NH_(3)/H_(2)掺混MILD燃烧及NO_(x)排放特性的数值模拟  

Numerical study on the combustion and emission characteristics of premixed NH_(3)/H_(2)jet flame

作　　者：刘祥涛 王国昌 司济沧 李鹏飞 米建春[1] LIU Xiangtao;WANG Guochang;SI Jicang;LI Pengfei;MI Jianchun(College of Engineering,Peking University,Beijing 100871,China;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology,Taiyuan 030024,China;Marine Engineering College,Dalian Maritime University,Dalian 116026,China;School of Energy and Power Engineering,Huazhong University of Science and Technology,Wuhan 430074,China)

机构地区：[1]北京大学工学院,北京100871 [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,太原030024 [3]大连海事大学轮机工程学院,大连116026 [4]华中科技大学能源与动力工程学院,武汉430074

出　　处：《洁净煤技术》2024年第8期107-116,共10页Clean Coal Technology

基　　金：国家自然科学基金资助项目(52206145,52076095)。

摘　　要：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_(2)O和NO是最主要来源,NO_(2)可忽略不计。整体上,N_(2)O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_(2)O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_(2)O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_(2)O and NO are the dominant sources,while NO_(2) is negligible.Generally,the emissions of N_(2)O and NO first increase and then decrease with increasing X H_(2),F.Moreover,when X(H_(2))_(F) is low,the peak concentrations and emissions of N_(2)O and NO are comparable.However,as X(H_(2))_(F) increases,the temperature rises,leading to the decomposition of N_(2)O,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 influe

关 键 词：氨/氢混合燃料 MILD燃烧 当量比 燃烧特性 NO_(x)排放 

分 类 号：TK16[动力工程及工程热物理—热能工程]