有轴向扩散的层流扩散火熖

在研究层流扩散火焰时,很多人都忽略了轴向扩散作用。而一般的层流扩散火焰应该具有轴向扩散现象,尤其是在研究短火焰时更不应该加以忽略。本文在扩散的意义上既考虑了一般的径向扩散,又考虑了轴向扩散,推广了文献[1]的理论。此外还计算了几个例子,初步作了一些分析,说明忽略轴向扩散时所造成的误差。     

湍流扩散多相流

湍流扩散多相流在许多工程和环境科学实际应用中十分常见.流体相中的湍流和扩散相的随机本质使得湍流扩散多相流中遇到的问题远比单一流体中遇到的湍流现象复杂得多.首先评述了湍流扩散多相流研究中实验技术和数值计算方面的现状、各自的优点与局限性,以及该领域研究中未来面临的挑战.主要关注湍流扩散多相流研究中以下3方面重点内容:颗粒、液滴和气泡的选择性聚积;湍流对流体相和扩散相耦合作用的影响以及颗粒物和气泡的存在对流体相中湍流的调节机制.     

分形介质中的反常扩散

本文利用适当的标度变换将欧氏空间中的经典扩散方程抗议为分形点阵上的标准扩散方程，并应用该标准扩散方程证明了分形布朗粒子的运动服从反常扩散，同时还讨论了一般分形扩散方程及其渐进解。     

条件矩模型模拟湍流扩散燃烧

对条件矩模型模拟湍流扩散燃烧进行了初步的研究.在条件矩模型中,标量的统计是以混合分数为条件的,条件平均使得非线性化学反应源项可以在一阶条件下被封闭.模拟结果和美国Sandia国家实验室的实验结果对比表明:对温度、主要组分浓度的预报结果是令人满意的,NO浓度的预报在趋势上也符合实验结果.误差分析表明,提高标量耗散率的预报精度和二阶条件矩模型都将有助于推动条件矩模型的发展.     

大气边界层内羽流扩散研究

主要研究了高架点源的污染,即``羽流扩散'. 由于大气边界层内的湍流运动,引 起污染物扩散的主要因素是湍流扩散, 研究湍流扩散有两种基本方法：统计理论和梯度理论. 采用拉格朗日粒子扩散模型 (Lagrangian particle dispersion model, LPDM)来评价羽流扩散的平均浓度,分别计算了表征扩散程度的3个参数：沿烟轴方向的 着地浓度、水平方向的羽流扩散宽度和垂直方向的羽流扩散宽度. 从计算结果和风洞实验的 数据对比来看,用该模式可以较好地模拟大气边界层内复杂气候条件下的羽流扩散.     

渗流网络上的反常扩散

本文通过合理地引入反常扩散系数，以均匀的，各向同性的分形介质中的反常扩散方程为基础，推导出了存在等待时间幂律分布的ｄ≥２和ｄ〈２两种情况下渗流网络上的一般反常扩散方程。     

力学系统的扩散运动及量子化

研究位形由扩散过程定义的力学系统．利用变分的路径计算给出系统广义坐标表示的动力学方程，该方程连同连续方程描述系统量子波动随时间演化的概率进程．文末的表示定理指出，在满足适当正规条件的扩散过程和Ｓｃｈｒｄｉｎｇｅｒ方程的解（波函数）之间存在一一对应关系     

湍流射流在等速流动中的扩散

在工程技术问题中,譬如冲压发动机燃烧室内燃料逆气流方向喷射发展的下游流动以及为了防热目的采用所谓气膜冷却等实际问题中,往往遇到湍流射流在等速流动中的热量扩散与质量扩散过程。本文建议采用扩散系数随流动发展距离与流动速度的乘积而变的关系来求解两个简单问题:1.无限平面平行射流的扩散;2.距射流出口相当远处的扩散。     

焊锡接点IMC层的扩散应力

钎焊过程中在焊锡接点中形成的金属间化合物(IMC)对焊锡接点可靠性具有重要影响。在原子扩散效应下,回流焊和等温时效过程中IMC层的生长会在其内部产生应力,其微结构也发生变化,致使IMC层和整个焊点的力学性能下降。本文基于扩散反应机制,研究了由于原子扩散产生的IMC层的扩散应力。首先建立了焊锡接点IMC层生长早期微结构特征的2界面(Cu/Cu6Sn5/Solder)分析模型,然后运用Laplace变换法求解扩散方程得到了Cu原子在IMC层中的浓度分布;采用把原子扩散作用转换为体应变方法,计算了IMC层在形成和生长过程中应力的解析解。结果表明：IMC层中的扩散应力为压应力,最大值位于Cu/IMC界面处,大小与扩散原子浓度密切相关;随着时效时间的增加,扩散应力增大,但最终趋于稳定并沿IMC厚度方向线性变化。     

The MHD properties of ambipolar diffusion and quasi—Ambipolar diffusion in a plasma column

In the present paper, based on the conservation law of mass and momentum for ion and electron, the distribution of velocity, density of ions and electrons along radial direction are solved numerically. Furthermore, the comparison between MHD properties of ambipolar and quasi-ambipolar diffusion is made. The numerical calculation is carried out for argon plasma. The results show that the ion density, ratio of ion and electron velocity at the cathode sheath boundary surface increase with the intensity of magnetic induction, meanwhile, the distance between sheaths decreases as well as the radial velocity of ion and electron at the anode sheath boundary. The ion density varies in accord with experiment qualitatively^[1]. All parameters mentioned above are not sensitive to magnetic field in ambipolar diffusion.     

