IMPROVEMENT OF TECHNOLOGICAL PARAMETERS OF GRAIN BUCKET CONVEYOR WITH GRAVITY-CENTRIFUGAL UNLOADING. THEORETICAL ASPECTS AND EXPERIMENTAL TESTS

Abstract

The results of research on the assessment of the quality of transportation and unloading of grain from various agricultural crops using bucket-type elevators are presented. The assessment indicators determine the degree of direct and reverse grain flow, the degree of mechanical damage and compression injury to the grain, the specific energy consumption for grain transportation, the material intensity of the elevator structure, etc. Experimental research and production tests of elevators with modernised buckets were carried out using the NF type elevator (Fadeev elevator) as an example. These steeply inclined or vertically positioned bucket elevators are used in production line complexes for cleaning and separating seed material from major agricultural crops. Accordingly, one of the main priorities in determining the parameters for transporting and unloading agricultural seeds is to minimise mechanical damage and compression destruction of the grain. Both of these factors affect the germination rate of the seeds, which is the dominant factor in this case. Based on preliminary design calculations, layout diagrams, and technological, spatial, and technical limitations, two types of buckets were proposed for experimental verification and testing: bucket No. 1 is the basic version of the NF-1 type bucket elevator, with a discharge wall angle of 43º; bucket No. 2 – experimental, improved by us based on the results of graphical analysis methods – has a discharge wall angle of 30º. The speed of grain transportation by the bucket belt was selected discretely, taking into account the technical characteristics of the power drive of such a belt, and amounted to 0.64 m/s and 0.76 m/s, respectively.
It has been experimentally proven that the most effective for the NF-1 type elevator is the gravitational-centrifugal unloading mode, as this mode allows maximum use of the bucket volume, since the centrifugal force contributes to the preliminary redistribution of grain and accelerated emptying of the bucket, which directly increases productivity and minimises seed spillage into the elevator shaft during unloading. At speeds of 0.76 m/s, the centrifugal force creates the necessary inertial ‘back pressure’ that pushes the grain out of the bucket before it begins to fall under its own weight. This mode ensures a stable ejection trajectory, which minimises grain impact on the inner walls of the elevator head.
The use of experimental bucket No. 2 with a 30° unloading shelf and a special bottom when operating in gravitational-centrifugal mode made it possible: for sunflower seeds: to overcome the windage of the seeds and direct them precisely into the discharge window; for wheat and soybeans: ensure stable discharge of mass without ‘rubbing’ the grain between the bucket and the shaft wall.
Regarding the productivity of grain transportation by bucket elevator, using sunflower as an example, it has been established that increasing the speed from 0.64 m/s to 0.74 m/s increases productivity from 1.4 t/h to 2.28 t/h (by 62%), This mode is achieved through better filling of the buckets and a clear discharge trajectory, which eliminates jams in the elevator head. The highest productivity of the NF-1 was recorded during the transportation and gravitational-centrifugal unloading of soybeans (4.78 t/h) and winter wheat (5.29 t/h), respectively, due to their high bulk density. At the same time, the NF-1 elevator, equipped with experimental buckets No. 2, demonstrates a stable flow without a critical increase in energy consumption.