A set of aeroacoustic optimization strategies for axial fans is presented. Their efficiency is demonstrated for small axial fans. Thereby, the generated noise could be reduced significantly while retaining or even improving the aerodynamic performance.
In particular, we discuss the following two optimization strategies in detail: Firstly, we consider the design of winglets using a parametric model for genetic optimization. The resulting winglet geometry helps to control the tip vortex over a large range of operating points, thereby reducing the generated noise. In addition, the power consumption of the fan could be reduced. Various choices of geometrical parameter sets for optimization are evaluated.
Secondly, we discuss the reduction of fan noise via contour optimized turbulators. For axial fans it is desirable to reduce sound emission across a broad operating range, not just for the design point. However, operation in off-design points may be accompanied by flow separation phenomena, which contribute predominantly to noise generation and reduce the aerodynamic performance of the fan. Turbulators can help to minimize these adverse effects. The advantages of various contoured turbulator geometries are discussed for off-design operating points.
The optimization of the above mentioned strategies was driven by aeroacoustic measurements via physical tests as well as numerical analysis based on the Lattice-Boltzmann method. The merits of either method are discussed with respect to the two optimization strategies.