反应器高度对气体发生器中炭粉燃烧的影响

将炭粉与空气按比例预混后在发生器中燃烧生成N2+CO2混合气体是经济制备镁熔体气体保护用载流气体的一种新方法。对自行开发的管状载流气体发生器中空气-炭粉两相流燃烧进行了数值模拟,结果表明,炭粉燃烬程度(用碳浓度表示)可以近似为反应器高度的递减对数函数;总存在一个临界值H0,当反应器高度H≥H0时,炭粉燃烬,在所模拟的工况下,H0≈1000mm。     

气相燃烧合成纳米二氧化钛粒子及其光催化降解三氯乙烯

在自行设计的多重射流燃烧反应器基础上,通过氢气和空气预混合辅助燃烧方法,用四氯化钛作为前驱体气相水解合成了纳米二氧化钛颗粒.并通过TEM、XRD、TG-DTA、X荧光半定量分析和UV-Vis吸收光谱对所制得的粒子进行了表征.以三氯乙烯(TCE)气体为模拟污染物,考察了粒子的气相光催化性能.在连续流动式玻璃反应器中,反应时间为2h时,所制样品对三氯乙烯的降解率和商品TiO2相当.     

探讨注汽锅炉热效率计算与提高对策

热效率就是锅炉输出的热量占燃料燃烧放出的热量的百分数。影响锅炉热效率的主要因素是排烟热损失、气体不完全燃烧热损失、炉体散热损失。其中排烟热损失是影响热效率的重要因素。通过对各项因素的分析,找出提高锅炉热效率的途径：降低排烟温度和过剩空气系数以降低排烟热焓,选用高效保温材料,提高辅射段、对流段、过渡段保温效果,降低炉体散热损失,调整合理的过剩空气系数,保证锅炉良好燃烧,降低气体不完全燃烧损失。     

稠油注汽热效率分析与提高措施

热效率就是锅炉输出的热量占燃料燃烧放出的热量的百分数。影响锅炉热效率的主要因素是排烟热损失、气体不完全燃烧热损失、炉体散热损失。其中排烟热损失是影响热效率的重要因素。通过对各项因素的分析，找出提高锅炉热效率的途径：降低排烟温度和过剩空气系数以降低排烟热焓；选用高效保温材料，提高辅射段、对流段、过渡段保温效果，降低炉体散热损失；调整合理的过剩空气系数，保证锅炉良好燃烧，降低气体不完全燃烧损失。     

过剩空气系数α对导热油炉热效率、腐蚀和NOx排放的影响

通过研究过剩空气系数的计算方法和过剩空气系数对导热油炉的影响，找出过剩空气系数与热油炉热效率和炉管腐蚀以及NOx排放量的关系，并确定最优的过剩空气系数，以此提高燃烧的热效率，同时减少炉管的腐蚀和NOx排放。     

超音速火焰喷涂简化数学模型及其应用

应用燃料燃烧理论、气体动力学和两相流原理,建立了超音速火焰喷涂焰流特性和粒子加速、加热行为的简化模型,并在计算机上进行了数值求解。研究了气、油质量比(空气过剩系数)对燃烧室焰流温度及相关参数的影响。结果表明,随着气、油质量比的增大,燃烧室焰流温度明显降低,因此气、油质量比不宜过大。另外,预热助燃气体是提高燃烧室焰流温度的重要措施。燃烧室焰流压力越快,焰流出枪速度越大,但焰流出枪温度越低。喷涂WC-Co系合金时,合理的燃烧室焰流压力约为0.6MPa。粒子出枪后,粒子速度和温度均先增大后降低,因此存在一个合理的喷涂距离。针对所研究的条件,合理的喷涂距离约为0.1m。     

烟火式气体发生器燃烧过程的数值模拟和试验研究?

建立了理论模型模拟烟火式气体发生器的燃烧过程,基于质量守恒、能量守恒、气体状态方程、气体发生剂的几何燃烧规律以及小孔气体流量规律,还考虑了与过滤网以及壳体的散热损失,获得了数值模拟的内压曲线和压力罐曲线,并与试验结果进行对比分析,证实了模拟结果的准确性。结果表明:燃速压力指数越大,发生器达到最大内压的时间越短,最大压力越高;气体发生剂厚度越小,发生器压力上升越快,最大压力越高,达到最大压力的时间越短;装药量越大,发生器压力上升得越快,最大压力越高,达到最大压力的时间越短;排气孔直径越大,最大压力越小,达到最大压力的时间越长。为烟火式气体发生器的设计提供了理论依据。     

音速喷嘴检定过程中几个问题的分析

本文介绍了音速喷嘴的工作原理及其数学模型,并对检定过程中流出系数C的不确定度进行评定,分析了空气密度、空气气体常数和临界流函数等因素对流出系数的影响.同时分析了空气湿度对各因素的影响,得出了关于音速喷嘴检定的几个重要的结论.     

