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The role of terminal velocity in paddy cleaner

Joined: 2018-06-06
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*Posted: Submitted by ricepolisher (0) on Thu, 2018-06-14 06:25. | Subject: The role of terminal velocity in paddy cleaner

Designing of the air conveying systems and the equipment for
cleaning, handling, aeration, storing, and processing requires the
knowledge of terminal velocity, which is equal to the air velocity at
which particle remains in suspended state in vertical pipe. The role of
terminal velocity in paddy cleaner
is important in grain cleaning by removing impurities like chaff,
dockage, immature, and hollow grains. The separation process by an air
stream in grain mix depends on the ratio between terminal and air
velocity of particles, and their entrained particle quantity in unit
volume of air flow.

To determine and recognize a database of physical and engineering
properties of grains of some main and popular feed, industrial crops
which play an important role in designing and developing of specific
machines and their operations such as planting, harvesting and grading
.The studied crops namely fennel flower, rice (Giza101), rice (Giza
177), broad bean, corn (hyb. 310), corn (hyb. 352), wheat (Giza9) and
wheat (Giza 168)and their selection based on their recent coverage area
and the expected future expansion of each variety. Various physical
properties including grain dimensions (length, width and thickness),
the weight of thous and grain, bulk density, percent of sphericity,
projected area , and the mechanical properties including angle of
repose and coefficient of friction, in addition to the aerodynamic
properties including terminal velocity, drag coefficient and Reynold's
number, were determined at storage moisture content 7-12%(wb).

Aerodynamic properties of wheat are important factors in pneumatic
conveying, separating and cleaning machines. Among the properties,
terminal velocity is very important. Terminal velocity of wheat
measured with a designed vertical wind column. Three different
varieties of wheat as Pishtaz, Mahdavi and Marvdasht were tested. The
wheat's verities were tested at different moisture contents of around
8%, 12%, 14%, 18%, to 22%. Wheat samples selected randomly and placed
on the column screen. A "hot wire" anemometer at the local point
measured the air velocity. The highest terminal velocity was 6.9 m/ s
for Mahdavi variety and the lowest terminal velocity was 6.0 m/ s for
Marvdasht variety. By increasing moisture content, the terminal
velocity of all wheat varieties increased. Linear regression modeling
for different varieties of wheat was determined.

rice destoner
was equipped with a blower (blast fan) which supplied air stream
across the flowing grains. This caused the mixture of grains and stones
to move at different velocities in different projectile directions. The
machine was operated with a single phase 3hp (2.250 kW, 1440 rpm)
electric motor and loaded.

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