Evaluation and Prediction of Blade-Passing Frequency Noise Generated by a Centrifugal Blower

Abstract

The blade-passing frequency noise, abbreviated to BPF noise, of low specific speed centrifugal blower is analyzed by separating the frequency-response of the transmission passage and the intensity of the noise source. Frequency-response has previously been evaluated by the authors using a one-dimensional linear wave model, and the results have agreed well with the experimental response in a practical range of the blower speed. In the present study, the intensity of the noise source is estimated by introducing the quasi-steady model of the blade wake impingement on the scroll surface. The effective location of the noise source is determined by analyzing the cross-correlation between measured data of the blower suction noise and pressure fluctuation on the scroll surface. Then, the surface density distribution of a dipole noise source is determined from pressure fluctuation expressed in terms of quasi-steady dynamic pressure of the traveling blade wake. Finally, the free-field noise level is predicted by integrating the density spectrum of the noise source over the effective source area. The sound pressure level of the blower suction noise is easily predicted by multiplying the free-field noise level by the frequency-response characteristics of the noise transmission passage.

Effects of vortex structure on performance characteristics of a multiblade fan with inclined tongue

“…It mainly possesses a great deal of outstanding advantages, for instance high pressure coefficient, small size coefficient, and low noise. 1,2 In general, the performance of centrifugal fans has drawn widespread concern. It is of great significance to improve the performance of centrifugal fans, which can not only achieve the purpose of energy conservation, but also benefit the development of the fan industry.…”

“…Forward curved centrifugal fans are compact and quiet, but classically have low efficiency and are consequently at risk of being regulated out of the market. 2,3 Lin and Wu 3 performed an extensive experiment to study the influences caused by the deep contour inlet section and the central body for a forward curved centrifugal fan. Their work showed that the central body does enhance the static efficiency by 10%, whereas the deep inlet section results in a negative effect on the fan performance.…”

Aerodynamic performance and noise characteristics of a centrifugal compressor with modified vaned diffusers

“…Since the noise, which is called an interaction tone noise (ITN), is considered to be caused by direct impingement of the impeller-discharged flow on the diffuser vane, the leading edge geometries of the diffuser vane play an important role in discussing the noise generation mechanisms. Although the interaction between impeller-discharged flow and diffuser vanes is an obvious and powerful noise source, surprisingly little research has been reported on the ITN [1][2][3][4][5]. Furthermore, the frequency of the ITN coincides with that of the blade-passing frequency components, abbreviated to BPF components, so the noise could dominate the overall noise level if sufficient care is not taken.…”

Reduction of the aerodynamic tonal noise of a forward-curved centrifugal fan by modification of the volute tongue geometry

“…Many authors have studied the noise generated by centrifugal fans and they have shown that the main source of aerodynamic tonal noise generation is the interaction between the non-uniform impeller flow and the fixed volute tongue [3,4]. According to these investigations, the location of the effective noise source is restricted to the vicinity of the volute tongue, and the extension of the effective source region could be determined by a correlation analysis between the acoustic pressure radiated by the fan and the pressure fluctuation on the volute surface.…”