一种新型粮食孔隙度就仓测量系统研究

Study of a New in-bin Porosity Measurement Method

提出了粮食孔隙度测量新思路,旨在探索一种就仓测量粮食孔隙度的新方法,为研发粮食孔隙度就仓测量仪提供理论依据。本研究在模型仓内测量小麦、玉米的孔隙度,各自测量75次。为了降低模型仓进气初始阶段的流量波动现象对结果造成的影响,需要求出所有实验中同一时刻流量的平均值,用Excel对不同时刻的平均值进行曲线拟合得到平均流量-时间曲线,用1stopt对曲线积分,将积分值连同测得的压力、温度代入相应公式可以计算出孔隙度。用该方法得到的小麦孔隙度为34.5%,玉米孔隙度为41.6%,与用排水法得出的参考值之间的相对误差分别为4.55%和4.00%。结果表明:由该测量系统测定时无需取样,可以测出粮食在仓储状态下的孔隙度,测定结果比取样后测定的数值更真实可靠。

The objective of this research was to develop a new method for in-bin grain porosity measurement without sam-pling .The new method was based on the gas volume-pressure relationship .Based on the amount of air pumped into the bin to fill the pore space and the corresponding pressure rise , the total pore volume was calculated .An experiment was conducted to validate this method .The experimental set up was made up of a model bin , with an air inlet controlled by a ball valve, an air pump, a duct, a hot wire anemometer , a thermometer, and a pressure gauge .Before the experiment , all connections were checked thoroughly to ensure the system was air-tight .As the air was pumped to the bin , the pres-sure increased from the atmospheric pressure to a maximum value .This maximum pressure , as well as the time took to reach this pressure were recorded .The flow rate measured by the anemometer was recorded continuously by using a video camera.Seventy-five （75） tests were performed on wheat and corn .To validate the proposed methods , the porosity of wheat and corn was also measured with the commonly used liquid displacement method .The average measured porosities for the wheat and corn were 34 .5%and 41 .6%, respectively .And the relative error between the in-bin measurement method and reference value gained by the liquid method （ wheat：33 .0%, corn：40 .0% ） were 4 .55% and 4 .00%, respectively .This showed that the proposed in-bin porosity measurement method was adequate and could be used to measure the porosity of grain as a new approach .The advantage of this method is that it could measure the grain porosity during storage without taking samples , and it reflects the true porosity in the bin .