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the classical mechanics through a fictitious total friction
coefficient, the progress resistance coefficient λ h , from
a known reference value, in our case the volume flow I V ,.
Thus the input power is calculated from
P = ρ ⋅ IV
⋅ g ⋅ λh
Issue 04 | 2010
( ⋅ L + H )
The bulk density ρ, the volume I V, the progres
resistance coefficient λ, as well as the geometry
parameters conveying length L and conveying height H.
Entscheidender The decisive difference in the new method
is the definition of the progress resistance coefficient λ h as
a multidimensional parameter. While the DIN 15262 defines
the progress resistance value as a constant value that is
specific to bulk materials, the new method takes stock of
the knowledge gained through experiments , so that the
progress resistance coefficient depends on geometry-,
operational and bulk material parameters. The calculation
can be obtained from the papers of Blomeyer [4].
Methods of dimensioning and sizing for vertically
operated screw conveyors are also mentioned in the
above-mentioned tasks. These methods were realized
as partly graphic methods. Since, as mentioned above,
purely rotational conveying characteristics are
present in a vertical conveyor, the bulk material
in the conveyor is conveyed upwards in a helix.
Thus the velocity of the goods is reduced by a
rotational portion, the angular speed of material
ω . Therefore the achievable volume flow I is
G V
calculated as.
I
V
= A⋅
v
= ϕ ⋅
ax
(2)
⎛ ω
⋅π
⋅ S ⋅⎜
n −
⎝ 2π
1 2
G
⋅ D 4
⎞
⎟
⎠
(3)
The angular speed of material ω G can be
calculated through an equation of motion.
However, since this should be done separately
for each individual case, determination of the
volume flow is offered as a graphic method. A
respective diagram for filling levels of φ = 0,4 is
shown in picture 3.
The calculation of the required driving
power is done similar to the procedure in range
I. Again a total friction power is calculated,
which is a product of a conveying factor and
the analytical determined power based on the
friction against the tube and the screw. The
power loss through lifting of the bulk material is
Volume Flow [m³/s]
0,50
0,40
0,30
0,20
0,10
0,00
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again added. Analog to the progress resistance coefficient,
the conveying factor is a parameter that is dependant on
geometry- operational and bulk materials parameters.
Accurate calculation formulas, as well as further diagrams
for determination of volume flow can be obtained from the
paper of Rong [6].
In previous years the Institute for Materials Handling
Material Flow Logistics (fml) has also done examinations
on highly inclined screw conveyors. Building on the
task of Gabler [7], Vollmann [1] developed even more
detailed calculation algorithms and programmes, which
allow for calculation of volume flow and driving power
of highly inclined screw conveyors. These are based on
0,4
0,6
0,8
1,0
1,2
1,4
Pic. 3:
Diagram to determine the volume flow in vertical
screw conveyors [3] for a filling level of 0.4
1,6
1,8
2,0
2,2
D = 0,800 m
vax =
2,4 m/s
0,630
0,500
1 3 5 7 9 11 13 15
Rotation Speed [1/s]
0,400
0,315
0,250
0,200
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