基于EDEM-Fluent的玉米储藏立筒仓环流通风与纵向通风仿真分析

Simulating the circulation and longitudinal ventilation of corn storage silos using EDEM-Fluent

为解决立筒仓中纵向通风方式储粮效果不佳,在储粮机械通风过程中存在通风不均匀等问题,该研究结合纵向通风与横向通风的优点建立了环流通风仓模型,应用EDEM-Fluent流固热耦合方法,对相同工况下,储粮仓两种风道结构在机械通风时的速度场、温度场进行仿真对比分析。结果表明:环流通风速度均匀性指数为0.92,纵向通风速度均匀性指数为0.88,相同工况下环流通风气流在粮仓内分布更均匀。在温度场仿真分析中,纵向通风初期入风口附近区域粮堆温度呈梯度下降,明显低于初始温度,上层粮堆由纵向通风引起的热量传递不明显,受仓顶环境温度影响,粮面温度较粮堆内部低;环流通风初期,上层粮堆在环流通风影响下已经开始进行热量交换,产生温度梯度,通风结束后,纵向通风在粮层高度H=0.5 m处,温度维持26.85℃,H=0.8 m处温度降到27.85℃,整体平均温度降至24.77℃,环流通风仓在这两处温度分别为24.85和25.85℃,整体平均温度降至23.43℃,环流通风整体降温效果优于纵向通风;在颗粒温度场仿真分析中,相较于纵向通风,环流通风仓上下部颗粒温度相差较小,整体降温均匀。在不同通风形式下的粮仓各层温度变化规律分析中,不同高度的粮层,环流通风的粮堆温度均低于纵向通风,环流通风的粮堆温度下降更快,降温效果更好。整体结果表明,加装环流风道后立筒仓内粮堆降温效果明显优于纵向通风结构,研究结果为立筒仓风道优化,解决储粮通风不均问题提供重要依据。

This study aims to improve the storage efficiency of longitudinal ventilation in vertical silos during mechanical ventilation of grain storage.A circulation ventilation silo model was established to combine the longitudinal and transverse ventilation.EDEM Fluent software was used to simulate the velocity and temperature fields of air duct structures in a grain storage silo under mechanical ventilation.The results show that the velocity uniformity indexes of the circulating and longitudinal ventilation were 0.92 and 0.88,respectively.The average velocities of circulating and longitudinal ventilation airflow were 2.51 and 1.91m/s,respectively.The circulation ventilation airflow was more evenly distributed in the grain silo.In the simulation of the temperature field,the temperature of the grain pile near the inlet of the longitudinal ventilation initially decreased in a gradient,which was significantly lower than the initial temperature.There was no outstanding heat transfer caused by longitudinal ventilation in the upper layer of the grain layer.But the temperature of the grain surface was lower than that inside the grain pile,due mainly to the environmental temperature at the top of the warehouse.Specifically,the upper layer of grain started the heat exchange in the early stage of circulation ventilation,thus generating a temperature gradient.Furthermore,the temperature of the longitudinal ventilation chamber dropped to 27.35℃at H=0.5 m and 28.85℃at H=0.8 m after ventilating for 20 s.There was no significant variation in the temperature of the grain pile near the warehouse wall.Correspondingly,the temperatures of the circulating ventilation warehouse were 26.85℃and 28.35℃,respectively.When ventilated for 30 s,the temperature of the longitudinal ventilation chamber dropped to 26.85℃at H=0.5 m,and to 28.35℃at H=0.8 m.The temperature of the circulating ventilation chamber were 25.35℃and 27.35℃,respectively.After the ventilation was completed,the longitudinal ventilation was maintained at a temperature of 26.85℃at H=0.5 m,and the temperature dropped to 27.85℃at H=0.8 m.The temperature values of the circulating ventilation chamber were 24.85℃and 25.85℃,respectively;The overall average temperature dropped to 24.77℃and 23.43℃,respectively,at the end of ventilation in the longitudinal and circulating ventilation.The cooling performance of circulating ventilation was significantly improved with the high and more uniform cooling rate,compared with the longitudinal one.In the simulation of the particle temperature field,the temperature of the lower half of the particles in the silo was relatively low after longitudinal ventilation,with an average particle temperature of 21.20℃and an average particle temperature of 22.85℃after circulating ventilation.There was relatively low cooling in the upper part of the particles after longitudinal ventilation.There was no significant change in the temperature of the particles near the warehouse wall.The average temperature of particles was 27.34℃after ventilation.There was more significant cooling of the particles in the upper part of the warehouse after circulating ventilation,where the average temperature of particles was 23.07℃after ventilation.Compared with longitudinal ventilation,the temperature difference of particles between the upper and lower parts of the circulating ventilation warehouse was relatively small,indicating uniform cooling.In the temperature changes in different layers of grain silos under the same ventilation conditions with different heights of grain piles,the temperature of circulating ventilation was lower than that of longitudinal ventilation grain piles.After ventilation,the average temperature of the circulating and longitudinal ventilation chamber dropped to 23.43℃,and 24.77℃,respectively.The temperature of circulating ventilation decreased significantly,where the average temperature of each layer was lower than that of longitudinal ventilation,resulting in better cooling.The grain pile in the vertical silo with a circulating air duct was better cooling than that of the longitudinal ventilation.This finding can provide an important basis to optimize the air duct in the vertical silo for better ventilation in grain storage.