考虑碳粒表面还原反应的移动火焰锋面(MFF)模型

在原始移动火焰锋面(MFF)模型的基础上,提出一种考虑碳粒表面还原反应的改进MFF模型。该模型给出了包括表面还原反应和 CO容积反应在内的碳粒燃烧反应速率的显式表达式,便于分析和讨论各种工况下碳粒的燃烧状态和影响因素。与原始的 MFF模型和单膜模型相比,所计算的颗粒温度和燃烧速率更符合严格的连续膜模型的预报结果,而计算时间只为连续膜模型的数十万分之一。研究结果表明,改进的 MFF模型是一种简单可行、适于工程应用的碳粒燃烧理论模型。     

移动火焰锋面(MFF)模型的理论对比与实验验证

本文根据碳粒非均相着火,有无颗粒温度跃变现象,来判断CO的均相着火,阐述了MFF模型中颗粒边界层CO着火燃烧假设的理论意义。通过实验与理论对比,证明了小于100μm的碳粒有可能发生CO着火。MFF模型预报与连续膜模型,以及实验点都有好的符合。利用MFF模型推导出三种极限情况的燃烧模式,揭示了MFF模型与连续膜模型的理论关联。从理论与实验对比中,进一步地验证了MFF模型。     

CO气相反应对碳颗粒燃烧的影响——连续膜理论的一种简化模拟方法

本文提出了一种新的考虑了颗粒边界层内CO气相反应效应的碳颗粒燃烧简化模型——移动火焰锋面(MFF)模型。该模型成功地实现了在“碳颗粒着火时表面等效生成物为CO_2”与“扩散扩制时全部成为CO”这两个极限之间的各种中间燃烧工况的连续转变,并很好地预报了Young等人测量得到的褐煤碳颗粒表面温度超过现有单膜模型理论极限值的实验结果。     

煤粉挥发分火焰行为的理论分析与简化模拟方法

考虑热解的扩展连续膜模型,可以详细预报煤粉挥发分析出、焦碳燃烧的全过程.模型以CH4燃烧的反应动力学特性,近似地描述了挥发分火焰.提出新的简化模拟方法均相着火后挥发分燃烧的移动火焰锋面(MFFVC)模型,弥补了挥发分现有计算方法中未考虑颗粒边界层内挥发分均相着火及燃烧的不足.与挥发分现有计算方法、扩散控制的挥发分燃烧(DLVC)模型相比, MFFVC模型预报与考虑热解的扩展连续膜模型符合较好.     

炭/碳粒燃烧速率的通用计算方法

本文介绍了计算炭/碳粒燃烧速率的通用方法。提出了一个新的无因次准则——燃烧速率控制准则(称F_b准则),它可定量地确定炭/碳粒处于动力、扩散还是动力-扩散控制;并得到了一种供工程计算用的计算炭/碳粒在空气中燃烧时的燃烧速率的通用曲线法。     

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。     

碳与氧反应时反应级数测定的研究

本文用自行研制的具有快速加热、快速分析功能的加压燃烧炉，进行了永安无烟煤和高纯石墨在不同空气压力下的燃烧试验，测定了试样重量和温度变化的连续曲线，得到了空气压力对碳燃烧速率的影响规律。在应用单反应扩散燃烧模型修正碳粒表面氧气分压力的条件下，由实验结果计算得到永安无烟煤和高纯石墨与氧反应时的反应级数。     

移动火焰锋面(MFF)模型火焰锋面确定条件的进一步改进

考虑碳粒表面还原反应的移动火焰锋面模型(MFF-Ⅰ)在推导火焰锋面位置时,仅考虑了碳粒表面氧化反应的影响.本文综合考虑碳粒表面的氧化反应、还原反应对火焰锋面位置的影响,给出更严格的推导,即MFF-Ⅱ模型.在通常的燃烧工况下,改进模型MFF-Ⅱ与原始模型MFF-Ⅰ相比,预报结论基本一致.但对于较低氧浓度的工况,比如再燃、气化问题,改进模型MFF-Ⅱ同样可以给出可信的预报结果,而这是MFF-Ⅰ模型所不及的.     

关于碳/炭粒表面氧化反应生成物CO/CO_2比值的研究

本文通过严格的求解一组包括空间反应在内的微分方程,并辅以准确的碳粒燃烧速率及其温度的实验测定,得到了计算碳/炭粒表面氧化反应生成物C0/CO_2比值的通用表达式,它较之前人的经验公式更准确、通用。从而为碳/炭粒的温升历程及其着火温度的预报提供了可靠的理论基础。     

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．     

Thermodynamic equilibrium for nitrogen species discharge: Comparison with global model

The equilibrium process of plasma nitrogen species by chemical kinetic reactions along various pressures is successfully investigated. The equilibrium process is required in industrial application to obtain the stable condition when heating up the material for having homogenous reaction. Nitrogen species densities is modeled by a continuity equation and extended Arrhenius form. These equations are used to integrate the change of density over the time. The integration is to acquire density and the reaction rate of each reaction where temperature and time dependence are imposed. A comparison is made with global model within pressure range of 1-100 mTorr and the temperature of electron is set to be higher than other nitrogen species. The results show that the chemical kinetic model only agrees for high pressure because of no power imposed; while the global model considers the external power along the pressure range then the electron and nitrogen species give highly quantity densities by factor of 3-5.     

