Computer solution of equations for three centrifugal distributor configurations

Centrifugal distributors are used extensively for the broadcast application of granular materials such as seed, granular fertilizer, and agricultural chemicals. A major problem with this equipment is nonuniform spreading which frequently results in reduced crop yield.

The object of this study is to provide information required for more satisfactory design of spreading equipment. The equations representing the motion of granular particles along the blades of three centrifugal distributor configurations were solved with the aid of an electronic analog computer. Straight, forward and backward-pitched blades and logarithmically spiraled blades, all on flat distributor bases, were studied. Straight radial blades on a concave, cone-shaped base were also investigated.

The results of this study were presented in graphs. Displacement, velocity, and departure angle versus the angular rotation of the distributor were plotted for a large range of parameters for each configuration. These variables were expressed in dimensionless form. From a study of the graphs it was noted that of all configurations investigated, the radial-blade arrangement requires the smallest 1·rotational displacement of the distributor to impart a specified velocity to granular material. As the pitch is increased, greater rotation is required. For a given amount of distributor rotation, higher values of the coefficient of friction cause a reduction in both displacement of the particle along the blade and its final velocity. The effect of increasing the ratio of gravity induced friction force to centrifugal force is similar but smaller than the effect of increased friction alone.