旋流对煤粉燃烧NO排放影响的数值模拟

本文用基于HCN释放的简化Solomon模型的NO生成湍流反应的统一二阶矩代数模型(AUSM)和煤粉燃烧的双流体模型,对不同旋流数下煤粉燃烧器内两相流动,煤粉燃烧和NO生成进行了数值模拟。模拟结果和文献中实验结果符合很好。模拟结果指出,随着旋流数的增加,NO的排放先减少后增加,燃尽率先增加后减小,和气体燃烧中得到的规律类似。     

湍流煤粉火焰中多相燃烧的跨尺度模拟方法及应用

通过"湍流涡团尺度"与"边界层反应尺度"的关联,建立了湍流煤粉火焰中多相燃烧的跨尺度模拟方法。该方法能够预报湍流脉动宏观规律对静止颗粒边界层内气相反应(如挥发分火焰、CO火焰)的影响。将该方法用于煤粉旋流燃烧数值模拟中,结果显示:与完全忽略边界层气相反应的单膜模型相比,跨尺度模拟的预报结果与Lockwood实验数据有更好的符合。     

径向浓淡旋流煤粉燃烧器气流湍流特性的冷态试验研究

本文利用ＩＦＡ３００型一维热膜风速仪系统对径向浓淡旋流煤粉燃烧器单相冷态湍流流场进行了试验研究,测量了流场内不同位置瞬时速度的数值,同时测量了脉动速度均方根、湍流度、平坦因子和偏斜因子在流场内的分布,得到了新型旋流燃烧器气流湍流特性参数的分布规律,可以用于研究径向浓淡旋流煤粉燃烧器的燃烧特性。     

旋流数对湍流燃烧中NO生成影响的研究

通过实验和用湍流燃烧二阶矩概率密度模型对不同旋流数下甲烷-空气湍流燃烧和NO生成进行了研究。在燃料中加入少量氨模拟燃料氮。研究结果表明,随旋流数的增大（由0到1）,热NO排放先上升后下降,而总NO和燃料NO排放则先下降后上升。旋流数增大使湍流强度先下降然后稍有上升,使进口附近温度先上升然后稍有下降。热NO的生成受温度的影响更大而燃料NO的生成受湍流的影响更大。     

高温空气煤粉直燃技术的数值模拟

本文通过数值计算的方法,对高温空气煤粉直燃燃烧器的多种运行工况进行了数值试验研究,分析了煤粉气流入口速度、煤粉浓度和高温空气速度等主要因素对煤粉气流着火的影响,模拟结果还可以反映出高温空气无油点火燃烧器内的流动、燃烧和传热情况。与试验数据的对比分析表明,数值模拟结果与试验数据趋势一致。研究结果对此燃烧器的结构及运行参数的优化提供了指导。     

煤粉旋风燃烧过程流场特性研究

煤粉旋风燃烧器可用于工业加热过程,实现以煤代油,本论文根据旋流燃烧流动特点,采用能考虑非均向湍流应力的雷诺应力模型,对煤粉旋风燃烧器内气流流动过程场进行数值模拟计算,流场计算结果表明,燃烧室几何参数对其内部的流动特性有很大的影响。计算结果与流场实验测试相吻合。     

旋流气粒两相流动的研究

旋流气粒两相流动广泛存在于燃气轮机燃烧室,旋风分离器和旋风炉,锅炉旋流燃烧器等装置中。用测量和数值模拟更好地了解其流动特性,对优化和放大设计,用以提高燃烧效率和收集效率、降低流动阻力和污染物排放,稳定火焰,都十分重要。对其进行了系统的实验测量和数值模拟研究,包括用相位多普勒仪等测量进行的实验研究,雷诺平均模拟和大涡模拟的数值研究,阐明了两相速度,两相湍流特性和颗粒浓度分布等规律,有助于研制低阻力和高效率低污染燃烧装置。     

MILD煤粉燃烧湍流与化学反应相互作用的数值分析

采用计算流体动力学(CFD)数值模拟方法分析了湍流与化学反应相互作用下MILD煤粉燃烧的微观特征。比较了涡耗散模型(EDM模型)和涡耗散概念模型(EDC模型)对MILD煤粉燃烧的影响,两者得到的速度场、温度场、烟气成分等结果与实验结果符合较好.在此基础上分析了MILD煤粉燃烧湍流和化学反应的微观特征尺度,发现采用EDC模型能更准确地反映MILD煤粉燃烧的微观特征,即山于强烈的烟气内部再循环导致的高湍流混合和烟气稀释后低氧浓度下的缓慢化学反应.     

