An inflow-outflow characterization of inhomogeneous permeable beds

It is proposed that the inflow to and outflow from a permeable bed be related by an integral. For vanishing fluid velocities, it is linear and its kernel is a material property characterizing the bed. Some of the properties of the kernel are considered here. The approach is particularly useful for tilted, fractured and other inhomogeneous beds, since no continuum characteristics need be assumed. The effects of nonlinearity are also discussed.     

纸类废弃物流化床热解气化研究

为开发低污染城市生活垃圾气化熔融处理技术,对城市生活垃圾中广泛存在的废纸组分进行了流化床热解与气化试验.在400～700℃、过量空气系数0～0.8的范围内,分析反应产物特性及其变化规律.结果表明,随热解温度的提高,热解油与热解气产量增大,热解炭产量减小,热解温度达到600℃及以上时,热解气产量达到60%左右;气化温度700℃、过量空气系数0.6时,气化效率最高,达到32%,此时气化气热值为2150 kJ/Nm3,固定碳转化率80%,气化气产率为2.3 Nm3/kg.     

A nonlinear stability analysis of a rotating double-diffusive magnetized ferrofluid

A nonlinear stability result for a double-diffusive magnetized ferrofluid layer rotating about a vertical axis for stress-free boundaries is derived via generalized energy method. The mathematical emphasis is on how to control the nonlinear terms caused by magnetic body and inertia forces. The result is compared with the result obtained by linear instability theory. The critical magnetic thermal Rayleigh number given by energy theory is slightly less than those given by linear theory and thus indicates the existence of subcritical instability for ferrofluids. For non-ferrofluids, it is observed that the nonlinear critical stability thermal Rayleigh number coincides with that of linear critical stability thermal Rayleigh number. For lower values of magnetic parameters, this coincidence is immediately lost. The effect of magnetic parameter, M₃, solute gradient, S₁, and Taylor number, T_A1, on subcritical instability region have been analyzed. We also demonstrate coupling between the buoyancy and magnetic forces in the nonlinear stability analysis.     

Effect of Anisotropic Ion Pressure on Solitary Waves in Magnetized Dusty Plasmas

The propagation of linear and nonlinear dust ion acoustic waves (DIAWs) are studied in a collisionless magnetized plasma which consists of warm ions having anisotropic thermal pressure, nonthermal (energetic) electrons and static dust particles of positive and negative charge polarity. The anisotropic ion pressure is defined using double adiabatic Chew‐Golberger‐Low (CGL) theory. In the linear regime, the propagation properties of the two possible modes are investigated via ion pressure anisotropy, dust particle polarity and nonthermality of electrons. Using reductive method Zakharov‐Kuznetsov (ZK) equation is derived for the propagation of two dimensional electrostatic dust ion acoustic solitary waves in dusty plasmas. It is found that both compressive and rarefactive solitons are formed in presence of nonthermal electrons using Cairn's distribution [R.A. Cairns, A.A. Mamun, R. Bingham, R.O. Dendy, R. Bostrom, C.M.C. Nairn and P.K. Shukla, Geophys.Res. Lett. 22 , 2709 (1995)] in the system. The ion pressure anisotropy, nonthermality of electrons and charge polarity of the dust particles have significant effects on the amplitude and width of the dust ion acoustic solitary waves in such anisotropic nonthermal magnetized dusty plasmas. The numerical results are also presented for illustration. Our finding is applicable to space dusty plasma regimes having anisotropic ion pressure and nonthermal electrons. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

FDTD Analysis of Magnetized Plasma with Arbitrary Magnetic Declination

In this paper, the frequency-dependent finite-difference time-domain (FDTD) method employing the piecewise linear recursive convolution (PLRC) scheme is applied to the numerical analysis of magnetized plasma with arbitrary magnetic declination. The PLRC-FDTD equations are derived in detail and are checked through practical examples. Excellent agreement between the numerical results and the exact analytical solutions is demonstrated.     

基于镍基载氧体的串行流化床煤化学链燃烧实验

以NiO/Al₂O₃为载氧体,在1 kW_th串行流化床反应器上进行了煤化学链燃烧实验,通过四个参数:碳转换效率η_C,coal、煤气化产物的转换效率、碳捕集效率η_C,cap及煤燃烧效率η_combust对煤燃烧过程进行表征,考察了燃料反应器温度t_FR、过量空气系数α、隔离器水煤比S_LS/C、燃料反应器水煤比S_FR/C和热负荷等参数的影响。结果表明,t_FR和S_LS/C的增大有利于煤气化产物的转换;t_FR、α和S_LS/C的增大有助于η_C,coal的提高,随着S_FR/C由0.8增加到1.8,η_C,coal呈先增加再减小的趋势,并在S_FR/C=1.2达到最大值;η_combust和η_C,coal变化趋势保持一致,主要受飞灰含碳量中残碳损失的影响;t_FR提高有助于提高η_C,cap,而α和S_LS/C的增大使得η_C,cap降低。     

FDTD Analysis of Electromagnetic Reflection by Conductive Plane Covered with Magnetized Inhomogeneous Plasmas

A novel finite-difference time-domain (FDTD) methodology which incorporates both anisotropy and frequency dispersion at the same time is developed for electromagnetic wave propagation in anisotropic magnetoactive plasmas in this paper. The numerical verification of the method are confirmed by computing the reflection and transmission of right-handed/left-handed circularly polarized (RCP/LCP) wave through a magnetized plasma layer, with the direction of propagation parallel to the direction of the biasing field. And, the right-handed / left-handed polarized wave reflection coefficients for electromagnetic signals normally incident upon a conductive plane covered with a layer of magnetized plasma are computed using the new FDTD method. The parabolic electron-number density profile varies only in the direction perpendicular to the plane. The function dependence of reflection coefficients on the number density, collision frequency and external magnetic field is studied.     

Mixed convective heat transfer characteristics and mechanisms in structured packed beds

The structured packed bed is considered a promising reactor owing to its low pressure drop and good heat transfer performance. In the heat transfer process of thermal storage in packed beds, natural convection plays an important role. To obtain the mixed convective heat transfer characteristics and mechanisms in packed beds, numerical simulations and coupling analyses were carried out in this study on the unsteady process of fluid flow and heat transfer. A three-dimensional model of the flow channel in the packed bed was established, and the Navier–Stokes equations and Laminar model were adopted for the computations. The effects of the driving force on fluid flow around a particle were studied in detail. The differences in velocity and density distributions under different flow directions due to effect of the aiding flow or opposing flow were intuitively demonstrated and quantitatively analyzed. It was found that the driving force strengthens the fluid flow near the particle surface when aiding flow occurs and inhibits the fluid flow when opposing flow occurs. The boundary layer structure was changed by the natural convection, which in turn influences the field synergy angle. For the aiding flow, the coordination between the velocity and density fields is higher than that for the opposing flow. By analysis the effects of physical parameters on mixed convective heat transfer, it is indicated that with an increase in the fluid-solid temperature difference or the particle diameter, or a decrease in the fluid temperature, the strengthening or inhibiting effect of natural convection on the heat transfer became more significant.