CYCLONE SEPERATOR USING ANSYS FLUENT

Objectives:

1. Write a few words about the four empirical models used for cyclone separator efficiency
2. Performing an analysis on the given cyclone separator model and apply four different boundary condition types at the inlet i.e. reflect, trap, escape and wall-jet and submit images on your findings on the different conditions.
3. Varying the number of particles through the inlet and run the simulation for 3 cases. Report the number of particles that pass through or remain in the cyclonic separator. Post images to show the same. For this question, use the “Reflect” option as the boundary condition for the Discrete Phase

1. Cyclones are the devices that employ a centrifugal force generated by a spinning gas stream to seperate particles from the carrier gas. Their simple design, low maintenance costs, and adaptability to a wide range of operating conditions such as sizes and flow rates make cyclones one of the most widely used particles removal devices. By using suitable materials and methods of construction, cyclones may be adapted for use in expreme operating conditions: high temperature, high pressure, and corrosive gases. Cyclones are important parcle removal devices in both engineering and process operations.

Emperical models used for cyclone seperator:

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 particle carried by the vortex enduces the influence of two forces: a centrifugal force(Z), flow resistance(W), core length(z),and core diameter(d) are given as.

LI 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:

The concentration distribution in a cyclone 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.

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

where N is the number of revolutions

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

GEOMETRY:

Volume extract

For the analysis create a fluid domain by volume extract using spaceclaim

MESHING:

Element size = 0.01

no of elements = 407492

SET UP:

Steadystate- Pressure-based

Gravity y-axis(-9.81m/s^2)

Viscous - k-epsilon - RNG - Swirl dominated

Discrete phase - injection properties - Material - Antracite - Velocity(3m/s) - Diameter = 5e-06 - Total flow rate = 1e-20kg/s

Velocity at inlet = 3m/s

iterations =500

REFLECT

Scalar Residuals:

Antracite Particle time:

Vortex shedding:

TRAP:

Scalar Residuals:

Antracite Particle time:

Vortex shedding:

ESCAPE

Scalar Residuals:

Antracite Particle time:

Vortex shedding:

WALL JET

Scalar Residuals:

Antracite Particle time:

Vortex shedding:

REFLECT

Particle size = 10e-06

Scalar Residuals:

Antracite Particle time:

Vortex shedding:

Particle size = 15e-06

Scalar Residuals:

Antracite Particle time:

Vortex shedding:

Particle size = 20e-06

Scalar Residuals:

Antracite Particle time:

Vortex shedding:

RESULTS:

The plot outcome was same for all the four different boundary contitions at the inlet(Reflect,Trap,Escape,Wall-Jet)

Mass flow rate is also same for all the different (Reflect,Trap,Escape,Wall-Jet) inlet is positive and the outlets are negative sign because the mass release from the body to the atmolsphere is at oulet.

The collection efficiency of cyclones varies as a function of density, particle size and the design of the body.

For changing the particle size the results are show below:

Particle size	No.of particles	Escaped	Aborted	Trapped	Incomplete
10e-06	364	167	0	0	197
15e-06	364	185	0	0	179
20e-06	364	270	0	0	94