'Fan Performance CFD Analysis' simulation project by Ali_Arafat


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I created a new simulation project called 'Fan Performance CFD Analysis':

Radial - Centrifugal forward curved fan performance CFD analysis project


More of my public projects can be found here.


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Description


Radial fans (also known as centrifugal fans) have a wide range of applications ranging from being used as draft fans in power plants to drying fans in the food industry. Being one of the most prevalent fans in the industry, it is paramount for engineers to bear in mind the performance characteristics and mechanical efficiency of the device.

Essentially, a radial fan is a simple mechanical device that changes the velocity and direction of a fluid passing through it. In this project, we consider air as the working fluid. The air-stream enters the fan intake at the central region in a direction parallel to the axis of the fan. The blades, run by an electric motor, push the air radially outwards in a direction that is tangential to the trailing (outer) edge of the fan blade. Therefore, not only does it increase the velocity of the airstream but also renders the direction of flow as perpendicular to the original one.

Project Goals


With the help of the SimScale platform, we have simulated a Radial fan in action. By altering various parameters such as flow intake rate, torque, and rpm, we can easily study the performance characteristics of the fan. With the ultimate goal of suggesting improvements in design, we trace the airflow trajectories which help us determine design flaws and unwanted regions of recirculation.

Geometry


A radial fan consists of a fan wheel and a housing. Trying to keep it lucid, we have created a clean CAD model using only these two components. The images shown below will give you a better idea of our geometry:
 
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Isometric view (fan+housing)
 
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Fan without casing
 
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Fan-blade geometry

Meshes


A hex-dominant parametric (only CFD) mesh has been created along with a Cartesian box enclosing the entire mesh of the fan. This would be the region considered for our study. Multiple mesh refinements are made on the surface of the rotor and casing before running the simulation.

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Background mesh box
 


 
Mesh Refinements
 
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Final Mesh

Simulations


Using the k-omega SST model, a steady state analysis is performed assuming air as an incompressible fluid. Due to the heavy geometry and multiple mesh refinements, the simulation is executed using 32 cores and takes approximately 13 hours to run.

Results and Conclusions


The image below shows the velocity streamlines of the air flow through the radial fan. The 90-degree change in direction of the flow and the increase in velocity can be seen clearly in the following image.

Fan Performance Analysis

Performance Plots:

Typically, fans have certain characteristic plots which are vital to the selection process for the type of fan to be installed. After performing the simulation, we plotted the characteristic plots as follows:

From the figure above, we can conclude that for an air flow rate of 0.0055 Kg/s, the fan under study achieves maximum efficiency. Therefore, selection of this type of fan would be ideal when we have flow rates at a similar range.

Another factor that is considered for fan selection is the static pressure induced by the fan. Based on the purpose for which it is to be used and the range of flow rates for that application, we can select a fan with a suitable static pressure.

Efficiency Plot:

Torque vs RPM Plot: