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。     

利用定容燃烧弹研究天然气掺氢混合燃料直喷燃烧循环变动

利用定容燃烧弹开展了天然气掺混0%～40%氢气混合燃料直喷燃烧循环变动研究,高压气体燃料(8.0 MPa)喷入定容燃烧弹模拟直喷发动机燃烧条件.在整体当量比为0.6和0.8下,试验采集了火焰发展图片和燃烧过程容弹内压力,从火焰发展图片和燃烧特征参数两个方面分析了掺氢和混合气分层分布对天然气直喷燃烧循环变动的影响.结果表明:燃烧循环变动起始于火焰发展初期阶段.随着掺氢比增加,火焰形态更规则且更集中于点火电极.同时,由于直喷燃烧方式混合气分层分布,能够实现低循环变动的稳定稀燃.循环变动随着掺氢比的增加而减小,这种趋势在稀燃工况((b=0.6)下更加明显.在直喷燃烧方式下,由于混合气分层分布减弱了火焰发展初期阶段对后续燃烧过程的影响,因此燃烧特征参数间呈现相互独立的关系.     

加湿燃烧研究现状

首先从两个方面详细介绍了燃料加湿燃烧的研究成果,一方面是加湿对燃气轮机燃烧室内燃烧特性的影响,另一方面是加湿对燃料着火特性、可燃极限的影响。分析了目前加湿燃烧研究所取得的结论,空气加湿燃烧可以降低火焰燃烧温度、改变燃烧过程中的化学反应以及传热传质过程,影响火焰的流场和结构,使火焰趋于不稳定。同时燃烧区温度的降低有利于降低NOx排放,对HAT、IGCC等热力循环中降低NOx排放有重要意义,最后指出了目前加湿燃烧存在的不足,并结合本课题组的研究结论为后续研究方向提出了建议。     

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。     

轻油的预蒸发燃烧——轻油预蒸发燃烧中的火焰稳定

分析了预蒸发燃烧中的火焰稳定问题，介绍了燃料燃烧中关于火焰稳定的原理和方法，重点介绍了目前实现轻油预蒸发燃烧中所采用的若干稳焰措施。     

W火焰锅炉燃烧稳定性影响因素分析

燃料的性质和炉内良好的燃烧环境是W火焰锅炉稳定燃烧的决定因素。通过对煤粉着火及稳燃机理的研究和对W火焰锅炉运行状况的了解,系统地对影响W火焰锅炉燃烧稳定性的各个因素进行了分析,对锅炉运行和实际生产都有积极意义。     

湿空气非预混火焰的稳定性

利用粒子图像测速技术对钝体后的湿空气回流非预混燃烧火焰流场进行了测量,研究湿空气燃烧火焰的结构特性,以及水蒸气的加入对火焰稳定性的影响,得到湿空气燃烧火焰的稳定性区域图.通过对比湿空气燃烧和普通燃烧火焰转变的临界值,发现湿空气燃烧回流火焰向过渡火焰转变时,燃空速度比的临界值比普通燃烧的低16%~22%,而发生局部熄火时的临界值与普通燃烧时的相比至少低25%.分析表明,湿空气火焰不稳定性主要是由于环流湿空气动量的减少引起的,另外稀释作用和化学发应的影响导致氧原子含量降低也是不稳定的一个原因.     

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     

小尺度乙醇扩散火焰及管壁温度场的实验研究

用不同的小尺度陶瓷圆管作为燃烧器,对液体乙醇在空气中的扩散火焰燃烧进行了实验研究.分析了火焰燃烧的三种不同的特性以及燃烧区域,考察了影响火焰高度与宽度的相关因素,并分析了燃烧时管壁的温度场.结果表明:稳定燃烧时火焰的高度与宽度均随流量的增大而线性增加,并随着内径的减小而减小.随着内径的减小,淬熄流量减小,振荡流量减小,稳定燃烧范围减小.同一流量下,管壁的温度以管口为基点呈指数规律递减.     

用紊流卷吸燃烧模型计算研究点火时刻紊流参数对燃烧循环的影响

利用准维紊流卷吸燃烧模型计算研究了点火时刻气缸内紊流参数的变化对汽油机燃烧循环变动的影响。结果表明，点火时刻紊流强度u′及紊流长度积分标尺L的变动对汽油机燃烧循环变动均有很大影响，增大u′或L均有利于加快燃烧速度及火焰传播速度，缩短火焰发展期；u′或L的变动加大，燃烧循环变动也随之加大，其中，u′对燃烧循环变动的影响尤其大。     

Experimental study on velocity characteristics of recirculation zone in humid air non-premixed flame

To examine the effect of the flow field within the recirculation zone on flame structure, the characteristic velocity fields of methane/humid air flame in non-premixed combustion behind a disc bluff-body burner were experimentally studied by particle image velocimeter (PIV).The results show that two stagnation points exist on the centerline in the recirculation zone flame. However, the distance of the two stagnation points in humid air combustion shortens, and the minimal dimensionless velocity increases compared with the conventional nonhumid air combustion. In addition, the positional curves of the minimal velocities can be partitioned into three phases representing three different flame patterns. The analysis of axial minimal velocities on the centerline and their positions under different co-flow air velocity conditions reveals that fuel-to-air velocity ratio is the crucial parameter that governs humid air combustion flame characteristics. __________ Translated from Journal of Shanghai Jiaotong University, 2007, 41(3): 357–360, 365 [译自: 上海交通大学学报]     

Experimental study of humid air reverse diffusion combustion in a turbulent flow field

Experiments were performed to investigate the differences between the propane/air turbulent diffusion reactive flows past bluff-body and the propane/humid air turbulent diffusion reactive flows in the same conditions. The velocity distributions of the non-humid reactive flow fields and the humid reactive flow fields were measured by particle image velocimetry (PIV) techniques. The temperature fields were measured by high temperature thermocouples, and NO_x distributions were obtained by using gas detection instruments. The results show that although humid air reactive flow fields are similar to non-humid flow fields in general, there are some differences in the humid air combustion flow field comparing with the non-humid combustion flow field: the center of the reversed-flow region goes forward; the dimension of the reversed-flow region is smaller; the peak temperature and NO_x formation are reduced. It is suggested that humid air combustion is helpful to shorten the axial length of combustors, and reduce the formation of pollutants. __________ Translated from Journal of Shanghai Jiaotong University, 2006, 40(8): 1 287–1 292 [译自: 上海交通大学学报]     

Experimental study on velocity characteristics of recirculation zone in humid air non-premixed flame

To examine the effect of the flow field within the recirculation zone on flame structure, the characteristic velocity fields of methane/humid air flame in non-premixed combustion behind a disc bluff-body burner were experimentally studied by particle image velocimeter (PIV).The results show that two stagnation points exist on the centerline in the recirculation zone flame. However, the distance of the two stagnation points in humid air combustion shortens, and the minimal dimensionless velocity increases compared with the conventional non-humid air combustion. In addition, the positional curves of the minimal velocities can be partitioned into three phases representing three different flame patterns. The analysis of axial minimal velocities on the centerline and their positions under different co-flow air velocity conditions reveals that fuel-to-air velocity ratio is the crucial parameter that governs humid air combustion flame characteristics.     

湿度对HAT循环燃烧室旋流扩散燃烧特性的影响

为研究湿度对燃烧特性的影响,采用湍流雷诺应力模型和层流小火焰模型,对湿空气透平(HAT)循环燃气轮机带有旋流器的燃烧室内甲烷扩散燃烧过程进行了数值模拟对比了在4种不同空气含湿量(0、100、200、300g／kg(DA))情况下的燃烧室内部温度场、速度场以及NO组分分布的情况,分析了湿度对HAT循环燃烧室扩散燃烧特性的影响结果表明,加湿降低了整个燃烧室的温度,并使其内部温度分布更加均匀;加湿使燃烧室的NO浓度大大降低;加湿减小了回流区长度。     

