On the Fundamental Polymer Chemistry of Inverse Vulcanization for Statistical and Segmented Copolymers from Elemental Sulfur

In this concept review, the fundamental and polymerization chemistry of inverse vulcanization for the preparation of statistical and segmented sulfur copolymers, which have been actively developed and advanced in various applications over the past decade is discussed. This concept review delves into a discussion of step-growth polymerization constructs to describe the inverse vulcanization process and discuss prepolymer approaches for the synthesis of segmented sulfur polyurethanes. Furthermore, this concept review discusses the advantages of inverse vulcanization in conjunction with dynamic covalent polymerization and post-polymerization modifications to prepare segmented block copolymers with enhanced thermomechanical and flame retardant properties of these materials.     

Combustion properties of H2/N2/O2/steam mixtures

The present work reports new experimental and numerical results of the combustion properties of hydrogen based mixtures diluted by nitrogen and steam. Spherical expanding flames have been studied in a spherical bomb over a large domain of equivalence ratios, initial temperatures and dilutions at an initial pressure of 100 kPa (T_ini = 296, 363, 413 K; N₂/O₂ = 3.76, 5.67, 9; %Steam = 0, 20, 30). From these experiments, the laminar flame speed $S_L^0$, the Markstein length L’, the activation energy Ea and the Zel'dovich β number have been determined. These parameters were also simulated using COSILAB^® in order to verify the validity of the Mével et al. [1] detailed kinetic mechanism. Other parameters as the laminar flame thickness δ and the effective Lewis number Le_eff were also simulated. These new results aim at providing an extended database that will be very useful in the hydrogen combustion hazard assessment for nuclear reactor power plant new design.     

A model for crack formation during active solid pyrolysis of a char-forming solid: crack patterns; surface area generation; volatile mass efflux

A model is developed for the formation and propagation of cracks in a material sample that is heated at its top surface, pyrolyses, and then thermally degrades to form char. In this work the sample is heated uniformly over its entire top surface by a hypothetical flame (a heat source). The pyrolysis mechanism is described by a one-step overall reaction that is dependent nonlinearly on the temperature (Arrhenius form). Stresses develop in response to the thermal degradation of the material by means of a shrinkage strain caused by local mass loss during pyrolysis. When the principal stress exceeds a prescribed threshold value, the material forms a local crack. Cracks are found to generally originate at the surface in response to heating, but occasionally they form in the bulk, away from ever-changing material boundaries. The resulting cracks evolve and form patterns whose characteristics are described. Quantities examined in detail are: the crack spacing in the pyrolysis zone; the crack length evolution; the formation and nature of crack loops which are defined as individual cracks that have joined to form loops that are disconnected from the remaining material; the formation of enhanced pyrolysis area; and the impact of all of the former quantities on mass flux. It is determined that the mass flux from the sample can be greatly enhanced over its nominal (non-cracking) counterpart. The mass efflux profile qualitatively resembles those observed in Cone Calorimeter tests.     

A time‐accurate pseudo‐compressibility approach based on an unstructured hybrid finite volume technique applied to unsteady turbulent premixed flame propagation

A preconditioning approach based on the artificial compressibility formulation is extended to solve the governing equations for unsteady turbulent reactive flows with heat release, at low Mach numbers, on an unstructured hybrid grid context. Premixed reactants are considered and a flamelet approach for combustion modelling is adopted using a continuous quenched mean reaction rate. An overlapped cell‐vertex finite volume method is adopted as a discretisation scheme. Artificial dissipation terms for hybrid grids are explicitly added to ensure a stable, discretised set of equations. A second‐order, explicit, hybrid Runge–Kutta scheme is applied for the time marching in pseudo‐time. A time derivative of the dependent variable is added to recover the time accuracy of the preconditioned set of equations. This derivative is discretised by an implicit, second‐order scheme. The resulting scheme is applied to the calculation of an infinite planar (one‐dimensional) turbulent premixed flame propagating freely in reactants whose turbulence is supposed to be frozen, homogeneous and isotropic. The accuracy of the results obtained with the proposed method proves to be excellent when compared to the data available in the literature. Copyright © 2004 John Wiley & Sons, Ltd.     

