• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.21 no.12
• /
• pp.1138-1145
• /
• 2011

The internal broadband noise of a centrifugal fan in a household refrigerator is predicted using hybrid CAA techniques based on stochastic turbulent synthetic model. First, the unsteady flow field around the centrifugal fan is predicted using computational fluid dynamics(CFD) method. Then, the turbulent flow field is synthesized by applying the stochastic turbulent synthetic technique to the predicted flow field. The aerodynamic noise sources of the centrifugal fan are modeled on a basis of the synthesized turbulent field. Finally, the internal broadband noise of the centrifugal fan is predicted using the boundary element method(BEM) and the modeled sources. The predicted noise spectrum is compared with the experimental data. It is found that the predicted result closely follows the experimental data. The proposed method can be used as an effective tool for designing low-noise fans without expensive computational cost required generally for the LES and DNS simulations to resolve the turbulence flow field responsible for the broadband noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.10a
• /
• pp.627-632
• /
• 2011

The internal broadband noise of a centrifugal fan in a household refrigerator is predicted by using hybrid CAA technique based on stochastic turbulent synthetic model. First, the unsteady flow field around the centrifugal fan is predicted using Computational Fluid Dynamics (CFD) method. Then, the turbulent flow field is synthesized by applying the stochastic turbulent synthetic technique to the predicted flow field. The aerodynamic noise sources of the centrifugal fan are modeled on a basis of the synthesized turbulent field. Finally, the broadband noise of the centrifugal fan is predicted using Boundary Element Method (BEM) and the modeled sources. The predicted result is compared with the experimental data. It is found that the predicted result closely follows the experimental data. The proposed method can be used as an effective tool for designing low-noise fans without expensive computational cost required generally for the LES and DNS simulations to resolve the turbulence flow field responsible for the broadband noise.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.9
• /
• pp.952-960
• /
• 2008

Fan noise prediction method is presented for air conditioning, automobile and electronic cooling system applications where fan acts as an internal equipment having very complicated flow interaction with other various system components. The internal flow paths and distribution in the fan-applied systems such as computer or air conditioner are analyzed by using the FNM(flow network modeling). Fan noise prediction method comprises two models for the discrete frequency noise due to rotating steady aerodynamic lift and blade interaction and for the broadband noise due to turbulent boundary layer and wake vortex shedding. Based on the fan operation point predicted from the FNM analysis results and fan design parameters, the present far noise model predicts overall sound pressure level and spectrum. The predictions for the flow distribution, the fan operation and the noise level in air cooling system by the present method are well agreed with 3-D CFD and actual noise test results.

• 유체기계공업학회:학술대회논문집
• /
• 1998.12a
• /
• pp.115-120
• /
• 1998

Aerodynamic noise generated by automobile cooling fan is investigated. Automobile cooling fans radiate both discrete frequency noise as well as broadband noise. In the present work, the former is considered through free-wake panel method coupled with acoustic analogy fully considering the retarded time variation on the blade surface, while the latter is taken into account by three well-established broadband noise components. Experiments were performed to supplement necessary inputs as well as to provide the final comparison with the predicted noise spectrum. The predicted noise levels at blade passing frequencies agree well with the experimental data for the first few harmonics. Although the predicted broadband noise levels at higher frequencies fall below the experimental data due to the fundamental shortcomings of the utilized formulations, the analysis offers a detailed physical understanding of the fan noise generation processes.

• The Journal of the Acoustical Society of Korea
• /
• v.31 no.6
• /
• pp.391-398
• /
• 2012

In this paper, prediction of centrifugal fan was conducted through combination the hybrid CAA method which was used to predict the fan noise with the FRPM technique which was used to generate the broadband noise source. Firstly, flow field surround the centrifugal fan was computed using the RANS equations and noise source region was deducted from the computed flow field. Then the FRPM technique was applied to the source region for generation of turbulence which satisfies the stochastic features. The noise source of the centrifugal fan was modeled by applying the acoustic analogy to the synthesized flow field from the computed and generated flow fields. Finally, the broadband noise of the centrifugal fan was predicted through combination the modeled noise source with the linear propagation which was realized using the boundary element method. It was confirmed that the proposed technique is efficient to predict the tonal and broadband noises of centrifugal fan through comparison with the measured data.

