Mass Flow Measurement of Granular Materials in Aerial Application — Part 2: Experimental Model Validation

A system was developed to measure the mass flow of granular fertilizer material in aerial spreader ducts. The flow process was regarded as the sequential passage of clusters containing multiple particles with varying diameters. An optical sensor was used to measure the cluster lengths on the fly. In a low–density flow regime, the diameter of each particle could be measured individually (this is called the “single–particle approach”). After conversion to a volume of a sphere and multiplication by the true material density, the mass flow could be computed. In a high–density mass flow regime (called the “mass flow approach”), particles form clusters, and cluster lengths would be measured instead of particle diameters. The first step in performing mass flow measurement was to develop a reconstruction algorithm that estimates the number of particles in a cluster from the measured cluster length. This algorithm, called the Exponential Estimator, was developed using simulation and is reported in Part 1. This article, Part 2, describes the use of the mass flow sensor as well as the reconstruction algorithm to assess the accuracy of the complete system. Tests were carried out under laboratory conditions, using mass flows of spherical particles as well as urea fertilizer under varying flow velocities and densities. The mass flow of identical spherical particles of 4.45 mm diameter was measured with an accuracy of 3%, even under high–density flow conditions. For granular fertilizer, the flow was measured with an accuracy of 2% for high–density flows and 4% for low–density flows.