刘祥涛,王国昌,司济沧,李鹏飞,米建春
LIU Xiangtao,WANG Guochang,SI Jicang,LI Pengfei,MI Jianchun

• 1:北京大学工学院
• 2:太原理工大学省部共建煤基能源清洁高效利用国家重点实验室
• 3:大连海事大学轮机工程学院
• 4:华中科技大学能源与动力工程学院

摘要(Abstract)：

化石能源的利用推动了人类社会的进步，但也造成了全球气候变化，威胁人类的生存与发展。在此背景下，氨和氢作为零碳燃料引起了人们的重视，但其燃烧利用面临诸多问题。MILD燃烧是一种新型燃烧方式，有望实现氨/氢混合燃料的清洁高效燃烧，但目前研究非常有限。采用数值模拟方法对预混NH_3/H_2射流火焰的MILD燃烧和排放特性进行研究。改变了射流中的氢气比例(X(H_2)_F)和当量比(Φ_J),并详细分析了温升、反应域、抬升高度、自由基浓度以及氮氧化物(NO_x)排放等。结果表明，添加少量H_2可显著增强NH_3火焰的稳定性，降低自着火温度并消除火焰抬升。此外，X(H_2)_F的增加能提高燃烧温度，加快H、O和OH自由基的产生，并使燃烧模式由MILD燃烧转变为高温燃烧。富燃料且氢气比例较低时，NH_3在燃烧前大量分解为H_2,导致燃烧温度较高。关于NO_x排放，N_2O和NO是最主要来源，NO_2可忽略不计。整体上，N_2O和NO的排放随X(H_2)_F的增加先升高再降低。当X(H_2)_F较低时，N_2O的浓度峰值与排放量和NO相当。提高X(H_2)_F,温度升高，导致N_2O转化为NO和N_2,因此NO变为主要的NO_x排放源。此外，富燃工况中，燃烧温度、OH浓度及射流对伴流中氧气的卷吸共同影响NO排放。
The utilization of fossil fuels has propelled the advancement of human society; however, it has also caused global climate change, posing a threat to the survival and development of humanity. In this context, ammonia and hydrogen, as zero-carbon fuels, have attracted much attention. However, their combustion utilization faces numerous challenges. MILD combustion is a new combustion technology that may achieve clean and efficient combustion of NH_3/H_2 blended fuel, but research in this area is currently very limited. The combustion and emission characteristics of a premixed NH_3/H_2 jet flame was thoroughly investigated by numerical simulation. Specially, the hydrogen proportion(X(H_2)_F) and jet equivalence ratio(Φ_J) were varied, and a detailed analysis on temperature rise, reaction zone size, lift-off height, radical concentrations, and NO_x emissions was conducted. Results indicate that the addition of a small amount of H_2 significantly enhances the stability of ammonia flame, lowers the auto-ignition temperature, and eliminates flame lift phenomenon. Moreover, an increase in X(H_2)_F elevates the combustion temperature, accelerates the production of H,O, and OH radicals, thereby leading to a transition in the combustion regime from MILD to high-temperature combustion. Under fuel-rich conditions and low X(H_2)_F, significant amounts of NH_3 decompose into H_2 prior to main combustion reactions, resulting in high combustion temperatures. As for NO_x emissions, N_2O and NO are the dominant sources, while NO_2 is negligible. Generally, the emissions of N_2O and NO first increase and then decrease with increasing X_(H2, F). Moreover, when X(H_2)_F is low, the peak concentrations and emissions of N_2O and NO are comparable. However, as X(H_2)_F increases, the temperature rises, leading to the decomposition of N_2O, with NO becoming the primary source of NO_x emissions. Furthermore, under fuel-rich conditions, the combustion temperature, OH concentration, and the entrainment of jet to the coflow O_2 collectively influence the NO_x emission.

关键词(KeyWords)： 氨/氢混合燃料;MILD燃烧;当量比;燃烧特性;NO_x排放
NH_3/H_2 blended fuel;MILD combustion;equivalence ratio;combustion characteristics;NO_x emissions

Abstract:

Keywords:

基金项目(Foundation): 国家自然科学基金资助项目(52206145,52076095)

作者(Author): 刘祥涛,王国昌,司济沧,李鹏飞,米建春
LIU Xiangtao,WANG Guochang,SI Jicang,LI Pengfei,MI Jianchun

DOI: 10.13226/j.issn.1006-6772.LC24020901

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