射流火焰微团特征反应时间

本文试图从非稳定射流火焰的燃烧噪声角度来研究火焰中的微团特性。定义火焰特征反应时间来反映火焰的化学反应动力学和火焰流场流动动力学特性。通过自相关系数测量火焰涡团的特征反应时间，结果表明：相同的燃气流量下，特征反应时间与射流速度成反比；特征反应时间随射流速度的变化斜率与燃气流量相关。     

层流预混气体多棱火焰燃烧现象的分析

在一定条件下,层流预混气体燃烧过程中可清晰地观察到多棱火焰现象。本文从燃料浓度、温度对燃烧速度、气流速度的影响出发,推导出了火焰面变化随空气消耗系数的关系式,并得出了形成多棱火焰现象的条件为:Kx<0。用该式判断的丁烷层流预混气体燃烧的多棱火焰区与实验结果基本吻合。     

湍流对多孔介质内预混火焰影响的初步研究

当气流速度较大时,多孔介质内预混燃烧的模拟需要考虑湍流的影响,本文利用简化的k-ε双方程湍流反应流模型对多孔介质内的预混火焰进行了数值模拟.结果表明,湍流大大加强了气流的组分和能世扩散,计算得到的火焰传播速度、CO及NO的排放量都与实验值符合得比较好,与层流模型相比,湍流模型能够改善计算结果.     

声激励下低旋流火焰动态响应特性研究

针对声激励下甲烷/空气预混低旋流火焰动态响应特性开展实验研究.声激励频率为55～295 Hz,相对幅值为0.1～0.3.采用光电倍增管记录火焰自发OH*荧光信号,采用双麦克风法测量入口气流速度脉动,采用高速相机捕获火焰结构动态响应过程.实验结果表明,小幅值激励下火焰时均结构变化不明显,大幅值低频激励下火焰长度明显增加,...     

双组分燃料的层流火焰速度模型

以往关于层流火焰速度的理论分析均只考虑单组分燃料,本文对双组分燃料的平面火焰进行了大活化能渐近理论分析。在理论分析中,将火焰结构分为预热区、化学反应区和平衡区,并在大活化能假设下对各个区域分别求解了关于温度与燃料质量分数的微分方程。根据每两个区域分界面上满足的结合条件,本文推导出了双组分燃料的层流火焰速度模型。该模型表明双组分燃料层流火焰速度的平方为各个单组分燃料层流火焰速度平方的加权平均。     

高压下湍流火焰速度测量与拟合

利用连续燃烧本生灯结合OH-PLIF火焰结构激光诊断技术获得了高压下预混湍流火焰瞬时前锋面图像,通过图像处理,得到了高压下多种混合气的湍流火焰速度及其拟合关系式。结果表明:高压预混湍流火焰前锋面为高度褶皱凹凸结构,现象上表现为大尺度的凸向未燃气的凸结构和小尺度的凸向已燃气的凹结构。合成气火焰比CH_4/air更加褶皱,前锋面更加精细。本文所有实验点高压湍流火焰速度可以拟合为S_T/S_L与[(P/P_0)(u′/S_L)]~n的形式,n约为0.4左右,表明湍流涡与火焰面的相互作用遵循自相似的规律。     

对冲火焰流场的二维分布对层流火焰传播速度测量的影响

在φ=0.6～0.75的条件下,利用PⅣ测得对冲火焰的二维速度场,分析使用偏移中心线一定距离提取的轴线速度分布曲线所得到的层流火焰传播速度SOL与沿中心线提取的速度分布曲线得到的SOL之间的误差大小.实验结果表明,在弱火焰时对冲火焰速度场具有明显的二维效应.φ=0.6,偏离中心轴线5 mm时,相对误差达到33%;而φ=...     

