Cyclone CFD Simulation Using DPM
Cyclones are one of the most widely used industrial systems in the field of air dewatering, dust disposal, or separation of solid particles from the gas flow.
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Cyclones are one of the most widely used industrial systems in the field of air dewatering, dust disposal, or separation of solid particles from the gas flow. In these types of systems, the operation of separating solid particles from gas flows is carried out with the help of centrifugal and gravity forces, without the use of filters. Cyclones, in addition to reducing air pollution, are also used to bring solid particles back into the production cycle. These systems are commonly used in wood, cement, and any other industries that produce suspended solid particles.
There are one inlet and two outlets for solid particles and pure air in cyclones. The air containing particles enters the cyclone from the inlet of the cyclone and moves in the space between the inner cylinder and the outer cylindrical body in a spiral and vortex manner, such that the solid particles suspended. Due to the centrifugal force and heavier weight, particles separate from the gas stream and move downward due to gravitational force. In this way, the solid particles in the air separate from the airflow. The gaseous flow also flows upward and reaches the upper part of the chamber after reaching the conical region.
Problem Description for Cyclone CFD Simulation using DPM
The present problem is a gas cyclone device CFD simulation. In this device, the gas flow enters continuously from the top to the inner space between the two cylinders and then the partial cone. Also, the solid particles enter the cyclone interior from the top as the discrete phase. The contact between these two flows and centrifugal force results in the separation of these two phases. In the present simulation, the air is defined as gas flow and ash as discrete phase solid particles.
Geometry & Mesh for Cyclone CFD Simulation
Gambit (or Design Modeler) software models the present 3-D geometry. The cyclone structure consists of a cylindrical part and a partially conical part. The designed cyclone structure consists of a cylindrical part and an incomplete conical section such that a smaller cylinder also fits into the inner part of the outer cylinder body. Above the geometry, a trapezoidal cross-section is designed as the inlet of air impregnated with dust and a circular cross-section as the outlet of pure air, and at the bottom of the geometry, a circular cross-section is designed as a place for dust particles to accumulate.
Gambit (or ANSYS Meshing) software grid the present model. The mesh was of an unstructured type and the element number was 142499.
To solve this problem, we consider several assumptions:
– Simulation is steady.
– Gravity effect is equal to -9.81 m.s-1.
– The solver is pressure-based.
Cyclone CFD Simulation using DPM
Here is a summary of the steps to define and solve the problem in the table:
|Standard wall function|
|discrete phase model||No interaction with continuous phase|
|DPM||The number of longitudinal steps||1000|
|Longitudinal step factor||5|
|(boundry conditions) DPM|
|impure air inlet||21 m.s-1|
|pure air outlet||1 (100%)|
|ash (particle) zone||trap|
|second order upwind|
Discrete Phase Definition (DPM)
This simulation examines the behavior of a discrete phase from a Lagrangian perspective in the presence of a continuous fluid in the Eulerian perspective. The gas flow as a continuous fluid is under the Eulerian view, while the ash particles are discretized and Lagrangian. The assumption is that the continuous phase does not affect discrete phase behavior. Therefore, we disable the Interaction With Continuous Phase for the discrete phase setting. We also define the discrete phase injection as the INERT of the cyclone inlet, meaning that the discrete phase is ineffective and does not exhibit specific behavior. In the present simulation, we define air as gas flow (continuous phase) and ash as solid particles (discrete phase).
At the inlet, the airflow has a significant velocity of 21 m.s-1 to cause a significant vortex phenomenon. The discrete phase (ash) behavior is Escape through the inlet and outlet of the air, which means, the ash passes through these boundaries, while in the other outlet the ash is Trapped because the ash particles accumulate at the end of the cyclone after separation. Particles reflected near the cyclone walls, which means they Reflect with a coefficient of 0.8 in the vertical and tangential directions.
Mesh file is available in this product. By the way, the Training File presents how to solve the problem and extract all desired results.