A simple semiempirical equation of state for cold nuclear matter

On the basis of gross properties of nuclei, a simple semiempirical equation of state is developed for cold hadronic matter composed of light quarks of two flavors. The source of binding energy in the model is the decreasing asymmetry between the number of up and down quarks in extended regions of overlapping nucleons. The resulting incompressibility of symmetric nuclear matter at equilibrium density is K=324 MeV. The incompressibility decreases rapidly with decreasing density but increases only slowly with increasing density until homogenous quark matter is reached at a density just above three times ordinary nuclear matter density.     

A classical model for stochastic multiphoton absorption processes of anharmonic molecules

Classical power absorption of an anharmonic molecule in intense infrared radiation is calculated. A generalized damping factor and an effective random phase are introduced for the stochastic field-molecule interaction. It is shown that the over-all broadening of the power response has a fundamental lorentzian, no matter what the source of line broadening is. Excellent agreement with the quantum-mechanical results is obtained by quantizing the classical model.     

Dynamics of locally rotationally symmetric Bianchi type VIII cosmologies with anisotropic matter

This paper is a study of the effects of anisotropic matter sources on the qualitative evolution of spatially homogenous cosmologies of Bianchi type VIII. The analysis is based on a dynamical system approach and makes use of an anisotropic matter family developed by Calogero and Heinzle which generalises perfect fluids and provides a measure of deviation from isotropy. Thereby the role of perfect fluid solutions is put into a broader context. The results of this paper concern the past and future asymptotic dynamics of locally rotationally symmetric solutions of type VIII with anisotropic matter. It is shown that solutions whose matter source is sufficiently close to being isotropic exhibit the same qualitative dynamics as perfect fluid solutions. However a high degree of anisotropy of the matter model can cause dynamics to differ significantly from the vacuum and perfect fluid case.     

Cross-correlation markers in stochastic dynamics of complex systems

The neuromagnetic activity (magnetoencephalogram, MEG) from healthy human brain and from an epileptic patient against chromatic flickering stimuli has been earlier analyzed on the basis of a memory functions formalism (MFF). Information measures of memory as well as relaxation parameters revealed high individuality and unique features in the neuromagnetic brain responses of each subject. The current paper demonstrates new capabilities of MFF by studying cross-correlations between MEG signals obtained from multiple and distant brain regions. It is shown that the MEG signals of healthy subjects are characterized by well-defined effects of frequency synchronization and at the same time by the domination of low-frequency processes. On the contrary, the MEG of a patient is characterized by a sharp abnormality of frequency synchronization, and also by prevalence of high-frequency quasi-periodic processes. Modification of synchronization effects and dynamics of cross-correlations offer a promising method of detecting pathological abnormalities in brain responses.     

Entanglement Dynamics Between Two Atoms Within Different W-like Initial States

We investigate the entanglement dynamics between two atoms which are trapped in an optical cavity with the help of the concurrence and the negativity for two different kinds of normalized W-like initial states. The results show that one of them can suffer the so-called entanglement sudden death (ESD) depending on parameters of the initial state when the optical cavity in the vacuum state, while the other one does not for whatever parameters. However when the initial optical cavity photon number is nonzero, no matter what W-like state as atoms’ initial state, the atoms’ subsystem always undergoes the ESD phenomenon. Meanwhile, by comparing concurrence with negativity, we find that our model gives a concrete example to support the conclusions in the previous reference.     

微尺度扩散火焰特性的数值解析

本文以均匀空气流中圆管形成的甲烷射流扩散火焰为对象,用数值解析的方法研究了微尺度扩散火焰的火焰结构和燃烧特性。燃烧反应采用甲烷/空气一步总包反应,喷管壁面采用绝热条件。在Re一定情况下,改变喷口尺寸和喷口流速考察了微扩散火焰的结构和火焰熄灭的尺度效应。数值结果表明,随着喷口直径的增大,微火焰的上方出现回流; Re=12条件下,在喷口直径=0.07 mm时存在熄灭极限;稳定燃烧区的最小发热率约为0.5 W;微尺度条件下,Da数对火焰结构和火焰的熄灭有一定的影响。     

Representation Theory of the Affine Lie Superalgebra at Fractional Level

N= 2 noncritical strings are closely related to the Wess-Zumino-Novikov-Witten model, and there is much hope to further probe the former by using the algebraic apparatus provided by the latter. An important ingredient is the precise knowledge of the representation theory at fractional level. In this paper, the embedding diagrams of singular vectors appearing in Verma modules for fractional values of the level (, p and q coprime) are derived analytically. The nilpotency of the fermionic generators in $\hslc$ requires the introduction of a nontrivial generalisation of the MFF construction to relate singular vectors among themselves. The diagrams reveal a striking similarity with the degenerate representations of the N= 2 superconformal algebra. Received: 10 June 1996\,/\,Accepted: 8 October 1996