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

Research Objective 
Development of a simple in design, energy and resource-saving device for cleaning seeds 
of cereal and leguminous crops from various impurities and weed seeds by separating them into 
fractions using an air flow. 
Agrotechnical requirements
for device
. During preliminary cleaning, the loss of grain in 
waste should be no more than 0.05%, crushing - 0.1%, and the completeness discharge of weed 
impurities - not less than 50%. During the initial cleaning, the loss of high-grade grain should be 
no more than 1.5% in fodder waste and 0.05% in impurities, crushing - no more than 1%, the 
completeness of the release of trash impurities - not less than 60%. During secondary treatment, 
the loss of seeds of the main crop in waste should be no more than 7%, crushing - no more than 
0.8% Secondary treatment should ensure the preparation of seeds of II and I classes. 
 
 

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№3/2021 year. 
Technical science and innovation
252 
 
Materials and research methods 
On the basis of a patent search and analysis of the designs of cleaning devices, as well as 
previously carried out research works in this direction, a schematic diagram of an energy and 
resource-saving device for cleaning seeds of cereal and leguminous crops from various 
impurities and weed seeds by separating them into fractions with air flow was designed. An 
experimental sample of the device was made according to the developed design documentation. 
Experimental studies on cleaning seeds of cereal and leguminous crops from various impurities 
and seeds of weeds were carried out on an experimental model of the device [7]. 
Separation of seeds by aerodynamic properties. Moving in the air, any body overcomes 
the air resistance, which depends on its size, shape, mass and location in the air flow. The greater 
the air resistance, the slower the freely falling body moves. This principle is the basis for the 
process of separating impurities and separating grain by horizontal or vertical air flow [8].
Typically, the mixture to be separated is introduced into an air flow created by a fan, or 
thrown up, causing it to move in the air. A body placed in a vertical air flow (channel) is acted 
upon by the force of gravity 
P 
and the force of resistance to the air flow 
R
. If
P> R
, then the 
body falls. If
R> P
, the body moves up. If
P = R
, the body is in suspension. It is motionless 
relative to the channel walls.
The speed of the vertical air flow, at which the body is in 
suspension, is called the soaring speed or the critical speed
V
cr

of the given body. The grain 
mixture can be separated by air flow only if the critical velocities of the seeds and impurities are 
different. The value of
V
cr
can be determined by the formula
V
cr
 g = K
w
 
where 
g
is the acceleration of gravity; 
К
w
- windage coefficient. 
Since
К
w 
depends on several changing factors, the value of
V
cr
is usually determined 
on a sail classifier or in a wind tunnel. The critical speed of seeds of grain crops is 8 ... 17 m/s 
(wheat - 8 ... 11.5 m/s, oats - 8.1 ... 9.1 m/s, peas - 15.5 ... 16 , 5 m/s). 
T
he critical speed and windage coefficient of the same body of irregular shape are variable 
values, since they depend on the surface area of the body on which the air flow acts. The bodies 
are separated according to their aerodynamic properties using pneumatic separators or aspiration 
systems built into grain cleaning machines. Pneumatic separators are used for preliminary 
cleaning of grain coming from the combine. Pieces of straw, chaff, dust and seeds of some weeds 
are separated from the grain by an air stream. Pneumatic separators are also used to clean the 
fruits of the machine collection from impurities.