变氧量工况下煤粉炉内辐射能检测特性

针对某台300 Mw双炉膛电站燃煤锅炉,利用安装在炉本体上的多个CCD火焰探头实时拍摄火焰图像,通过计算机图像处理技术得到反映炉内燃烧工况的辐射能检测值,同时在300 MW和250 MW两个稳定负荷变氧量工况下进行炉内辐射能特性检测实验.实验结果表明,辐射能与氧量信号之间存在着良好的负相关性,低负荷下负相关系数的绝对值高达0.9以上;辐射能信号超前氧量信号的变化,超前时间为30～40 s.     

三岔火焰及分层火焰的直接数值模拟分析

采用甲烷-空气详细反应机理对4种部分超出可燃极限的层流火焰状态开展了直接数值模拟,包括"焰后支持"和"焰前支持"两种布局的分层火焰和两种不同当量比分布的三岔火焰,并对火焰结构进行了分析.将计算域内各网格单元的热力学状态投影到二维化学反应-扩散流形(REDIM)表格中,发现N_2和CO_2的散点图分布都位于同一个二维REDIM表格中,表明该二维REDIM表格对这4个燃烧状态均能良好描述.此外,为了检验火焰指数的概念,对这4个燃烧状态的火焰结构进行了分析.结果表明:虽然火焰指数可以部分反映火焰内部的燃烧状态,但对于火焰-三岔点的描述不够合理,有必要对其表达式进行改进和完善.     

应用火焰探测诊断煤粉燃烧的试验研究

本文通过火焰探测对煤粉燃烧诊断技术进行了试验研究.首先,利用单色仪获取了煤粉火焰的光谱分布特性,计算了煤粉火焰的色度坐标,发现其煤粉浓度的变化.对稳定燃烧工况和非稳定燃烧工况的火焰信号进行了频谱估计.以上研究成果可用于实际燃烧设备的燃烧监测与管理系统中.图8参8     

基于火焰OH自发光技术的贫燃旋流预混燃烧吹熄机理

利用火焰OH自发光技术研究了湍流状态下贫燃旋流预混燃烧的吹熄过程,获取了不同当量比下的平均火焰图像、瞬时火焰图像、二维火焰表面密度和OH平均强度.将当量比从0.90降低至0.46,即由火焰的稳定燃烧状态转变至临界吹熄状态,火焰由中间凹陷的紧缩形变为柱状.当量比位于0.90～0.55时,火焰表面密度下降约10%,可以认为此时火焰处于稳定燃烧状态.当量比位于0.55～0.50时,进度变量最大值从1.0变为0.5,说明火焰锋面处于强烈脉动中,且OH强度骤降约为67%.通过观察OH强度突变区域内的瞬时火焰图像,发现火焰锋面经历了脱离钝体、向燃烧室下游移动,再燃的往复过程.最后比较了不同旋流数(0.45、0.61和0.90)对于OH强度突变区间的影响,结果表明旋流数对于该区间的影响并不明显.     

基于小波变换的气化燃烧状态诊断试验研究

提出了一种通过压力信号分析气流床气化炉火焰气化燃烧状态的有效方法,该方法运用尺度分解法分析炉膛压力时域信号。研究结果发现：在点火前冷态,没有特征频率存在;在点火和灭火状态下,压力信号有一阶跃变化,信号在0Hz处有一较大的冲击;火焰剧烈波动时,存在2Hz左右的特征频率;火焰稳定燃烧时,存在着一个40Hz左右的特征频率。这个现象表明,压力信号在一定频段内的分布与气化炉内火焰燃烧的状态密切相关,随着火焰燃烧稳定性加强,压力信号向高频方向移动。     

基于关联维数的鼓泡流化床风帽压力波动特性研究

通过采集鼓泡流化床风帽入口的压力信号,利用小波方法对信号进行消噪处理后,对流化床风帽入口压力信号的时间序列进行了相空间重构,利用G-P算法计算了重构相空间的关联维数,并对冷态实验台采集的风帽压力数据进行了分析处理.结果表明：鼓泡流化床风帽压力波动信号具有混沌特性;自相关函数为0.1时,对应的延迟时间较为合适;典型冷态试验工况下,当表观气速增大时,关联维数呈上升趋势;当静床高增大时,关联维数随之减小.     

