http://www.mv.uni-kl.de/tvt/ CFD investigation of erosion in particulate flows Mehdi Azimian & Hans-Jörg Bart University of Kaiserslautern, Chair of Separation Science and Technology, 67653 Kaiserslautern, Germany E-Mail: [email protected] Aims: • Investigation of particulate (solid-liquid) flows • Comparison of different numerical methods • Validation of simulation results with exp. data • Erosion mechanisms of various materials DEM: Ductile behavior of material under erosion modeled FEM: Chip separation and material pile-up due to particle impact CFD: Particulate flow such as in Francis turbine Exp.: Tester setup and erosion studies of different materials Details: Azimian et al., Open Chem. Eng. J. 8 (2014). * Ref.: M. Takaffoli, M. Papini, Wear 267 (2009). Acknowledgement: The authors would like to thank “Stiftung Rheinland-Pfalz für Innovation” for financial support. Poster to go Outlook: • FEM: Particle abrasion modeling • CFD: Coupling techniques for surface deformation modeling CFX simulation Euler-Lagrange approach Integration of force balance on particles Momentum transfer from fluid to discrete phase ProcessNet-Jahrestagung und 31. DECHEMA-Jahrestagung der Biotechnologen 2014, 30. Sep. - 2. Okt. 2014, Eurogress Aachen Introduction DEM simulation Conclusions DEM modeling of Erosion Cohesion force models implemented in EDEM: • Linear bonding model No damping component & no bond breakage under compression • Johnson-Kendall-Roberts (JKR) model Applicable only for small cohesion forces like high porous mediums Fig. 2: Random distribution of tensile strength 30° 30 m/s 30 m/s 30° Fig. 3: Impact effects of different particle forms Definition of a material model as unit cell bonds Bond reconnecting number: Brittle material: 0 Ductile material> 5 Time step Based on particle size & contact forces: 5×10 -12 - 2×10 -11 s Bond status 0: New contact 1, 2: Intact contact 3: Destructed contact Fig. 1: Applied numerical techniques from DEM to CFD Simulation tool: ANSYS-AutoDyn Element erosion approach: Chip separation and material pile-up modeling Equation of state (EOS): Shock equation of state (for solid metallic material) Critical plastic strain: 1.5 Dynamic friction coefficient: 0.1 (neglected mostly in previous studies) Particle material model: Rigid body Target material model: Johnson-Cook viscoplastic strength model Boundary conditions: Zero displacement at bottom & sides FEM simulation Table 2: Material properties of particle & surface Material properties Symbol Steel OFHC copper Density ρ 7800 kg/m 3 8960 kg/m 3 Young's modulus E 200 Gpa 123.28 Gpa Shear modulus G 76.923 Gpa 46 Gpa Bulk modulus K 166.7 Gpa 128.42 Gpa Poisson's ratio ν 0.3 0.34 Hardness HB 752 26 Table 1: DEM simulation outputs Case Impact velocity & angle Rebound velocity Destructed bonds Round particle 30 m/s, 30° 29.5 m/s 10145 Unround particle 30 m/s, 30° 18.1 m/s 18090 Incident direction Rebound direction Target sample Fig. 4: Experimental tester and a particle during impact h lip d max Fig. 5: Particle and crater parameters definition Fig. 7: Chip separation & material pile-up in case 2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1 2 3 4 5 6 7 8 d max (mm) Simulation case 1-8 Comparison of d max in experiment and simulation Experiment* Autodyn (3-D) LS-DYNA* (2-D) Case V i (m/s) α i (°) θ i (°) 1 80 80 20 2 81 60 20 3 46 60 20 4 81 60 40 5 50 60 40 6 85 50 50 7 51 50 50 8 80 40 40 Fig. 6: Comparison of d max in experiment & simulation for eight cases Fig. 12: From left to right: Geometry generation, meshing & grid study, boundary conditions definition and final CFD simulation Fig. 8: Schema of experimental setup Fig. 9: Centrifugal accelerator disc Fig. 10: Sample holder adjustment 0 0.5 1 1.5 2 2.5 3 3.5 4 1.5 2 2.5 3 3.5 Material loss in 4 h (mg) Sand concentration (%) Aluminium alloy (WNR 3.1645) Stainless steel (WNR 1.4305) Cast iron HBN 480 (WNR 0.9650) Cast iron HBN 450 (WNR 0.9635) Hawiflex Fig. 11: Erosion of five different materials Experiments Tester setup by application of a slurry centrifugal pump Sample weight measurement with balance with 0.1 mg sensitivity stationary roughness tester Hommel T8000 for surface analysis Francis turbine parameters • Runner diameter: 4 m • Blade thickness: 5 cm • Rotational speed: 300 rpm • Hub diameter: 1 m • Number of blades: 13 • Efficiency: 92% Pros of DEM & FEM in comparison with CFD: • Fundamental mechanisms of material removal • Material properties & process parameters effects • Rebound kinematics of particles DEM: No. of destructed bonds in micro scale FEM: Single particle impacts & rebound kinematics CFD: Investigation of real particulate flows Exp. & CFD simulation of particulate flows Single particle exp.* • Compressed nitrogen gas gus • Rectangular cross-section barrel • Constant particle orientation angle during inject • High speed camera for impact parameters capturing • Optical profilometer for deformation analysis
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
http://www.mv.uni-kl.de/tvt/
CFD investigation of erosion in particulate flows
Mehdi Azimian & Hans-Jörg Bart
University of Kaiserslautern, Chair of Separation Science and
Technology, 67653 Kaiserslautern, Germany
E-Mail: [email protected]
Aims:
• Investigation of particulate (solid-liquid) flows
• Comparison of different numerical methods
• Validation of simulation results with exp. data
• Erosion mechanisms of various materials
DEM: Ductile behavior of material under erosion modeled
FEM: Chip separation and material pile-up due to particle impact
CFD: Particulate flow such as in Francis turbine
Exp.: Tester setup and erosion studies of different materials
Details: Azimian et al., Open Chem. Eng. J. 8 (2014).
