Week 8 - Simulating Cyclone separator with Discrete Phase Modelling
SIMULATIION OF CYCLONE SEPARATOR WITH DISCRETE PHASE MODELLING
AIM;
To perform analysis on cyclone separator and calculate the separation efficiency and pressure drop
OBJECTIVE:
1.To list four empirical models used to calculate the cyclone separator efficiency.
2.To perform an analysis on a given cyclone separator model by varying the particle diameter from 1 μm to 5 μm
3.To perform an analysis on a given cyclone separator model by varying the particle velocity from 1 m/sec to 5 m/sec
4.To calculate the separation efficiency and pressure drop in each case.
Four empirical models used to calculate the cyclone separator efficiency:-
1. Lapple :-
Lapple [1] 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. The semi empirical relationship developed by Lapple [1] to calculate a 50% cut diameter, `dpc` is
Where Ne is the number of revolutions,
The efficiency of collection of any size of particles is given by
2. Koch and Licht :-
Koch and Licht collection theory recognized the inherently turbulent nature of cyclones and the distribution of gas residence times within the cyclone. Koch and Licht described 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`uRn=constant.
A force balance and an equation on the particles collection yields the grade efficiency ηi
where
G is a factor related to the configuration of the cyclone, n is related to the vortex and τ">τ is the relaxation term.
3. Li and wang model :-
The Li and Wang model includes particle bounce or reentrainment 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 cyclone.
- Boundary conditions with the consideration of turbulent diffusion coefficient and particle bounce reentrainment on the cyclone wall are:
C=0,at θ=0
The tangential velocity is related to the radius of cyclone by: μR=constant.
The concentration distribution in a cyclone is given as:
where,
and,
The resultant expression of the collection efficiency for particle of any size is given as
where,
4. Iozia and Leith Model :-
Iozia and Leith logistic model is a modified version of Barth 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 a flow resistance, W.The collection efficiency ηi of particle diameter dpi can be calculated from
Do you want to interrupt the operation and retain any available generated data, or abort the operation immediately and discard any available generated data
and dpc">dpc is the 50 % cut size.
MODELLING APPROACH;
Importing the Geometry,
Extracting the Fluid Volume,
MESHING;
For all cases,
| MESH PARAMETERS | |
| Mesh Size | 10 mm |
| Nodes | 23071 |
| Elements | 113281 |
SOLVER INPUTS:
| SOLVER INPUTS | |
| Solver Time | steady |
| Solver Type | Pressure |
| Energy | off |
| Models | K-Epsilon RNG/Swirl Dominated flow |
| Material | air |
| Iterations | 300 |
| Gravity (in y direction ) | -9.81 |
| Models | Discrete phase |
| Discrete phase | on |
| Particle Velocity | 3m/s |
| Particle Diameter | 1 micron |
| Inlet velocity | 3m/s |
Residual Plot,
Particle time plot,
Pressure plot,
Separation Efficiency=No.of Particles Trapped / No.of particles tracked
| Efficiency = (103/120)*100 = 86% |
Simulation file link,
https://drive.google.com/file/d/12PM-mzsNws8Ziz_AVNDPvFh0v4na0dzX/view?usp=share_link
For velocity - 3m/s and particle diameter - 3 micron,
Residual plot,
Particle time plot,
Pressure plot,
Separation Efficiency=No.of Particles Trapped / No.of particles tracked
| Efficiency = (102/120)*100 = 85% |
Simulation file link,
https://drive.google.com/file/d/1ZfVYho142YlWg6fyEldJRkuit0Zc6Gom/view?usp=share_link
For velocity - 3m/s and particle diameter - 5 micron,
Residual plot,
Particle Time Plot,
Pressure Plot,
Separation Efficiency=No.of Particles Trapped / No.of particles tracked
| Efficiency = (98/120)*100 = 82% |
Simulation file link,
https://drive.google.com/file/d/19mBWtYn7nTXsZ5oRQ80wQFRs7jkdrcM_/view?usp=share_link
FOR DIFFERENT VELOCITY,
For Particle Diameter 5 microns , Velocity - 1m/s,
Residual Plot,
Particle Time plot,
Pressure Plot,
Separation Efficiency=No.of Particles Trapped / No.of particles tracked
| Efficiency = (8/120)*100 = 7% |
Simulation file link,
https://drive.google.com/file/d/1Dpf2shNkEU_WEY_YvmrixEr4pIICjJXR/view?usp=share_link
For Particle Diameter 5 microns , Velocity - 3m/s,
Residual plot,
Particle Time plot,
Pressure Plot,
Separation Efficiency=No.of Particles Trapped / No.of particles tracked
| Efficiency = (111/120)*100 = 93% |
Simulation file link,
https://drive.google.com/file/d/16PAlQriKsZiACeAqYE8CHkyVXSZ6WIY5/view?usp=share_link
For Particle Diameter 5 microns , Velocity - 5m/s,
Residual Plot,
Particle Time Plot,
Pressure Plot,
Separation Efficiency=No.of Particles Trapped / No.of particles tracked
| Efficiency = (119/120)*100 = 99% |
Simulation file link,
https://drive.google.com/file/d/1L6otzXKSlLlbVMCi8b9jYwfqpAmLaV1D/view?usp=share_link
Conclusion;
Hence, Simulatiion of cyclone separator with Discrete phase Modelling is carried out and the results are plotted.
In conclusion, the separation efficiency of a cyclone separator depends on the inlet velocity and the particle diameter, In the above cases it is clearly observed that the large particle size with high velocity has greater separation efficiency,
whereas the large particle size with low velocity shows poor separation efficiency since the pressue required t drive the particle is less which makes the particle attach towards the wall.
In contrast with the velocity and particle diameter , pressure drop also plays an important role,also pressure drop across the separator should be low to achieve the maximum efficiency.