Volute characteristics of centrifugal fan based on dynamic moment correction method

The multi-blade centrifugal fan features an abundance of vanes (>48) and a spiral volute. The flowability and noise characteristics of the centrifugal fan are dependent on the type-line of volute and tongue geometries at the volute exit. The aim of this research was to find a better volute type-line for fan noise reduction without compromising on the performance. First, the viscosity factors of gas were used to modify the type-line shape of the volute by introducing a dynamic moment correction coefficient; a modified volute was then obtained to match the new fan system. Next, the performance of the original fan and retrofit fan were tested. The optimization scheme was verified and the feasibility of the proposed numerical calculation technique was confirmed.

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Flow and Noise Characteristics of Centrifugal Fan in Low Pressure Environment

Processes ◽

10.3390/pr8080985 ◽

2020 ◽

Vol 8 (8) ◽

pp. 985 ◽

Cited By ~ 1

Author(s):

Xilong Zhang ◽

Yongliang Zhang ◽

Chenggang Lu

Keyword(s):

Ambient Pressure ◽

Characteristic Curve ◽

Normal Pressure ◽

Low Pressure ◽

Centrifugal Fan ◽

Working Process ◽

Fan Noise ◽

Environmental Pressure ◽

Noise Characteristics ◽

Consumption Curve

The influence of low-pressure environment on centrifugal fan’s flow and noise characteristics was studied experimentally and numerically. A testbed was established to conduct the experimental test on the performance of a centrifugal fan, and the characteristic curve and power consumption curve of the fan under different pressure were obtained. Then the simulation model of the centrifugal fan was established, which was used to simulate the working process of centrifugal fan under different negative pressures. The results showed that the total pressure and static pressure of the fan decrease with the decrease of the ambient pressure. The total and static pressures of the fan under 60 kPa pressure condition decreased by 42.3% and 38.3%, respectively, compared with those of fan under the normal pressure. The main reason for this phenomenon is that the decrease of the environmental pressure leads to the decrease of air density. Besides, with the drop of environmental pressure, the sound pressure and sound power of the fan noise decreases.

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The Influence of Geometric Parameters on F. C. Centrifugal Fan Noise

Journal of Vibration and Acoustics ◽

10.1115/1.3269425 ◽

1987 ◽

Vol 109 (3) ◽

pp. 227-234 ◽

Cited By ~ 24

Author(s):

Ken Morinushi

Keyword(s):

Low Noise ◽

Diameter Ratio ◽

Geometric Parameters ◽

Centrifugal Fan ◽

Fan Noise ◽

Noise Characteristics ◽

Centrifugal Fans ◽

Inner Diameter ◽

Optimal Values ◽

Axial Clearance

In this report, through experiments the influence of five major geometric parameters on noise and aerodynamic performance of forward curved (F.C.) centrifugal fans was studied. The parameters considered are: (1) width-inner diameter ratio of impeller, (2) axial clearance between the fan inlet nozzle and the impeller shroud plate, (3) blade-setting angle, (4) blade pitch-chord ratio, and (5) spiral extension index of the scroll. Noise characteristics were evaluated by means of the specific noise level (A-weighted) at every operating point except the surging region. The optimal values for the parameters to realize low noise are discussed. Design diagrams for low noise F.C. centrifugal fans are shown.

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Performance of the FMI cosine error correction method for the Brewer spectral UV measurements

Atmospheric Measurement Techniques ◽

10.5194/amt-11-5167-2018 ◽

2018 ◽

Vol 11 (9) ◽

pp. 5167-5180 ◽

Cited By ~ 4

Author(s):

Kaisa Lakkala ◽

Antti Arola ◽

Julian Gröbner ◽

Sergio Fabian León-Luis ◽

Alberto Redondas ◽

...

