Advances in Cyclonic Flow Regimes

Dr. Dimitrios Papoulias, Thomas Eppinger

Introduction Cyclones & Hydrocyclones Modeling Approaches in STAR-CCM+

Turbulence Modeling Case 1: Air-Air Cyclone Case 2: Oil-Water Hydrocyclone with LMP & EMP Case 3: Gas-Solid Cyclone Summary

Agenda

Separation of particulates from a continuous stream (air/liquid) without filter medium Separation based on rotational effects/centrifugal forces and gravity (density difference!)

Cyclones

Advantages Disadvantages

Low capital cost High operating cost (pressure drop)

High temperature Low efficiency for small particles

Low maintenance cost (no moving parts)

Low space requirement

Two-Phase Modeling techniques:

Eulerian-Lagrangian model (LMP): dispersed phase is realized as discrete populations of droplets droplet trajectories are tracked by Newton's 2nd law of motion integrated forces included drag, lift, pressure-grad. & added-mass turbulent dispersion effects (random-walk model)

Eulerian-Eulerian model (EMP): two-fluid method based on the interpenetrating continua assumption; each flow-

phase is treated by its own set of N-S the continuous & dispersed phases are coupled by incorporating source-terms for

the acting forces i.e. drag, lift, virtual mass & turbulent dispersion

Modeling Approaches

Verification of the applicability of EMP-RSM for cyclone simulation. Overcome Lagrangian limitations: Low volume fraction of the

dispersed phase Including disperse phase interaction Performance

Testing RSM on ERCOFTAC single-phase cyclone Model predictions are compared against LDV measurements

Case 1: EMP-RSM Model Verification

700k trimmed cells (polys also tested) Single-phase: Air. EMP with two identical phases (Air) and VF ratios of: 0.5 0.5 0.4 0.6 0.2 0.8

Velocity inlet (20m/s) and pressure outlet. RSM (k-epsilon also tested) Transient (dt = 0.005s) Drag and TDF included.

Case 1: EMP-RSM Model Verification

RSM can successfully replicate the experimental measurements for single phase flow as well as for EMP.

position Y (m)

Mea

n-ax

ial v

eloc

ity (m

/s)

Case 1: EMP-RSM Model Verification

Uax

ial/U

in

x/D

z=0.77

RLZ: Realizable k-e STD: Standard

0 uz (m/s) 25

Polyhedral (0.8M)

Trim-Hex (0.2M)

Trim-Hex (0.7M)

BA

SE

LIN

E

RSM STD RLZ

BA

SE

LIN

E

Trim-Hex (0.7M)

Case 1: EMP-RSM Model Verification

Property Value Chamber Diameter D 60 mm Outlet D_o 3.6 mm Dn / D 0.5 20 1.5 Lc / D 1 Lo / D 15 Total height 1200 mm

Hydrocyclones for oil/water separation, Int. Confer. Hydrocyclones, Colman et al.

Case 2: Geometry Description

The RSM turbulence model is used in order to capture vortical two-phase dynamics i.e. pressure-drop, flow mixing & separation) Two-phase flow interactions and separation occurs at length-scale equivalent to the size of the dispersed droplets i.e. in order of a few m Resolution of vortex separation regimes requires fine spatial discretization (14M

trimmed cells (hexahedrons).

Turbulence and Mesh Resolution

top-view

mid-section

CAD model generated in STAR-CCM+ 2 inlets = 1.02 kg/s, = 0.007 kg/s

Flow split outlet Top(oil) = 0.1, bottom(water) = 0.9

Density Water = 997 kg/m^3; Oil = 840 kg/m^3

Phase interaction Drag (Schiller-Naumann) Turbulent Dispersion Virtual Mass Shear Lift (Sommerfeld) Pressure gradient Particel Size Distribution (log-normal, [20-

100 m]) Rebound at wall.

Lagrangian: One-way coupling, steady (C=0.01) EMP: Fully coupled, transient (dt = 0.001s)

in in

Out_top

Out_bottom

Case 2: Simulation Setup

Pressure drop (inlet/oil_outlet) of 4bar agrees well with exp. Data.

Separation efficiency well predicted.

p

Droplet diam. (m)

effic

ienc

y (

)

Case 2: Results LMP & EMP

Two-phase air & solid-particles cyclone case Eulerian-Lagrangian validation calculations in Stairmands cyclone geometry. Single-phase simulations for different flow-rates & Multiphase cases for different particle diameters

tangential vel

p pressure-drop

P

(Pa)

Uinlet (m/s)

Case 3: Gas-Solid Cyclone

d=10 m d=0.1

m

diam. [m] 0.5 1.0 4.0 5.0

exp. % 20.5 25.7 98.5 100

cfd % 14.6 24.2 98.3 99.9

mean tangential-velocity

Z=0.18

Z=0.58

x/D

Uta

ng./U

in

Case 3: LMP Results

STAR-CCM+ predicts for cyclones and hydrocyclones pressure drop, Flow profile and Separation efficiency.

Both approaches (EMP and LMP) shows very good agreement with experimental data. Turbulence modeling and mesh resolution are key parameters for an accurate result.

Summary

Thank you !

Advances in Cyclonic Flow Regimes Dr. Dimitrios Papoulias, Thomas EppingerAgendaCyclones Modeling ApproachesCase 1: EMP-RSM Model Verification Case 1: EMP-RSM Model Verification Case 1: EMP-RSM Model Verification Case 1: EMP-RSM Model Verification Slide Number 9Turbulence and Mesh ResolutionSlide Number 12Case 2: Results LMP & EMPCase 3: Gas-Solid Cyclone Case 3: LMP ResultsSummary Slide Number 18