + H 2 O and NH 3 + OH = NH 2 + H 2 O, while the main OH of H 2 ROP is OH + H 2 = H + H 2 O, which may be the reason why the LFLs of NH 3 and H 2 are different. [ABSTRACT FROM AUTHOR]