Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 3, pp. 505−514.
Pleiades Publishing, Ltd., 2012.
Original Russian Text
I.O. Mikulionok, L.B. Radchenko, 2011, published in Khimicheskaya Promyshlennost’, 2011, Vol. 88, No. 7, pp. 325−334.
PROCESSES AND DEVICES
OF CHEMICAL MANUFACTURES
Screw Extrusion of Thermoplastics: II. Simulation of Feeding
Zone of the Single Screw Extruder
I. O. Mikulionok and L. B. Radchenko
National Technical University of Ukraine “Kyiv Polytechnic Institute,” Kyiv, Ukraine
Received September 24, 2011
Abstract—The technique of calculation of a feeding zone for a single screw extruder is developed taking into
account the nonisothermal process and the actual boundary geometric conditions and speed conditions (the screw
is rotated, the cylinder is ﬁ xed). An analysis of the inﬂ uence of the screw geometry was performed and also of an
effect of a ratio of friction coefﬁ cients of the processed material on the cylinder and worm, on a change in pressure
and temperature of the processed material along the length of the feeding zone.
In developing the mathematical models and
calculation techniques of the feeding zone (supply,
loading, conveying of the solid material) of the single
screw extruders it is assumed that motion of a granular
thermoplastics (TP) in the channel of the screw occurs
as a continuous compressible plug without moving
granules of TP relative to each other [1–8].
The disadvantage of these models is that they do
not take into account the heat transfer TP with surfaces
of the screw and cylinder, which signiﬁ cantly affects
the operation of the feeding zone. Under certain
conditions in the zone of supply a pressure can reach
100 MPa or more , which leads to signiﬁ cant heat
release due to dry friction of the polymer granules
on the wall of the screw and cylinder. On the other
hand, in the traditional examinations of the feeding
zone an effect on it of the subsequent zone, melting
and homogenization was not taken into account, and
thus, the output of the feeding zone calculated by the
traditional dependencies in most cases differs from
the actual output of the extruder, which is usually
determined by that of the zone of homogenization [10,
11]. At the same time for ensuring stable operation
of the single screw extruder the potentially possible
output of the feeding zone should exceed the output
of the melting zone, which, in turn, must be greater
than that of zone homogenisation.
In this regard, in the development of the mathematical
model for the feeding zone its output is assumed to be
known. Others assumptions are the same as in [1–8]: no
moving of granules in the bulk of TP and TP moves as
a continuous elastic body, and, in addition, a slippage
of the granules occurs relative to the surfaces of the
cylinder and screw.
The purpose of this work is to develop the technique
for calculating the feeding zone of the single screw
extruder in view of non-isothermality of the process, the
actual geometric boundary conditions, and conditions
on the speed of working bodies.
OF THE FEEDING ZONE
To develop a model of the feeding zone, we assume
that the screw is rotated and the cylinder is stationary,
as in the real process. In addition, unlike the plane-
parallel model the problem is solved in a cylindrical
coordinate system r, θ, z (Fig. 1a). Moreover, the
volume corresponding to that of one pitch of the screw
thread was selected with its length ΔL, and, in addition,
we conditionally turn this volume by the value of ﬂ ank
of the screw thread, therewith the selected
volume takes a shape of an annular cylinder (Fig. 1b).
The cylindrical coordinate system r, θ, z is unmovable