Study of the pore structure characteristics of soybean grain piles using image processing technology

Pore structure is an important factor affecting the airflow distribution in a grain pile, and hence the variation in its structural parameters under different vertical pressures should be studied further. In this study, grain slice imaging and image processing technologies were comprehensively used to study the changes in the number, size, and shape of the pores in soybean grain piles under vertical pressures of 0, 50, 100, 150, 200, 250, and 300 kPa, and to explore the effects of vertical pressure on the porosity, pore volume, pore diameter, and pore fractal dimen-sion of the grain piles. The results show that the porosity of the grain pile decreased with an increase in the vertical pressure, and the change rate of grain pile porosity was 28% when the verti-cal pressure was 0-300 kPa. When the vertical pressure increased from 50 to 300 kPa, the grain pile porosity variation increased from 6.49 to 24.33% as compared with the natural state (0 kPa). The pore area and diameter of the grain pile gradually decreased with the increase in vertical pressure. The distribution of the grain pile pore area along the horizontal direction from the side wall to centre showed great differences under different vertical pressures. With an increase in vertical pressure, the proportion of the pore diameter of < 2.5 mm increased, whereas the proportion of the pore diameter of > 2.5 mm decreased. An increase in the verti-cal pressure will lead to an increase in the grain pile pore fractal dimension. When the vertical pressure was 0-300 kPa, the change rate of the grain pile pore fractal dimension was 10%. The rele-vant research methods and conclusions drawn in this study may be used to provide theoretical support and a reference source for the airflow distribution and resistance in the bulk