Molecular Dynamics Simulation of Hydrate Decomposition Under Action of Alcohol Inhibitors

The molecular dynamics method is used to investigate decomposition of methane hydrate at different temperatures,pressures and concentrations of inhibitor.By analyzing the parameters of system conformation,mean square displacement and radial distribution function,the decomposition of hydrate in the presence of alcohol inhibitors ethylene glycol and glycerol is explored.The results show that the hydroxyl groups in alcohol molecules can destroy the cage structure of hydrate,and form hydrogen bonds with nearby water molecules to effectively prevent the reformation of hydrate.Therefore,ethylene glycol and glycerol serve as inhibitors of methane hydrate,furthermore,in terms of inhibition effect,glycerol is better than ethylene glycol by comparing rate of hydrate decomposition.

Simulations of vertical jet penetration using a filtered two-fluid model in a gas-solid fluidized bed

The influence of a vertical jet located at the distributor in a cylindrical fluidized bed on the flow behavior of gas and particles was predicted using a filtered two-fluid model proposed by Sundaresan and coworkers. The distributions of volume fraction and the velocity of particles along the lateral direction were investigated for different jet velocities by analyzing the simulated results. The vertical jet penetration lengths at the different gas jet velocities have been obtained and compared with predictions derived from empirical correlations; the predicted air jet penetration length is discussed. Agreement between the numerical simulations and experimental results has been achieved.

Effects of ionic impurities on crystallization of cobalamin

In this paper,the influence of two typical ionic impurities(Na_(+)and Mg_(2+))is investigated with the focused beam reflectance measurement(FBRM)technique.In this system,the on-line FBRM is used as a tool for monitoring the crystallization process of cobalamin by measuring the chord length distribution of particles and the particle counts.It is noted that impurity Mg_(2+)has a more significant effect than Na_(2+)in crystal growth of the whole crystallization process.From the microscopic observation of crystals,Mg_(2+)has an obvious effect on the crystal habit,while Na_(2+)has little effect.In addition,the crystal habit changes can be monitored by particle vision measurement(PVM).Understanding these effects is helpful to aid optimization and improve process control.

多孔介质内颗粒流动特性的格子Boltzmann模拟

地下岩石孔隙中小颗粒的运移和沉积会使得储层渗透性能降低,影响石油开发。为了探究悬浮颗粒在多孔介质中的流动过程,采用格子Boltzmann方法对三维多孔介质内流体和颗粒的运动过程进行了数值模拟,采用有限体积颗粒法构建多孔介质中骨架颗粒和悬浮颗粒。通过Half-Way反弹格式实现流体与颗粒间的相互作用,考虑孔隙结构、入口流速、孔隙率和颗粒直径对颗粒流动特性的影响,探究颗粒的运移和沉积规律。结果表明,入口速度对不同孔隙结构下颗粒的运动作用显著。随着入口速度增大,颗粒与颗粒、孔隙壁面以及流体之间的动量和能量交换作用增强,缩短了颗粒的运移路径,颗粒沉积率逐渐变小,颗粒拟温度增大。孔隙率的下降强化了颗粒间的碰撞,孔隙率由0.581降低至0.400,使得颗粒拟温度提升至9倍。颗粒拟温度随颗粒直径的增加而增加。但随着孔隙率增加,颗粒轴向速度增加,颗粒最高轴向速度可达入口流速的11倍,而颗粒接触力降低。

Investigation on effect of drag models on flow behavior of power-law fluid–solid two-phase flow in fluidized bed

In this study,a Eulerian-Eulerian two-fluid model combined with the kinetic theory of granular flow is adopted to simulate power-law fluid–solid two-phase flow in the fluidized bed.Two new power-law liquid–solid drag models are proposed based on the rheological equation of power-law fluid and pressure drop.One called model A is a modified drag model considering tortuosity of flow channel and ratio of the throat to pore,and the other called model B is a blending drag model combining drag coefficients of high and low particle concentrations.Predictions are compared with experimental data measured by Lali et al.,where the computed porosities from model B are closer to the measured data than other models.Furthermore,the predicted pressure drop rises as liquid velocity increases,while it decreases with the increase of particle size.Simulation results indicate that the increases of consistency coefficient and flow behavior index lead to the decrease of drag coefficient,and particle concentration,granular temperature,granular pressure,and granular viscosity go down accordingly.