• The KSFM Journal of Fluid Machinery
• /
• v.13 no.6
• /
• pp.30-35
• /
• 2010

The aerodynamic performance of axial flow fans for outdoor unit of air-conditioner is investigated by numerical and experimental approaches in this study. The pressure drop and volumetric flow rate are compared each other in several different conditions and fan speeds. It is shown that the predicted fan performances are quite well matched with the experimental results. It is also shown that the curvature of the fan arc and hub height have significant influences on the flow distribution after hub. By the results of this study, it can be suggested that several ways to improve the aerodynamic performance of the axial flow fan can be found using the numerical analysis.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.6
• /
• pp.25-29
• /
• 2010

In this paper, a numerical study has been carried out to investigate the influence of silencer design variables on the performance of a jet fan. In order to achieve an optimum jet fan design and to explain the interactions between the different geometric configurations in the jet fan, three-dimensional computational fluid dynamics and the Design of Experiments method have been applied. Two geometric variables, i.e., cap size and silencer length, were employed to improve the performance of the jet fan. The objective functions of the jet fan are defined as the effective velocity and total efficiency at the operating condition. Based on the results of computational analyses, the flow characteristics were discussed. The effect of silencer with a specific roughness on the performance was also discussed.

• 유체기계공업학회:학술대회논문집
• /
• 2000.12a
• /
• pp.91-98
• /
• 2000

Developed is a computer program for the prediction of the aero-acoustic performance characteristics such as discharge pressure, efficiency, power and noise level in the basic design step of axial flow fan. The flow field and the aerodynamic performance of fan are analyzed by using the streamline curvature computing scheme with total pressure loss and flow deviation models. Fan noise is assumed to be generated due to the pressure fluctuations induced by wake vortices of fan blades and to radiate via dipole distribution. The vortex-induced fluctuating pressure on blade surface is calculated by combining thin airfoil theory and the predicted flow field data. The predicted aerodynamic performances, sound pressure level and noise directivity patterns of fan by the present computer program are favorably compared with the test data of actual fan. Furthermore, the present computer program is shown to be very useful in optimizing design variables of fan with high efficiency and low noise level and in analyzing their design sensitivities.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.11
• /
• pp.954-963
• /
• 2002

For the optimal design of an automotive blower system, effects of the scroll cut-off starting angle, the clearance between blade tip and bellmouth, and the scroll expansion angle on the performance of sirocco fan are investigated experimentally. Best performance is achieved at fan exposure ratio $\Deltae/r_c$,/TEX> =1.0, and clearance ratio $\DeltaeC/C=0.62. Flow characteristics inside sirocco fan are also studied by using LDV. Flow patterns in the inside of fan can be classified into three regions. Velocity vector has the same direction as rotational direction of fan at 0~$120^{\circ}$, toward the fan blades at 150～$180^{\circ}$, and opposite direction at 210~$330^{\circ}$. Turbulent intensity is relatively high near the cut-off edge in the scroll housing.

• Journal of KSNVE
• /
• v.6 no.5
• /
• pp.661-669
• /
• 1996

Proposed is an aero-acoustic performance prediction method of axial fan. The fan aerodynamic performance is predicted by combining pitch-averaged quasi 3-D flow analysis with pressure loss models for blade boundary layer and wake, secondary flow, endwall boundary layer and tip leakage flows. Fan noise is assumed to be radiated as dipole distribution type, and its generation is assumed to be mainly due to the vortex street shed from blade trailing edge. The fluctuating pressure and lift on the blade surface are analyzed by incorporating the wake vortex stree shed from blade trailing edge. The fluctuating pressure and lift on the blade surface are analyzed by incorporating the wake vortex street model with thin airfoil theory. The aero-acoustic performance prediction results by the present method are in good agreement with the measured results of several axial fans. With the present prediction method, parametric studies are carried out to investigate the effects of blade chord length and spacing on the efficiency and the noise level of fan. In the case of lightly loaded fan, both efficiency improvement and noise reduction can be achieved by decreasing chord length or by increasing blade specing. However, when fan is designed at highly loaded condition, the noise reduction by increasing blade spacing penalizes the attaninable efficiency of fan.