Evolution of ion–ion acoustic instability in multi-ion plasma sheaths

Nonlinear Dynamics - The generation of ion-acoustic solitary waves is investigated in a nonuniform multicomponent collisional plasma sheath containing cold ions and Boltzmann electrons to probe the...     

Structure of anode sheath in self-sustaining discharge with closed electron drift

The structure of the anode sheath and the characteristics of the closed Hall current discharge occurring in plasma accelerators are investigated in the diffusion approximation. The analysis takes account of weak processes (variation of ionization frequency with electron energy, electron energy losses, presence of a detachment region at the anode). The distributions along the sheath of potential, particle densities, currents, and other parameters are obtained. The effect on the characteristics of the discharge of varying the magnetic field and the input of working substance is considered. Weak processes are shown to have a significant effect on the structure of the sheath.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 9–16, March–April, 1976.     

Experiments with gas-filled triodes

Summary In this paper experiments are described showing the different types of electrical discharges in a gas-filled triode. The determining parameters are the following: the cathode emission, the spacing of cathode, grid and anode, the diameter of the meshes of the grid, the potentials of the grid and the anode, the gas pressure and the differential ionization function of the gas. The anode voltage may be concentrated in a space charge sheath. If this space charge sheath is located at the grid, the anode current may be modulated with moderate grid potentials. If not, much larger voltages are required for modulation.     

Analytic investigation of the anode zone of a higher-pressure glow discharge

The structure of the glow-discharge anode sheath is investigated analytically in the one-dimensional formulation within the framework of a diffusion-drift approximation. Charged particle recombination reduces significantly the anode potential drop and the width of the anode zone. Given fairly heavy current, which is typical of anode spots, the contribution of the diffusion processes becomes significant because of the reduced width of the anode sheath. Analytical estimates of the anode potential drop and the width of the anode sheath which satisfactorily describe the results of numerical calculations are obtained. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.2, pp. 172–180, March–April, 1994.     

Electron-beam diagnostics of rarefied gases: Activation by short electron packets

The excitation of light emission of the 0-0 band of the first negative system of the nitrogen ion by activation of nitrogen molecules using short pulses of fast electrons was studied. The intensity and width of the light response were measured as functions of the duration and amplitude of the exciting current pulse and of the density of nitrogen molecules. The contribution of slow secondary electrons to the excitation of the ions increases with increase in both the gas density and the duration of the current pulse. Since the processes of excitation of ions by fast primary and slow secondary electrons are separated in time, when measuring the light-signal intensity, it is possible to determine the contribution of secondary electrons to the excitation. Novosibirsk State University, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 2, pp. 20–24, March–April, 2000.     

Subsonic electrically quasi-neutralweakly-ionized gas flow past a spherical probe

The electric characteristics of a sphere located in a flow of viscous, electrically quasi-neutral weakly-ionized gas containing electrons and monovalent ions are investigated theoretically and numerically. As in the majority of applications, the electrogasdynamic (EGD) interaction parameter is assumed to be small. This makes it possible to solve the gasdynamic and electric equations successively. The spherical surface is assumed to be conducting and heat-insulated. At low free-stream Mach numbers the gas temperature is almost constant in the region of flow past the sphere. This makes it possible to use the model of a viscous incompressible medium. The flow past a sphere is analyzed for gasdynamic Reynolds numbers varying over the interval 0 ≤ Re ≤ 1000. The electrodynamic equations in which the convection and diffusion of the electrons and ions and their electrical drift are taken into account are reduced to three elliptic equations for the electron and ion concentrations and the electric potential. A constant potential is assigned on the boundary of the computation region simulating infinity. The entire problem is simulated numerically using specially constructed grids. The charged-component, potential, and electric current fields are determined and the volt-ampere characteristics of the sphere are constructed for various gas velocities. The results obtained generalize the available data on the voltampere characteristics of a sphere (probe) in a weakly-ionized medium at rest.     

不同集流方式下对称双阴极固体氧化物燃料电池的电-化-热-力数值模拟及失效分析

 本文围绕新型对称双阴极固体氧化物燃料电池电堆单元在不同集流位置下热应力分布情况和优化集流方式，建立了一个基于电-化-热-力多场耦合理论的三维SOFC 电堆单元数值模型．引入固体力学热-力学理论，结合Weibull 失效概率分析方法，讨论了不同集流方式对SOFC 内部应力分布及失效的影响．研究结果表明，双侧阴极同时开展电子集流方式下的电解质平均电流密度比单侧单一集流方式下高，改变阳极集流位置会改变电极高温区的分布；SOFC 电堆单元上电极结构处的最大主应力明显大于其他组件上的最大主应力；阳极集流位置设置在阳极气体入口处时电极结构上的最大主应力和失效概率大于集流位置设置在阳极气体出口处的最大主应力和失效概率．     

Application of mercury arc theory to the design of industrial rectifiers

Summary A new theory of the mercury arc has been developed which allows the calculation of some parameters of an industrial rectifier. It takes into account the following phenomena: gas ionization by electrons, electron extraction at the cathode spot by ionic bombardment, magnetic autostriction and the scattering of electrons by the Coulomb field of positive ions. Agreement with experiment is very good.The latter part of this work has been sponsored by the European Office of A.R.D.C., U.S.A.F.     

Theory of the temperature relaxation of an electron-ion plasma in a high-frequency electric and constant magnetic field

The effective collision frequency of electrons and ions which leads to temperature equalization in a plasma in a constant magnetic field and a weak high-frequency electric field when the gyroscopic radius of the electrons is less than the Debye screening radius is determined. The corresponding values of the relaxation time are determined over a wide range of values of the ratio between the electron and ion temperatures, over a wide range of values of the magnetic and electric fields, and also as a function of the frequency of the external electric field.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 41–48, November–December, 1970.