旋流扩散燃烧中旋流数对热NO生成的影响

本文对旋流扩散燃烧进行了数值模拟，研究旋流数对热ＮＯ生成的影响，其中对湍流采用Ｒｅｙｎｏｌｄｓ应力方程模型，对燃烧采用ＥＢＵ－Ａｒｒｈｅｎｉｕｓ模型，对热ＮＯ生成采用设定ＰＤＦ的模型。预报了不同旋流数下轴向和切向的平均和脉动速度、温度和ＮＯ浓度，指出随着旋流数的增大，计算得到的出口平均ＮＯ浓度首先升高然后下降。这一趋势和本文作者最近的实验结果的趋势一致．随着旋流数的增大，湍流脉动首先下阵然后升高，而进口附近的温度上升，二者综合效果造成上述趋势、因此在实际燃烧器中，完全靠改变族流数来控制ＮＯ生成是不现实的。应该采取其他方法来降低ＮＯ的生成。     

径向浓浓淡旋流煤粉燃烧器直流二次风对气固流动的影响

本文综述了旋流燃烧器直流二次风对燃烧器区单相流动、烟气温度、煤粉燃尽及ＮＯｘ生成的影响,采用三维ＰＤＡ系统对不同直流二次风率下的气固速度分布、颗粒体积流量分布进行了测量,得出了其对气固流动的影响,分析了对燃烧器性能的影响。     

水泥回转窑内NO生成及其分布规律研究

本文在气固流动、煤粉燃烧和NO生成数学模型的基础上,对水泥回转窑内物料烧成过程的物理化学反应热效应采用分区段拟合的方法,建立了一套描述水泥回转窑窑内过程的数学模型。并对某3000吨／天生产能力的带四通道燃烧器的水泥回转窑进行了数值模拟,得到了回转窑内气体速度场、气体温度和组分浓度沿窑长的变化规律,对窑内NO生成进行了深入研究。研究结果表明:水泥回转窑内NO生成按机理可分为热力型NO和燃料型NO,由于窑内存在着高温、富氧环境,热力型NO为主要生成方式;热力型NO和燃料型NO生成过程存在着相互抑制作用。     

NO_x生成的有限反应速率二阶矩封闭模型

本文用有限反应速率二阶矩封闭模型对大速差射流燃烧室内煤粉燃烧过程中NO的生成进行了数值模拟，并将该模型的计算结果与Arrhenius模型的计算结果进行了比较，模拟结果表明，燃烧室中NO的生成是由燃料NO的生成机理来控制，Arrhenius模型计算得到的NO的浓度值高于有限反应速率二阶矩封闭模型的计算结果．     

进口浓度对水力旋流器颗粒分级的影响

通过对水力旋流器内液固多相流动的固体颗粒运动进行理论分析、数值模拟和实验测试,探讨了进口颗粒浓度对采用水力旋流器进行高炉污泥颗粒分级的影响。液固多相流动的数值模拟证实,固体颗粒在水力旋流器内的径向沉降速度近似与颗粒粒径的平方成正比。实验给出了不同进口浓度的颗粒分级效率曲线。本文的实验结果、数值模拟结果以及颗粒离心沉降的理论分析都表明,进口浓度对水力旋流器内高炉污泥的颗粒分级影响不大,该结果诠释了在高炉污泥脱锌操作所考虑的颗粒浓度范围内为什么低浓度下水力旋流器颗粒分级的数值模拟结果与较高浓度下的实验结果基本一致。     

CFD和电容成像对旋风简浓缩特性的对比研究

设计了一种无排气管旋风浓缩简,运用CFD对无排气管旋风筒浓缩特性进行了计算,验证了设计参数的有效性。同时,采用ECT测量了管道截面上固体颗粒的浓度分布。两种方法所得结果具有很好的一致性.这两种方法的结合,为浓缩器的进一步深入研究提供了有效的方法。     