Keyword(s):

Error Correction ◽

Correction Method ◽

Uv Spectra ◽

Correction Coefficient ◽

Finnish Meteorological Institute ◽

Angular Response ◽

Error Correction Method ◽

Radiation Distribution ◽

Rapid Changes ◽

Relative Differences

Abstract. Non-ideal angular response of a spectroradiometer is a well-known error source of spectral UV measurements and for that reason instrument specific cosine error correction is applied. In this paper, the performance of the cosine error correction method of Brewer spectral UV measurements in use at the Finnish Meteorological Institute (FMI) is studied. Ideally, the correction depends on the actual sky radiation distribution, which can change even during one spectral scan due to rapid changes in cloudiness. The FMI method has been developed to take into account the changes in the ratio of direct to diffuse sky radiation and it derives a correction coefficient for each measured wavelength. Measurements of five Brewers were corrected for the cosine error and the results were compared to the reference travelling spectroradiometer (QASUME). Measurements were performed during the RBCC-E (Regional Brewer Calibration Center – Europe) X Campaign held at El Arenosillo, Huelva (37∘ N, 7∘ W), Spain, in 2015. In addition, results of site audits of FMI's Brewers in Sodankylä (67∘ N, 27∘ E) and Jokioinen (61∘ N, 24∘ E) during 2002–2014 were studied. The results show that the spectral cosine error correction varied between 4 and 14 %. After that the correction was applied to Brewer UV spectra the relative differences between the QASUME and the Brewer diminished even by 10 %. The study confirms that the method, originally developed for measurements at high latitudes, can be used at mid-latitudes as well. The method is applicable to other Brewers as far as the required input parameters, i.e. total ozone, aerosol information, albedo, instrument specific angular response and slit function are available.

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Terrain-Based Shadow Correction Method for Assessing Supraglacial Features on the Greenland Ice Sheet

Frontiers in Remote Sensing ◽

10.3389/frsen.2021.690474 ◽

2021 ◽

Vol 2 ◽

Author(s):

Sasha. Z. Leidman ◽

Åsa K. Rennermalm ◽

Richard G. Lathrop ◽

Matthew. G. Cooper

Keyword(s):

Land Surface ◽

Greenland Ice Sheet ◽

Correction Method ◽

Correction Coefficient ◽

Digital Elevation ◽

Aerial Vehicle ◽

Sediment Cover ◽

Elevation Model ◽

Uav Images ◽

Gis Software

The presence of shadows in remotely sensed images can reduce the accuracy of land surface classifications. Commonly used methods for removing shadows often use multi-spectral image analysis techniques that perform poorly for dark objects, complex geometric models, or shaded relief methods that do not account for shadows cast on adjacent terrain. Here we present a new method of removing topographic shadows using readily available GIS software. The method corrects for cast shadows, reduces the amount of over-correction, and can be performed on imagery of any spectral resolution. We demonstrate this method using imagery collected with an uncrewed aerial vehicle (UAV) over a supraglacial stream catchment in southwest Greenland. The structure-from-motion digital elevation model showed highly variable topography resulting in substantial shadowing and variable reflectance values for similar surface types. The distribution of bare ice, sediment, and water within the catchment was determined using a supervised classification scheme applied to the corrected and original UAV images. The correction resulted in an insignificant change in overall classification accuracy, however, visual inspection showed that the corrected classification more closely followed the expected distribution of classes indicating that shadow correction can aid in identification of glaciological features hidden within shadowed regions. Shadow correction also caused a substantial decrease in the areal coverage of dark sediment. Sediment cover was highly dependent on the degree of shadow correction (k coefficient), yet, for a correction coefficient optimized to maximize shadow brightness without over-exposing illuminated surfaces, terrain correction resulted in a 49% decrease in the area covered by sediment and a 29% increase in the area covered by water. Shadow correction therefore reduces the overestimation of the dark surface coverage due to shadowing and is a useful tool for investigating supraglacial processes and land cover change over a wide variety of complex terrain.

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A Numerical Study of the Blade Passing Frequency Noise of a Centrifugal Fan

Volume 12: Vibration, Acoustics and Wave Propagation ◽

10.1115/imece2012-86745 ◽

2012 ◽

Cited By ~ 1

Author(s):

Jian-Cheng Cai ◽

Da-Tong Qi ◽

Yong-Hai Zhang

Keyword(s):

