燃烧火焰特征的数字图像处理系统

介绍了一个作者自行开发的注蒸汽的燃气轮机燃烧室火焰特征分析软件，借助于数字图像处理技术和光学辐射理论对燃烧火焰的结构、层次和轮廓进行了分析和处理，同时依据火焰图像推算出其温度场，从而为燃烧室理论设计和实验处理提供一个强有力的分析工具。     

红外图像法研究富氧火焰燃烧特性

利用红外图像对设计的新型石油焦富氧燃烧器进行热态试验分析,并提出了基于红外测温原理的火焰温度修正方法。基于红外热像仪采集到的红外图像,研究了该石油焦富氧燃烧器的着火特性,对不同工况下石油焦富氧火焰温度场进行了分析探讨,并对富氧火焰的红外测温模型进行了修正研究。实验结果表明,该燃烧器一次氧的增加能促进石油焦粉更快完全燃烧,单位时间释放更多的热量;随着一次风量的增加,炉内火焰平均温度呈现的是先增加后减小的变化趋势;一次氧直流喷射时的整体温度场较旋流喷射时更高,更适合此扁平火焰燃烧器的双一次风孔结构。研究提出的火焰红外测温模型和后期修正方法科学有效,可有效减小红外测温的误差。     

Three-dimensional modeling of utility boiler pulverized coal tangentially fired furnace

This paper presents selected results of numerical simulations of processes in utility boiler pulverized coal tangentially fired dry-bottom furnace. The simulations have been performed by specially developed comprehensive mathematical model. The main features of the model are a three-dimensional geometry, k–ε gas turbulence model, Eulerian–Lagrangian approach, particles-to-turbulence interaction, diffusion model of particle dispersion, six-flux method for radiation modeling and pulverized coal combustion model based on the global particle kinetics and experimentally obtained kinetic parameters. Five operation regimes of 210 MW_e boiler furnace burning Serbian lignites, with different grinding fineness of coal and coal quality, have been simulated. The model successfully predicts the influence of the parameters on the furnace processes and operation characteristics (like the flue gas temperature and the furnace walls radiation fluxes). The predicted flame temperature and percentage combustibles in bottom ash are in good agreement with the measurements. The developed model can find different applications, both in research and practice.     

燃煤气单元玻璃熔窑火焰空间数值模拟

通过建立火焰空间三维数学模型来模拟燃煤气单元玻璃熔窑火焰空间内的流动、燃烧、传热等过程。针对煤气的燃烧特点，单元窑的火焰特征等进行了较深入的研究。结果表明，该三维数学模型能够比较全面地反映火焰空间速度场、温度场分布的规律；模型具有通用性好，不易受环境波动影响的优点，具有一定的实用意义。     

我国电站燃煤锅炉节油点火技术的分析及现状

针对现阶段我国电站燃煤锅炉运行状况,分析微油点火技术和等离子点火技术的工作原理、系统组成及应用,从技术和经济的角度指出其各自的特点,并对节油及运行中出现的问题提出改进措施。     

基于图像处理的炉膛火焰燃烧诊断技术

在燃烧火焰监测试验台上,对同种煤粉在三种不同配风条件下的燃烧过程进行了研究,利用CCD(电荷耦合元件)图像传感器进行实时监测,并利用图像处理技术对火焰的相关参数进行提取,得到了火焰的温度场。通过对比分析不同稳定工况下的火焰图像,对燃烧的情况进行了评价,并对燃烧污染物NOx排放浓度进行了分析。     

Three dimensional modeling of pulverized coal combustion in a 600 MW corner fired boiler

IntroductionThe developments relative to coal combustion havebeen performed into a general purpose 3D code namedESTET under quality assurance, and used to modelcomplex turbulent reactive flows. In the case ofindustrial boilers we can assume a no-slip conditionbetween gas and particles which is the case for the mostpart of the furnace, except possibly in the near field ofthe burners. With such an assumption, the equations for apafticle-gas fixture with a mean density can be written.The combu…     

PDA research on a novel pulverized coal combustion technology for a large utility boiler

In this paper, a new technology for a tangential firing pulverized coal boiler, high efficiency and low NO_x combustion technology with multiple air-staged and a large-angle counter flow fuel-rich jet (ACCT for short) is proposed. To verify the characteristics of this technology, experiments of two combustion technologies, ACCT and CFS-1 (Concentric Firing System-1), are carried out under a cold model of a 1025 t/h tangential firing boiler with a PDA (particle dynamics anemometer). The distributions of velocity, particle concentration, particle diameters and the particle volume flux of primary air and secondary air are obtained. The results show that the fuel-rich primary air of ACCT can go deeper into the furnace and mix with the main flow better, which means that the counter flow of fuel-rich jets in ACCT can realize stable combustion, low NO_x emission and slagging prevention.     

