Strategies to mitigate dead-zones in on-farm stored grain silos fitted with aeration ducting modelled using computational fluid dynamics

Abstract

Centre filling of a cylindrical silo results in a peaked grain pile with a high concentration of fines in the bulk core restricting airflow. Fines are also known to have higher mycotoxin levels than whole grain. Coring is recommended to minimise fines and to increase localised airflow through the top grain regions. However, the proportion of coring is not a generalised factor when silo dimensions and fan capacities are considered. Also, the coring proportion used should be minimised to maximise storage capacity and provide good economic returns. A study of sequential coring was conducted using a computational fluid dynamics method to predict the optimised coring volume for a 1000 t silo fitted with 3 kW and 5 kW fans. Each configuration following coring was validated using airflow data measured on the top grain surface of the 12.8 m diameter on-farm silo. Results showed that the model predicted standard errors of 0.0009–0.0024 m s −1 for 16 t, 32 t, 48 t, 80 t, and 158 t coring cases. When fully loaded, around 9% (80 t) of the total mass was required to be unloaded to exhibit the desired airflow in the top-grain region using a 3 kW fan. However, the unloaded mass decreased to 2% (16 t) for the same effect with a 5 kW fan. Thus, a 5 kW fan was recommended as it decreased the proportion of dead zones in the lower bulk region by 65% in a typical 1000 t silo. • Large-scale sequential coring was implemented in a 1000 t On-farm silo. • Optimum storage with coring was evaluated with 3 kW and 5 kW fan power. • CFD model showed negligible prediction error with different coring options. • 9% of fully loaded silo should be cored with 3 kW fan but only 2% with 5 kW fan. • Doubling airflow decreased dead zones by 65% at lower bulk with V-shape duct system.