Masato Hirota
MRI Measurements of Fibre-Suspension Flow in a SuddenContraction/Expansion
FP1005 & SIG43 Workshop NTNU, Trondheim 24-26 October 2012
3/17
Fibre-suspension flow
• Fluid motion in papermaking process affects quality of paper– Clarifying and controlling the flow is consistent
way to increase quality of paper
• Studying in practical condition is necessary– Contraction and expansion of the flow– Steady and unsteady flow
4/17
Nuclear Magnetic Resonance Imaging (NMRI)
for flow measurement
• Protons in fluid are traced– Non-invasive flow measurement method– Not adversely affected by optical
opaqueness
• Local velocities of fluid are measured by phase encode imaging
5/17
Target and objective of the study
Target
Objective
Fibre-suspension flow in a pipe through a sudden contraction and expansion
Obtaining velocity profiles using MRI and determining the effect of the pulp fibre
8/17
Experimental conditions
Ox
r
175 [mm]130 [mm]100 [mm]
D d
Diameter of the pipe : D =45 [mm]Diameter of the contraction : d = 23 [mm]Bulk velocity : U = 78.6 [mm / s]
Flow
U
3105.3
UDReBulk Reynolds number :
Fraction of fibre (Softwood) : 0, 0.5, 1.0 wt %
10/17
Vertical direction
g1.0% pulp
0% pulp
0.5% pulp
Velocity profile at upstream (x=-130)
xO
130100
Flow
Horizontal direction
Plug flow
Turbulent flow
Laminar flow
–Paper pulp stabilizes the flow and forms plug flow–Paper pulp makes sedimentation
11/17
Velocity profile around contraction (x=-105, -70, Horizontal)
xO
70
Flow
x=-105 x=-70
105
1.0% pulp
0% pulp
0.5% pulp
1.0% pulp
0% pulp
0.5% pulp
12/17
30
Velocity profile around expansion (x=-30, 30, Horizontal)
xO
30
Flow
x=-30 x=30
1.0% pulp
0% pulp
0.5% pulp
1.0% pulp
0% pulp
0.5% pulp
13/17
1.0% pulp
0% pulp
0.5% pulp
g1.0% pulp
0% pulp
0.5% pulp
Effect of sedimentation
30
xO
130
Flow
x=30 (Horizontal)x=-130 (Vertical)
Upstream velocity profile might affect downstream
Flow of 0.5% suspension has remarkable velocity profile
14/17
Velocity profile at downstream (x=120, Horizontal)
x=120
xO
120
Flow
1.0% pulp
0% pulp
0.5% pulp
15/17
Effect of turbulence
MRI measurement in unsteady flow is still challenging
xO
120
Flow
0% pulp (Turbulent)
Acquired signal at x=120
1.0% pulp (Laminar)
Turbulence attenuates signal intensity
17/17
Conclusions and future works
MRI measurement of pulp suspension flow in a sudden contraction and expansion has been performed
• Conclusions– Pulp in water behaves like increasing of viscosity
before it forms plug flow– Sedimentation affects velocity profile
• Future works– Improving MRI protocols– Coupling between horizontal and vertical direction