Simon Lo 9/11/09Simon Lo 9/11/09 Lo 9/11/09Simon Lo 9/11/09 Contents • Breakup and coalescence in...
-
Upload
hoangkhanh -
Category
Documents
-
view
225 -
download
2
Transcript of Simon Lo 9/11/09Simon Lo 9/11/09 Lo 9/11/09Simon Lo 9/11/09 Contents • Breakup and coalescence in...
Modelling multiphase flows in the Chemical and Process IndustrySimon Lo 9/11/09Simon Lo 9/11/09
Contents
Breakup and coalescence in bubbly flows• Breakup and coalescence in bubbly flows
• Particle flows with the Discrete Element Modelling approachParticle flows with the Discrete Element Modelling approach
• Multiphase flows in pipelines
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 2
Bubbly flows in pipes and pipe bends
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 3
Bubble size distribution models
•Population balance equation:
, , , ,i
i br i br i cl i clDn
B D B DDt
= − + −
•Interfacial area concentration transport (e.g. Ishii’s model):
iDaφ φ= +br clDtφ φ= +
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 4
Moments of particle size distribution
• 0th moment is the particle number density:Sn =
• 2nd moment is related to interfacial area density:
∫∞
2 )( SdddPdA
0Sn =
• 3rd moment is related to dispersed phase volume fraction:
∫ ==0
22 )( SdddPdnAi ππ
30
3
6)(
6SdddPdn ππα == ∫
∞
• The Sauter mean diameter is:3
3216SS
Sd
πα
==22 SS π
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 5
Transport equation
S∂
•The transport equation:
.( )d br cl
SS s s
tγ
γ
∂+∇ = +
∂u
•Breakup:•Breakup:3
3
0
( ( ) 1)( ) ( )
( )f
br
d N ds nP d d d
d
γγ
−
∞ −= ∫
•Coalescence:
0 ( )br dτ∫
, , 2,0 0
( ) ' ( ) ( )d d d dcl cl cls K S n P d dd P d d dγ
∞ ∞ ′ ′ ′= Δ∫ ∫
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 6
Hibiki bubble column (2001)
– Air/Water Cylindrical Test Section50 8 mm ID 3 06 m Height50.8 mm ID, 3.06 m Height
– Ideal Gas Law for Air (297K)– Inlet B.C. at z/D=6
Air/Water Velocities, Void Fraction– Atmospheric Exit (pressure boundary)– Two-dimensional axisymmetricTwo dimensional axisymmetric
simulation (20×150 cells)– Steady state flow
0 3– CL = -0.3– CVM = 0.5– CD = 1.071CD 1.071
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 7
Fields distribution
bubble size interfacial area density gas phase volume fractiony g p
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 8
Radial void and velocity distributions
2 0
1.5
2.0
)1.5
2.0
s)
0.3
0.4
-)
0.5
1.0
axial velocity profile sim. with star-CD exp. Hibiki et al., 2001
jG=0.321 m/s, jL=0.986 m/s, z/D=53.5
v L (m
/s)
1.0
axial velocity profile sim. with star-CD exp. Hibiki et al., 2001
jG=0.321 m/s, jL=0.986 m/s, z/D=53.5
v G
(m/s
0.1
0.2
a G
(-
voidage radial distribution sim. with star-CD exp. Hibiki et al., 2001
jG=0.321 m/s, jL=0.986 m/s, z/D=53.5
0.0 0.2 0.4 0.6 0.8 1.00.0
r/R (-)
0.0 0.2 0.4 0.6 0.8 1.0
r/R (-)
Void fraction
0.0 0.2 0.4 0.6 0.8 1.00.0
r/R (-)
Liquid velocity Gas velocityVoid fraction Liquid velocity Gas velocity
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 9
Bubble size distributions
3
4
5
4
5
6
)3
4
5
m)
1
2bubble size radial distribution
sim. with star-CD exp. Hibiki et al., 2001
jG=0.471 m/s, jL=2.01 m/s, z/D=53.5
d B (m
m)
1
2
3
bubble size radial distribution sim. with star-CD exp. Hibiki et al., 2001
jG=0.624 m/s, jL=2.01 m/s, z/D=53.5
d B
(mm
)
1
2 bubble size radial distribution sim. with star-CD exp. Hibiki et al., 2001
jG=0.321 m/s, jL=0.986 m/s, z/D=53.5
d B (
mm
0.0 0.2 0.4 0.6 0.8 1.00
r/R (-)0.0 0.2 0.4 0.6 0.8 1.00
r/R (-)0.0 0.2 0.4 0.6 0.8 1.00
r/R (-)
jG and jL .
Bubble size distribution in radial direction. Different gas and liquid fluxes are investigated with S modelliquid fluxes are investigated with Sγ model.
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 10
Nottingham – Multiphase flow in bend pipes
Bubble accumulate at top of the bend
Gas vol. fraction
Bubble size
2 phase model2-phase model + S-gamma
Uniform bubble distribution in vertical section
11STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009
Nottingham – Multiphase flow in bend pipes
L b bblLarge bubbles
Medium bubbles
Small bubbles
Liquid
4-phase model
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 12
DEM – Rotating drum
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 13
DEM – Calculation scheme
Solve continuous phase on “flow” grid. Solve particle tracks accounting for particle-Solve particle tracks accounting for particleparticle and particle-wall interactions.
Calculate porosity and sources from particles over a “DEM” grid.
Apply porosity and sources from “DEM” grid to “flow” grid.
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 14
DEM – Particle equations
• Linear momentum of particle:
OtherContactDragi
i FFFdtvdm ++=
• Angular momentum:
[ ]∑k
i MdIrrω [ ]∑
=
+=j
ijiji
i Mdt
dI1
rτω
iContactrollij FM ωμrrr
−=
• = rolling torque opposes particle rotation= rolling friction coefficient
iContactrollij μ
ijMr
μ• = rolling friction coefficient.rollμSTAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 15
DEM – Multiple inlets
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 16
DEM – Buoyant particles
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 17
DEM – Particle transport in pipe
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 18
DEM – Non-spherical particles
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 19
DEM - Break-off of cohesive particle
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 20
10m riser section of a 100m long pipeline
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 21
OLGA-STAR coupled model
To study 3D effects in in-line equipment: valve, junction, elbow, obstacle, jumper, separator, slug catcher, compressor, ...
Fl t f OLGA t STAR
Flow rates from STAR to OLGA
InletOutlet
Flow rates from OLGA to STAR
Outlet
Pressure from STAR to OLGA Pressure from OLGA to STAR
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 22
Summary
• Active development of advanced models for multiphase flows found in the chemical and process industryfound in the chemical and process industry.
• Breakup and coalescence of bubbles in bubbly flows.• Particle-particle, particle-wall collision modelling using the p p g g
Discrete Element Model (DEM).• Modelling of multiphase flows in long pipelines.
C li 3D CFD t 1D i li d• Coupling 3D CFD to 1D pipeline codes.
STAR Konferenz Deutschland 2009, Nürnberg 9-10 Nov. 2009 23