撞击气化火焰边缘的分形特性

气化炉是IGCC发电系统的关键设备,在试验中采用火焰摄像系统拍摄了多喷嘴对置气化炉内撞击气化火焰图像,用像素点覆盖法计算了撞击气化火焰边缘的分形维数,提供了一种有效判断撞击气化火焰燃烧状态的方法。试验结果表明,撞击气化火焰边缘曲线具有分形特征。撞击火焰的边缘分形维数在点火阶段逐渐降低;从两喷嘴撞击向四喷嘴撞击过渡时火焰边缘曲线分形维数逐渐增大;随着操作负荷的增大,分形维数增大,但两喷嘴和四喷嘴撞击火焰之间的分形维数相差逐渐减小。     

柴油双喷射撞击喷雾和燃烧可视化研究

利用高速相机基于纹影法获取上置喷油器和侧置喷油器在单独喷射和垂直喷射状态下的喷雾和燃烧火焰发展图像。柴油喷射压力设置为80、120、140 MPa,环境背压设置为4 MPa,环境温度在喷雾和燃烧研究中分别设置为500 K和800 K。结果表明：随着喷射压力的增加,不管是单独喷射还是垂直喷射,喷雾贯穿距和面积均增大;垂直喷射状态下,两油束碰撞后损失部分能量,导致其喷雾面积小于两单独喷射状态下的喷雾面积之和。采用双色法研究不同工况下燃料燃烧特性,结果表明：在喷射后1.50～3.50 ms的燃烧稳定时期内,随着喷油压力的提高,各喷射状态下的火焰面积均增大,燃烧温度提高,碳烟生成量降低;垂直喷射状态下的火焰面积小于两单独喷射状态下的火焰面积之和,燃烧温度和碳烟生成量均高于两单独喷射状态。     

基于功率谱的一种新型燃烧器燃烧状况识别

为有效地对新型燃烧器火焰燃烧状况进行识别,通过光电传感器获得一系列火焰光强信号,然后利用快速傅里叶变换(FFT)对火焰光强信号采样时间序列进行分析得出功率谱曲线,判断出非接触式的辐射式燃烧器燃烧状况稳定,进而得出了该种燃烧器燃烧孔开口大小及位置合理的结论.应用结果表明,燃烧火焰时域信号的采样频率至少要1 000 Hz,稳定的火焰信号功率谱低频部分波动小,不稳定的火焰信号功率谱波动相对于稳定的要大很多.     

缸内直接喷射式汽油机点火稳定性的数值分析

缸内直接喷射式汽油机的一个显著特点是依靠火花塞点燃喷入缸内的汽油油束。由于缸内混合气浓度极不均匀，所以其点火及火焰传播过程与普通均质燃烧式发动机有很大的不同。火焰核心的稳定形成及初始火焰发展对缸内的整个燃烧过程有极其重要的影响。本文利用二维两相混合模型模拟喷雾过程，利用一个详细的准维模型模拟火花塞的点火过程，并采用特殊处理方法使两个子模型相匹配，计算了缸内直接喷射式汽油机从喷雾到形成稳定火核的全过程，分析了多种因素对点火稳定性的影响，尤其是对涡流比、点火时刻和喷油定时之间的适当配合进行了模拟分析。计算结果对优化实验有明显的指导作用。     

Electrical control of the thermodiffusive instability in premixed propane-air flames

