煤粉复合旋流火焰燃烧特性研究（1）：实验研究

本文实验研究了煤粉复合旋流火焰燃烧特性，进行了包括３个典型煤种：褐煤、烟煤和无烟煤，在不同煤粉浓度下的燃烧试验，测量了火焰场的温度分布、气体组份分布、火焰周界辐射和煤颗粒燃烧参数，对火焰场特性、不同煤种影响和煤粉浓度作用做了较系统的试验研究，揭示了该燃烧方式的稳定着火、强化燃烧机理，获得了这种煤粉火焰的燃烧特性。     

应用图像处理技术进行预混层流火焰传播速度的在线测量

利用图像处理技术，根据层流预混火焰稳定燃烧的条件结合预混火焰燃烧模型，设计了火焰传播速度在线实时测量系统，通过图像采集在线获取火焰的静态图像，然后自动对图像进行滤波，边缘提取，再进行计算得到火焰传播前沿面积，在线算出火焰传播速度，这种方法具有非接触式测量的优点，利用它不仅可以测量层流预混火焰的传播速度，同时还为层流火焰的燃烧机理的研究提供一种直接的手段．     

利用可视化炉膛火焰检测对两种不同燃烧方式的实验研究

燃烧火焰是燃烧状态稳定与否的最直接反映。利用可视化火焰检测系统对两台机组进行实炉测量,从火焰图像中提取更多的监视和诊断信息,对实验结果进行了分析。实验结果表明:该系统能够正确、实时跟踪燃烧火焰的温度变化,定量给出火焰温度变化,快速地对燃烧状态进行检测。     

汽油机射流燃烧系统火焰传播过程的研究

根据汽油机燃烧火焰电离原理，试制成功了一台火焰传播测试仪，由于火焰前锋内离子浓度的变化将引起电位差的相应变化，所以通过装在气缸盖上的传感器，可使仪器显示出火焰到达燃烧室中某一位置的时刻和燃烧的持续时间，如用微机采样，则可同时检测３２个点，也可以用示波器显示任一个传感器输入的电位差变化波形。用此仪器对４９２ＱＳ汽油机进行了火焰传播过程的测试，从中可看出射流燃烧系统燃烧过程的特点，有利于今后进一步改进     

用光纤燃烧传感器测量汽油机的燃烧时间参数的研究

本文介绍了一个光纤燃烧传感器及ＯＭＡ４光多通道分析仪组成的测量系统，用以测量汽油机燃烧火焰光谱。光谱分析结果再次证实了燃烧火焰中ＣＨ（４３１．５ｎｍ），Ｃ２（５１６．５ｎｍ），Ｈ２Ｏ（５８９ｎｍ）等自由基的特征光谱同Ｃ粒子的热辐射连续光谱叠加在一起，构成了火焰光谱。根据光谱曲线中Ｈ２Ｏ光强峰值变化，可以确定汽油机燃烧过程中重要的时间参数：着火延迟期和燃烧持续期。由于汽油机燃烧循环变动大，与单色仪和ＢＯＸＣＡＲ积分平均器组成的测量系统相比，光纤燃烧传感器＋ＯＭＡ４用光多通道分析仪系统测量汽油机燃烧火焰光谱，测量精度高，工作效率高。     

5个待定系数的修正韦伯函数在发动机多火焰区燃烧模型中的应用

提出了含5个待定系数的修正韦伯函数，并应用多元非线性回归技术确定这些系数，模拟了具有双火焰区燃烧模式和稀燃－速燃特性的汽油机射流燃烧系统燃烧室中混合气的燃烧特性，从而成功地借助示功图分离出对分析整个燃烧过程至关重要的各火焰区中的质量燃烧率和火焰速比等参数，构成了实用的附有双火焰区的三区准维燃烧分析模型。应用实例表明，该函数与多区模型相结合，将在火花点火发动机燃烧模拟中具有强大生命力。     