炭黑生成过程的研究

研究了炭黑在工业丙烷/空气体系中通过不完全燃烧方法生成的过程.通过改变氧化气体种类和进气条件,计算了炉气成分及含量,并对燃料的气化和热解过程以及中间产物对炭黑物理化学性能的影响进行了分析,得到炭黑产量最高的工况和乙炔浓度沿反应器垂直方向的分布函数,并对燃烧中颗粒的生长过程进行了计算与分析.     

炉内CO测量在降低NO_x排放中的应用

锅炉低氮改造后,对过剩空气系数要求炉内燃烧器区域为0.8左右,到SOFA层及以上,逐渐提高到1.0～1.25。现有的燃烧测控手段无法实现这一要求,所以很多低氮改造后的锅炉,仍有脱硝入口NO_x偏高或者飞灰上升较大的情况。该文针对上述问题,阐述了通过对四角切圆锅炉炉内水冷壁区域烟气中CO含量值的测量以及其与燃烧的对应关系,使各燃烧层的过剩空气系数达到锅炉设计要求,既能降低脱硝入口的NO_x值,又不至于飞灰含碳量增高较多的目的。     

高炉煤粉喷吹燃烧行为的数值模拟

为探究煤粉喷吹微观机理,分析煤粉喷吹行为规律及其它相态物料对其影响,采用计算流体动力学(CFD)技术对高炉内多相流动过程进行建模。以某1 750 m3炼铁高炉为研究对象,将喷入的煤粉作为粉相,计算得到典型炉况下多相态的温度、速度等物理量可视化结果,以及高煤比时炉内温度状态。实践运行与计算结果表明,适当调整布料结构、富氧量等因素,可进一步加大煤粉喷吹量,从而提高炉利用系数,降低焦比和生产成本。     

燃气发生器条件下穿刺C/C复合材料喷管的烧蚀性能研究

研究了穿刺C/C复合材料喷管在酒精/氧气燃气发生器模拟的液体火箭发动机富氧燃气环境中的烧蚀性能, 分析了穿刺C/C复合材料的烧蚀机理及燃气参数对烧蚀性能的影响. 结果表明, 喷管喉部线烧蚀率为(0.055±0.029)mm/s, 质量烧蚀率为0.186kg/(m²·s). 喷管收敛段下游到喉部区域烧蚀最严重, 收敛段上游其次, 扩散段烧蚀最弱. 烧蚀过程是热化学烧蚀和气流冲刷综合作用的结果, 燃气温度和氧化性组分H₂O和CO₂含量决定穿刺C/C复合材料热化学烧蚀率, 压强和流速影响穿刺C/C复合材料的机械剥蚀.     

微油点火燃烧器一级燃烧室点火性能试验研究

试验研究了不同一次风速和煤粉质量分数条件下微油点火燃烧器一级燃烧室的点火性能.研究结果表明,燃烧室中心温度随一次风速和煤粉质量分数的增加,呈先降低后增加的趋势;燃烧室中心线上的CO体积分数随一次风速的增加而增大,但随煤粉质量分数的增加而减小;燃烧室出口中心处的NOx体积分数随一次风速和煤粉浓度的增加则均呈现上升趋势.     

基于硅材料的微型气体涡轮机中微型燃烧器的设计和加工

由微型燃烧器、微型压缩机和涡轮组成的微型气体涡轮发动机有望成为微机电系统的能源系统.阐述了一种微型燃烧器的设计和加工.设计时力图增加流路的长度,其目的是减少微型燃烧腔的热损失和有效地对燃料和空气进行预热.该微型燃烧器由7片厚度不同的单晶硅片组成,通过ICP DRIE干刻蚀加工而成.组装后的微燃烧器的样件尺寸为21.5 mm×21.5 mm×4.4 mm,已成功地进行了氢气燃烧实验和测试.该微型燃烧器和转子组合后可以应用于微型气体涡轮发动机,与压电元件组合后可用于微型发电机.     

