Effects of methane addition on combustion characteristics of ammonia-air co-flow flames

Liang Mengqing, He Yituan, Wu Yuhao and Liao Shiyong

Energy, 2025, vol. 335, issue C

Abstract: The study on ammonia-light hydrocarbon blended fuels has garnered significant attention due to their low carbon benefits and relatively high burning velocity. However, new challenges have emerged regarding the balance between combustion efficiency and NOx emissions during combustion of blended fuels. This study elucidates the effects of methane blending on the combustion of ammonia-light hydrocarbon hybrid fuels. Results indicate that methane addition enhances air entrainment between the fuel and air streams. This enhancement stems from thermal expansion, which accelerates the flow and elongates the flame tips. Concurrently, delayed methane oxidation extends the reaction zone and elongates the flame roots toward the outlet. Methane shifts HNO formation upstream, accelerating early ammonia decomposition, while flame acceleration drives downstream migration of HNO peaks. Fuel conversion exhibits "slow-fast-slow" kinetics, with ammonia decomposition spatially preceding methane conversion. The delayed methane oxidation further extends the reaction zone, elongating the overall flame structure. Despite these changes, fuel-nitrogen remains the dominant sourse controller of total NO emissions in ammonia-containing flames at methane blending ratios below 40 %.

Keywords: Ammonia; Methane; Co-flow flame; Conversion rate; Nitric oxide kinetics (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:335:y:2025:i:c:s0360544225036497

DOI: 10.1016/j.energy.2025.138007

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