The influence of solid particles on the flow characteristics of the boundary layer for cross flow over a tube has been experimentally studied. A phase-Doppler anemometer was used to measure the mean and fluctuation velocities of both phases. Two separate tests were conducted with two particle size ranges (30-60μm and 80-150μm) and the freestream velocity and solid mass loading ratio were fixed, allowing the effects of particle sizes on the shape of the mean velocity profile and on the turbulent intensity levels. The measureraents clearly demonstrated that the larger particles damped fluid turbulence. For the smaller particies, this damping effect was less noticeable. The measurements further showed a delay in the separation point for two phase turbulent cross flow over a tube.

A modified model for particle-eddy interaction in two-phase turbulent flows is proposed to account for the turbulent dispersion of particles in a turbulent flow. In order to validate the proposed model, the structure of a turbulent, particle-laden, round jet, injected into a still environment, is studied both theoretically and experimentally. The numerical results show good agreement with the experimental data.

Erosion of tubes in tube banks by particles suspended in gas flows is a major problem in the chemical and power industry. In this paper, a numerical study has been conducted for the flow of a dilute turbulent particle-laden gas moving past two rows of staggered tubes undergoing erosion. Eulerian equations are used to describe gas-pbase motion, with the turbulence viscosity evaluated from a k-c model of turbulence. The prediction of impacting particle velocities and trajectories takes into account the effect of the turbulence with a stochastic particle dispersion model, as described by the authors. The particle impaetion/rebound model and the erosion model of ductile alloys obtained by Tabakoff et al. are used to predict the particle rebound phenomena and the erosion damage to tile tubes. The results from this study include the distributions of particle collision frequency and erosion damage to tube surfaces. The locations of maximum erosion damage to the tubes are predicted. Results indicate that the erosion damage to the second row of tubes in staggered tube banks is approximately twice that of the first row of tubes. The present paper also discusses the effect of free stream velocity and particle size on particle collision frequency and erosion damage.

Erosion of tubes by coal particles or coal ash impingement has caused serious problems to many pulverized coal energy conversion systems (such as the circulating fluidized bed combustion system). It is important to study erosion protection methods for tubes undergoing erosion. In this paper we present the results of numerical and experimental investigation of a new type of erosion-protection method: the finned tube erosion protection method. An experimental investigation of finned tube erosion processes was made by placing erosionprone wax cylinders with fins in a bench-scale cold flow circulating fluidized bed to simulate the long-term erosion effect. A numerical study was conducted for the flow of a dilute particle-laden gas moving past a finned tube undergoing erosion. An orthogonal curvilinear coordinate system was used to calculate turbulent flow around the finned tube. The calculation of particle trajectories took into account the effect of the turbulence with a stochastic particle dispersion model. The results from this study show that the finned tube is a simple and efficient erosion protection method in most industrial two-phase systems where erosion occurs. The fin relative height, the fin number and the ang]e between two adjacent fins are three important parameters which affect finned tube erosion protection abilities.

Erosion of tubes by coal particles or coal ash impingement has caused serious problems for many pulverized coal energy conversion systems. This type of erosion has led to many experimental investigations. This paper presents the numerical results of an investigation of coal particle dynamics about a tube. The calculation of particle trajectories takes into account the eftect of turbulence using a stochastic particle dispersion model. The results from this study include the frequency of particle impact and the erosion distribution on the tube surface. Good agreement is found between the numerical method and exoerhnent.

A two-dimensional across-the-channel mathematical model for the simulation of a direct methanol fuel cell is described. The model accounts simultaneously for electrochemical kinetics, hydrodynamics, and multicomponent transport. The two-dimensional distributions of concentrations of reactants, the two-dimensional distributions of current densities, the crossover flux of methanol from the anode to the cathode, and current-voltage curve for the fuel cell have been calculated. The obtained results indicate that the concentrations of reactants in the catalyst layers in front of the current collectors are very low, which reduce the utility of catalyst; the current density at the edges of the channels is many times greater than the mean current density, which may lead to local overheat.

A three-dimensional temporally evolving mixing layer and particle dispersion patterns with different Stokes numbers were investigated. The coherent structures in a plane mixing layer between two parallel streams were numerically simulated using a pseudo-spectral method. Particles with different Stokes numbers were traced using the Lagrangian approach. The results showed that particle dispersion patterns were strongly governed by large-scale vortex structures and three-dimensionality. Particles with Stokes number of the order of unity were found to be concentrated near the outer edges of the large-scale vortex structures. With the development of threedimensionality, the variation of particle distribution increased along the spanwise direction. Some particles were thrown out of the high-concentration area due to the pairs of counter-rotating 'rib' vortices, and finally developed into a 'mushroom' pattern of the particle distribution in the spanwise direction.

Erosion of heat exchanger tubes by coal particles or coal ash impingement has caused serious problems to the utility boilers. It is important to study erosion-protection techniques for tubes undergoing erosion. The present paper shows the results of the numerical investigation of the finned tube erosion-protection techniques. The numerical results indicate that fins fixed on tubes provide a simple and efficient erosion-protection method in most industrial particle-laden systems where erosion occurs.

A model has been developed to simulate deposit growth under slagging conditions. The model was coupled with a comprehensive combustion code to predict the flow field, the temperature field and the deposit growth behavior. The predictions indicate that the numerical model can be used to optimize the design and operation of pulverized coal-fired boilers.

本文运用谱元方法对气固两相圆柱绕流进行了直接数值模拟。在获得高精度计算流场信息基础上，进行颗粒扩散运动的研究。通过研究颗粒大小对颗粒扩散运动的影响来刻画气固两相圆柱绕流的物理特征。研究时发现，由于圆柱尾流独特的涡结构特征，颗粒在流场中心轴线附近区域的扩散机理主要是决定于吸力作用，该作用会驱使小颗粒卷吸进入圆柱尾部近壁区，甚至与圆柱后壁发生碰撞，这种扩散机理b-"混合层中颗粒扩散机理明显不同。