几何结构影响高温空气燃烧特性的数值分析

通过改变燃料喷口周围空气喷口分布夹角,采用数值计算的方法研究了高温空气燃烧特性的变化,包括燃烧温度场、速度场和NOx的生成和出口排放情况。模拟结果说明,减小空气分布夹角可以降低燃烧区最高温度和平均温度,扩大燃烧室内低氧范围,有效抑制热力型NOx的生成和排放。所采用的计算模型和计算方法可以较好地模拟高温空气燃烧过程,计算结果可信。     

高温低氧燃烧方法的热工规律和扩大应用

提出了用烟气直接入炉循环建立低氧气氛，实现高温低氧的燃烧方法，导出描述该气氛氧浓度和温度变化规律的数学模型，浅析了燃烧过程的机理，对该方法重新给予定义，分析了该方法节能作用的数量关系，阐述了换热式高温低氧燃烧的优越性，主张换热式高温低氧燃烧方法应该在多种炉窑上使用，以便取得重大的节能环保效果。     

O_2/CO_2气氛下煤粉燃烧特性模拟研究

针对煤粉燃烧器燃烧工况,采用Fluent软件,探索辐射模型、气氛和煤粉粒径对煤粉燃烧过程的影响及污染物生成情况。结果表明:采用DO+WSGG模型时,煤粉的燃烧温度有所降低;跟空气气氛相比O_2/CO_2气氛下煤粉的燃烧温度降低,NO的量也降低;氧浓度增大,煤粉燃烧的温度峰值增加;随着超细煤粉混合比的增加,燃烧高温区而向前移。     

顶燃式热风炉高温低氧燃烧技术

 NOx是制约热风炉实现高风温长寿的主要技术障碍。为有效抑制和降低热风炉燃烧过程生成的NOx,研究分析了NOx的生成机制,运用热力型NOx生成模型计算了热风炉燃烧过程NOx生成速率和生成量,开发设计了基于高温低氧燃烧技术（HTAC）的新型顶燃式热风炉,采用CFD仿真模型对比研究了常规热风炉和高温低氧热风炉的燃烧过程和特性。计算得出2种热风炉的温度场分布和火焰形状、浓度场分布以及NOx的浓度分布。研究结果表明,高温低氧热风炉的温度场分布均匀,在相同拱顶温度下,NOx生成量仅为80×10-6,比常规热风炉降低约76%。高温低氧热风炉可以获得更高的风温并可以有效减少NOx排放,实现热风炉高效长寿和节能减排。     

不同O_2/CO_2浓度下燃烧器燃烧特性数值模拟

针对叶片角度为30°的旋流式天然气纯氧燃烧器,采用Fluent软件对不同助燃风成分为23%O_2/77%CO_2、30%O_2/70%CO_2及40%O_2/60%CO_2配比条件下的燃烧器燃烧特性进行模拟,获得燃烧室内的温度场和浓度场分布。结果表明:不同的O_2/CO_2浓度配比对燃烧室内温度分布影响较大。不同的O_2/CO_2浓度配比对燃烧中间产物CO和H2的浓度分布影响不大,但直接决定了CO_2和H_2O的含量。     

高温竖窑煅烧区的燃烧数值模拟

利用Fluent的前处理软件Gambit建立了高温竖窑煅烧区的几何模型,并利用Fluent软件进行了数值模拟。采用标准的k-ε湍流模型、一般的有限速率模型以及P-1辐射模型进行模拟,成功地计算出燃油燃烧的温度场和浓度场分布情况,验证了数值模拟所用模型和数值模拟结果的可靠性,为研究炉内燃烧状况和实际生产运行中工艺参数的调整提供了依据。     

烟气自循环高温低氧空气燃烧特性的数值模拟

以烟气自循环燃烧室为模型做了大量的数值模拟,通过改变其助燃空气预热温度和含氧量,分析了炉内的温度和组分浓度的分布以及炉尾NO_x排放量的变化,为高温低氧空气燃烧技术的应用提供了理论参考。     

二次空气对高温低氧空气燃烧污染物排放的影响

利用数值模拟软件分析了二次空气对高温低氧空气燃烧污染物排放的影响.应用分级燃烧技术的燃烧器不仅使燃烧室内具有较高的温度水平,温度场均匀,燃烧效率高,而且NOx的生成量也较低,可以达到节约燃料和降低污染物的综合效果.计算结果分析表明:分级燃烧的二次空气配比对燃烧室内的NOx排放有较大影响.当一次空气占40%左右时NOx排放最少.     

化学动力学机理耦合EDC燃烧模型对湍流扩散火焰的数值模拟

将化学动力学机理耦合燃烧模型进行湍流燃烧数值模拟有重要意义.在分析目前现有燃烧模型的基础上,采用CH4/空气化学反应动力学机理和EDC燃烧模型对燃烧器中的二维湍流扩散燃烧进行模拟,得到了燃烧温度、物种浓度随空间的变化曲线图,经分析发现,计算结果可以较好反应文献中的解析解.由此得出结论:将化学动力学机理耦合EDC燃烧模型可以较好地模拟湍流扩散燃烧的火焰结构,从而为工程实际复杂燃烧情况下的污染物、中间物种和痕迹量物种生成机理的研究提供基础.     

蓄热冷态烧嘴结构优化的模拟研究

高温和低氧是高温空气燃烧技术的两个基本特点,蓄热烧嘴的结构对炉内氧浓度的分布具有决定性影响.应用Fluent软件计算了蓄热烧嘴在冷态工况下结构和炉内氧浓度分布的关系,并通过实验进行了验证.     

