Single ammonia droplet combustion in a high-pressure environment in microgravity

IF 5.3 2区 工程技术 Q2 ENERGY & FUELS Proceedings of the Combustion Institute Pub Date : 2024-09-02 DOI:10.1016/j.proci.2024.105503
Yuto Matsuura, Ayana Banno, Masato Mikami
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Abstract

Since ammonia is a carbon neutral fuel, it is expected to be widely utilized in the near future. Although there have been many researches on ammonia combustion, no research has been conducted on ammonia droplet combustion, which is a fundamental research on spray combustion, because ammonia is in a gaseous state at room temperature and atmospheric pressure. This study investigated the combustion characteristics of single ammonia droplets in microgravity for the first time. Single ammonia droplets were formed in high pressure air and were successfully ignited in microgravity. In an early stage of burning, the droplet vaporized with an almost constant vaporization rate of 0.87–1.0 mm/s. After such a quasi-steady period, the vaporization rate decreased over time. In accordance with the decrease in the vaporization rate, the flame standoff ratio also decreased over time. After that, the droplet exhibited unique phenomena such as droplet disruption, puffing, or droplet re-expansion although the fuel was initially pure. These types of unique behavior are caused by the diffusion of water vapor, a combustion product, to the droplet surface, and dissolution and accumulation of water on the droplet surface. Since water has a lower volatility than ammonia, the concentration of dissolved water at the droplet surface increases rapidly as the droplet diameter decreases. As a result, the vaporization of ammonia is suppressed and the flame standoff ratio decreases. Additionally, as the water concentration at the droplet surface increases, the boiling point at the droplet surface also increases, resulting in superheating of the liquid ammonia and homogeneous bubble nucleation. The growth of bubbles caused droplet disruption, puffing, and droplet re-expansion.
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微重力高压环境下的单氨液滴燃烧
由于氨是碳中性燃料,预计在不久的将来会得到广泛应用。虽然关于氨燃烧的研究很多,但由于氨在常温常压下呈气态,因此还没有关于氨滴燃烧的研究,而氨滴燃烧是喷雾燃烧的基础研究。本研究首次研究了单个氨滴在微重力环境下的燃烧特性。单个氨液滴在高压空气中形成,并在微重力环境下被成功点燃。在燃烧初期,液滴以 0.87-1.0 mm/s 的几乎恒定的汽化速率汽化。经过这样一个准稳定期后,汽化率随着时间的推移而下降。随着汽化速率的降低,火焰对峙比也随时间的推移而降低。此后,尽管燃料最初是纯净的,但液滴却出现了独特的现象,如液滴中断、膨化或液滴再膨胀。出现这些独特现象的原因是水蒸气(一种燃烧产物)扩散到液滴表面,以及水在液滴表面的溶解和积累。由于水的挥发性低于氨,液滴表面溶解水的浓度会随着液滴直径的减小而迅速增加。因此,氨的汽化受到抑制,火焰对峙比降低。此外,随着液滴表面水浓度的增加,液滴表面的沸点也随之升高,从而导致液氨过热和均匀气泡成核。气泡的增长导致液滴破坏、膨化和液滴再膨胀。
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来源期刊
Proceedings of the Combustion Institute
Proceedings of the Combustion Institute 工程技术-工程:化工
CiteScore
7.00
自引率
0.00%
发文量
420
审稿时长
3.0 months
期刊介绍: The Proceedings of the Combustion Institute contains forefront contributions in fundamentals and applications of combustion science. For more than 50 years, the Combustion Institute has served as the peak international society for dissemination of scientific and technical research in the combustion field. In addition to author submissions, the Proceedings of the Combustion Institute includes the Institute''s prestigious invited strategic and topical reviews that represent indispensable resources for emergent research in the field. All papers are subjected to rigorous peer review. Research papers and invited topical reviews; Reaction Kinetics; Soot, PAH, and other large molecules; Diagnostics; Laminar Flames; Turbulent Flames; Heterogeneous Combustion; Spray and Droplet Combustion; Detonations, Explosions & Supersonic Combustion; Fire Research; Stationary Combustion Systems; IC Engine and Gas Turbine Combustion; New Technology Concepts The electronic version of Proceedings of the Combustion Institute contains supplemental material such as reaction mechanisms, illustrating movies, and other data.
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