粗重颗粒轻介共流气力输送机理及特性

Mechanism and Characteristics of Light Medium Mixed Flow Pneumatic Conveying for Coarse Particle

密相气力输送是散体物料清洁高效输送技术发展的趋势,粗重颗粒受物料属性限制难以形成稳定密相输送。提出适用于粗重颗粒密相输送的轻介共流气力输送方法,在粗重颗粒动理分析基础上对输送系统进行设计,然后从输送机理上阐明该方法较于传统气力输送技术的理论优势,最后采用计算流体力学-离散元(Computationalfluid dynamics-discreteelementmethod,CFD-DEM)耦合数值模拟方法,从输送流态、颗粒分布自组织行为和入口压力波动与料栓形态关联等方面研究粗重颗粒轻介共流气力输送过程的颗粒输运特性。研究表明:颗粒密度和粒径是影响轻介共流气力输送系统流态的主要因素,颗粒密度影响更为显著,轻介共流输送可形成散栓与固栓行为并存的准周期动态稳定栓流输送状态;轻介共流输送过程中,存在粗重颗粒在上、轻介颗粒在下的混合颗粒分聚自组织行为和轻细颗粒润滑混合移动颗粒床现象;入口压力波动与混合颗粒的输送流态和质量流量具有强关联,输送能效与颗粒质量流量变化图可联合估算料栓速度和长度。研究有利于拓宽气力输送适用领域,为粗重颗粒密相气力输送提供了新途径。

Dense phase pneumatic conveying is the tendency of clean and efficient transport technology of granular materials.Coarse particles are difficult to be driven by stable dense phase pneumatic conveying because of their properties.The light medium mixed flow pneumatic conveying is proposed and designed to realize coarse particles stable dense phase transport.Compared to traditional pneumatic conveying technology,the light medium mixed flow pneumatic conveying has theoretical advantages.Conveying characteristics,including flow regime,particle self-organization,and the relationship between inlet pressure fluctuation and particle slug formation,are studied by computational fluid dynamics-discrete element method(CFD-DEM) coupling numerical simulation method.Results indicated that particle density and size are the main factors of flow regime in the light medium mixed flow pneumatic conveying,and the particle density has remarkable effect.By analysis of slug collapse and building process,quasi-periodicity and dynamic stability slug flow could been found in the new proposed method.Meanwhile,particle segregation self-organization(coarse particles on the top,and fine particles on the bottom) and self-lubrication phenomenon of fine particle could be also found.There are strong correlations among the inlet pressure fluctuation,mass flow rate of mixed particles,and the flow regime.The move velocity and the solid slug length could be estimated by conveying energy efficiency and mixed particles mass flow rate.This work is beneficial to broaden the application field of pneumatic conveying,and provides a new approach for coarse particle dense phase pneumatic conveying.