摘要
发动机内的湍流射流推举火焰具有部分预混燃烧的特征,并且伴随着与冷焰的强耦合作用,因此对其开展基础研究具有重要的理论与应用价值。基于高压热伴流条件下二甲醚(dimethyl ether,DME)湍流狭缝射流燃烧过程的直接数值模拟结果,采用化学爆炸模式分析(chemical explosive mode analysis,CEMA)方法,研究了推举高度内的冷焰结构与反应动力学特性、冷焰与湍流的相互作用,以及它对推举稳定性的影响。结果表明:冷焰反应主要发生在富燃当量比的范围内,冷焰的自着火过程由参与燃料裂解反应的大分子碳氢组分所控制,而热焰的自着火过程由小分子氧化放热反应所控制。CEMA分析表明,火焰不同区域内具有不同的火焰结构、燃烧模式、以及主导组分与基元反应。DME推举火焰的稳定性由稳定点上游贫燃侧窄带区内由链分支反应所引起的自着火过程所控制。尽管湍流拉伸作用会抑制冷焰反应,但是由冷焰反应所产生的低温组分,对于诱导高温着火、形成推举稳定点具有重要作用。
Study on the turbulent lifted jet flame in cylinder is of theoretical and practical significances,since it features with the characteristics of partially-premixed combustion with strong coupling with the cool-flame chemistry.In this paper,the chemical explosive mode analysis(CEMA)method was applied to the DNS database of an elevated-pressure dimethyl ether(DME)turbulent lifted jet flame in hot co-flow,to investigate the cool-flame structure and chemical kinetics within the lift-off length,turbulence/cool flame interaction,as well as its impact on the lift-off stability mechanism.The results show that cool-flame chemistry happened in the fuel-rich zone.Cool-flame ignition was controlled by the fuel cracking reactions involving large hydrocarbons,while the hot-flame ignition by heat production reactions involving small molecules.The CEMA analysis reveals the distinct flame structure,combustion mode,and dominant species and elementary reactions in different subzones.The lift-off stability was controlled by auto-ignition due to the chain branching reactions in the fuel-lean banding zone upstream of the lift-off stability point.Although the cool-flame chemistry was depressed by turbulence,it produced some low-temperature intermediates which played an important role in inducing the high-temperature ignition reactions and thus the lift-off stability mechanism.
作者
亢银虎
张弋
张朋远
卢啸风
KANG Yinhu;ZHANG Yi;ZHANG Pengyuan;LU Xiaofeng(Chongqing University,Shapingba Distinct,Chongqing 400044,China)
出处
《中国电机工程学报》
EI
CSCD
北大核心
2020年第7期2306-2317,共12页
Proceedings of the CSEE
基金
国家自然科学基金项目(51706027)
重庆市自然科学基金项目(cstc2019jcyj-msxmX0584)。
关键词
冷焰
湍流火焰
化学爆炸模式分析
稳定性
cool flame
turbulent flame
chemical explosive mode analysis
stability
