Simulated biomass tar removal mechanism by a Quench Coupled with ADsorption Technology (QCADT)

Tar removal is a bottleneck in the smooth commercialization of biomass gasification technology. Based on introducing adsorption process into Quench Coupled with ABsorption Technology (QCABT) previously proposed by the author's group, Quench Coupled with ADsorption Technology (QCADT) has been developed to narrow this gap. Additionally, benzene and naphthalene, which are more similar to the real tar for containing aromatic ring structures, were adopted as light and heavy simulated tar, respectively. Also their removal behavior by QCADT was investigated. The results show that the removal mechanism of QCADT is similar to that of QCABT, except for the higher overall tar removal rate due to adsorption effect. Adsorbents with both micro- and narrow mesopores exhibit a better benzene removal performance, while narrow mesopores play dominant roles in naphthalene removal. Penetration adsorption loading of benzene and naphthalene on AC-1 can reach 0.38 g·g^-1 and 0.34 g·g^-1, respectively. The sawdust hardly has any tar removal effect. Combined micro- and meso-pores, will benefit both deep tar removal and large adsorption rate, providing a high tar removal efficiency.     

光纤透镜研磨抛光的轮廓成形控制系统的研究

为了有效地减小光纤透镜的研磨抛光轮廓误差,设计一种两轴联动的交叉耦合轮廓控制器,并且针对光纤透镜研磨抛光机床的运动特点,给出了交叉耦合轮廓误差模型.然后利用Matlab软件对该交叉耦合轮廓控制的效果进行了仿真研究与分析.仿真结果表明,利用该控制器能使系统轮廓误差从0.075 μm减小到0.03 μm,但由于加入了交叉耦合器的补偿量,Z轴的跟随误差也从0.05 μm增大到0.07 μm.同时也表明两轴联动的交叉耦合控制系统远远优于单轴PID控制系统.     

Modeling macroscopic extended continua with the aid of numerical homogenization schemes

Even in the range of small elastic deformations the behavior of foams is not well described by only two elastic constants. Usually the manufacturers give values of the material parameters depending on the loading conditions. This problem is investigated on a microscopic scale by a simple beam model and on the macroscopic scale by an extended continuum model. It has been found that this approach shows the size effect [J. Mater. Sci. 18 (1983) 2572] that cannot be described within the framework of the standard continuum mechanical setting. The existence of the size effect within this model can be explained by independent rotations which do not scale with the displacement field.While macroscopic material parameters are generally unknown for foams the macroscopic properties are derived from the microscale where the parameters are assumed to be known. After evaluation of the microscopic constitutive equations, which are also considered to be known, the quantities are mappped back to the macroscale by a homogenization procedure. This approach is known from literature as FE² model, see e.g. [V. Kouznetsova, Computational homogenization for the multi-scale analysis of multi-phase materials, PhD-thesis, Technical University of Eindhoven, 2002], [Int. J. Numer. Meth. Eng., 54 (2002) 1235] or [Arch. Appl. Mech., 72 (2002) 300]. It is shown that the Cosserat continuum and the FE² model are able to describe the same effects qualitatively.     

Stress and couple stress in foams

Even in the range of small elastic deformations the behavior of foams is not well described by only two elastic constants. Usually the manufacturers give values of the material parameters depending on the loading conditions. This problem is investigated on a microscopic scale by a simple beam model. It has been found that this approach shows the size effect that cannot be described within the framework of the standard continuum mechanical setting. The size effect within this model can be explained by independent rotations which do not scale with the displacement field.

A homogenization procedure is proposed that allows for the determination of macroscopic quantities like stress and couple stress in terms of volumetrical averages. The homogenized results of the microscopic model are compared to the results obtained by an enhanced macroscopic model, namely a Cosserat model. Both approaches show good agreement.     

Examining the physical foundation of continuum theories from the viewpoint of phonon dispersion relation

An overview of crystal types and their interatomic force models are given and the basic feature of the dynamics of atoms in crystal is introduced. Elastic waves described by classical continuum theory, phonon dispersion relations by micromorphic theory, micropolar theory, couple stress theories and nonlocal theory are calculated and presented. The physical foundation and the applicability are examined from the viewpoint of phonon dispersion relation. Two physical examples, including the apparent change of material constants at different length scales and the macroscopic phenomenon of piezoelectricity are discussed.     

微机控制隧道式烘槽

介绍了一种恒温烘槽的结构、主要性能指标、工作原理和系统组成。系统的特点是从生产实践要求出发，对技术方案及制造工艺进行灵活的处理。文中着重对系统的3大方面进行了介绍：一是根据系统的特点和温度的特性，采用积分分离式PID控制的原因和方法；二是主要的硬件、软件功能的实施方法；三是准确、简单实用的热电偶非线性补偿的处理方法。     

Optimal film shape for two-dimensional slider bearings lubricated with couple stress fluids

The shape of a slider bearing is one of the major geometric conditions influencing the performance of the bearing. The aim of this study is to design the optimum shapes of the surfaces of sliders to meet the load and center of pressure demands specified by the designers. The design strategy uses COMSOL Multiphysics software package to solve the modified Reynolds equation derived on the basis of stokes microcontinuum theory. The sequential quadratic programming (SQP) is used to optimize the shape of the slider bearing. Results show that designers seeking to effectively reduce friction should consider a reducing the aspect ratio since it is the most significant parameter affecting optimal friction. In addition, slider bearings should be optimized with a polynomial profile of order 6 to reduce the computational effort and yield a solution that is very close to the solution of higher order polynomials.     

Nonlinear stability boundary of journal bearing systems operating with non-Newtonian couple stress fluids

The non-Newtonian effects on the nonlinear stability boundary of short journal bearings are investigated through the transient nonlinear analysis. Two coupled nonlinear equations are solved by using the fourth-order Runge-Kutta method. According to the results, there exists a nonlinear stability boundary within the clearance circle. Any initial positions of the shaft center outside of this boundary would yield an unstable trajectory, even though the bearing should be stable in accordance with the linear stability theory. The non-Newtonian effects provide a larger stability boundary within the clearance circle as compared to the bearing lubricated with a Newtonian fluid.     

Effects of external circuit on MHD channel flow with couple stresses

An exact analysis of MHD channel flow of an electrically conducting fluid exhibiting couple stresses carried out, taking into account the external circuit consisting of the terminal voltage, total current etc. Expressions derived for the velocity profiles, the current density, the electric field and the normalised flow rate. The effects of the couple stress parameter a and the magnetic field parameter M are studied.     

Inertia Effects on Inclined Slider Bearings Lubricated by a Couple Stress Fluid

This article deals with a numerical investigation of fluid inertia effects on inclined slider bearings lubricated by couple stress fluids. Convective inertial forces are considered in the film fluid. A reduced version of the Navier-Stokes equations is thus derived. The non-Newtonian couple stress behavior of the lubricant is described based on the microcontinuum Stokes theory. The governing partial differential equations are discretized by finite differences based on boundary layer–type equations. The resulting algebraic equations are solved using a Gauss-Seidel method. Compared to the case of the non-inertia Newtonian lubricant, the couple effects of fluid inertia forces and non-Newtonian couple stresses provide a significant improvement in slider bearing load capacity.