刮板结构对刮壁型分散机流场特性的影响

Influence of Scraper Structure on the Flow Field Characteristics in the Scraper Dispersers

基于Fluent仿真软件,模拟研究了4种不同刮板结构的刮壁型分散机内的流场,对比分析了其混合效果。分散机对槽内固-液两相进行差速搅拌,其中刮板转速为60 r/min,搅拌桨转速为1200 r/min。并分别采用层流模型、欧拉(Eulerian)模型和多重参考系法(MRF)对刮壁型分散机在高黏度液体-固体混合物中产生的流场进行了模拟计算。模拟结果表明:4种刮壁型分散机槽内的最高速均在叶片两端;因刮板型1上的叶片长度高于其他刮板结构,故刮板型1的最低速度仅在槽底区域;刮板型3的槽底低速区域最大,因为其下叶片为水平放置,且离底为100 mm;刮板型4的槽底低速区域最小,因为其下叶片紧贴槽底;刮板型1,3和4搅拌槽内的固体体积分数分布均出现了分层现象;刮板型2槽内的固体体积分数分布曲线变化最小,此外其搅拌功率损耗最低,说明刮板型2的搅拌混合效果最好。

Based on the Fluent simulation software,the flow field in the scraper disperser with four different scraper structures was studied and the mixing effect was compared and analyzed.The solid-liquid material in the tank was stirred by the disperser with differential speed,the rotating speed of scraper was 60 r/min and that of agitator was 1200 r/min.The laminar flow model,Euler model and multiple reference frame method(MRF)were used to simulate the flow field of high viscosity liquids and solids in the scraper-type disperser.The simulation results showed that the highest speed was at both ends of the blade for four types of scraper structures The lowest speed in scraper type 1 disperser was only at the bottom of the tank because the blade length on scraper type 1 was longer than other scraper structures.The low-speed area at the bottom of tank for scraper type 3 disperser was the largest because the lower blades were placed horizontally and 100 mm from the bottom.The low-speed area at the bottom of tank for the scraper type 4 disperser was the smallest,this is due to the lower blades were close to the bottom of the tank.The solid volume fraction distribution in the scraper type 1,3,and 4 mixing tanks appeared Layering phenomenon.But the change of solid volume fraction distribution curve in the scraper type 2 mixing tank was the smallest,furthermore,the stirring power loss was the lowest,which meant the scraper type 2 had the best mixing effect.