INFLUENCE OF SMALL FRACTION OF POLYGRANULAR FILL OF ROTATING DRUM ON SELF-OSCILLATION SWING

Abstract

The influence of the structure of two-fractional polygranular fill of a rotating drum on the self-oscillation swing is considered. The pulsating mode of flow of such intrachamber fill is used in the self-oscillating grinding process in a tumbling mill. Spherical particles of non-coherent granular material of 2.2 mm size were used as a large fraction modeling the grinding bodies. Cement was used as the small fraction modeling the particles of the crushed material. The factors of experimental studies were accepted: the gaps between particles of large fraction degree of filling at rest dispersed particles of small fraction 0, 25, 50 and 100%, the relative size of particles of large fraction in the drum chamber 0.519, 0.733, 1.04, 1.47, 2.08, 2.93, 4.15 and 5.87% (drum chamber radius 212, 150, 106, 75, 53, 37.5, 26.5 and 18.75 mm), the chamber degree of filling at rest 25, 35 and 45%. The method of visual analysis of fill motion patterns in the cross section of a rotating chamber and measurement of dilatation was applied.Video of the fill pulsating flow was taken. The magnitude of the self-oscillation swing was estimated by the increase in the difference of the maximum and minimum values of the fill dilatation over one period of pulsating. The maximum range of self-oscillation swing reached the value of 1.36. The change of the self-oscillation swing from zero at the beginning of self-excitation of pulsations to the maximum value with the greatest increase of dilatation was revealed. The effect of a decrease in the maximum range of self-oscillation swing with enhanced fill coherent properties has been registered. The attenuation of the spray of particles of large fraction in the chamber due to the coherent effect of the small fraction was established. An increase in the self-oscillation swing of single-grain fill was found with a decrease in the relative particle size and the chamber degree of filling. A decrease in the self-oscillation swing of two-fractional fill was found with an increase in the content of small fraction, a decrease in the relative size of particles of a large fraction, and an increase in the chamber degree of filling.