Study on flame stability in oxygen-enriched ammonia/N₂/O₂ laminar diffusion flame

Abstract

Ammonia is regarded as one of the alternative fuels because CO 2 is not emitted during the combustion process of ammonia. The physical properties of ammonia are suitable for transportation and storage as a "hydrogen carrier". Also, a large amount of ammonia can be easily produced through the Haber-Bosch process with low price. To use ammonia as a fuel, it is necessary to understand the fundamental combustion characteristics of ammonia. Flammability of ammonia coaxial jet diffusion flame is important to know for developing the industrial furnace. Ammonia laminar diffusion flame is difficult to be stable under atmospheric oxidizer (O 2 21%) of room temperature. In this study, therefore, the oxygen-enriched combustion is applied to make the stable ammonia laminar diffusion flame. In this study, effects of the fuel velocity and the oxidizer velocity on the ammonia laminar diffusion flame are investigated in detail under the conditions of O 2 volume fraction of 24% and 25% at the burner rim thickness of 6.0 mm. Results showed that there were three regions with different extinction mechanism of the ammonia coaxial jet diffusion flame under the relatively higher fuel velocity. Particularly, the flame extinction also occurred under the low fuel velocity under the condition of O 2 volume fraction of 24%.Keywords : Renewable energy, Ammonia fuel, Alternative fuel, Carbon free fuel, Oxygen-enriched combustion, Flame stabilization 1. 緒 言 and Dincer, 2008, Takizawa et al., 2008, Ronny, 1988, Kumar and Meyer, 2013, Duynslaegher et al., 2009, Duynslaegher et al., 2010, Pfahl et al., 2000, Li et al., 2014, Hayakawa et al., 2015a, Hayakawa et al., 2015b, Ichikawa et al., 2015, 武石他, 2015, 武石他, 2016, 小林, 早川, 2016, 小池他, 2016, 武石他, 2017 Duynslaegher, C., Jeanmart, H. and Vandooren, J., Flame structure studies of premixed ammonia/hydrogen/oxygen/argon flames: experimental and numerical investigation, 近年，欧米をはじめとする諸外国を中心にアンモニアを代替燃料とするための研究が行われている(Zamfirescu