Application of flamelet/progress-variable approach to the large eddy simulation of a turbulent jet flame of pulverized coals

In this study, the flamelet/progress-variable (FPV) approach was applied to a large eddy simulation of a pulverized coal jet flame. The FPV approach considers the characteristics of the pulverized coal flame, e.g., non-adiabatic system and several types of fuel streams, via additional representative variables. First, the applicability of the FPV approach to a turbulent flame with pulverized coals was confirmed through a comparison of the numerical solutions and experimental data. In this study, the pure pilot case was also investigated to clarify the effects of pulverized coals on the flame. The flame structure changes significantly upon the injection of pulverized coals, and the flame index suggests the coexistence of premixed and diffusion combustion modes even in the downstream region. In particular, the combustion mode fluctuates with time in the middle region of the flame. The fuel gas released from the pulverized coals should increase in this region; therefore, the release and combustion behavior of the volatile matter must be involved in the combustion mode variation. The evaluation of the combustion modes of fuel gas in the coal flame is useful for the design and optimization of pulverized coal combustors with next-generation technologies.     

Numerical study of air staging in a coke oven heating system

The air staging to combustion approach introduced to a coke oven heating system as a primary method of nitrogen oxide (NO) formation reduction is considered in this paper. To numerically investigate the thermal and prompt NO formation, a heating flue model representing the most popular Polish coke oven battery was used. The model was developed and experimentally validated as a transient coupled model for the representative heating flue and the two coke ovens. Numerical simulations were performed to estimate the amount of NO passing into the atmosphere during the operation of such a heating system with and without the secondary air inlets. Various strategies for the secondary air distribution along the flue gas flow as well as the secondary air velocity were studied. The results of the numerical investigation demonstrated the substantial positive effect of the considered air staging on NO formation reduction.     

Effect of copper oxide on the structure of nano-sized Ni(x)Zn(y)Fe2O4 powders prepared by using self-propagating high temperature synthesis

Nano-sized Cu(x)Ni(x)Zn(1-x-y)Fe2O4 ferrites were prepared by using self-propagating high-temperature synthesis (SHS) and mechanical ball milling. As oxygen pressure increases and copper content decreases in the initial composition, average combustion temperature and combustion velocity increases in the ranges of 947 to 1150 degrees C and 4.2 to 6.5 mm/sec, respectively. The SHS products were agglomerated crystalline powders in which fine particles were present. The average particle of the pulverized SHS product was about 200 nm. Lattice parameters determined by neutron diffractometry are 8.4125 angstroms for Ni0.38Zn0.62Fe2O4 and a = 8.3540 angstroms for Cu0.29Ni0.28Zn0.43Fe2O4.     

ANN–GA approach for predictive modeling and optimization of NOx emission in a tangentially fired boiler

An artificial neural network (ANN) and genetic algorithm (GA) approach to predict NOx emission of a 210 MW capacity pulverized coal-fired boiler and combustion parameter optimization to reduce NOx emission in flue gas, is proposed. The effects of oxygen concentration in flue gas, coal properties, coal flow, boiler load, air distribution scheme, flue gas outlet temperature, and nozzle tilt were studied. The data collected from parametric field experiments was used to build a feed-forward back-propagation neural net. The coal combustion parameters were used as inputs and NOx emission as outputs of the model. The ANN model was developed for full load conditions and its predicted values were verified with the actual values. The algebraic equation containing weights and biases of the trained net was used as fitness function in GA. The genetic search was used to find the optimum level of input operating conditions corresponding to low NOx emission. The results proved that the proposed approach could be used for generating feasible operating conditions.     

Mathematical modeling of the aerodynamics and physicochemical processes in the free board zone of a circulating fluidized bed furnace. IV. Heat and mass transfer and combustion

A mathematical model describing the motion of a highly concentrated coke-ash mixture in the pneumatic transport region within the free board zone of a circulating fluidized bed reactor was developed earlier in [1–3]. In the present work it is extended to the case of a nonisothermal flow with heterogeneous combustion of carbon. Equations of mass, momentum, and energy conservation are obtained for the gas components and the coke fractions. Distinctive features of the heat transfer, combustion, and particle motion are investigated numerically.Institute of Problems of Energy Conservation, Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 1–2, pp. 32–38, July–August, 1994.     

混合导体透氧膜反应器中焦炉煤气重整制合成气的实验研究

研究了以焦炉煤气为原料在BaCo0.7Fe0.2Nb0.1O3-δ(BCFNO)透氧膜反应器中制合成气。实验结果表明,BCFNO膜反应器的自催化性能差。加入催化剂后,膜反应器的重整性能得到明显提高,在875℃,焦炉煤气中甲烷转化率为87.0%,产物中氢气和一氧化碳选择性分别为78.3%、105.6%,透氧量达到15.8ml/(cm2.min)。焦炉煤气中的甲烷在膜反应器中反应路径为首先焦炉煤气中的氢气与膜片透过去的氧反应生成水,然后甲烷再与水重整生成氢气和一氧化碳。实验过程中,透氧膜没有出现破裂,BCFNO透氧膜反应器在富氢的焦炉煤气下显示出很好的稳定性。