Week 8 - Simulating Cyclone separator with Discrete Phase Modelling

The cyclone separator is a used for separating solid particles from contaminated gas streams, and has long been used in industrial applications such as power generations, gas turbines, chemical processes and so forth.

You can see here, how cyclone separator is separating the dirst particles feom gas streams .

Four empirical models used to calculate the cyclone separator efficiency-

1. Lapple :- Lapple (1951) model was developed based on force balance
without considering the flow resistance. Lapple assumed that a
particle entering the cyclone is evenly distributed across the
inlet opening. The particle that travels from inlet half width to
the wall in the cyclone is collected with 50% efficiency.

2. Koch and Licht:- Koch and Licht (1977) collection theory recognized the
inherently turbulent nature of cyclones and the distribution of
gas residence times within the cyclone. Koch and Licht
describe particle motion in the entry and collection regions
with the additional following assumptions:
• The tangential velocity of a particle is equal to the tangential
velocity of the gas flow, i.e. there is no slip in the tangential
direction between the particle and the gas.
• The tangential velocity is related to the radius of cyclone by:
uRn = constant.

3. Li and Wang :- The Li and Wang model includes particle bounce or
re-entrainment and turbulent diffusion at the cyclone wall. A
two-dimensional analytical expression of particle distribution
in the cyclone is obtained. Li and Wang model was developed
based on the following assumptions:
• The radial particle velocity and the radial concentration
profile are not constant, for uncollected particles within the
cyclones.

4. Iozia and Leith:- Iozia and Leith (1990) logistic model is a modified version of Barth (1956) model which is developed based on force balance. The model assumes that a particle carried by the vortex endures the influence of two forces: a centrifugal force, Z, and flow resistance, W. Core length, z_c, and core diameter, d_c, are given as

1. Start the anys fluent workbanch

2. First import the geometry in spaceclaim

3. Extract the fluid volume and supress the solid volume

4. Meshing - baseline and refinement and named selection

5. Energy off

6. Steady state simulation using viscous K epsilon (RNG) model

7. DPM enabled - Surface Injection ( Particle diameter and velocity)

8. Creating material (Fluid)

9. Boundary condition (Velocity Inlet , DPM-reflect)

10. Standard initializing (Compute from inlet)

11. Run Fluent solver

12. Post-processign and animation plots

Importing the object in spaceclaim :-

As the object is already given , just need to import the object in spaceclaim and extract the fluid volume and suppress the solid volume as solid volume is not needednhere.

Given Geometry

Fluid volume

Meshing :-

1. Open the meshing console.
2. Click on the mesh and select generate mesh option.
3. Now a basic mesh pattern will be created.
4. Now we will run a baseline mesh having default size . We go to mesh size and put the desired value>> click on generate mesh tab.
5. Now on the next step we will refine the mesh size by 30 mm and will go for methods(Body fitted cartesian ) in mesh module.

For each case we have used same mesh size . We have changed the velocity and particles diameter in order to observe the change in result .

Number of total elements = 93883

Pressure Based Transient State simulation

Gravity with -9.81m/s^2 in y-axis was enabled

K -epsilon RNG model is used here as it will give more accurate result in our case .

Here gravity is -9.81 m/s^2 as here gravity is in the negative y direction .

DPM enabled - Surface Injection ( Particle diameter and velocity)

Case 1 ( Inlet velocity = 3 m/s , Particles diameter = 1 micro meter )-

Meshing

Residual plot

Anthrasite particle flow

Velocity vector

Pressure contour at yz plane

Velocity contour at yz plane

Animation of anthrasite particle flow

Case 2 ( Inlet velocity = 3 m/s , Particles diameter = 3 micro meter )-

Meshing

Residual plot

Anthrasite particle flow

Velocity vector

Pressure contour at yz plane

Velocity contour at yz plane

Animation of anthrasite particle flow

Case 3 ( Inlet velocity = 3 m/s , Particles diameter = 5 micro meter )-

Residual plot

Anthrasite particle flow

Velocity vector

Pressure contour at yz plane

Velocity contour at yz plane

Animation of anthrasite particle flow

Case 4 ( Inlet velocity = 1 m/s , Particles diameter = 5 micro meter )-

Residual plot

Anthrasite particle flow

Velocity vector

Pressure contour at yz plane

Velocity contour at yz plane

Animation of anthrasite particle flow

Case 5 ( Inlet velocity = 5 m/s , Particles diameter = 5 micro meter )-

Residual plot

Anthrasite particle flow

Velocity vector

Pressure contour at yz plane

Velocity contour at yz plane

Animation of anthrasite particle flow

Observation from this result :-

Efficiency = (Trapped Particle / Total number of particle)*100

Pressure drop = Total pressure in inlet - Total pressure in outlet excape

To observe the change in separotor efficiency and pressure drop whie changing the Particles diameter from 1 to 5 micro meter by keeping the inlet velocity constant as 3 m/s

We can give this statement from this result that pressure drop is incresing with increasing of particles diameter.

And to see the difference in result we have changed the velocity from 1 to 5 m/s by keeping particles diameter constant as 5 micro meter .

While increasing the velocity the pressure drop is increasing .

References :-

https://skill-lync.com/knowledgebase/theory-guide-for-discrete-phase-modelling

https://www.sciencedirect.com/science/article/pii/S0307904X06000291

Heat_Transfer_-A_Practical_Approach-_Yunus_A._Cengel