The effects of oxygen concentration and gas temperature on coal stream ignition and particle surface temperature in reducing-to-oxidizing environments

In the near-burner region of pulverized coal burners, two zones exist, with very different oxygen concentrations. The first zone is a locally reducing environment, caused by the fast release of volatiles from a region of dense coal particles, and the second zone, which is surrounding the first zone, is a hot oxidizing environment. The transition of coal particles from the reducing zone to the oxidizing zone affects early stage coal combustion characteristics, such as devolatilization, ignition and particle temperature history. In this work, we used a two-stage Hencken flat-flame burner to simulate the conditions that coal particles experience in practical combustors when they transition from a reducing environment to an oxidizing environments. The composition of the reducing environment was chosen to approximate that of a typical coal volatile. Three oxygen concentrations (5, 10 and 15 vol%) in the “ambient” oxidizing environment were tested, corresponding to those at different distances downstream from a commercial burner. The corresponding gas temperatures for the oxidizing environments were adjusted for the different oxygen concentrations such that the “volatile” flame temperatures were the same, as this is what would be expected in a commercial combustor. High speed videography was used to obtain the ignition characteristics, and RGB color pyrometry was used to measure particle surface temperatures. Two different sizes of coal particles were used. It is found that when particles undergo a reducing-to-oxidizing transition at high temperatures, the particles are preheated such that the critical factor for ignition delay is point at which the particle is in the presence of oxygen, not the concentration of oxygen. The ignition delay of large particles is found to be 53% longer than that of small particles due to their higher thermal mass and slower devolatilization. The oxygen concentration in the ambient have a negligible effect on early-stage particle temperatures.     

Spherical turbulent flame propagation of pulverized coal particle clouds in an O2/N2 atmosphere

The present study aims to clarify the effects of turbulence intensity and coal concentration on the spherical turbulent flame propagation of a pulverized coal particle cloud. A unique experimental apparatus was developed in which coal particles can be dispersed homogeneously in a turbulent flow field generated by two fans. Experiments on spherical turbulent flame propagation of pulverized coal particle clouds in a constant volume spherical chamber in various turbulence intensities and coal concentrations were conducted. A common bituminous coal was used in the present study. The flame propagation velocity was obtained from an analysis of flame propagation images taken using a high-speed camera. It was found that the flame propagation velocity increased with increasing flame radius. The flame propagation velocity increases as the turbulence intensity increases. Similar trends were observed in spherical flames using gaseous fuel. The coal concentration has a weak effect on the flame propagation velocity, which is unique to pulverized coal combustions in a turbulent field. These are the first reports of experimental results for the spherical turbulent flame propagation behavior of pulverized coal particle clouds. The results obtained in the present study are obviously different from those of previous pulverized coal combustion studies and any other results of gaseous fuel combustion research.     

Numerical analysis on the electrostatic capture of airborne nanoparticles and viruses in a homemade particle concentrator without a unipolar charger

A numerical analysis on the electrostatic capture of airborne viruses and nanoparticles in a homemade particle concentrator without a unipolar charger using commercial CFD software (CFD-ACE+) was presented. We simulated the effects of inlet/outlet configurations and particle diameters on the collection efficiency of the particle concentrator, and the simulation was in good agreement with the experimental measurements. We investigated the effects of the electrode arrangement on the collection efficiency. We also discussed the maximum collection efficiency and the relationship between the electric field intensity, the positions of the simulated particles on the inlet surface, and the collection efficiency.     

稠密气固流动二阶矩摩擦应力模型和模拟

基于统一二阶矩两相湍流应力模型和稠密颗粒动力学理论,建立了欧拉-欧拉双流体二阶矩颗粒摩擦应力模型。模型充分反映各向异性的气固两相相间雷诺应力相互作用,并引入有效颗粒弹性恢复系数,考虑了因颗粒表面不光滑产生的摩擦力对湍流流动结构和颗粒弥散特性的影响,对于下降管的计算结果与实验吻合较好。因颗粒摩擦产生能量耗散降低了颗粒温度和导致颗粒雷诺应力再分布。在入口和出口区域因颗粒碰撞频率较高而产生的能量耗散对流动结构影响明显。