Experimental and modeling study on the oxidation of ammonia fuel blends at low-to-intermediate temperatures

Ammonia (NH3), as a suitable hydrogen energy carrier, has the potential to be directly used as a fuel in combustion facilities. However, the low reactivity of ammonia limits its application. Blending NH3 with fuel promoters like hydrogen (H2), methane (CH4), and methanol (CH3OH) or oxidizer promoters like ozone (O3) can be a promising solution. In the work of this thesis, the oxidation characteristics of NH3/promoters fuel blends were investigated in the intermediate-temperature range (700-1200 K). The effects of O3 addition were explored in the extreme-low-temperature range. A rapid compression machine (RCM) was used to measure the ignition delay times (IDT) of the NH3 blends at elevated pressures (20 bar and 40 bar). A jet-stirred reactor (JSR) coupled to molecular beam mass spectrometry (JSR-MBMS) was newly designed and developed. This research facility was used to measure the speciation in the oxidation of the NH3 fuel blends at atmospheric pressures. Blending with the three fuels, H2, CH4 and CH3OH, was proven effective for promoting NH3 autoignition in the RCM and NH3 consumption in the JSR. A reaction mechanism was constructed by combining several sub-mechanisms from the literature. The model provided a reasonable performance for predicting the results from JSR and RCM experiments. This mechanism can help to develop advanced NH3 combustion systems. The kinetic studies explained the performance of the mechanism and proposed further directions for improvement. The JSR experiments revealed that O3 addition could initiate NH3 reactions at temperatures below 450 K. However, adding O3 showed an inhibiting effect on NH3 consumption at temperatures above 900 K. These findings are valuable references for studying plasma-assisted NH3 combustion.