俄罗斯电站锅炉无油电加热煤粉点火燃烧技术

综述俄罗斯运用电加热与稳燃技术结合实施的煤粉无油点火技术。介绍点火煤粉制备系统的构成。     

An image processing technique for automatically detecting forest fire

In this paper we present an automatic system for early smoke source detection through the real time processing of landscape images. The first part describes the segmentation technique we use to extract persistent dynamical envelopes of pixels into the images. We describe the temporal algorithm at the pixel level (filtering) and the spatial analysis to bring together connected pixels into the same envelopes (object labeling). The second part deals with the method we use to discriminate the various natural phenomena that may cause such envelopes. We describe the image sequence analysis we developed to discriminate distant smokes from other phenomena, by extracting the transitory and complex motions into little pre-processed envelopes. We present then our main criterion for smoke recognition based on the analysis of the smoke plumes velocity.     

Bidirectional light-scattering image processing method for high-concentration jet sprays

In order to study the distributions of droplet size and volume density in high-concentration jet sprays, a new technique is developed, which combines the forward and backward light scattering method and an image processing method. A pulsed ruby laser is used as the light source. The Mie scattering theory is applied to the results obtained form image processing on the scattering photographs. The time history is obtained for the droplet size and volume density distributions, and the method is demonstrated by diesel fuel sprays under various injecting conditions. The validity of the technique is verified by a good agreement in the injected fuel volume distributions obtained by the present method and by injection rate measurements.     

Evaluation of flame emission models combined with the discrete transfer method for combustion system simulation

This article considers the application of flame emission models used for predicting the thermal radiation fluxes from flames and fires within a computational fluid dynamic framework, used in conjunction with the discrete transfer method. The flame emission models differ in their generality, sophistication, accuracy and computational cost, and are assessed in terms of their ability to predict radiation transfer in idealised situations, as well as flames in tubes representative of burner systems, laboratory-scale jet flames and wind-blown jet fires. It is concluded that the implementation of simple flame emission models, based on the grey gas assumption, must be treated with caution due to convergence problems. The key problem occurs when the grey absorption coefficient is based on a length scale linked to the size of the control volume. This issue is well known in the radiation modelling community, but not so in the combustion modelling community. Use of models based on the banded mixed grey gas, TTNH, wide and narrow band approaches yield satisfactory results for all the simulated flames and fires considered, typically being within 20% of the measured radiation heat flux.     

Sulphur impacts during pulverised coal combustion in oxy-fuel technology for carbon capture and storage

The oxy-fuel process is one of three carbon capture technologies which supply CO₂ ready for sequestration - the others being post-combustion capture and IGCC with carbon capture. As yet no technology has emerged as a clear winner in the race to commercial deployment. The oxy-fuel process relies on recycled flue gas as the main heat carrier through the boiler and results in significantly different flue gas compositions. Sulphur has been shown in the study to have impacts in the furnace, during ash collection, CO₂ compression and transport as well as storage, with many options for its removal or impact control. In particular, the effect of sulphur containing species can pose a risk for corrosion throughout the plant and transport pipelines. This paper presents a technical review of all laboratory and pilot work to identify impacts of sulphur impurities from throughout the oxy-fuel process, from combustion, gas cleaning, compression to sequestration with removal and remedial options. An economic assessment of the optimum removal is not considered. Recent oxy-fuel pilot trials performed in support of the Callide Oxy-fuel Project and other pilot scale data are interpreted and combined with thermodynamic simulations to develop a greater fundamental understanding of the changes incurred by recycling the flue gas. The simulations include a sensitivity analysis of process variables and comparisons between air fired and oxy-fuel fired conditions - such as combustion products, SO₃ conversion and limestone addition.     

