OPTIMIZATION OF A PROFILE- EXTRUSION DIE DESIGN USING INVERSE CFD SIMULATION June Department of Mechanical Engineering, NORTHERN ILLINOIS UNIVERSITY Fluent UGM 2004 By Prof. M. Kostic, Ph.D, P.E. Srinivasa Rao Vaddiraju, M.S. Prof. M. Kostic, Ph.D, P.E. Srinivasa Rao Vaddiraju, M.S.
Introduction Twin-screw extrusion line Fermi National Accelerator Laboratory (FNAL) Northern Illinois Center for Accelerator and Detector Development (NICADD) Department of Mechanical Engineering Cast plastic scintillator - $40/kg Extruded plastic scintillator - $10/kg
Berstorff 40-mm diameter, 1.36 m long, twin-screw extruder Two K-Tron automated feeders Conair downstream equipment Novatec compressed-nitrogen drier Profile Extrusion Line at FNAL Gear pump Dryer Cutter Feeding Hopper Extruder Die Calibrator Cooling Measurement Haul-off Polymer pellets Dopants Breaker plate
Objectives Effective die design strategy Die swell and optimum die profile-shape Mass flow balance Flow and heat transfer Simulation
POLYFLOW Finite-element CFD code Predict three-dimensional free surfaces Inverse extrusion capability Strong non-linearities Evolution procedure
Flowchart for Numerical Simulation 1. Draw the geometry using a CAD software 2. Mesh the geometry 3. Specify Polymer properties and boundary conditions 6.Is the solution converged? Stop 4. Specify remeshing technique, solver method and evolution parameters Yes No 5. Solver solves the conservation equations using the specified data and boundary conditions Modify remeshing techniques, solver methods and/or evolution parameters Modify the mesh
General Assumptions and incompressible Body forces and Inertia effects are negligible in comparison with viscous and pressure forces. The flow is steady Specific heat at constant pressure, C p, and thermal conductivity, k, are constant
Material Data η 0 = 36,580 Pa-s η ∞ = 0 Pa-s λ = a = n = Styron 663, with Scintillator dopant additives Carreau-Yasuda Law for viscosity data: Measured by, Datapoint Labs, NY ρ = 1040 Kg/m 3 Cp = 1200 J/Kg-K k = W/m-K β = 0.5e-5 m/m-K NOTE: Viscoelastic properties were neglected in our simulation
Styron viscosity data, with and without Scintillator dopants C C C η – Styron 663 η d – Doped Styron Viscosity (Pa-s)
Required Extrudate profile All dimensions are in cm Rectangular cross section of 10 cm 0.5 cm with ten equally spaced centerline circular holes of 1.1 mm diameter, to accommodate wavelength-shifting optical fiber
Exploded view of the extrusion die Melt pump adapter Adapter 1 Adapter 2 Preland Melt flow direction Dieland
Half domain of the extrusion die Melt Pump Adapter, Adapter 1 and Adapter 2 Spider Die land Melt flow direction Die lip Free Surface
Simulation domain with boundary conditions Inlet (Fully Developed Flow) 2. Wall (V n = 0, V s = 0) 3. Symmetry (V n = 0, F s = 0) 4. Free Surface (F s = 0, F n = 0, V.n = 0) 5. Outlet (F n = 0, V s = 0) Melt flow direction
Finite element 3-D domain and die-lip mesh Melt flow direction 19,479 elements Skewness < 0.5
Half domain of the extrusion die (without free surface) and division of outlet into 10 areas d0 d1 d2 Melt flow direction out1 out2 out3 out4 out5 out6 out7 out8 out9 out10
Percentage of Mass flow rate in different exit segments
Windows XP 2.52 GHz Processor 1 GB RAM One hour of CPU time Computation time
Contours of static pressure Melt flow direction Die lip
Contours of Velocity magnitude Melt flow direction Die lip Velocity Magnitude (m/s) X-Coordinate (m)
Contours of temperature distribution Melt flow direction Die lip
Contours of Shear rate and Viscosity Melt flow direction Melt flow direction Die lip Shear rate Viscosity
Simulated Die Required Extrudate Simulated die and required extrudate profiles
Percentage of mass flow rate for designed and balanced die 0
Conclusions Optimum dimensions of the die More balanced flow Flow in the die - no re-circulation regions.
Recommendations for future improvements Polymer viscoelastic properties Include flow, cooling, solidification and vacuuming in and after the calibrator Radiation effects for free surface flow Pulling force at the end of the free surface Pressure of the compressed air More non-uniform mesh
NICADD (Northern Illinois Centre for Accelerator and Detector Development), NIU Fermi National Accelerator Laboratory, Batavia, IL
QUESTIONS ?
Contact Information mailto: mailto: Department of Mechanical Engineering NORTHERN ILLINOIS UNIVERSITY