Aim:- To perform analysis on cyclone separator and calculate the separation efficiency and pressure drop.
Objective:-
- To write a few words about any four empirical models used to calculate the cyclone separator efficiency.
- To perform an analysis on a given cyclone separator model by varying the particle diameter from 1 μm to and calculate the separation efficiency in each case. Discuss the results. [Use both the velocity's as 3m/sec.]
- 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]
Software used: ANSYS FLUENT 2020 R1
Q1. Ans:
Four different cyclone efficiency empirical models:-
1) IOZIA 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 and flow resistance, Core length
and core diameter.
2) LI AND WANG MODEL
The Li and Wang (1989) model include 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's 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=c0c=c0 at θ=0θ=0
3) 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 hurricane. Koch and Licht describe particle motion in the entry and collection regions with the following additional 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 uRnuRn = Constant
4) 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.
Experimental setup:
Volume Extraction -
Meshing :
Element Size : 10 mm
Nodes: 34290
Elements: 180144
Q2. Ans:
Particle diameter ranges from 1µm to 10µm
Velocity is taken as a constant of 3 m/s.
Boundary Conditions:-
Inlet and wall:- Reflect
Outlet(Top):- Escape
Outlet(Bottom) - Trap
Case 1 : Diameter = 1µm and velocity = 3 m/s
Numbers tracked: 124
Escaped: 32
Trapped: 40
Incompleted: 52
Residual Plot :
Solutions Converged: At 692 iterations.
Anthracite Particle Time:
Vortex core:
Mass Flow rate :
Inlet : 0.018375 Kg/s
Outlet_top: -0.0154168 Kg/s
Outlet_Bottom: -0.00295331
Case 2: Diameter = 2µm and velocity = 3 m/s
Numbers tracked: 124
Escaped: 31
Trapped: 86
Incompleted: 7
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Mass Flow rate :
Inlet : 0.018375 Kg/s
Outlet_top: -0.015533 Kg/s
Outlet_Bottom: -0.00283843 Kg/s
Case 3: Diameter = 3µm and velocity = 3m/s
Numbers tracked: 124
Escaped: 14
Trapped: 34
Incompleted: 76
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Mass Flow rate :
Inlet : 0.018375 Kg/s
Outlet_top: -0.014948 Kg/s
Outlet_Bottom: -0.00343691 Kg/s
Case 4: Diameter = 4µm and velocity = 3m/s
Numbers tracked: 124
Escaped: 8
Trapped: 116
Incompleted: 0
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Mass Flow rate :
Inlet : 0.018375 Kg/s
Outlet_top: -0.0156009
Outlet_Bottom: -0.00276714
Case 5: Diameter = 5µm and Velocity = 3 m/s
Numbers tracked: 124
Escaped: 0
Trapped: 124
Incompleted: 0
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Mass Flow rate :
Inlet : 0.018375 Kg/s
Outlet_top: -0.0155287 Kg/s
Outlet_Bottom: -0.00284116 Kg/s
Case 6: Diameter = 6µm and velocity = 3m/s
Numbers tracked: 124
Escaped:2
Trapped: 122
Incompleted:0
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Mass Flow rate :
Inlet : 0.018375 Kg/s
Outlet_top: -0.0156027 Kg/s
Outlet_Bottom: -0.00277124 Kg/s
Case 7: Diameter = 7µm and velocity = 3m/s
Numbers tracked: 124
Escaped: 4
Trapped: 120
Incompleted: 0
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Mass Flow rate :
Inlet : 0.018375 Kg/s
Outlet_top: -0.0157207 Kg/s
Outlet_Bottom: -0.0026581 Kg/s
Case 8: Diameter = 8µm and velocity = 3m/s
Numbers tracked: 124
Escaped: 1
Trapped: 0
Incompleted: 123
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Mass Flow rate :
Inlet : 0.018375 Kg/s
Outlet_top: -0.0150247 Kg/s
Outlet_Bottom: -0.00336179 Kg/s
Case 9: Diameter = 9µm and velocity = 3m/s
Numbers tracked: 124
Escaped: 0
Trapped: 124
Incompleted: 0
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Mass Flow rate :
Inlet : 0.018375 Kg/s
Outlet_top: -0.0154428 Kg/s
Outlet_Bottom: -0.00292674 Kg/s
Case 10: Diameter = 10µm and velocity = 3m/s
Numbers tracked: 124
Escaped: 0
Trapped: 0
Incompleted: 124
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Mass Flow rate :
Inlet : 0.018375 Kg/s
Outlet_top: -0.0149803 Kg/s
Outlet_Bottom: -0.00340679 Kg/s
Q3. Velocity is varied from 1 m/s to 5 m/s
Diameter is set at a constant 5µm.
Case 1: Velocity = 1m/s and diameter = 5µm
Numbers tracked: 124
Escaped: 6
Trapped: 1
Incompleted: 117
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Pressure Contour:
Mass weighted Average at total pressure is 1.70 Pa.
Mass Flow rate :
Inlet : 0.006125 Kg/s
Outlet_top: -0.00495185 Kg/s
Outlet_Bottom: -0.00117541 Kg/s
Case 2: Velocity = 2 m/s and diameter = 5µm
Numbers tracked: 124
Escaped: 61
Trapped: 42
Incompleted:21
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Pressure contour:
Mass weighted Average at total pressure is 3.16 Pa.
Mass Flow rate :
Inlet : 0.005 Kg/s
Outlet_top: 0.0078003 Kg/s
Outlet_Bottom: 0.00193133 Kg/s
Case 3: Velocity = 3m/s and diameter = 5µm
Numbers tracked: 124
Escaped:0
Trapped: 124
Incompleted: 0
Pressure plot:
Mass weighted Average at total pressure is 14.56 Pa.
Case 4: Velocity = 4m/s and diameter = 5µm
Numbers tracked: 124
Escaped: 0
Trapped: 124
Incompleted: 0
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Pressure plot:
Mass weighted Average at total pressure is 26.52 Pa.
Mass Flow rate :
Inlet : 0.0245 Kg/s
Outlet_top: -0.0207706 Kg/s
Outlet_Bottom: -0.00372511 Kg/s
Case 5: Velocity = 5m/s and diameter = 5µm
Numbers tracked: 124
Escaped: 0
Trapped: 124
Incompleted: 0
Residual Plot :
Solutions Converged :
Anthracite Particle Time:
Vortex core:
Pressure plot:
Mass weighted Average at total pressure is 42.2067 Pa.
Mass Flow rate :
Inlet : 0.030625 Kg/s
Outlet_top: -0.0260611 Kg/s
Outlet_Bottom: -0.0045057 Kg/s
Conclusion:- By the above simulation, we have shown that the number of particles from the inlet depends upon the mesh element size or grid size. Less the mesh element size means more number of particles. Finer mesh shows less incomplete particles. We also observed that the mass flow from outlet 1 is more by finer mesh. So, If we have finer mesh or more number of particles flow inside the cyclone separator, then it gives less number of incomplete particle and giver better result. The negative sign in the mass flow rate from outlet 1 & 2 means that the mass is released from the body to the atmosphere or outside. If the particle size is more substantial and the sectional area of entry into a cyclone is smaller, the separation efficiency of the cyclone is higher. The collection efficiency of cyclones varies as a function of density, particle size and cyclone design. Cyclone efficiency will generally increase with increases in particle size. Mass weighted Average of total pressure is increasing when velocity is increased at constant particle diameter.
Separation Efficiency for the above cases ranges from 98% to 100%.