# CFD Analysis of a Blower for a Small Dust Collector

I recently came across an interesting fluid dynamics project modestly titled "Small Dust Collector" by Matthias Wandel of Woodgears. The unusual twist - at least from my metal-orientated view of the world - was the use of wood as the primary construction material. The project includes the construction of a blower, cyclone, filter housing, and filter manifold - all prime candidates for Computational Fluid Dynamics (CFD) simulations. I sense a series of blog posts, so first let's take a look at the blower also known as a centrifugal fan or squirrel cage fan.

CFD Simulation of a Blower

### 3D Model Construction

Within the plans Matthias sells online for a very reasonable US\$15 are detailed descriptions of each component along with supporting SketchUp files.

Small Dust Collector SketchUp Model

Using these plans for the blower I constructed a 3D model from scratch. To simplify the simulation and reduce the need to resolve narrow edges I used zero-thickness faces for the blades and blade-tip-disks. All the other geometry, including the spiral cavity, was constructed according to the original specifications.

Blower CFD Model

### Performance Test

I thought it would be interesting to determine the performance characteristics of the blower, so I ran a series of 30 simulations for a range of volume flow rates and measured the pressure rise across the blower along with the torque to maintain each condition. Given these measurements I could determine the fan curve and efficiency.

Blower Fan Curve

Blower Torque Curve

Blower Efficiency Curve

### Summary

The results from this study show that the peak efficiency for this blower is 49%, at a pressure rise of 2720 N/m2 (to match a pressure drop of equal magnitude due to the resistance of constituent fluid components), which results in a volume flow rate of 0.085 m3/s. While these results may not exactly match the measured characteristics of the as-built device, they should be in the right ballpark.

### Flow Visualization

Pressure Iso-SurfacesBlower CFD simulation for 0.085 m3/s

Velocity Magnitude Iso-SurfacesBlower CFD simulation for 0.085 m3/s

Velocity ArrowsBlower CFD simulation for 0.085 m3/s

### Notes

The fixed speed for the blower was 3500 RPM.

The blower geometry was created in Caedium Professional. The CFD simulations were automated using a Python script and were performed using the incompressible, steady-state RANS solver, with a MRF for the rotor, and the k-omega SST turbulence model.

Check out Matthias' craftsmanship and ingenuity in his video on the construction of the blower for his small dust collector.

Small Dust Collector Blower Construction