Perform analysis on cyclone separator and calculate the separation efficiency and pressure drop

Objective: Perform analysis on cyclone separator and calculate the separation efficiency and pressure drop and write a detailed report explaining the results obtained.

Question:

1. To write a few words about any 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 and calculate the separation efficiency in each case. Discuss the results. [Use both the velocity's as 3m/sec.]
3. To perform an analysis on a given cyclone separator model by varying the particle velocity from 1 m/sec to 5 m/sec and calculate the separation efficiency and pressure drop in each case. Discuss the results. [Use particle diameter size as 5 μm for all cases & keep flow velocity same as particle velocity]

Boundary Conditions:-

Inlet and wall:- Reflect

Outlet(Top):- Escape

Outlet(Bottom/dustbin) - Trap

Note:

Structural mesh gives the best results, so you can use cutcell meshing approach available in Ansys Meshing.

From the above information, following cases can be analyzed:

CASE-1: To perform an analysis on a given cyclone separator model by varying the particle diameter from 1 μm to 5 μm and calculate the separation efficiency in each case. Discuss the results. [Use both the velocity's as 3m/sec.]

Case-1A: Particle Diameter: 5 μm, Particle & Inlet Flow Velocity: 3m/s.

Case-1B: Particle Diameter: 3 μm, Particle & Inlet Flow Velocity: 3m/s.

Case-1C: Particle Diameter: 1 μm, Particle & Inlet Flow Velocity: 3m/s.

CASE-2:To perform an analysis on a given cyclone separator model by varying the particle velocity from 1 m/sec to 5 m/sec and calculate the separation efficiency and pressure drop in each case. Discuss the results. [Use particle diameter size as 5 μm for all cases & keep flow velocity same as particle velocity]

Case-2A: Particle Diameter: 5 μm, Particle & Inlet Flow Velocity: 1m/s.

Case-2B: Particle Diameter: 5 μm, Particle & Inlet Flow Velocity: 4m/s.

Case-2C: Particle Diameter: 5 μm, Particle & Inlet Flow Velocity: 5m/s.

Few words about any four empirical models used to calculate the cyclone separator efficiency.

Cyclone Seperator: Cyclonic or particle separation is a process used to extract specifically identified particulates from a fluid stream (air, gas or liquid). This cyclone separator design forgoes filters, and instead relies on vortex separation for the operation. These applications vary depending on the fluid from which particles are removed.

• Iozai and Leith Model:

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 a flow resistance, W. Core length, zc, and core diameter,dc, are given as

The addition made by Iozia and Leith on the original Barth (1956) model are the core length zc and slope parameter β expression which is derived based on the statistical analysis of
experimental data of cyclone with D = 0.25 m. The collection efficiency ηi of particle diameter dpi can be calculated from

• Lia and wang Model:

The Li and Wang (1989) 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.
• Boundary conditions with the consideration of turbulent diffusion coefficient and particle bounce re-entrainment on the cyclone wall are:c=c0,at θ=0
• The tangential velocity is related to the radius of cyclone by: uRn = constant.

• The resultant expression of the collection efficiency for particle of my size is given as

• Koch and Licht Model:

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.

A force balance and an equation on the particles collection yields the grade efficiency ηi

G is a factor related to the configuration of the cyclone,n is the related to vortex and τ is the relaxation term.

• Lapple Model:

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. The semi empirical relationship developed by Lapple (1951) to
calculate a 50% cut diameter, dpc,is

The efficiency of collection the any size of particle is given by

Case Setup and Execution:

Geometry:

Geometry is imported to Ansys Space Claim.

Meshing:

Assembly Meshing: Cut Cell Method

Nodes: 509271

Elements: 498053

Named Selections:

Setup:

Solver Time:Steady state

Type: Pressure based

Gravity: -9.81m/s2 in Y axis

Viscous Model: RNG K-epsilon model with swirl dominated flow and enhanced wall treatment.

Discrete Phase Model:

Injections:

Injection Type: Surface

Particle Type: Inert

Material: Anthracite

Inject Using Face Normal Direction

Boundary Conditions:

Inlet and wall: Reflect

Outlet(Top): Escape

Outlet(Bottom/dustbin): Trap

Initialization: Standard Initialization

Number of Iterations: 500

CASE-1: To perform an analysis on a given cyclone separator model by varying the particle diameter from 1 μm to 5 μm and calculate the separation efficiency in each case. Discuss the results. [Use both the velocity's as 3m/sec]

Case-1A: Particle Diameter: 5 μm, Particle & Inlet Flow Velocity: 3m/s.