甲烷/空气湍流扩散燃烧的小火焰模拟

以甲烷/空气的湍流射流扩散燃烧为基础,对通用的反应标量方程在火焰面上进行坐标变换,建立二维稳态湍流扩散火焰的小火焰模型。利用湍流流动模型、甲烷/空气半详细化学反应机理和小火焰模型耦合求解,分别计算出过量空气系数为1.2和1.4的速度在燃烧室内的分布状况以及混合分数、温度和组分的径向分布,模拟结果表明小火焰模型能够用来描述燃烧室内燃烧机理。     

稳态湍流非预混燃烧的小火焰模拟

以甲烷/空气的湍流射流非预混燃烧为对象,建立二维稳态湍流非预混火焰的小火焰模型.利用湍流流动模型和小火焰模型耦合求解,计算出速度、混合分数、温度以及反应标量的摩尔分数在燃烧室内的分布,模拟结果表明小火焰模型能够用来描述燃烧室内燃烧机理.     

在CFB锅炉中煤粉不同喷入位置对炉内固相运动特性的影响

针对循环流化床结合煤粉燃烧技术,建立了炉内气固运动特性的三维数学模型,研究分析了煤粉不同喷入位置及不同二次风速度对炉内气固运动特性的影响.结果表明:在不同二次风速下,煤粉燃烧器布置位置距布风板2600 mm和2000 mm时,颗粒速度波动大,流动不稳定,不能在悬浮段形成局部颗粒流浓度;布置位置为距布风板2300 mm时,流动状态较稳定,而且能够在悬浮段形成高浓度颗粒流.因此在采用联合燃烧技术的循环流化床中,保持流化风速为2 m/s时,煤粉燃烧器布置位置在距布风板2300 mm时,能使煤颗粒在炉膛整个上升过程中处于高温燃烧氛围.     

火花点火式发动机燃烧过程中缸内气流运动研究

通常在发动机倒拖工况下测量和研究缸内气流运动,对于燃烧过程中缸内流动规律的测量和研究还很少。在一台单缸四气门火花点火式发动机上,用激光多普勒测速仪分别在发动机着火和倒拖条件下测量和分析了燃烧室气流运动的规律。研究结果表明,在燃烧和排气阶段,缸内气流的平均速度与倒拖时有较大差别,而且燃烧速度越快,燃烧过程中气流运动速度的变化越剧烈。     

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。     

Highly resolved numerical simulation of combustion in supersonic hydrogen–air coflowing jets

The present study is focused on the analysis of non-premixed combustion in high-velocity (supersonic) flows. The computations make use of a large eddy simulation (LES) model, which has been recently introduced to address combustion in high Reynolds number turbulent flows featuring moderate Damköhler values. We expect that the corresponding closure is able to account for the specificities encountered in high Mach number turbulent reactive flows featuring chemical reaction time scales with the same order of magnitude as flow time scales. The model takes finite-rate chemistry and micro-mixing effects into account within the framework of the partially stirred reactor (PaSR) concept, it is hereafter denoted by U-PaSR (unsteady partially stirred reactor). (i) In a first step of the present investigation, the capabilities of the U-PaSR closure hence proposed are evaluated through a detailed comparison performed between numerical results and the data obtained from an experimental study devoted to non-premixed combustion in supersonic co-flowing jets of hydrogen and vitiated air. The simulated test case corresponds to a well-documented experimental database that includes Raman scattering and laser-induced pre-dissociative fluorescence measurements. The comparisons performed between computational results and experimental data establish that the physical processes are well-described by the performed simulation. (ii) In a second step of this study, the flame structure and associated stabilization zone are analysed in the light of numerical simulation results. The post-processing to the computational results indeed confirms the importance of self-ignition processes, as well as the relevance of diagnostic tools recently introduced by Boivin et al. [1,2]. Considering the stabilization zone, it also emphasizes the essential importance of the pressure dynamics associated with the discharge of compressible coflowing jets into the atmosphere – an importance that was not so clearly evidenced from previous numerical simulations conducted on the same experimental benchmark.