掺氢甲烷射流扩散火焰燃烧特性分析

采用数值计算与实验相结合的方法研究了掺氢甲烷射流扩散火焰的燃烧特性。结果表明，热量的传递主要是通过热气流对流进行，上游高温气流快速沿轴向流动，径向热量传递较弱；而下游轴向速度降低，热量径向传递增强。喷嘴附近伴流气边界较为稳定，而下游在涡旋作用下出现显著的扰动。射流速度对火焰特性有较大影响，增大射流速度后，火焰高度、辐射强度以及CO、NO、CO₂、H₂O浓度皆显著增加，且辐射强度峰值向下游移动。掺氢量对火焰特性也有重要影响，随着H₂含量增加，燃料向下游传播距离缩短，CO、NO、CO₂浓度降低，H₂O浓度增加。     

含氧有机物对碱金属火焰原子发射光谱发射强度的影响规律

火焰原子发射光谱法(FAES)常用于分析检测碱金属各元素。实验结果表明,当试样中含有在水中溶解度较大的含氧有机物时,会对碱金属元素的火焰原子发射辐射强度产生影响。不同种类,不同浓度的含氧有机物使碱金属元素的发射强度改变的幅度是不同的,影响规律也有很大差异。有机物同分异构体以及官能团数量上的差异也对碱金属元素的发射强度产生影响,其影响规律也不相同。     

湍流扩散火焰的非稳态火焰面模拟

采用稳态的和非稳态的火焰面模型同时对一个湍流甲烷射流扩散火焰进行了数值模拟,比较了两者对湍流平均火焰结构、活性自由基和污染物(氮氧化物)排放的模拟效果。速度场采用κ-ε模型计算,守恒标量混合物分数的分布通过其概率密度函数(PDF)输运方程的求解得到。稳态的火焰面结构由查询火焰面数据库得到,而非稳态的火焰面结构由火焰面方程和流场方程耦合求解来计算。采用详细的GRI—Mech 3.0机理描述甲烷的氧化和氮氧化物的形成。数值模拟结果和实验数据作了广泛的对比,验证了火焰面模型对湍流扩散燃烧的定量模拟能力。     

火焰特征发射谱线研究

本文利用CCD光纤光谱仪,通过实验确定了木基燃料燃烧火焰光谱中出现的特征谱线是K,Na 的原子发射谱线,测定了特征谱线出现时的火焰温度,指出可以通过特征谱线的出现与否来确定火焰的温度范围。还发现火焰的光谱形状和火焰的燃烧状态密切相关,包含大量和燃烧有关的信息,并且对煤烟颗粒有较强的抗干扰性。通过对火焰光谱形状的分析可判断出火焰的燃烧状况,进行燃烧诊断。     

小火焰模型在贫燃预混火焰中的研究

由层流小火焰库引入详细化学反应机理,通过简化的PDF方法计算组分浓度、平均温度和密度等变量,以钝体火焰稳定燃烧室和某燃气轮机上的燃烧室为例,模拟甲烷/空气贫燃条件下预混燃烧的平均火焰位置和火焰厚度,计算结果与实验结果吻合良好,这表明此方法能够较好计算出平均湍流火焰的主要特征。     

微重力下环境压力对火焰传播的影响

研究表明,在微重力环境中,当强制对流速度很小时,环境压力的增大会加强氧气的扩散,减弱辐射热损失对火焰的冷却效应,使火焰传播速度增大。但随着强制对流速度的增大,对流成为质量传递的主要途径,化学反应速率受化学反应动力学因素控制,火焰传播速度对压力的变化不敏感。     

直喷柴油机火焰浮起长度的数值模拟研究

采用三维CFD模型模拟了直喷柴油机缸内喷雾燃烧过程,模拟缸压曲线得到了实验的验证.通过高温区与喷嘴之间的稳定距离来确定柴油机火焰浮起长度,研究在不同进气条件下火焰浮起长度的变化情况.该模型成功地预测了火焰浮起长度随着初始进气压力的增大而减少,随着进气温度的升高出现先增大后减少的趋势.同时模拟了在不同EGR率下柴油机缸内燃烧情况,发现火焰浮起长度和燃料着火延迟时间都随EGR率的增加而增大.     

Stabilization of a premixed CH4/O2/N2 flame using femtosecond laser-induced plasma

The influence of femtosecond laser-induced plasma (FLIP) on the stability of a premixed CH(4)/O(2)/N(2) flame is investigated at atmospheric pressure. The laser energy, laser repetition rate, the equivalence ratios, and the volume percentage of oxygen in O(2)/N(2) blends are varied. Our findings indicate that the flame blow-off velocity is a function of these parameters. It has been experimentally found that the flame blow-off velocity increases by a factor of two with FLIP than without FLIP. A high-repetition-rate and a great energy laser-induced plasma flameholding, as a non-intrusive optical flameholding, may be a feasible alternative for any combustor.     

