Three dimensional models of pore structure and airflow distribution inside grain bulks

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The grain cooling or drying process is always at risk of failure because of its weather dependency. The non-uniform airflow resistance results in over-dried grain at high airflow locations and wet (spoiled) grain at low airflow locations inside the same bin. The two major factors influencing the airflow resistance distribution are the pore structure among grain kernels (size, shape, connectivity, tortuosity of the pores, and orientation of the pore to the airflow direction) and properties of fluids (air velocity and viscosity). The pore structure is influenced by kernel size, shape, and amount of dockage, fines, foreign materials and broken kernels (DFFB). Published mathematical models mainly used Finite Element Method (FEM) to simulate airflow resistance and assumed continuum inside each element without considering the effect of DFFB on pore structure. Therefore, these developed models did not consider 3D pore structure distribution inside stored grain bulks and the effect of air velocity inside pores on airflow resistance distribution. This results in low prediction accuracy. No model of pore structure inside grain bulks has been developed. A pore structure model can be developed by using Discrete Element Method (DEM). To take advantage of both the FEM and DEM methods, a method to combine FEM and DEM model has been developed for pharmaceutical tableting. In the next 5 years, I will focus on objectives to fill this gap by developing 3D pore structure DEM and airflow resistance distribution FEM models inside stored grain bulks by considering the effect of DFFB on pore structure and airflow resistance. These two models will be coupled together. To validate these developed models, I propose to determine loose and compacted porosity of grains at different moisture contents and DFFB, to model the distribution of DFFB inside bins with different loading heights, and measure airflow resistance distribution inside grain bins under different air velocities. The proposed experiments will use novel technique to characterize pore structures and measure air flow resistance distribution.The long term objective of the proposed program is to advance the knowledge of bulk solid systems with applications to stored grain ecosystems. Therefore, the results from this proposed research will not only provide a rational analysis tool for the design and operation of bulk solid storage systems, but also contribute to the fundamental knowledge of pore structure and flow through grain bulks. The developed airflow distribution model will help design engineers to lay out the aeration system correctly and grain owners to conduct a right ventilation strategy. One MSc, two PhD and five undergraduate students will be trained through this proposed program. The knowledge and skills acquired by students will be beneficial to them in preparing them to work in industry or academia.