This work focuses upon the effects of DC electric fields on the stability of downward propagating atmospheric pressure premixed propane-air flames under experimental conditions that provide close coupling of the electric field to the flame. With the appropriate electrode geometry, modest applied voltages are shown to drive a stable conical flame first into a wrinkled-laminar flamelet geometry, and then further toward either a highly unstable distributed flamelet regime or a collective oscillation of the flame front. Applied potentials up through +5 kV over a 40-mm gap encompassing the flame front have been used to force the above transition sequence in flames with equivalence ratios between 0.8 and 1.3 and flow velocities up to 1.7 m/s. Experiments are reported that characterize the field-induced changes in the geometry of the reaction zone and the structure of the resulting unstable flame. The former is quantified by combustion intensity enhancement estimates derived from high-speed two-dimensional direct and spectroscopic imaging of chemiluminescence signals. The flame fluid mechanical response to the applied field, brought about by forcing positive flame ions counter to the flow, drives the effective flame Lewis number to values suitable for the onset of the thermodiffusive instability, even near stoichiometric conditions. Possible field-driven flame ion recombination chemistry that would produce light reactants near the burner head and precipitate the onset of the thermodiffusive instability is proposed. Electrical measurements are also reported that establish that minimal electrical power input is required to produce the observed flame instabilities. Current continuity-based calculations allow estimates of the level of deficient light reactant necessary to cause the flame to become unstable. This applied-electric-field-induced modification of the thermodiffusive effect could serve as a potentially attractive means of controlling flame fluid-mechanical characteristics and validating combustion instability models over a wide range of equivalence ratios.     

基于频谱分析和自组织神经网络的火焰燃烧诊断研究

通过对实验室煤粉燃烧炉实验数据的采集与分析，介绍了一种基于FFT变换处理与自组织神经网络状态识别相结合的燃烧诊断方法。首先，通过光电传感器获得一系列以一定的频率、在某个均值左右上下波动的火焰强度值。然后，利用FFT程序将获得的时域信号转换成频域上的功率谱信号。因为在稳定和不稳定的燃烧状态下，转换后得到的低频分量有明显的区别，所以把每个功率谱中前30个低频分量取出，将其作为神经网络的训练输入。通过自组织训练，神经网络将得到对应于稳定和不稳定燃烧状态火焰信号的不同输出区域。经过验证，这种方法能非常有效地识别燃烧火焰状态的稳定与否，在信号采样频率的选择，神经网络算法的改进等方面作了有意义的探索。图4表3参12     

Flame characteristics of a cavity-based scramjet combustor using OH-PLIF and feature extraction

It is vital to analyze the flame characteristics and identify the flame states efficiently in scramjet. Flame combustion and oscillation behaviors in a hydrogen-fueled cavity-stabilized scramjet combustor have been investigated in this study. A 500 Hz high-speed PLIF (planar laser-induced fluorescence) technique with a 20-cm-wide view field is introduced to characterize the combustion flow. The spatial distribution of the flame structure under different fuel injection conditions is studied. The results indicate that the position of the flame peak shifted downstream of the cavity when increasing the injection pressure to a high level. The dynamic characteristics of flames under different flow conditions are analyzed, and the correlation between flame features and hydrogen injection conditions is obtained. These flame features include the vertical range, the flow direction position of the peak flame, the flow direction position of the centroid, the vertical position of the centroid, the flame area, and the flame circumference. For the present cases, the flame of 4.0 Mpa is more unstable than that of 1.5 Mpa under any flow conditions. Moreover, an experiment based on feature extraction results shows that the KNN (K-nearest neighbor) classifier could achieve high accuracy for flame state recognition in this scramjet combustor.     

