Microscopic insights into the ammonia-methanol blended combustion at high temperatures

Abstract

Ammonia and methanol have a broad application prospect in the future as green renewable liquid fuels. Methanol has high reactivity and good solubility with ammonia, which is conducive to solving the dilemma of ammonia combustion. However, there are few studies on ammonia-methanol blended combustion, and the effect of blended combustion on the reaction pathways needs to be further investigated. Therefore, this study used the reaction molecular dynamics simulations to reveal the role of methanol on the ammonia combustion and emission process at the microscopic level, focusing on the effects of different fuel blending ratios and oxygen concentration in the air under stoichiometric conditions. The variation of oxidation pathways from ammonia to NO and methanol to CO under different conditions was analyzed in detail. It was found that the methanol accelerated ammonia combustion mainly through enhancing OH production, but methanol and its intermediates inhibited the initial oxidation of ammonia. When the fuel blending ratio was 0.75, the system had lower fuel-type NO production alongside a higher ammonia consumption rate under stoichiometric conditions. The crucial role of NH in the HNO formation at high-temperature ammonia oxidation conditions was revealed. The pathway of HNO + OH → NO + H2O dominated the conversion of HNO to NO in this study. Increasing the methanol content promoted the conversion of NH to HNO and the pyrolysis of HNO while inhibiting the reaction between HNO and O2. In addition, the finding indicated that the high O2 level in air can enhance the reactions between ammonia and OH radicals but inhibit the pyrolysis of CH2OH/CH3O significantly.