Axial Fan Noise Reduc­tion: How To Boost It With Smarter Geometry Models

The design of axial fans typ­i­cally con­sid­ers the effi­ciency but also the reduc­tion of noise. Axial fan noise reduc­tion is a rather huge and complex topic when it comes to all the details, but there are a few simple geometry tech­niques that you can apply to your standard blade designs, to imme­di­ately lower the fan’s noise level.

The CAD and opti­miza­tion solution CAESES gives you the toolbox to imple­ment any kinds of such features, and lets you automate the blade geometry gen­er­a­tion within CFD-driven opti­miza­tion loops. This short article gives you a quick idea of what you can do with CAESES, to improve the axial fan noise level and the overall acoustic behavior.

Axial Fan Noise Reduc­tion: Beveled Blade Tips 

A beveled blade tip is one geo­met­ric feature that can imme­di­ately reduce the rotor-stator inter­ac­tions and hence reduces the noise level of the axial fan. Basi­cally, you cut out some parts at the tip region of your blade. Your para­met­ric model needs to have controls for the shape and the depths of these dif­fer­ent tip features, to create a variety of design can­di­dates in an auto­mated process. 

Trailing Edge Serrations

Another geo­met­ri­cally simple thing is to cut out parts of the trailing edge, to influ­ence how the flow from the suction and pressure side are mixed into each other. By having an improved tran­si­tion of the two flows, you can reduce the tur­bu­lence patterns, which results in an improved effi­ciency and a further noise reduc­tion. You would also intro­duce controls (design vari­ables with lower and upper bounds) e.g. for the shape of these ser­ra­tions, their loca­tions, as well as for the number of serrations.

Axial Fan Noise Reduc­tion: How To Find the Optimal Geometry 

In order to find the optimal para­me­ters for the beveled blade tips and the vortex controls at the trailing edge, you typ­i­cally run design explo­rations and shape opti­miza­tions with sim­u­la­tion tools, in par­tic­u­lar with CFD. In such a multi-objec­tive pro­ce­dure, the blade’s shape para­me­ters are varied auto­mat­i­cally, while the opti­miza­tion strate­gies try to improve the effi­ciency and the noise emis­sions. The sim­u­la­tion tools are also con­nected and auto­mated, to automate the entire meshing and analysis process.

More Infor­ma­tion

See the tur­bo­ma­chin­ery section for more infor­ma­tion about blade design in the context of sim­u­la­tion-driven studies. The case study ​“Axial Fan Opti­miza­tion Using TCFD and CAESES” gives you an example of coupling CAESES and TCFD for opti­miz­ing an axial fan (in this case without taking into account axial fan noise reduc­tion features).

CAESES is a spe­cial­ized CAD solution for the advanced and auto­mated design of complex shapes with CFD. There are many other features that you can inte­grate into your blade model. CAESES is no black box, and allows you to quickly consider all your ideas in an opti­miza­tion process.

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