Numerical Prediction of Tonal Noise in Centrifugal Blowers

Centrifugal blowers are widely used in automotive, heating, ventilating, air-conditioning and other industrial purposes. In fact, they allow high-pressure increase to a moderately high mass flow rate, despite the reduced overall dimensions of the system. Numerous authors have worked to increase the fluid dynamic efficiency of the impeller and the volute. However, the recent sound emission standards have imposed tighter constraints, making the noise reduction one of the most challenging target for the design. The reduction of the tonal noise is the main concern for these blowers because the noise at the first harmonic is clearly distinguishable in the noise spectrum. Techniques to reduce this peak generally rely on experimental measurements in aeroacoustics laboratory. In this work, a CFD procedure has been developed to accurately predict the tonal noise in radial bowers. The approach has been validated using real geometries and experimental data. Various turbulence models have been tested to find the best results without the use of excessive computational resources. Moreover, unsteady simulations of the 3D blower have been carried out to analyze the influence of the main geometric parameters on the tonal noise reduction. A parametric design code developed by the authors have been used to change the geometry in order to identify the effect of the main geometrical design parameters on both fluid dynamic and aeroacoustics performance.