Education of the republic of uzbekistan tashkent state technical university named after islam karimov

Mechanical Engineering
251 
transported from the combines to the units and complexes for post-harvest processing of grain, in 
which it is subjected to cleaning, drying and sorting. Cleaning is the division (separation) of the 
grain mixture into separate fractions, which are separated by some physical and mechanical 
properties (size, density, etc.). Allocate preliminary, primary and secondary cleaning. 
Pre-cleaning is used to treat freshly harvested grain with a moisture content of up to 
35%. As a result of its application in refined grain, the content of the largest and smallest 
impurities decreases (from 15 ... 20 to 3%), part of excess moisture is removed, its flowability 
increases, subsequent processes (especially drying) are facilitated, the grain resistance to self-
heating increases during temporary storage in an embankment [4]. 
Pretreated and dried grain with a moisture content of not more than 18% is subjected to 
primary cleaning. At the same time, large, light and small impurities, crushed and shriveled grain 
are released from the grain; the content of impurities in the grain is reduced from 8 ... 10 to 1 ... 
3%. The original grain heap is divided into three fractions: refined grain, feed waste and 
impurities. 
Secondary cleaning promotes the release of impurities close to it in size, difficult to 
separate weed seeds from the grain. As a result, the original grain heap is divided into seed 
fraction, grain of the second grade, light, small and large impurities. Food and feed grains are 
mainly subjected to preliminary and primary cleaning, and seed - also secondary. Drying is the 
process of reducing grain moisture content from original to conditional (14 ... 17%), due to 
which it can be stored for a long time. Air cleaning is widely used in grain cleaning machines. 
This method is based on the difference in gravity and aerodynamic properties of seeds and 
impurities. The different effects of air flow on grain and impurities depend on aerodynamic 
properties. The aerodynamic properties of grain impurities include the critical speed (soaring 
speed), the air drag coefficient m
k,
and the windage coefficient k
р
. Soaring speed - the speed of 
vertical ascending air flow. 
However, until now in agricultural production there are no simple in design, easy to 
manufacture, as well as energy and resource saving devices for cleaning seeds of cereals and 
leguminous crops from various impurities and seeds of weeds. Considering the above, as a result 
of the research work carried out in recent years, we have developed a device that is simple in 
design, easy to manufacture, as well as energy and resource saving for cleaning seeds of cereals 
and leguminous crops from various impurities and weed seeds using an air flow by separating 
them into fractions [5, 6].