【摘要】 在模拟仓内装满稻谷后,埋入5层3列N2传感器,从仓底进气口充入流速为10 L/min的N2,时间约为70 min,室内温度20℃,关闭N2气源后测定氮气浓度至300 min,研究氮气的自由扩散规律。结果表明:在充气阶段,距离进气口越近的点的氮气浓度上升越快;在同一层面上,以进气口所在处对称的点浓度比较接近,可以由已知点的浓度来判断未知点的浓度;由于氮气密度较空气小,氮气在纵向传递的速率高于横向传递的速率15%~25%。氮气的扩散速率在充气的过程中与进气口的距离呈正相关,在自由扩散过程中,靠近粮面的氮气可以维持在一个比较恒定的速率(0.05%/min),下层氮气扩散速率最快(约为0.2%/min),中层的次之(约为0.09%/min)。粮堆内各层之间具有显著性相关,而受到氮气密度的影响下层和中层的相关性要高于中层和上层;距离进气口越远的层,氮气的浓度变化越为稳定。更多还原

【Abstract】 After the paddy rice was filled,within the simulation silo,nitrogen sensors were buried(in the form of 5×3). The nitrogen was charged through the inlet,which was located at the bottom of the silo,and the flowrate was 10 L/min. The charging time was 70 min,approximately,and the ambient temperature was 20 ℃. As the inlet valve was switched off,the concentration of nitrogen was monitored,for the sake of studying free diffusion of nitrogen. The results demonstrate that,during the aeration stage,the concentration of nitrogen increased as the distance between the checking point from the inlet decreased. At the same layer,due to concentrations of symmetrical points of inlet were relatively close,unknown figures could be deduced by the concentration which was recorded. Since the density of nitrogen is smaller than the air,the vertical flowrate was faster than the horizontal one, at about 15~25%. In addition,during the charging,there was a positive correlation between diffusion rate of nitrogen and the distance to the inlet. The flowrate of nitrogen closing to the surface of grain stayed relatively constant,at about 0.05 %/min,during the free diffusion. The fastest rate was found at the bottom(around 0.2 %/min),followed by middle’s(about 0.09 %/min). Layers in the pile held significant correlations. It should be noted that the correlation between bottom and middle was much tighter than the one between middle and top. This is probably due to the influence of density of nitrogen. What is more,there was a tendency that the concentration of nitrogen became stable as the layer farther to the inlet.更多还原