Investigation of Impurity Ion Transport with Laser Blow-off in HL-2A Tokamak

Transient perturbation methods are most appropriate to study particle transport in tokamaks. Two most commonly used techniques of impurity injection are laser blow-off and gas puffing. The laser blow-off injection technique is undoubtedly the best one to study impurity transport because the injection time and the alnount of injected material can be controlled in a certain phase of the discharge with a minimum perturbation of the plasma parameters. The information of the impurity transport is obtained from the detection of emission of injected impurity ions located in different spatial regions. The radiation includes line emission, soft X-ray emission and plasma global radiation.     

Ultra-lean hydrogen-enriched oscillating flames behind a heat conducting bluff-body: Anomalous and normal blow–off

This paper presents a numerical study of ultra-lean hydrogen-methane flames stabilized behind a rectangular, highly conducting metallic bluff body acting as a flame holder. Using high fidelity numerical simulations, we show that lean inverted steady flames exist below normal flammability limits. They have distinct stabilization mechanism from pure methane flames. These flames are blown-off for sufficiently small velocities, a phenomenon called anomalous blow-off. At even leaner conditions oscillating ultra–lean hydrogen-methane flames can be established. These oscillating flames exist within a rather small range of equivalence ratios and inflow velocities, and move to mean locations closer to the flame holder as the reactant flow is increased. We show that the oscillations are associated with the shedding of flame balls from the downstream end of a “residual flame” that remains attached. Unlike their steady counterparts, the oscillating flames exhibit blow-off at both low velocities (anomalous blow-off) and at sufficiently high inflow velocities (normal blow-off). We show that normal blow-off is linked to heat losses to the flame holder.     

Injector spacing influences on flame blow-off in a linear array

Lean premixed flame stabilization at atmospheric conditions, in a linear array of five swirl injectors, was modeled using well-resolved large eddy simulation (LES) and chemical kinetics that were accurate both for ignition and flame speed. The effects of injector spacing were studied by selectively blocking injectors in the array to obtain five (F), two (T) and single (S) injector configurations. Each of these was simulated at well-anchored as well as near blow-off conditions. Experiments indicated a blow-off trend that was non-monotonic with spacing: the two-injector configuration exhibited the greatest resistance to blow-off, followed by the single-injector setup. The five-injector configuration proved to be the least resistant (by far) in comparison. In an earlier computational study [1], preferential blow-off in configuration F was successfully modeled and strong flame-flame interference could be investigated. This work is continued to assess the ability of a numerical model to study flames near blow-off, but with varying levels of flame-flame interaction. Passive scalar tracking was used to relate cross-injector transport of material to a given injector’s flame-holding ability. The non-monotonic blow-off trend could not be explained by stretch and heat release rate trends, but well-stirred reactor (WSR) theory was found to be more relevant as trends in recirculation zone residence times correlate well with blow-off sequences. In addition, cross-injector transport was studied due to the multi-injector scenario to assess how flameholding zones may be diluted. This work is expected to be useful for analyzing part-load behavior in multi-injector power-generating gas turbine combustion systems, and helps to characterize injector performance towards extending the range of lean operability.     

原子吸收和发射法测定重质油中钠含量

在乙炔－空气火焰中，用吸收和发射测定原油，渣油等重质油品中的钠含量，认为用发射法既可节省元素灯，又能提高测量精度。吸收和发射法的特征浓度分别为：０．０１５ｍｇ／Ｌ和０．００９ｍｇ／Ｌ。     

一种求解逆风下火焰沿柱状燃料传播的数值方法

1引言近十几年来，国内外许多人对火焰沿薄燃料层的传播进行了研究，但很少涉及到火焰沿柱状燃料的传播。图1为所研究问题的物理模型。火焰的传播涉及到气固两相的相互作用，两相界面上存在能量和质量的交换，气相中存在着气气间的化学反应，固相中存在着裂解反应。当参考坐标系团结在火焰前锋上时，该火焰传播问题成为一准稳态问题，燃料以一固定速度供给火焰。2数学模型2．1守恒方程气相的所有守恒方程均服从下列通用方程：其中、，L和一分别表示通用变量、广义扩散系数和广义源项。固相包括：质量守恒方程：。。能量守恒方程：2．2边界…