Generation of PDFS for flame curvature and for flame stretch rate in premixed turbulent combustion

Experimentally derived pdfs of turbulent, premixed, flame curvatures from a variety of sources, for a wide range of conditions are surveyed and a suitable expression sought to generalize these. This proves to be one based on the Damköhler number, Da. This is tantamount to normalizing the curvature by multiplying it by the Taylor scale of turbulence. It enables the distribution of flame curvature when normalized by the laminar flame thickness, to be expressed in terms of the Karlovitz stretch factor, K, and the turbulent Reynolds number, R_l. The value of the pdf at zero curvature is linearly related to Da^1/2.The pdf expressions of Yeung et al. [3] obtained from numerical simulations are used for the strain rate distribution and, on the assumption that these and that for flame curvature are statistically independent, values of flame stretch rate pdfs are generated numerically. It is necessary to define an appropriate surface to define the burning velocity, flame stretch rate, and appropriate Markstein numbers. Two surfaces are considered and employed in the computations, one located at the start of the preheat zone, the other at the start of the reaction zone. The latter seems more rational and gives the better generalisation of the pdfs of flame stretch rate.An assumed linearity of laminar burning velocity with flame stretch rate, extending over both positive and negative stretch rates, enables flame stretch rate pdfs to be generated. It is concluded that negative values of burning velocity are unlikely and that burning velocities should tend to zero rather than attain negative values. This modifies the derivation of flame stretch rate pdfs. These depend on the Markstein number, Karlovitz stretch factor and turbulent Reynolds number. Computations suggest that, for values of K above 0.1 and of R_l above 100, the pdf of stretch rate is similar to that of strain rate. At very low values of K and negative values of Markstein number, pronounced flamelet instability might be anticipated.     

制粉系统防堵煤综合治理改造技术研究及工程实践

本文通过分析某电厂制粉系统雨季堵煤的原因,提出使用降低给煤机出口煤流的速度的方法,并加大给煤机到磨煤机之间落煤管的距离,同时对磨煤机内部流动过程进行了三维数值模拟,获得了磨煤机内部风粉混合物运动的规律,达到了煤流顺利通过落煤管而不与内壁接触的目的,取得了良好的工程改造效果。     

Application of distributed combustion technique to hydrogen-rich coal gases: A numerical investigation

Distributed combustion has been a promising combustion technique, for enabling a more uniform thermal field, resulting in ultra-low pollutant emissions, reduced combustion noise, and enhanced combustion efficiency. This work examines combustion of hydrogen-rich coal gases derived from Turkish coal under distributed combustion conditions. Focus here is on obtaining a broadened flame and reducing pollutant emissions. Numerical modelling was carried out using a commercial code in order to predict the thermal field and pollutant emissions of the hydrogen-rich coal gases under distributed combustion conditions. A gas mixture (90% N₂ and 10% CO₂) was utilized to simulate controlled entrainment of hot reactive product gases into the fresh mixture prior to ignition in order to seek distributed combustion. The results showed that distributed combustion provided far more uniform thermal field that resulted in greatly reduced NOx emissions. The results also showed that the temperature difference between the maximum and exit temperature was reduced to approximately 200 K under distributed conditions. In addition, the NOx pollutant emissions predicted for each gas were reduced to near zero levels under high intensity distributed combustion conditions supporting the available experimental data. It has been concluded that enhanced thermal field uniformity and significantly reduced NOx emissions were achieved for hydrogen-rich coal gases under distributed conditions.     

电站煤粉锅炉火焰监测与燃烧诊断优化控制研究

为保证锅炉安全运行,必须进行切实有效的火焰监测和燃烧诊断措施。基于火焰图像处理技术的电站锅炉火焰监测和燃烧诊断优化控制系统,能够实时在线地监视火焰图像,对火焰图像特征进行分析,对炉内温度场进行重建,同时进行燃烧稳定性、经济性和清洁性的判断,提出运行建议,并利用炉内辐射能信号响应灵敏、迅速的特点将其作为负荷控制的前馈信号,接入DCS控制逻辑中以提高锅炉的负荷响应能力和抗干扰能力。     

电站主流煤粉锅炉飞灰含碳量升高对供电煤耗的影响计算与分析

用简化方法计算了亚临界、超临界、超超临界凝汽式火电机组的煤粉锅炉飞灰含碳量对电厂供电煤耗的影响,并对计算结果进行分析讨论.计算结果表明:当飞灰含碳量提高1%时,电厂的供电煤耗提高约0.8～2.09g/kWh.煤的发热量越低,供电煤耗的增加幅度越大.锅炉的压力等级越低,供电煤耗的提高幅度越大.