基于图像灰度复杂性测度的炉膛燃烧状况评价

基于非线性动力系统的复杂性刻画理论，提出用Kolmogorov复杂性测定定量评价炉膛燃烧的波动程序，弥补了用图像灰度序列序性描述燃烧工况的不足，分析结果表明，Kolmogorov复杂性测度能有效地区分火焰燃烧时的正常工况和波动工况，可作为反映炉膛燃烧工况的定量指标，并能在一定程度上实现燃烧恶化的预警，图7表1参2。     

微细通道内可燃气体预混燃烧实验与微型发动机燃烧方案

针对微型涡轮气体发动机的研制现状，讨论了微细通道稳定燃烧面临的难题。开展了微细通道内燃气与空气预混燃烧的火焰稳定性实验研究，通过测试获得了氢气和乙炔燃烧的着火浓度极限。结果表明：微细通道内可燃气体与空气的预混燃烧具有可行性，但可燃浓度范围明显缩小；采用增压燃烧，可以扩大其可燃浓度范围，提高燃烧稳定性；与大通道相比，微细通道不易发生回火，但容易发生火焰吹熄，而燃气浓度较高的混合气流相对不易被吹熄，燃烧稳定性较好。     

一种基于自适应小波变换的火焰检测方法的研究

1引言锅炉煤粉燃烧已成为工业生产和人民生活所必须的一种能量和动力来源,而火焰检测系统是保障锅炉安全运行的关键所在。为避免炉膛爆燃事故的发生,火检系统必须能对炉膛的燃烧状况进行实时准确的判别。由于可见光波动强度较小,频谱范围较窄,利用单燃烧器检测可见光信号比依靠     

有序堆积床内预混气体燃烧特性实验研究

为研究预混气体在多孔介质燃烧器中的火焰燃烧特性,设计了一种新型多孔介质燃烧器,其中多孔介质区域由氧化铝圆柱体有序堆积而成。分别研究了当量比和入口速度对甲烷/空气预混气体在多孔介质燃烧器中的火焰温度分布、火焰最高温度以及火焰传播速度的影响。结果表明:在当量比0.162~0.324、入口速度0.287~0.860 m/s的实验工况下火焰均可以稳定向前传播,并且都发生了超绝热燃烧;当量比越大,入口速度越大,火焰最高温度越高;当入口速度为0.430 m/s时,贫可燃极限的当量比可以扩展到0.162;火焰传播速度随着入口速度的增加和当量比的减小而增大,其数量级为0.100 mm/s,属于一种十分典型的低速过滤燃烧。     

微细圆管中的稳定火焰传播

研究了火焰在有壁面散热的微细圆管中的传播过程.流动马赫数很小时,假定流体满足理想气体状态方程,采用详细化学反应机理.火焰面形状由壁面散热和流场共同决定.壁面散热增大时会导致熄火.引入二维流场使维持火焰稳定传播的壁面散热范围扩大.计算结果表明,微细圆管燃烧器内较大的火焰面曲率能促进燃烧.     

Oxidizer effects on ammonia combustion using a generated non-premixed burner

In the present study, the pure ammonia combustion in a model combustor is performed to seek ammonia-fueled applications. To this aim, effects of the oxygen enrichment with an oxygen concentration of 100% in the oxidizer on flame characteristics, temperature profiles and NO profiles during the ammonia combustion were evaluated in terms of excess air/oxygen coefficients. Furthermore, in order to better understand the effect of an oxygen of 100% usage under the oxy-ammonia combustion conditions, the air-ammonia combustion has been studied as well and their results are compared and discussed each other. According to the results predicted, the oxidizer with an oxygen content of %100 provides better flame stability in the case of pure ammonia combustion. The most stable flame for oxy-ammonia combustion can be achieved when the excess oxygen coefficient is 1.0 or 1.2. Furthermore, the minimum NO levels emerge under the fuel-rich condition. Temperature and NO emissions decrease considerably under the air-ammonia combustion. However, except the fuel-rich conditions, flame stabilities are not satisfactory due to ammonia's flame speed under the air-ammonia combustion. Moreover, the air-ammonia combustion under the fuel-rich condition seems as a good option for obtaining the lowest NO levels. On the other hand, the oxy-enrichment condition is thought as a promising method for pure ammonia combustion provided that NO emissions should be optimized by using NO reduction methods.