Aeroacoustics noise considerations: Reduction of noise from fans and impellers

Noise emission is an important factor to be considered in various applications for high quality end results. A product/engineering project involving fans will inevitably deal with noise generated from fans and that from the air passage system. Noise emission has to be taken into account either for regulatory compliance reasons or to be superior to competitors all while without compromising performance.

Noise emissions from fans can be induced by mechanical vibration and pressure variation due to blade interference, flow separation and turbulence intensity over the blades and surfaces of fan casing or volute as well as jet effect for an exhaust flow releasing.

Fan noise can be reduced in different ways according to the feasibility of each individual cases by smoothing flow to reduce scale of flow separation or avoid its occurrence mostly or reduce the maximum velocity over the blades.

We use different techniques to evaluate fan noise, which includes:

(i) engineering empirical and (ii) theoretical methodologies as well as (iii) computational fluid dynamics. As an example, the noise calculator is a simple tools to predict the 1/3 octave band centered frequency to estimate the sound pressure level(SPL) and sound power level(SWL). Frequency distribution estimation helps to give indication to decide which mitigation could be effective in further process of noise reduction.

Low noise fan design is an optimizing process in aerodynamic flow around the blades, passage between the blade, fan casing, stators and all the other parts or components exposing to the airflow. Special care will be taken through the use of computer aided aerodynamics design, flow simulation based optimization and experimentation.

It is important to note that noise reduction methods are not one-size-fit-all solutions; each fan must be examined and optimized individually, with noise reduction solution tailored for that particular fan's acoustic profile. Generally a meaningful noise reduction will be no less than 3dB, without affecting performance.

All objects and/or renderings depicted were created and owned by
Turbomoni Applied Dynamics Lab

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