• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.66-69
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• 2009

New design configurations were developed based on the closed ventilation type igloo nozzle in contrast to the conventional open distribution type. To validate the enhanced performance, the prediction of the exhaust flow patterns of the igloo diffuser was carried out by both experimental and computational simulations. CFD provided detailed parametric studies that significantly reduced the amount of experimentation necessary to alter the design of existing the F-15K igloo exhaust diffuser.

• The KSFM Journal of Fluid Machinery
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• v.15 no.2
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• pp.45-50
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• 2012

The flow characteristics in a vaneless diffuser with a backswept radial impeller have been experimentally investigated according to the variation of discharge flow rate. Particle image velocimetry(PIV) system was applied to measure velocity fields with several operating conditions and on some diffuser horizontal planes. Pressure transducers were installed on hub wall of the diffuser in order to analyze the pressure fluctuations and their corresponding velocity fields. The results show that the location of the main flow center moves from the hub to the shroud side as the flow rate decreases, and the reverse flow is locally generated on the hub side.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.142-148
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• 1998

Recently for the impressive gains of performance and efficiency over vaneless diffuser with apparently little or no loss in flow range, the use of LSVD(Low Solidity Vaned Diffuser) is well recommended. The experiments on the effect of the vane turning angle variation(positive, negative, zero) with other design parameters fixed on the performance and flow range were carried out. Diffuser with zero turning angle has the best characteristics in terms of performance and efficiency and The FFT results show the different frequency characteristics due to the vane turning angle in low flow range.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.110-113
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• 2005

This paper presents flow regime maps of two-dimensional, planar diffusers with constant-area ducts at very low Reynolds numbers. They are obtained from numerical calculations using the commercial CFD program CFD-ACE+. The Reynolds numbers considered are 63, 105, and 210. For each Reynolds number, a wide range of geometric parameters of dimensionless diffuser length, which is a ratio of diffuser length to throat width, $1 and divergence half angle $1^{\circ}<\phi<50^{\circ}$ are selected to obtain steady-state solutions. These maps can be served as a guideline to designers for very low Reynolds number diffuser flows.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.300-303
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• 2008

The stratification effect was investigated with four different types of diffuser shape in a thermal storage tank. For this study, experimental facility was constructed, which was composed of experimental thermal storage tank, hot and cold water storage tanks, boiler, chiller, data acquisition system, etc.. Visualization and lab scale experimental result showed that radial curved type diffuser was the highest degree of stratification among the four diffuser shapes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.344-352
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• 2006

Evacuation performance, starting transient, and plume blowback at diffuser breakdown of a straight cylindrical supersonic exhaust diffuser with no externally supplied secondary flow are investigated. Pressure records in the transitional periods are measured by a small-scale cold-gas simulator. Flow-fields evolving in the diffuser-type ejector are solved by preconditioned Favre-averaged Navier-Stokes equations with a low-Reynolds number $k-{\varepsilon}$ turbulence model edited for turbulence compressibility effects. The present RANS method is properly validated with measured static wall pressure distributions and evacuation level at steady operation as well as the pressure records during the transition regime.

• The KSFM Journal of Fluid Machinery
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• v.4 no.3 s.12
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• pp.21-28
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• 2001

The effects of diffuser shapes on the flowfields of a small-size turbo-compressor have been investigated numerically and experimentally. The optimal design of elements shapes is important to develop the high efficiency turbo-compressor. Typical range of rotating speed for a small-size turbo-compressor is 40,000-70,000rpm. Numerical analyses were conducted to the rectangular and conical shapes of diffuser Three-dimensional, steady and viscous governing equations were solved by SIMPLE algorithm. To confirm the numerical results, the experimental measurements for the static pressure and temperature at the inlet and outlet boundaries were performed. Comparisons of these results were done, and the reasonable agreements were acquired.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.91-98
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• 2001

As the second part of the author's study, off-design behavior of the design and performance parameters in the low-solidity cascade diffuser in a centrifugal compressor is investigated. The experimental flange-to-flange compressor map serves the validity of application of the present CFD work to the detailed investigation of the low-solidity cascade diffuser. Some meanline design and performance parameters as well as three-dimensional internal secondary flow fields are studied when the flow rate is changed from deep choke to stall.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.211-218
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• 2000

Off-design experimental performance was investigated for a small centrifugal compressor, whose impeller diameter is about 125mm, used in an industrial gas turbine. Test rig was designed and manufactured with a radial inflow turbine and a combustor to supply driving power to the compressor. Static pressure was measured on the casing of the impeller, vaneless diffuser, vaned diffuser and volute. Total pressure was obtained using specially fabricated rakes at the vaned diffuser throat and exit. Circumferential nonuniformity was found, near surge, in the Impeller, vaned diffuser and volute region. Spanwise nonuniform flow from the impeller affected the total pressure defects in the vaned diffuser region. Static pressure distortion in the circumferential direction in the volute was found near surge, where the minimum occurred near 140 degree position.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.645-645
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• 2009

In many practical applications of the centrifugal fan, the impeller-diffuser interaction noise is considered as a main source of fan noise. The housing for an electric motor is also expected to play an important role on noise propagation because of its complicated configuration. This study investigates the impeller-diffuser interaction noise and its sources by computing three-dimensional, incompressible flow field of the centrifugal fan in motor housing. The effect of motor case on fan noise characteristic is then investigated using the Brinkman penalization method, while the noise source associated with impeller-diffuser interaction is mathematically modeled. It is found that the present methodology combined with mathematical description of noise source provides a fairly good agreement with the experimental results, indicating that the motor housing has significant effect on noise characteristics. Finally, aeroacoustic noise prediction for various impeller-diffuser blade count ratios is conducted for noise reduction.