四溴双酚A锑铝双金属化合物的合成及其阻燃性能

以四溴双酚Ａ（ＴＢＡ）合成了在水和空气中稳定的四溴双酚Ａ合锑铝双金属化合物（ＴＢＡＳＡ）．通过ＩＲ、１ＨＮＭＲ和元素分析予以表征，并研究了其对聚乙烯（ＰＥ）和聚环氧乙烷（ＰＥＯ）的阻燃性能．结果表明，这种分子中含有溴、锑和铝的化合物，对聚乙烯和聚环氧乙烷等高聚物材料有高的阻燃性能与消烟效果．     

乙烷对冲扩散火焰中PAHs的生成

本文使用详细的化学反应机理模拟了C2H6／O2／N2／AR层流对冲扩散火焰中多环芳烃的生成动力学过程。反应机理包括96种组分的502个基元反应。通过数值计算分析了层流对冲火焰的结构和主要反应物、中间物质和反应产物的浓度变化,并与相关文献的实验结果进行了比较。结果表明,数值模拟在燃烧过程和PAH生成规律上与实验结果是一致的,但在某些组分的定量预报上存在一定的差别。     

Faraday镜预转角对FMOCT输出光偏振态的影响

通过计算机仿真，运用琼斯矩阵理论分析了Faraday镜预转角对法拉第镜式光学电流互感器输出光偏振态的影响.实验测量了Faraday镜实际预转角的大小，测量了外磁场的改变对Faraday镜预转角的影响.外磁场的存在和变化使Faraday镜预转角偏离初始值，并使系统输出光由理想状态下的线偏振光退化成椭圆偏振光，并引起法拉第镜式光学电流互感器工作灵敏度和稳定性的下降.提出了用电磁屏蔽解决外界磁场影响的方法.     

Simulation of a turbulent premixed open V-shaped flame using contour advection with surgery

Despite its capability of high spatial resolution, simulation of turbulent flows with traditional Lagrangian (front tracking) scheme is often discouraged by numerical instability caused by clustering of marker nodes and topological changes of fronts. Contour advection surgery (CAS), being a robust front tracking scheme, can limit the growth of front complexity during simulation without jeopardizing accuracy or efficiency. This allows it to open up an advantage over traditional front-tracking schemes. It has already been demonstrated that CAS, with incorporation of the reaction sheet model, can accurately simulate the propagation and advection of a turbulent premixed V-shaped flame. In this study, it is further tested with 10 values of vortex circulation. A range of upstream turbulence levels of 1.8–19.8% was obtained. Results indicate that upstream turbulence increase the average flame length, flame zone area and the overall burning rate. Flame surface density Σ was also estimated. Maximum values of Σ obtained lie in the range 0.1–1.4 mm⁻¹. Skewness towards the burnt region was observed in all profiles of Σ. Similar to results from laboratory experiments, it was found that Σ values decreases with upstream turbulence. From this study, the ability of CAS to cope with intense turbulence is demonstrated and a better quantitative understanding on the scheme has also been acquired.     

The thermolysis of dicarbonylcyclopentadienyliron dimer: The formation of biferrocene

The thermolysis of dicarbonylcyclopentadienyliron dimer in a sealed tube at 300°C has been reported to produce ferrocene, carbon monoxide, carbon dioxide, cyclopentadiene and elemental iron. We observe in addition to these products the production of biferrocene and elemental carbon. Thermolysis of carbonylcyclopentadienyliron tetramer (produced from the dimer by thermolysis in refluxing xylene) produces ferrocene, iron and carbon monoxidre; no biferrocene, carbon dioxide or elemental carbon are produced. A scheme is proposed to account for these products.     

多功能旋流燃烧器的工业性试验研究

秦皇岛热电厂2＃锅炉燃烧不稳定、燃烧效率低等问题主要是由于燃烧器的一次风管道结构不合理造成的。本文采用多功能旋流燃烧器的设计思想对旋流燃烧器进行了技术改造和工业性试验研究。结果表明,改造后的旋流燃烧器其着火点提前,并且仅改造6只主力燃烧器就可以使锅炉在50％负荷时达到不投油而稳定燃烧,排烟温度、飞灰含碳量和NOx排放量明显下降。