• 유체기계공업학회:학술대회논문집
• /
• 2006.08a
• /
• pp.205-208
• /
• 2006

This paper proposes a new computational aeroacoustics method for an axial fan analysis. The major aeroacoustic noise source of an outdoor air-conditioner is the axial fan. It was revealed that the dominant noise source is the aerodynamic interactions between the rotating blade and stationary orifice. Many researches were focused on the fan only case. However, it does not fit to a real outdoor unit of air-conditioner. Especially, the inlet part of the axial fan of real system case is complex and not uniform. So, in order to identify the dominant noise source of axial fan, full outdoor unit analysis is important. Transient CFD analysis of full system was performed by commercial CFD code - SC/Tetra. Dominant noise source of the system was calculated by commercial CFN code - FlowNoise. The results show that not only BPF peaks but also broadband noise are similar to the measured data.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.2
• /
• pp.59-64
• /
• 2010

A design method of Sirocco fan is developed for constructing 3-D impeller and scroll geometries, and for predicting both the aerodynamic performance and the noise characteristics of the designed fan. The aerodynamic blading design of fan is conducted by blade angle, camber line determinations and airfoil thickness distribution, and then the scroll geometry of fan is designed by using logarithmic spiral. The aerodynamic performance of designed fan is predicted by the meanline analysis with flow blockage, slip and pressure loss correlations. Based on the predicted performance data, fan noise is predicted by two models for cutoff frequency and broadband noise sources. The present predictions for the performance and the noise level of actual fans are well agreed with measurement results.

• 유체기계공업학회:학술대회논문집
• /
• 2002.12a
• /
• pp.123-128
• /
• 2002

Over the range(OTR) has been applied for cooking and ventilation functions especially in northern Amarica. Because flow rate and operating rpm of the double sided sirocco fan for ventilation are much higher and than the microwave oven system, the major noise source is the sirocco fm. Recently, the quiet fan development is one of very important issues for amenity. In this study, the noise source identification using multi-microphone array system was carefully carried out and numerical simulations for understanding the aerodynamic and aeroacoustic of the fan were peformed. The sound level of tonal noise is predicted with a good accuracy but that of the broadband shows some discrepancy. In order to reduce the broadband noise, the inlet region of sirocco fan have to be modified that the secondary flow should be suppressed. Based on these results, new low noise fan and OTR is now developing.

• Journal of KSNVE
• /
• v.7 no.1
• /
• pp.99-106
• /
• 1997

Centrigugal fans are widely used due to their ability to achieve relatively high pressure ratios in a short axial distance compared to axial fans. Because of their widespread use, the noise generated by these machines causes one of serious problems. In general, centrigugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the periodic flow discharged radially from the impeller and the stator blades or the cutoff. But in vacuum cleaner fan the noise is dominated by not only the discrete tones of BPF but also broadband frequencies. In this study we investigate the mechanism of broadband noise and predict for the unsteady flow field and the acoustic pressure field associated with the centrifugal fan. DVM(discrete vortex method) is used to calculates the flow field and the Lowson's method is used to predict the acoustic pressures. From the results we find that the broadband noise of a circular casing centrifugal fan is due to the unsteady force fluctuation around the impeller blades related to the vortex shedding. The unsteady forces associated with the shed vortices at impeller and related to the interactions to the diffuser and the exit.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.2
• /
• pp.48-53
• /
• 2010

A computerized design system of axial fan is developed for constructing 3-D blade geometry and predicting both aerodynamic performance and noise. The aerodynamic blading design of fan is conducted by blade angle distribution, camber line determination, airfoil thickness distribution and blade element stacking along spanwise distance. The internal flow and the aerodynamic performance of designed fan are predicted by the through-flow modeling technique with flow deviation and pressure loss correlations. Based on the predicted internal flow field and performance data, fan noise is predicted by two models for discrete frequency and broadband noise sources. The present predictions of the flow distribution, the performance and the noise level of actual fans are well agreed with measurement results.