RESISTANCE OF BULK CANOLA OILSEED TO AIRFLOW
Jayas, Digvir S
The distributions of chaff and fines were studied in a 4.6 m diameter bin filled with canola (variety Tobin, Brassica campestris) using either a spreader or central spout. The resistance of canola to airflow and the effect of variety, moisture content, method of fill, direction of airflow and the amount and size of foreign material on the airflow resistance was determined using a laboratory apparatus. A mathematical model incorporating the effect of distributed foreign material and the effect of various parameters on airflow resistance was developed for predicting pressure patterns in a bulk having an axisymmetric configuration. The predicted pressures were compared with measured pressures at several locations in the 4.6 m diameter bin. In both spout and spreader fills, the chaff concentration was maximum near the wall and was minimum at a distance of 0.6 to 0.8 m from the center of the bin. The fines were concentrated around the center and near the wall with the minimum concentration occurring midway between the center and the wall. The resistance of canola to airflow was about eight times the resistance of corn and about two times the resistance of wheat at similar airflow rates. An increase in moisture content of canola from 6.5 to 14 percent resulted in a decrease in resistance to airflow of 20 percent. The resistance of canola, variety Westar (B. napus), was about 60 percent of the resistance of canola, variety Tobin (B. campestris), at a given airflow rate. The resistance for airflow in the horizontal direction was 60 percent of the resistance for vertical airflow. The sprinkle fill, that simulates use of a spreader when filling a farm scale bin, produced a bulk density about 9-10 percent greater and more than doubled the resistarice to airflow compared with spout fill. An increase in the fraction of fines increased airflow resistance linearly while an increase in the fraction of chaff decreased airflow resistance. Predicted pressures compared well with measured pressures in the 4.6 m diameter bin. The prediction model can be used for designing near-ambient drying and aeration systems.