Emission spectrum from an Al/Mg tracer in the blow-off region of a radiatively ablated capsule

A study of X-ray emissions from Al/Mg tracers buried at two different depths in a plastic shell is presented. The X-rays originating from the K-shell transitions of the Al/Mg ions begin to irradiate after the ablative heating wave has passed through the trace layer and are recorded with a streaked crystal spectrometer. Only emissions from the capsule with the trace layer buried at a smaller depth are observed. Hydrodynamic simulations and a collisional—radiative model including detailed atomic physics are used to investigate the measured spectrum. It is found that the effects of the radiative heating play important roles in the formation of the K-shell emission. The time correlation between the simulations and the measurements is obtained by comparing the measured time profile of the He α emission with the calculated one. The line ratio of Ly α to He α is also calculated and is found to be in fairly good agreement with the experimental data. Finally, the relation between the time profile of the He α emission and the ablation velocity is also discussed.     

辅助气燃烧接口对有机化合物碳同位素测定的影响

对多种烷烃及芳香化合物采用不同类型的反应管进行了碳同位素分析, 旨在阐明燃烧接口对有机化合物色谱行为的影响. 结果表明, 在反应管中填充较少的催化剂有助于提高化合物的分离度, 这可能是由于反应管中载气具有较高的线速度, 从而减少了化合物的扩散加宽. 然而, 不同反应管对分离度的改善作用相对有限. 对于不同的反应管, 化合物的灵敏度变化主要与开口分流处分流比的变化有关, 而这种变化可能是由反应管内载气流速的变化所致.     

Reactive gas-solids flows in large volumes--3D modeling of industrial circulating fluidized bed combustors

A model is presented for the simulation of reactive gas-solids flows in large industrial reactors. Circulating fluidized bed （CFB） combustors with several thousands of cubic meters reaction volume are probably the largest reactors of this type. A semi-empirical modeling approach has been chosen to model the three-dimensional concentration distributions of gas and solids components and temperatures inside the combustion chamber of such boilers. Two industrial CFB boilers are investigated in detail： the 105 MWe Duisburg combustor in Germany and the 235 MWe Turow combustor in Poland. The semi-empirical model approach is described first. Then the model is used to show how the three-dimensional concentration and temperature fields are formed by the interaction of several local phenomena. Good agreement between simulation and measurements has been achieved.     

大气压直流氩等离子体光谱诊断研究

通过光谱诊断系统测量了大气压直流氩等离子体射流在弧室内和弧室出口的发射光谱,利用波尔兹曼曲线斜率法计算了射流的电子温度,根据Ar Ⅰ谱线的斯塔克展宽得到射流的电子密度,并对氩等离子体射流满足局域热力学平衡(LTE)状态的判定标准进行了分析,结果表明在文章的实验条件下大气压直流氩等离子体射流达到局域热力学平衡。     

纳米2,4-二羟基苯甲酸铅(Ⅱ)配合物的合成及其燃烧催化性能研究

采用液相分散沉淀法制备了纳米2,4-二羟基苯甲酸-Pb(Ⅱ)配合物粉体,并用TG,XRD,TEM,IR和元素分析对产物进行了表征.研究了反应条件对产物粒径和粒子形貌的影响.用DSC考察了产物对吸收药热分解的催化作用.结果表明,在水溶液中得到的产物为15nm×40nm的棒状粒子,而在乙醇溶液中得到的是粒径约为50nm的球形粒子.产物对吸收药热分解有显著的催化效果,使吸收药的分解峰温降低5.6℃,分解热增加918J/g.     

土体腐殖酸组分对水泥土强度影响效果试验

利用高速阴影照相系统,对方形管道内火焰流经悬吊圆柱时所产生的变化及其诱导的 流场进行了实验研究,并利用高精度PPM格式对上述现象进行了数值模拟,其中,湍流采用 大涡模拟(LES)方法,燃烧采用旋涡破碎(EBU)模型,圆柱边界采用沉浸边界法(IBM). 实验结果与计算结果比较吻合,在一定程度上揭示了火焰阵面变形和加速的规律. 根据研究 结果,对火焰与悬吊圆柱相互作用过程中火焰的三维形状、流场中涡量和湍流强度的分布、 火焰与流场的相互影响以及火焰传播轨迹等进行了讨论.     

Numerical and analytical investigation of the indirect combustion noise in a nozzle

Analytical and numerical assessments of the indirect noise generated through a nozzle are presented. The configuration corresponds to an experimental setup operated at DLR by Bake et al. (2008) where an entropy wave is generated upstream of the nozzle by means of an electrical heating device. Both 3-D and 2-D axisymmetric simulations are performed to demonstrate that the experiment is mostly driven by linear acoustic phenomena, including pressure wave reflection at the outlet and entropy-to-acoustic conversion in the accelerated regions. Results show that the acoustic impedance downstream of the nozzle must be accounted for appropriately in order to recover the experimental pressure signal. A good agreement is also obtained with a purely analytical assessment based on the Marble and Candel compact nozzle approximation. To cite this article: M. Leyko et al., C. R. Mecanique 337 (2009).     

太赫兹波段火焰碳黑的光学特性研究

火焰碳黑是碳氢燃料不完全燃烧的重要固体产物,对于一些污染物的生成具有重要影响,其光学特性是光学燃烧诊断的基础。利用太赫兹时域光谱技术研究了0.2～1.6 THz火焰碳黑的光学特性,通过傅里叶变换得到了碳黑的频域光谱,利用定点迭代法获得了太赫兹波段火焰碳黑的复折射率,把太赫兹波段的复折射率与热辐射波段的复折射率进行了比较,此外还对比了两种光学参数提取方法所得到的结果,结果表明,碳黑在太赫兹波段的吸收性较强,其折射率在太赫兹波段与在热辐射波段的差别不是很大,而吸收率在热辐射波段变化更大一些,两种参数提取方法得到的复折射率差别不是很大,研究结果可为太赫兹波技术应用于光学燃烧诊断提供基础性数据,扩展了光学燃烧诊断应用的范围。     

Experiments for Combustion-LES Validation

Designs of future combustors increasingly rely on numerical combustion simulations. Large-eddy simulation (LES) emerged as a method to better describe turbulence than Reynolds-averaged Navier–Stokes (RANS) approaches. Processes at the subgrid scale, however, need to be modelled. Validation using comprehensive and reliable experimental data sets is therefore a crucial part in the development of combustion-LES. Using well-defined benchmark flames and advanced laser diagnostics, different physical and chemical quantities can be precisely measured with high temporal and reasonable spatial resolution. In this contribution, quantities important to combustion-LES validation and the most frequently used laser diagnostic methods are briefly reviewed. New challenges in the field of diagnostics at high repetition rates and at walls are highlighted. In a closing chapter, some critical aspects on the comparison of experimental measurands and combustion-LES-predicted counterparts are discussed.     

Utilization of chemical looping strategy in coal gasification processes

Three chemical looping gasification processes, i. e. Syngas Chemical Looping (SCL) process, Coal Direct Chemical Looping (CDCL) process, and Calcium Looping process (CLP), are being developed at the Ohio State University (OSU). These processes utilize simple reaction schemes to convert carbonaceous fuels into products such as hydrogen, electricity, and synthetic fuels through the transformation of a highly reactive, highly recyclable chemical intermediate. In this paper, these novel chemical looping gasification processes are described and their advantages and potential challenges for commercialization are discussed.