电站锅炉火焰检测及燃烧诊断技术

电站锅炉的安全运行主要决定于燃烧的稳定性，实时探测燃烧火焰是否稳定，及时作出判断，对电站锅炉安全运行有着重要的实际意义。本文分析了炉膛火焰特征与火焰检测和燃烧诊断的关系，论述了火焰检测的基本原理和方法以及燃烧诊断理论和技术，并对目前火电厂燃煤锅炉应用的各种火焰检测器和燃烧诊断系统进行了分析比较，最后讨论了火焰检测及燃烧诊断技术的进一步研究方向。     

高温低氧燃烧火焰辐射特性的实验研究

对高温低氧燃烧火焰的辐射特性进行了实验测试，同时利用CFD通用软件对火焰热辐射行性进行了数值计算，得到了在不同预热空气温度、不同预热空气含氧量条件下，火焰形状及火焰热辐射特性的变化规律。结果表明：高温低氧燃烧火焰的体积与长度随着预热空气中含氧量的降低而扩大，而预热空气温度对燃烧火焰体积的影响不大。高温低氧燃烧火焰对炉膛壁面的热辐射能力随着预热空气温度的降低而下降，同时也随着预热空气含氧量的降低而下降。图4参9     

地沟油生物柴油与正丁醇/乙醇混合燃料燃烧火焰特性

为研究不同配比下生物柴油混合燃料燃烧特性,设计了一套生物质液体燃料雾化蒸发燃烧系统,该系统可产生生物柴油及其混合燃料层流预混火焰,结合OH-PLIF平面激光诱导荧光技术测定并分析燃烧火焰的高度和锋面面积以及层流预混火焰的传播速度和OH-PLIF总信号强度等燃烧特性.结果表明随着正丁醇或乙醇添加比例的增大,两种混合燃料燃烧火焰高度、火焰锋面面积呈下降趋势;火焰传播速度呈上升趋势.在混合燃料中,正丁醇的体积分数越大,燃烧火焰OH-PLIF总信号强度越大,而乙醇的体积分数越大,混合燃料燃烧火焰OH-PLIF总信号强度越小.     

数字式火焰电视监测系统研制及应用

本文介绍了东方锅炉研制的基于双波长理论、采用内窥式成像传感器获取锅炉燃烧火焰图像、通过计算机处理得到炉膛火焰温度场的数字式火焰电视监测系统的结构特点、系统功能和实际使用效果。数字式火焰电视系统与常规炉膛火焰电视和光电高温计的相比，同时具有看火和测温功能，优点明显，是常规炉膛火焰电视系统或光电高温计的替代升级产品。     

脉动供燃料燃烧技术及火焰频率特征

介绍了一种天然气的新型脉动供燃料燃烧技术,该技术能有效降低NOx,提高传热效率,节约能源,且改造简易,运行经济;阐述了其技术原理,综述了其发展状况,指出对我国燃烧技术改进的重要意义.利用直接摄像技术,对一个采用该燃烧方式的射流火焰在不同流量脉动频率下的火焰类型和结构特征进行了研究.结果发现,随脉动频率变化出现了丰富的火焰类型.燃气脉动与系统共振特性相耦合影响火焰脉动特性,在系统共振和谐振频率附近,火焰根部出现崩溃混合,且火焰湍动升起,火焰长度变短.在某些频率下火焰直长,具有清晰的贫富燃交替结构.     

同轴离心式喷注器火焰特性实验研究

为了研究高压补燃循环液氧,煤油发动机燃烧室同轴离心式喷注器的火焰特性,分别用富氧空气和煤油蒸气以及空气和甲烷在大气环境下进行了喷注器的燃烧实验,前者采用红外热像仪测量了火焰温度场,后者采用激光诱导荧光技术测量了火焰中CO2和OH的分子浓度分布.结果表明,该型喷注器的火焰形状和燃烧产物组分随氧化剂和燃料的混合比而变化;火焰稳定在喷注器出口处,剧烈的燃烧发生在火焰中心;平面激光诱导荧光技术用于燃烧过程研究,可以提供燃烧场组分分子浓度的信息.     

