cyclone
ANS 1 : Cyclone sepreators are the devices that use principle of inertia to remove particulate matter from flue gases. They have a low maintainence cost and simple design makes them easy to use highly adaptable for any use of different flow rates.
Four different cyclone efficiency emperical models are :
1) LI AND WANG MODEL
The Li and Wang model (1989) includes particle bounce and turbulent diffusion at the cyclone wall. A 2-D analytical expression of particle distribution in the cyclone wall is obtained. Assumptions in the model are :
1. The radial particle velocity and the radial concentration profile are not constant for uncollected particles within the cyclone.
2. Boundary condition with the consideration of diffusion coefficient and particle bounce on the cyclone wall are `c=co` at θ=0.
2) IOZIA AND LEITH MODEL:
Iozia and Leith model (1990) is a modifies version of Barth model which is developed based on force balance. According to this model a particle carried by a vortex endures the influence of two forces a centrifugal and a flow resistence force along the core length and core diameter respectively.
3) LAPPLE MODEL :
Lapple model (1951) was based on the force balance without consedering the flow resistence. It\'s based on the assumption that a particle entering the cyclone is evenly distributed across the inlet opening the particle is then travelling from inlet half width to the wall in the cyclone that is collected with 50% efficiency.
4) KOCH AND LICHT MODEL :
Koch and Licht model (1977) collection theory recognised the inherent turbulent nature of the cyclones and distribution of gas residence time within the cyclone. Following assumptions were made:
1.The tangential velocity of the particles is equal to the tangential velocity of the gas.
2. The tangential velocity is realteds with the radius of the cyclone by `uR^n=c`
ANS 2:
CASE 1: Boundary condition : wall-jet
# GEOMETRY
# extracted volume
# MESH
size: 10 mm , which will remain same for all of the following cases.
number of elements: 407130, which will remain same for all of the cases.
# PHYSICS
1. steady state
2. pressure based
3.absolute velocity
4. gravity enabled ( Y=-9.81)
5. k epsilon model swirl dominant mdel.
6. DPM ( discrete phase model)
interaction with continous phase.
iteratiion interval of DPM - 10
7. injection :
type: surface
surface: inlet
particle : inert
material : anthracite
velocity (x): 3m/s
diameter: 5e -06 m
8. solution method:
Turbulent kinetic energy: second order upwind
turbulent dissipation rate: second order upwind
everything else remains default
9. standard initialisation
10. compute from : inlet
11. boundry conditions :
inlet vel : 3m/s
DPM type : wall jet
12. number of iterations : 600
# NOTE : the above conditions remains the same throughout only change in DPM type in the following question.
# RESULTS
1. residuals
here ,
number of particles tracked : 364
escaped : 145
aborted : 0
evaporated : 0
incomplete : 219
incomplete parallel : 0
2. particle path tracked :
3. vortex :
# CASE 2: BOUNDARY CONDITION : REFLECT
# RESULT :
1. residuals
number of particles tracked : 364
escaped : 145
aborted : 0
evaporated : 0
incomplete : 219
incomplete parallel : 0
2. particle path tracked :
3. vortex
# CASE 3: BOUNDARY CONDITION : TRAP
# result
1. residuals :
number of particles tracked : 364
escaped : 145
aborted : 0
evaporated : 0
incomplete : 219
incomplete parallel : 0
2. particle path tracked :
3. vortex:
CASE 3: BOUNDARY CONDITION : ESCAPE
# result
1. residuals :
number of particles tracked : 364
escaped : 145
aborted : 0
evaporated : 0
incomplete : 219
incomplete parallel : 0
2. particle path tracked :
3. vortex:
ANS 3:
Here we will be seeing the results for different mesh sizes for the same boundary condition of (reflect type) . The geometry remains the same as well all the operating conditions.
# case 1:
1. mesh
size: 10 mm
number of elements: 407130
2. results:
residuals :
number of particles tracked : 364
escaped : 145
aborted : 0
evaporated : 0
incomplete : 219
incomplete parallel : 0
particle path :
vortex:
# case 2 :
1. mesh
size: 15 mm
number of elements: 157237
2. results:
residuals :
number of particles tracked : 132
escaped : 71
aborted : 0
evaporated : 0
incomplete : 61
incomplete parallel : 0
particle path time :
vortex
# CASE 3:
1. MESH
size: 20 mm
number of elements : 76723
2. results:
residuals :
number of particles tracked : 94
escaped : 94
aborted : 0
evaporated : 0
incomplete : 0
incomplete parallel : 0
particle path time :
vortex