CaO—SiO2—Na2O—CaF2—Al2O3—MgO保护渣系的Al2O3吸收速率和粘度

采用CaO-SiO2-Na2O-CaF2-Al2O3-MgO渣系,通过测定熔渣的粘度和Al2O3吸收速率,研究连铸保护渣的Al2O3吸收速率与粘度及化学成分之间的关系。在一定条件下,当CaO/SiO2为1.2左右时,粘度达到最小值,Al2O3吸收速率达到最大值,分别为0.10?Pa*s、8.403×10-4?kg*m-2*s-1。随着渣中Na2CO3含量、CaF2含量和MgO含量的增加,粘度减小,Al2O3吸收速率增大。随着渣中Al2O3含量的增加,粘度增大,Al2O3吸收速率减小。粘度为Al2O3吸收速率的主要控制因素。随着熔渣粘度的增加,连铸保护渣的Al2O3吸收速率逐渐减小。     

Effects of SrO/Li2O/La2O3/Ta2O5/TiO2-coating on electrochemical performance of LiCoO2

Commercial cathode material (LiCoO2) was modified by coating with a thin layer of SrO/Li2O/La2O3/Ta2O5/TiO2 for improving its performance in lithium ion battery. The morphology and structure of the modified cathode material were characterized by scanning elec-tron microscopy (SEM) and X-ray diffraction (XRD). The performance including cycling stability, diffusion coefficient under different volt-age, C-rate discharge of the batteries with this modified cathode material was examined. The results showed that the battery with the coated cathode material could discharge at a large current density, and it possessed a stable cycle performance in the range from 3.0 V to 4.2 V. It was explained that the rate of Li ion diffusion increased in the batteries using SrO/Li2O/La2O3/Ta2O5/TiO2-coated LiCoO2 as the cathode and the coated layer could act as a fast ion conductor (Sr0.5La0.05Li0.35Ti0.5Ta0.5O3) and as a protecting shell to prevent LiCoO2 particles from be-ing attacked by the acidic electrolyte.     

Effects of La2O3/Li2O/TiO2- Coating on Electrochemical Performance of LiCoO2 Cathode

Conventional cathode material （LiCoO2） was modified by coating with a thin layer of La2O3/Li2O/TiO2 for improving its performance for lithium ion battery. The morphology and structure of the modified cathode material was characterized by SEM, XRD, and Auger electron spectroscopy. The performance of the cells with the modified cathode material was examined, including the cycling stability, the diffusion coefficient under different voltages, and the C-rate discharge. The results showed that the cell composed of the coated cathode material discharged at a large current density, and possesses a stable cycle performance in the range from 3.0 to 4.4 V. It was explained that the rate of Li ion diffusion increased in the cell while using La2O3/Li2O/TiO2-coated LiCoO2 as the cathode and the coating layer may act as a faster ion conductor （La2O3/Li2O/TiO2）.     

Reduction of solid wustite in H2/H2O/CO/CO2 gas mixtures

The reduction of dense wustite in H₂/H₂O/CO/CO₂ gas mixtures has been carried out at temperatures between 1073 and 1373 K. The critical conditions for the formation of porous iron product morphologies have been identified and the results discussed in relation to the breakdown of dense iron layers on wustite surfaces. Formerly with the University of Queensland.     

Kinetics of reduction of ferric iron in Fe2O3-CaO-SiO2-Al2O3 slags under argon, CO-CO2, or H2-H2O

The rates of reduction of ferric iron in Fe₂O₃-CaO-SiO₂-Al₂O₃ slags containing 3 to 21 wt pct Fe₂O₃ under impinging argon, CO-CO₂, or H₂-H₂O have been studied at 1370 °C under conditions of enhanced mass transfer in the slag using a rotating alumina disc just in contact with the slag surface. For a 6 wt pct Fe slag at a stirring speed of 900 rpm the observed reduction rates by 50 pct H₂-H₂O were a factor of 2 to 3 times higher than those by 50 pct CO-CO₂ and more than one order of magnitude higher than those under pure argon. The observed rates were analyzed to determine the rate-controlling mechanisms for the present conditions. Analysis of the rate data suggests that the rates under 50 pct H₂-H₂O are predominantly controlled by the slag mass transfer. The derived values of the mass-transfer coefficient followed a square-root dependence on the stirring speed for a given slag and, at a given stirring speed, a linear function of the total iron content of the slags. The rates of oxygen evolution during reduction under pure argon were shown to be consistent with a rate-controlling mechanism involving a fast chemical reaction at the interface and relatively slow mass transfer in the gaseous and the slag phases. The rates of reduction by CO-CO₂ (pCO=0.02 to 0.82 atm) were found to be likely of a mixed control by the slag mass transfer and the interfacial reaction. A significant contribution of oxygen evolution to the overall rates was observed for more-oxidized slags and for experiments with relatively low values of pCO. Assuming a parallel reaction mechanism, the estimated net reduction rates due to CO were found to be of the first order in pCO, with the first-order rate constants being approximately a linear function of the ferric concentration. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS. The original symposium appeared in the October 2000 Vol. 31B issue.     

Synthesis of ZrO2-HfO2-Y2O3-Sc2O3 Nano-Particles by Sol-Gel Technique in Aqueous Solution of Alcohol

Zirconium dioxide is a significant material withgood physicochemical characteristics . It is used inmanyfields such as energysources ,material and envi-ronment . Cubic phase zirconium dioxide doped withyttria (YSZ) is alreadyin wide use in solid oxygenfu-…