摘要
粮堆孔隙率是粮堆基本物理参数之一,对粮堆温度场、湿度场和生物场的分布和变化具有重要的影响。以小麦粮堆为研究对象,采集不同压力下粮堆表层图像,用OTSU大津阈值分割法处理图像,分割粮食籽粒与孔隙,根据分割后的图像计算不同压力下的粮堆孔隙率,提出了一种基于图像测量技术的粮堆孔隙率测量方法。通过与理论计算结果对比可知:图像测量法测得小麦粮堆孔隙率随着压力增大成幂函数关系减小,与理论法测得变化规律一致;图像法测得的小麦粮堆孔隙率大于理论法测量结果。图像法能快速测量粮堆在动态压力场、温度场、湿度场下的边界孔隙率变化,无须取样,对试验粮堆没有扰动,为小麦粮堆数值模拟研究提供参考。
Porosity is a fundamental physical parameter,which has a significant impact on temperature,humidity,and biological field of bulk grain.A study of digital image method was carried to investigate porosity of bulk wheat grain under different overburden pressures.The tested material was wheat produced in Henan province,China.It has a natural bulk density of 793 kg/m3,moisture content of 10.9%,and the average particle diameter of 4.6 mm.The bulk wheat was tested in a new designed compression apparatus for bulk grain,which has a dimension of 120 mm×120 mm×50 mm.The height of the compression apparatus is larger than 10 times of the wheat particle,and complies with the requirement of compression test.The pressure applied on bulk wheat specimen was 4,1,15,30,59,119,178,237,296,and 333 kPa,the maximum pressure of which is considered as the maximum pressure in large grain bins.The digital image was collected through CMOS lens,a DC regulated light source was adopted with an illuminance of lux,and a procedure compiled by MATH WORKS was used to revise the distortion of the image.The digital images of bulk wheat were collected under different overburden pressures,the space of void and wheat was distinguished by the gray level of the images,then grain particle and void was segmented through OTSU threshold method,and the porosity of bulk wheat was defined by picture element quantity of void divided by the total picture element quantity.The threshold pixel point value of bulk wheat digital image was investigated,and the results showed that,when the threshold pixel point value was 71,the determined porosity was consistent with the test result.Bulk grain porosity was also calculated by consolidation theory,which considers the wheat kernel as a non-compressible material.The digital image method was verified with the theoretical method.The results showed that:the porosity of bulk wheat grain decreased with the increase of overburden pressure,and the relation between porosity and overburden pressure can be expressed by the power function.The coefficients of a and b were-0.006 89 and 0.424 9,respectively,in theoretical method,and the coefficients of a and b were-0.000 46 and 0.840 2,respectively,in digital image method.Porosity calculated by theoretical method was consistent with digital image method.Therefore,digital image method can be used to determine the porosity of bulk grain under different overburden pressure,temperature and humidity fields without sampling or disturbing the material.The results can provide parameters for numerical simulation of grain in bins.
作者
边浩
蒋敏敏
刘超赛
尹君
BIAN Hao;JIANG Minmin;LIU Chaosai;YIN Jun(College of Civil Engineering,Henan University of Technology,Zhengzhou 450001,China;Academy of National Food and Strategic Reserves Administration,Beijing 100037,China)
出处
《河南工业大学学报（自然科学版）》
CAS
北大核心
2021年第2期107-111,120,共6页
Journal of Henan University of Technology：Natural Science Edition
基金
国家粮食公益性行业科研专项(201513001)
国家自然科学基金项目(51408197)
河南省科技厅自然科学项目(182102210387)
河南省科技攻关项目(162102210188)。
关键词
粮堆
孔隙率
图像测量
阈值分割
bulk grain
porosity
digital image method
threshold segmentation
