KINEMATICS OF GRAIN MOVEMENT ON A SPIRAL DEVICE WITH VARIABLE ANGLE OF DESCENT

Abstract

Cylindrical tanks, called siloes, are used to store grain material. The height of such structures is limited
by soil bearing capacity and does not exceed 30 ... 60 m. The loading of siloes with grain is usually conduct-
ed by gravitation method in a compact flow. In this case, the stability of functioning cylindrical tank capaci-
ties depends on certain internal and external factors. The internal factors include physical, mechanical and
biological properties of grain material, and the external ones include environmental conditions and struc-
tural parameters of silo itself. The loading of siloes with a compact flow results in grain hitting concrete bot-
tom and inner side surface of the structure and damaging. Under such loading, intensive settlement of dam-
aged grain at the bottom of the silo is observed. This negative phenomenon leads to grain spoilage or death.
To eliminate this drawback, various devices are used to reduce the speed of falling grain material to the bot-
tom of silo. The purpose of this article is theoretical studies of grain material movement along the peripheral
open screw channel (POSC) U – of the like shape. The descent angle (α) of screw channel constantly chang-
es from the maximum value (αmax) to the minimum one (αmin). The angle α within 30 ... 40 degrees in the area
of  grain  mass  acceleration  is  accepted.  In  the  lower  part  of  the  POSC,  the  angle  α  decreases and is
10...20 % smaller than αmax. This enables to stabilize the linear speed of grain movement. Practical experi-
ence has made it possible to draw up a scheme of forces affecting grain material, which, under the action of
gravitational force, descends on a screw chute. The presented scheme of forces enables to consider the main
and auxiliary factors, which influence this technological process. The equation, obtained using mathematical
modeling, describes the speed of grain material movement along the POSC with a variable descent angle.
The movement of grain material takes place at almost constant linear speed at the bottom of the device.
When deriving the equation to determine the speed of grain movement on a spiral device with a variable an-
gle of descent, there was a need in developing a stand to study the technological process of filling siloes with
grain without its damaging