基于颗粒动力学理论的气力输送特性研究

Research of the Pneumatic Transport Characteristics Based on Kinetic Theory of Particle Flows

考虑气力输送过程中气体与颗粒间的曳力作用、升力作用、颗粒与颗粒间的碰撞以及颗粒与壁面的碰撞对气固两相流的影响,采用双流体欧拉模型与颗粒动力学相结合的方法对多尺度和不同工况条件下垂直提升管内的管程特性进行了计算分析,以期揭示气力输送过程中的运动规律。通过对初始物理模型的验证,后期计算得到了不同参数情况下的气相速度、固相速度、气相湍动能以及管程压降值的分布特性。结果表明:固体之间的碰撞大都聚集在近壁面处,镜面反射系数对于管程压降的影响较大,但对两相速度分布没有太大的影响;颗粒粒径的增加导致了相间滑移速度和颗粒表面积的增加,输送过程中所受到的阻力也随之升高;随着固相颗粒体积分数的增加,碰撞和冲击的剧烈程度就会上升,因此也会损失更多的能量,当体积分数越低时,颗粒密度对压降的主导作用也会越小。

Considering the effects of drag force,lift force,particle-particle collision and the particle-wall collision on the pneumatic transporting process,we used the method of Euler two-fluid model incorporating the kinetic theory of particle flows to calculate the characteristics of vertical tube with multiple scales under different working conditions,which reveals the movement of pneumatic transporting process.Through the verification of the initial physical model,the gas phase velocity,solid phase velocity,gas phase turbulent kinetic energy and the distribution of the pressure drop of the tube were obtained under the different parameter conditions.The experimental results indicate that most of the collisions are gathered near the wall,and the specularity coefficient has great influence on the pressure drop of the tube,but it plays an insignificant role in the velocity distribution of the two phases;the increase of the particle size results in the increase of the slip velocity and the particle surface area,and the resistance also increases in the transporting process.With the increase of the particle volume fraction,collision and impact intensity will increase,so it will lose more energy,and the particle density on the pressure drop of the leading role will increasingly small when the particle volume fraction is low.