Buckling Analysis of a Cyclonic Separator Stand to Find the Optimum Position of the Stiffener using FEA

Aim:- Buckling Analysis of a Cyclonic Separator Stand to Find the Optimum Position of the Stiffener using FEA

Objective:-

1. Create a metallic stiffener on the legs of the stand and run the analysis to find out the change in the buckling factor of safety.
2. To run a design study and find the optimum position for the stiffener. Compare the results for all the cases using tables and highlight the best one.

Introduction:-

In engineering, buckling is the sudden change in the shape of a structural component under loads such as the bowing of a column under compression or the wrinkling of a plate under shear. If a structure is subjected to a gradually increasing load when the load reaches a critical level, a member may suddenly change shape and the structure and component are said to have buckled.

Buckling may occur even though the stresses that develop in the structure are well below those needed to cause failure in the material of which the structure is composed. Further loading may cause significant and somewhat unpredictable deformations, possibly leading to complete loss of the member's load-carrying capacity. However, if the deformations that occur after buckling do not cause the complete collapse of that member, the member will continue to support the load that caused it to buckle. If the buckled member is part of a larger assemblage of components such as a building, any load applied to the buckled part of the structure beyond that which caused the member to buckle will be redistributed within the structure. Some aircraft are designed for thin skin panels to continue carrying load even in the buckled state.

Cyclone separators utilize gravity and a vortex to remove particulates from gaseous streams. Industrial cyclones are used in pollution control applications most commonly as a first stage, a lower-cost method for removing larger particulate matter (PM) from effluent gas streams. Because cyclone separators do not incorporate filter media or moving parts, the pressure drop (therefore, operating costs) and maintenance requirements tend to be low. They can also be constructed to withstand harsh operating conditions, and since separation in cyclones is a dry process, the equipment is less prone to moisture corrosion.

A widely used type of dust-collection equipment is the cyclone separator. A cyclone is essentially a settling chamber in which gravitational acceleration is replaced by centrifugal acceleration. Dust-laden air or gas enters a cylindrical or conical chamber tangentially at one or more points and leaves through a central opening. The dust particles, by virtue of their inertia, tend to move toward the outside separator wall from where they are led into a receiver. Under common operating conditions, the centrifugal separating force or acceleration may range from five times gravity in very large diameter, low-resistance cyclones to 2500 times gravity in very small, high-resistance units.

Within the range of their performance capabilities, cyclones are one of the least expensive dust-collection systems. Their major limitation is that, unless very small units are used, efficiency is low for particles smaller than five microns. Although cyclones may be used to collect particles larger than 200 microns, gravity-settling chambers or simple inertial separators are usually satisfactory and less subject to abrasion.

Operation:-

Cyclone separators operate by incorporating centrifugal, gravitational, and inertial forces to remove fine particles suspended in air or gas. These types of separators use cyclonic action to separate particulates from a gas stream. Typically, PM enters the cyclone separator at an angle (perpendicular to the flow stream, tangentially, or from the side), and is then spun rapidly. A centrifugal force is created by the circular airflow that throws the particulate towards the wall of the cyclone. Once the PM hits the wall, it falls into a hopper below. “Clean” exhaust is then either blown through or recirculated to be filtered again.

General layout and function of a reverse flow cyclone, indicating the flow paths of the gas and particulate matter (labeled powder in this diagram). Image Credit: GEA Niro

It is important to keep in mind that the centrifugal force (F_c) a cyclone generates on a particle is related to the tangential air velocity (v_t), particle mass (m), and the particle’s radial distance from the cyclone wall (r) by the function:

F_c = m • v_t² / r

3D Models:-

  Cyclone Seperator Assembly

  Cyclone Separator Stand with Stiffener

Procedure:-

1. In the part file of the stand, a sketch is made on a reference plane from the top plane at an offset of 1700 mm and extruded up to 80mm to make a stiffener.
2. Apply material as Alloy Steel.
3. The base of the legs are fixed and the force of 150 KN is applied on the top face of the stand.
4. Fine mesh is created for better results.
5. Study 1 is created for buckling analysis with a stiffener at 1200mm offset from the top plane.
6. Study 2 is created for a design study with varying stiffener position in a range between 700mm and 1750mm with a range step of 250mm.
7. Study 3 is created for a design study with varying stiffener position in a range between 800mm and 1200mm with a range step of 50mm.

Material and properties for this analysis:-

Name: Alloy steel

Model type: Linear elastic isotropic

Failure criterion set: Max Von Mises stress

Yield strength: 6.20422e+08 N/m²

Tensile strength: 7,23826e+08 N/m²

Mass density: 7700 kg/m³

Elastic modulus: 2.1e+11 N/m²

Poisson’s ratio: 0.28

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Study 1-  Buckling Analysis with Stiffener at 1200mm offset from the top plane

Study name = Buckling 1

Offset from top plane = 1200mm

Load factor = 21.248

Force on top plate = 150 KN

The base of the legs are  fixed

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Study 2- Design Study 1

Study Properties

Design Study Setup  

Design Variables

Here the offset of stiffener from the top is selected as a variable that will vary from 700 mm to 1750 mm with a range step of 250 mm.

Constraints

The buckling factor of safety is contained as greater than 25 for this study.

Goals

Our goal of this study is to maximize the buckling factor of safety and to be greater than 25.

Study Results:- 

8 of 8 scenarios ran successfully.

In this study, we came to an optimal solution that the buckling factor of safety greater than 25 is if the stiffener is at the offset of 950 mm from the top plane which is scenario 2 in this case.

Therefore at this point, the buckling factor of safety is 25.82.

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Study 3- Design Study 2

Study Properties

Design Study Setup:-

Design Variables

Here the offset of stiffener from the top is selected as a variable that will vary from 800 mm to 1200 mm with a range step of 50 mm.

Constraints

The buckling factor of safety is contained as greater than 25 for this study.

Goals

Our goal of this study is to maximize the buckling factor of safety and to be greater than 25.

 Study Results:-

11 of 11 scenarios ran successfully.

This study is done to get the precise optimal solution for better positioning of the stiffener. In this study, scenario 3, 4, 5, and 6 satisfies our goal but scenario 4 is the best amongst all because at that point the buckling factor of safety is maximum.

In this study, we came to an optimal solution that the buckling factor of safety greater than 25 is if the stiffener is at the offset of 950 mm from the top plane which is scenario 4 in this case. Therefore at this point, the buckling factor of safety is 25.82.

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Conclusion:-

1. The ratio of the buckling loads to the applied loads is the factor of safety against buckling (BFS). It is crucial to design a component for safe operations.

2. In design study, after varying the position of the stiffener we concluded that at a certain point the buckling factor of safety is maximum. Therefore at that point, the stand will be able to sustain the load for a longer period of time without any deflection in the legs.
3. In this case, the buckling factor of safety varies with the dimensions of the stiffener used. A stiffener with a broad face will have a maximum factor of safety that a thin-faced stiffener due to the area of contact with the legs.
4. After all, if the stiffener is positioned at an offset of 950 mm from the top plane is best suited for this case with a maximum buckling factor of safety that is 25.82.

Reference:-

https://www.globalspec.com/learnmore/manufacturing_process_equipment/air_quality/cyclone_separators#:~:text=Cyclone%20separators%20utilize%20gravity%20and%20a%20vortex%20to,larger%20particulate%20matter%20%28PM%29%20from%20effluent%20gas%20streams.

https://www.sciencedirect.com/topics/engineering/cyclone-separator