• International Journal of Fluid Machinery and Systems
• /
• v.5 no.4
• /
• pp.168-173
• /
• 2012

This paper presents a numerical investigation on the aerodynamic performance according to the application of splitter blades in an impeller of a centrifugal fan used for a refuse collection system. Numerical analysis of a centrifugal fan was carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. A validation of numerical results was conducted by comparison with experimental data for the pressure and efficiency. From analyses of the internal flow field of the reference fan, the losses by the reverse-flows were observed in the region of the blade passage. In order to reduce these losses and enhance fan performance, two splitter blades were applied evenly between the main blades, and centrifugal impellers having the different numbers of the main blades were tested with their application. Throughout the numerical analyses of the centrifugal fan with splitter blades, it was found that the reverse-flow regions in the blade passage can be reduced by controlling the main blade numbers with splitter blades. The application of splitter blades in a centrifugal fan leads to significant improvement in the overall fan performance.

• Journal of the Korean Society of Visualization
• /
• v.16 no.3
• /
• pp.52-58
• /
• 2018

In this study, an experimental facility has been built to measure the cooling performance of a piezoelectric fan. The facility is composed of a heat source made of $50{\mu}m$ Ni-Cr foil, a piezoelectric fan and a rotary fan for cooling the heat source. For two cases where the foil is vertical or horizontal, the surface temperature on the foil has been measured by an IR camera with and without cooling and the cooling performance of both fans has been analyzed. With cooling by both fans, the rotary fan lowers the surface temperature of the foil as a whole, while the piezoelectric fan lowers the surface temperature at the center of the foil locally. It is also found that the cooling effectiveness of the piezoelectric fan is higher on the horizontal foil than on the vertical foil because the natural convection interferes with the jet from the piezoelectric fan.

• Journal of Power System Engineering
• /
• v.13 no.4
• /
• pp.31-37
• /
• 2009

The purpose of this numerical study was to investigate performance characteristics for cooling tower axial fans with sweep. Performance data for the fans with various sweep angles were obtained in terms of the setting angle at a constant flow rate. Viscous flow calculations were carried out to obtain Performance data of the total pressure rise and hydraulic efficiency. A solution of the Ffowcs Williams-Hawkings equations was used to calculate the sound pressure level at three times fan diameter away from the fan. The calculated performance data well represented performance characteristics of the cooling tower axial fan. The total pressure rise and hydraulic efficiency at the same setting angle decreased with sweep angle. Sound pressure level slightly decreased for the fan with a sweep angle of 10 degree. No significant effect of the sweep geometry was found on the sound pressure level.

• Journal of Mechanical Science and Technology
• /
• v.15 no.12
• /
• pp.1728-1738
• /
• 2001

Measurements have been made in an automotive HVAC b1ower for two different centrifugal fans. This work is directed at improving the performance of a conventional forward-curved centrifugal fan for a given small blower casing. Mean velocities and pressure have been measured using a miniature five-hole probe and a pressure scanning unit connected to an online data acquisition system. First, we obtained the fan performance versus flow rates showing a significant attenuation of unstable nature achieved with the new fan rotor in the surging operation range. Second, aerodynamic characterizations were carried out by investigating the velocity and pressure fields in the casing flow passage for different fan operating conditions. The measurements stowed that performance coefficients are strongly influenced by flow characteristics at the throat region. The main flow features ware common in both fans, but improved performance is achieved with tole new fan rotor, particularly in lower flow rate legions. Based on the measured results, design improvements were carried out in an acceptable operation range, which gave considerable insight into what features of flow behavior ware most important.

• Journal of Power System Engineering
• /
• v.17 no.1
• /
• pp.58-63
• /
• 2013

The aerodynamic performance of double inlet sirocco fan is strongly dependent upon the design factors of impeller and scroll. In this paper, the change of scroll size was adopted to investigate the aerodynamic performances of double inlet sirocco fan and indoor PAC. Especially, a scroll expansion angle and a cut-off clearance ratio were considered to change the scroll size. In addition, the installation depth between double inlet sirocco fan and indoor PAC was considered. As a result, the total pressure efficiency of double inlet sirocco fan shows about 62%~73% according to the change of scroll expansion angles. Moreover, the flowrate performance of indoor PAC is the best at the condition of a scroll expansion angle of 8°, an installation depth of 15 mm and a cut-off clearance ratio of 8%.