Numerical optimization of the tonal noise of a backward centrifugal fan using a flow obstruction

This paper focuses on a passive noise control device based on a flow obstruction of a certain shape which can reduce a fan's Blade Passing Frequency tonal noise. The obstruction is located upstream of a centrifugal fan with a heat exchanger placed in between. Measurements performed at various operating conditions show that for an optimal position and orientation of the obstruction, the blade passing frequency noise is reduced by 10-13 dB. This paper uses a CFD/CAA approach for modeling this problem and numerically determining the optimized position of the obstruction. Simulations results are also used to provide a better understanding of the physical mechanisms involved in the noise reduction.