甲烷/氧气层流同轴射流扩散火焰OH~*自由基的数值研究  

Numerical Study on OH~* Radicals in the Laminar Methane/Oxygen Co-Flowing Jet Diffusion Flame

作　　者：何磊[1] 龚岩[1] 郭庆华[1] 胡翀赫 于广锁[1] HE Lei;GONG Yan;GUO Qing-hua;HU Chong-he;YU Guang-suo(Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education,East China University of Science and Technology,Shanghai　200237,China)

机构地区：[1]华东理工大学煤气化及能源化工教育部重点实验室,上海200237

出　　处：《光谱学与光谱分析》2018年第3期685-691,共7页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(21676091;51406056);中央高校基本科研业务费专项资金项目(222201514336);上海市浦江人才计划(15PJD011)资助

摘　　要：OH~*自由基是火焰中主要的激发态自由基之一,它所产生的化学发光可用于描述火焰的结构、拉伸率、氧燃当量比和热释放速率等特征信息,因此被广泛应用于火焰燃烧状态的在线诊断。以甲烷/氧气层流同轴射流扩散火焰作为研究对象,采用GRI-Mech 3.0机理结合OH~*自由基生成和淬灭反应进行数值计算,对OH~*自由基的二维分布特性进行研究,分析不同区域内OH~*自由基的生成路径,并探讨不同氧燃当量比例和不同喷嘴出口尺寸对OH~*自由基强度和分布特性的影响。模拟结果与实验研究基本吻合,表明计算模型能够准确描述火焰中OH~*自由基的二维分布。结果表明:在甲烷/氧气层流同轴射流扩散火焰中,OH~*自由基存在两种不同形态的分布区域,分别由反应CH+O_2=OH~*+CO和H+O+M=OH~*+M生成;随着氧燃当量比提高,OH~*自由基的分布区域逐渐向火焰下游扩张,根据其分布形态的变化可以对火焰燃烧状况进行判断;如果OH~*自由基仅分布于火焰的上游区域且呈断开形态,则说明火焰处于贫氧燃烧状态。如果OH~*分布呈环状形态,则说明火焰处于富氧燃烧状态;相同氧气流量条件下,缩小喷嘴出口的环隙尺寸有助于加强燃料和氧气的化学反应程度,从而使火焰中OH~*自由基的摩尔分数显著提高,增强OH~*化学发光的辐射强度,提高火焰光谱诊断的准确性。OH*is one of the major excited radicals in flame.The chemiluminescence infor mation is generally applied in combustion diagnostics to indicate the flame stru cture,strain rate,equivalence ratio,heat release rate,etc.In this pape r,the numerical study on OH*radicals was conducted in the laminar methane/o xygen co-flowing jet diffusion flames.The detailed GRI 3.0 mechanism combine d with OH*radicals reaction mechanism was used in the numerical model.Based on the two-dimensional OH*distributions,the pathways of OH*formation in different area were analyzed.The effects of oxygen-fuel equivalence ratio an d coaxial nozzle structure on OH*intensity and distribution were also discuss ed.The simulation results were consistent with the experiment results,indica ting that the numerical model can effectively describe the two-dimensional OH*distributions.The results show that there are two different types of OH*d istribution areas,and the OH*radicals in these two areas are formed respect ively through the reactions CH+O 2=OH*+CO and H+O+M=OH*+M.The flame struc ture can be indicated according to the distribution area of OH*radicals.With increasing the oxygen-fuel equivalence ratio,the distribution area of OH*radicals gradually expands to the downstream of flame.The distinctions of OH*distribution can be used to characterize the combustion condition.If OH*ra dicals only distribute over the upstream of the flame and appear discrete in sha pe,the flame is under the oxygen-deficient combustion.If OH*radicals dis tribution appears as a ring shape,the flame is under the oxygen-enriched comb ustion.Under the same oxygen flow rate,the size of annular channel has a sig nificant impact on the mole fraction of OH*.Reducing the size of annular cha nnel can enhance the mixture of fuel and oxygen as well as improve the radiation intensity of the OH*chemiluminescence,which makes the flame diagnosis more convenient.

关 键 词：甲烷 扩散火焰 OH*自由基 数值模拟 

分 类 号：O433.5[机械工程—光学工程]