Calibration and Experimental Research of a Multiple-wavelength Flame Temperature Instrumentation System

This paper presents a study on a novel instrumentation system for the measurement of temperature distribution of combustion flames. This system operates upon the three-color principle combining advanced optical sensing and digital image processing techniques. It comprises an endoscope, a light splitter assembly, a CCD camera, a frame-grabber and associated software. This system was calibrated using a blackbody furnace as standard temperature source. The relationship between flame temperatures and grey-level of the images was established through image processing and function correlation. Experimental results obtained on a gas-fired combustion rig provide flame images and temperature distributions on three different wavelengths. Based on the flame temperature distribution the combustion conditions can be analyzed. Experimental results also reveal that this system is capable of online measurement of temperature distribution in a combustion zone. This system can potentially be applied to many areas such as power generation, metallurgy, chemical engineering. It is also a powerful tool for improving the control of combustion process.     

Experimental Study on Measurement of Flame Temperature Distribution Using the Two-Color Method

A novel optical instrumentation system for flame characterization was developed and tested. The two-color system is capable of performing on-line measurement of flame and temperature distribution, providing temporal and spatial characterization of the combustion process. In addition, the system has the advantage of being non-intrusive. The on-line measurement of temperature distribution on a methane-air combustor revealed some interesting characteristics. When air flow rate was kept constant, an increase in CH4 flow rate would enhance the combustion intensity and elevate the flame temperature. While under constant CH4 flow rate, the increase of air flow rate would lead the measured flame temperature first to increase and then decrease. The drop of temperature might partially be caused by the heat losses due to excessive air. However, with insufficient soot particles in the flame, the temperature could be under-evaluated.     

亚/超临界环境下燃料的喷雾燃烧特性研究

采用高温高压定容燃烧弹系统对亚/超临界环境下燃料在纯氧中的喷射燃烧现象进行试验研究,通过高速相机和阴影法进行燃烧图像信息的采集,研究在相同的超临界温度下,正己烷和乙醚两种燃料喷射燃烧火焰特性随环境压力和喷油脉宽的改变而呈现的差异性。试验结果表明:在亚临界压力下,两种燃料在不同喷油脉宽下的燃烧时间均随着环境压力的升高而升高,火焰发展后期基本保持较为稳定的形态和亮度,符合传统的喷射燃烧过程。正己烷在临界压力点下火焰长度最短,形态较为规则;超临界压力下,火焰形态有稳定趋势但仍有轻微波动,且火焰长度略短于亚临界;喷油脉宽改变时,燃烧时间在临界压力附近呈现出不同的趋势。乙醚的燃烧时间随压力的升高而增大,在临界压力处达到最大值,后随着压力的继续升高而下降,不同压力条件下火焰形态略有差别。燃烧现象存在差异性主要是由于亚/超临界坏境下燃料的物性参数和破碎蒸发机理不同。     

缸内涡流比对冷起动燃烧火焰的影响探究

针对汽油发动机冷起动存在的燃烧不稳定、燃烧效率低的问题,基于单缸可视化发动机在冷起动工况下调节进气涡流,通过分析缸内燃烧火焰特性来探究增强进气涡流对发动机循环波动及输出功率的影响。试验所用发动机为单缸四气门(两进两出)缸内直喷汽油机,其中一个进气道加装有涡流控制阀,通过将一个进气道关闭或者开启来改变缸内涡流的强度。利用高速相机从活塞上的光学通道得到发动机缸内的火焰传播图像,并计算火焰传播面积,提取火焰边界,获取火焰中心速度及火焰扩散速度等信息,同时也利用燃烧分析仪对缸内压力、燃烧放热率等特性进行同步测量和记录,通过多角度的对比和分析揭示缸内燃烧状况与发动机宏观性能的相关联系,有效地发掘了在不同涡流强度下缸内火焰的传播特征。研究结果从缸内燃烧火焰的角度解释了提高涡流比能够很好地提高冷起动的燃烧稳定性,促进发动机缸内燃烧。研究表明,早期火核分布越集中,波动越小,后期循环波动就越小。试验结果还表明,由缸压计算的瞬时放热率与火焰面积存在很好的线性关系。     