* Ref.: M. Takaffoli, M. Papini, Wear 267 (2009).
Acknowledgement: The authors would like to thank “Stiftung Rheinland-Pfalz für Innovation” for financial support.
Poster to go
Outlook:
• FEM: Particle abrasion modeling
• CFD: Coupling techniques for surface deformation modeling
CFX simulation
Euler-Lagrange approach
Integration of force balance on particles
Momentum transfer from fluid to discrete phase
ProcessNet-Jahrestagung und 31. DECHEMA-Jahrestagung der Biotechnologen 2014, 30. Sep. - 2. Okt. 2014, Eurogress Aachen
Introduction
DEM simulation
Conclusions
DEM modeling of Erosion
Cohesion force models implemented in EDEM:
• Linear bonding model
No damping component & no bond breakage under compression
• Johnson-Kendall-Roberts (JKR) model
Applicable only for small cohesion forces like high porous mediums
Fig. 2: Random distribution of tensile strength
30°30 m/s
30 m/s30°
Fig. 3: Impact effects of different particle forms
Definition of a material model as unit cell bonds
Bond reconnecting number: Brittle material: 0 Ductile material> 5
Time step
Based on particle size & contact forces: 5×10-12 - 2×10-11 s
Bond status
0: New contact 1, 2: Intact contact 3: Destructed contact
Fig. 1: Applied numerical techniques from DEM to CFD
Simulation tool: ANSYS-AutoDyn
Element erosion approach:
Chip separation and material pile-up modeling
Equation of state (EOS):
Shock equation of state (for solid metallic
material)
Critical plastic strain: 1.5
Dynamic friction coefficient: 0.1
(neglected mostly in previous studies)
Particle material model: Rigid body
Target material model: Johnson-Cook viscoplastic strength model
Boundary conditions: Zero displacement at bottom & sides
FEM simulation Table 2: Material properties of particle & surface
Material properties Symbol Steel OFHC copper
Density ρ 7800 kg/m3 8960 kg/m3
Young's modulus E 200 Gpa 123.28 Gpa
Shear modulus G 76.923 Gpa 46 Gpa
Bulk modulus K 166.7 Gpa 128.42 Gpa
Poisson's ratio ν 0.3 0.34
Hardness HB 752 26
Table 1: DEM simulation outputs
CaseImpact
velocity & angle
Rebound velocity
Destructed bonds
Roundparticle
30 m/s, 30° 29.5 m/s 10145
Unround particle
30 m/s, 30° 18.1 m/s 18090
Incident direction
Rebound direction
Target sample
Fig. 4: Experimental tester and a particle during impact
hlip
dmax
Fig. 5: Particle and crater parameters definition
Fig. 7: Chip separation & material pile-up in case 2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1 2 3 4 5 6 7 8
dm
ax
(mm
)
Simulation case 1-8
Comparison of dmax in experiment and simulation
Experiment*
Autodyn (3-D)
LS-DYNA* (2-D)
CaseVi
(m/s)αi (°) θi (°)
1 80 80 20
2 81 60 20
3 46 60 20
4 81 60 40
5 50 60 40
6 85 50 50
7 51 50 50
8 80 40 40
Fig. 6: Comparison of dmax in experiment & simulation for eight cases
Fig. 12: From left to right: Geometry generation, meshing & grid study, boundary conditions definition and final CFD simulation
Fig. 8: Schema of experimental setup Fig. 9: Centrifugal accelerator disc Fig. 10: Sample holder adjustment
0
0.5
1
1.5
2
2.5
3
3.5
4
1.5 2 2.5 3 3.5
Mate
rial lo
ss in 4
h (
mg)
Sand concentration (%)
Aluminium alloy (WNR 3.1645)
Stainless steel (WNR 1.4305)
Cast iron HBN 480 (WNR 0.9650)
Cast iron HBN 450 (WNR 0.9635)
Hawiflex
Fig. 11: Erosion of five different materials
Experiments
Tester setup by application of a slurry centrifugal pump
Sample weight measurement with balance with 0.1 mg sensitivity
stationary roughness tester Hommel T8000 for surface analysis
Francis turbine parameters
• Runner diameter: 4 m
• Blade thickness: 5 cm
• Rotational speed: 300 rpm
• Hub diameter: 1 m
• Number of blades: 13
• Efficiency: 92%
Pros of DEM & FEM in comparison with CFD:
• Fundamental mechanisms of material removal
• Material properties & process parameters effects
• Rebound kinematics of particles
DEM: No. of destructed bonds in micro scale
FEM: Single particle impacts & rebound kinematics
CFD: Investigation of real particulate flows
Exp. & CFD simulation of particulate flows
Single particle exp.*
• Compressed nitrogen gas gus
• Rectangular cross-section barrel
• Constant particle orientation angle during inject
• High speed camera for impact parameters capturing
• Optical profilometer for deformation analysis
Related Documents