Pressure Fluctuation ◽

Sound Radiation ◽

Aerodynamic Noise ◽

Sound Power ◽

Centrifugal Fan ◽

Structural Noise ◽

Tonal Noise ◽

Fan Noise ◽

Blade Passing Frequency ◽

Dipole Sources

Tonal noise constitutes the major part of the overall fan noise, especially the blade passing frequency (BPF) noise which is generally the most dominant component. This paper studies the BPF tonal noise of a centrifugal fan, including the blade noise, casing aerodynamic noise, and casing structural noise caused by the flow-induced casing vibration. Firstly, generation mechanism and propagation process of fan noise were discussed and the measured spectra of fan noise and casing vibration were presented. Secondly, a fully 3-D transient simulation of the internal flow field of the centrifugal fan was carried out by the computational fluid dynamics (CFD) approach. The results revealed that the flow interactions between the impeller and the volute casing caused periodic pressure fluctuations on the solid walls of the impeller and casing. This pressure fluctuation induces aerodynamic noise radiation as dipole sources, as well as structural vibration as force excitations. Thirdly, using the acoustic analogy theory, the aeroacoustic dipole sources on the casing and blade surface were extracted. The BPF casing and blade aerodynamic sound radiation were solved by the boundary element method (BEM) taking into account the scattering effect of the casing structure. Finally, the casing structural noise was studied. The casing forced vibration and sound radiation under the excitation of BPF pressure fluctuation were calculated by finite element method (FEM) and BEM, respectively. The result indicates that at the studied flow rate, the sound power levels of the casing aerodynamic noise, blade aerodynamic noise and casing structural noise are 103 dB, 91 dB and 79 dB with the reference sound power of 1×10−12 W, respectively.

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Active control of axial and centrifugal fan noise

10.1121/1.4799648 ◽

2013 ◽

Author(s):

Scott D. Sommerfeldt ◽

Kent L. Gee

Keyword(s):

Active Control ◽

Centrifugal Fan ◽

Fan Noise

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Discrete Frequency Noise From Lifting Fans

Journal of Engineering for Power ◽

10.1115/1.3445603 ◽

1971 ◽

Vol 93 (4) ◽

pp. 431-440

Author(s):

A. N. Abdelhamid

Keyword(s):

Sound Pressure ◽

Frequency Noise ◽

Noise Emission ◽

Aerodynamic Forces ◽

Fan Noise ◽

Unsteady Forces ◽

Discrete Frequency ◽

Unsteady Aerodynamic ◽

Noise Characteristics ◽

Good Agreement

Discrete frequency noise characteristics of a research lifting fan is investigated analytically. Based on steady aerodynamic data of the fan, unsteady aerodynamic forces acting on the rotor and stator blades were calculated using the results of previous investigators and an analysis which determines the effect of fluctuating velocity disturbance parallel to blade chord on the unsteady lift of cambered thin airfoils. The calculated unsteady forces were then used to determine the characteristics of discrete frequency noise emission from the fan. For the fan under consideration it is shown that the rotor interaction noise dominates the fan noise. Comparison between the predicted sound pressure levels and experimental observations shows good agreement. Based on the calculated detailed contributions of the different force harmonics acting on the blades to the fan noise, possible means of reducing lifting fan noise are discussed.

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Optimization of Low-Noise and Large Air Volume Blower Based on Load Characteristic

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.656-657.700 ◽

2015 ◽

Vol 656-657 ◽

pp. 700-705

Author(s):

Jian Dong Chen ◽

Bei Bei Sun

Keyword(s):

Flow Rate ◽

Low Noise ◽

Aerodynamic Noise ◽

Strong Wind ◽

Centrifugal Fan ◽

Fan Noise ◽

Load Characteristic ◽

Air Volume ◽

Actual Working ◽

Working Point

The blower is a kind of garden machinery, which blows strong wind to clean up leaves by a centrifugal fan, but it causes a loud aerodynamic noise. To compromise the contradiction between large air flow rate and low fan noise, some optimizations are proposed to reduce fan noise without lowering its air volume. In this paper, a CFD numerical model to compute airflow field of blower is established, where the centrifugal fan is simulated by the MRF model, and theturbulent model is selected. By smoothing the transition section, improving the volute tongue and optimizing the shape and optimizing number of fan blade, the blower work performance is increased obviously. In order to find out the actual working point, both the fan and motor load characteristic curves are drawn out. The simulation results show that, at the actual working point, the speed of the centrifugal fan is reduced, while the flow rate of blower is raised up. The optimizations are applied to the blower, and the experiment of the improved blower shows the flow rate is increased 5%, and the noise is reduced 2dB.

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