Results:

Residuals

Vortex Flow

Particle Time

DPM Iteration Result

Seperation efficiency: Number of Particles escaped/Number of Particles Tracked = `5/435=1.14%`

Case-1B: Particle Diameter: 3 μm, Particle & Inlet Flow Velocity: 3m/s.

Results:

Residuals

Vortex Flow

Particle Time

DPM Iteration Result

Seperation efficiency: Number of Particles escaped/Number of Particles Tracked = `46/435=10.57%`

Case-1C: Particle Diameter: 1 μm, Particle & Inlet Flow Velocity: 3m/s.

Results:

Residuals

Vortex Flow

Particle Time

DPM Iteration Result

Seperation efficiency: Number of Particles escaped/Number of Particles Tracked = `153/435=35.17%`

CASE-2: To perform an analysis on a given cyclone separator model by varying the particle velocity from 1 m/sec to 5 m/sec and calculate the separation efficiency and pressure drop in each case. Discuss the results. [Use particle diameter size as 5 μm for all cases & keep flow velocity same as particle velocity]

Case-2A: Particle Diameter: 5 μm, Particle & Inlet Flow Velocity: 1m/s.

Results:

Residuals

Vortex Flow

Particle Time

DPM Iteration Result

Seperation efficiency: Number of Particles escaped/Number of Particles Tracked = `68/435=15.63%`

Pressure at Inlet: 3.42Pa

Pressure at Outlet 2 (Dustbin): 0.229Pa

Pressure Drop at Outlet 2= Pressure at inlet - Pressure at Outlet 2 = `3.42-0.229 = 3.191 Pa`

Case-2B: Particle Diameter: 5 μm, Particle & Inlet Flow Velocity: 4m/s.

Results:

Residuals

Vortex Flow

Particle Time

DPM Iteration Result

Seperation efficiency: Number of Particles escaped/Number of Particles Tracked = `10/435=2.29%`

Pressure at Inlet: 75.8Pa

Pressure at Outlet 2 (Dustbin): 4.371Pa

Pressure Drop at Outlet 2= Pressure at inlet - Pressure at Outlet 2 = `75.8-4.371 = 71.429 Pa`

Case-2C: Particle Diameter: 5 μm, Particle & Inlet Flow Velocity: 5m/s.

Results:

Residuals

Vortex Flow

Particle Time

DPM Iteration Result

Seperation efficiency: Number of Particles escaped/Number of Particles Tracked = `14/435=3.21%`

Pressure at Inlet: 121.652Pa

Pressure at Outlet 2 (Dustbin): 7.008Pa

Pressure Drop at Outlet 2= Pressure at inlet - Pressure at Outlet 2 = `121.652-7.008 = 114.644 Pa`

Conclusion:

Results Comparison:

S.NO	CASE	No. Of Particles Tracked	No. Of Particles Escaped	No. Of Particles Trapped	No. Of Particles Incomplete	Seperator Efficiency	Pressure at Inlet in Pa.	Pressure at Outlet_2 in Pa.	Pressure Drop in Pa.
1	1A	435	5	0	430	1.14%	*	*	*
2	1B	435	46	0	389	10.57%	*	*	*
3	1C	435	153	4	278	35.17%	*	*	*
4	2A	435	68	14	353	15.63%	3.42	0.229	3.191
5	2B	435	10	8	417	2.29%	75.8	4.371	71.429
6	2C	435	14	4	417	3.21%	121.652	7.008	114.644

• Number Of Particles Tracked depends on the size of element, smaller the size of element greater the Particles tracked.
• With the same particle and inlet flow velocity an increase in Particle Diameter, seperator efficiency decreased which can be observed in Case-1.
• With the same Particle Diameter an increase in particle and inlet flow velocity, seperator efficiency decreased which can be observed in Case-2.
• With an increase in velocity, pressure at inlet and outlet increases.
• Pressure drop is higher when the particle and inlet flow velocity is higher.