Cool flame characteristics of methane/oxygen mixtures

As one of the most important clean fuels, methane plays a significant role in the energy supply system, and its combustion characteristics directly affect the efficiency and emission. In order to avoid the production of a large number of nitrogen oxides, the low temperature combustion associated with cool flame is getting more and more attention. But until now the cool flame characteristics of methane is still unclear, even its existence is controversial. In this work, the property of premixed methane/oxygen cool flame has been experimentally studied in a cylindrical reactor and numerically analyzed using different mechanisms. The effects of pressure, temperature and equivalence ratio on methane cool flame have been investigated experimentally. The experimental results show that the cool flame can be obtained in the range of 0.2–4.8 equivalent ratio. The lower limit of pressure of the cool flame region decreases with the increasing initial temperature. The sensitivity and reaction path have been analyzed through the numerical simulation, which reveals that the bifurcation in CH₃ oxidation process has remarkable effects on cool flame formation.     

挥发分火焰对碳粒燃烧的影响

建立了球坐标系下传热、传质、化学反应全耦合的煤粉燃烧数值模拟程序．通过煤粉与事先脱除挥发分的焦炭的对比实验及数值模拟,研究了挥发分火焰对碳粒表面一次产物CO火焰的点燃及碳粒燃烧的影响．傅里叶变换红外光谱仪(FTIR)测温实验及煤粉燃烧动态过程的数值模拟结果不仅进一步验证了碳粒着火初期CO火焰所引起的颗粒高温现象,而且给出了挥发分引燃表面反应一次产物CO的直接证据．由于挥发分火焰的引燃作用,碳粒可以在较其非均相着火温度为低的温度下被点燃,阐明了Juntgen提出的联合着火方式的物理本质．     

Flame stretch analysis in diffusion flames with inert gas

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Reexamination on methane/oxygen combustion in a rapidly mixed type tubular flame burner

To fundamentally elucidate the requirement for an inherently safe technique of rapidly mixed type tubular flame combustion, experiments have been made to investigate (1) the mixing process of fuel and oxidizer, and (2) the appearances of methane flames under various oxygen mole fractions. Three optically accessible quartz burners of different slit widths were made for measuring the mixing layer thickness with a PIV system. Under various rates of flow of the oxidizer to the fuel, a boundary layer type flow is recognized to dominate the mixing of fuel and oxidizer around the exit of the injection slit, namely the mixing layer thickness is inversely proportional to the square root of mean injection velocity. Using two stainless steel burners, combustion tests were conducted with the oxidizers of oxygen/air mixtures. To quantitatively investigate the requirement for tubular flame establishment, the Damköhler number, which is the ratio of characteristic mixing time to characteristic chemical reaction time, has been discussed in detail. The mixing time was calculated according to estimated mixing layer thickness, while the chemical reaction time was computed with the Chemkin code. The Damköhler number has proved to be a useful measure for success/failure of tubular flame combustion. When the Damköhler number is larger than unity, chemical reaction starts before complete fuel/air mixing and the tubular flame fails to be established; when the Damköhler number is much smaller than unity, the fuel and the oxidizer are completely mixed before the onset of reaction, resulting in successful tubular flame combustion. The results confirm our hypothesis in a previous study. Furthermore, based on the concept of Damköhler number, the minimum flow rate to achieve the tubular flame combustion could be estimated.