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

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Ammonia (NH3) is a promising hydrogen energy carrier that can be used as a fuel in combustion facilities, though its low reactivity poses challenges. To enhance its application, blending NH3 with fuel promoters like hydrogen (H2), methane (CH4), and methanol (CH3OH), or oxidizer promoters such as ozone (O3) is explored. This research investigates the oxidation characteristics of NH3/promoter blends within the intermediate-temperature range of 700-1200 K, while also examining O3 effects at extremely low temperatures. A rapid compression machine (RCM) measured ignition delay times (IDT) of the blends at high pressures (20 and 40 bar). A newly designed jet-stirred reactor (JSR) coupled with molecular beam mass spectrometry (JSR-MBMS) assessed the speciation of NH3 fuel blends at atmospheric pressure. Results confirmed that blending with H2, CH4, and CH3OH effectively promotes NH3 autoignition in the RCM and its consumption in the JSR. A reaction mechanism was developed from various literature sub-mechanisms, accurately predicting experimental outcomes. Kinetic studies provided insights for further refinement. Notably, JSR experiments indicated that O3 could initiate NH3 reactions below 450 K but inhibited NH3 consumption above 900 K. These findings offer valuable insights for advancing plasma-assisted NH3 combustion research.