• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.561-566
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• 2008

The reciprocating compressor is widely used in the industry field, because it has simple principle and high efficiency. In this work, in order to improve design of discharge passage line in hydrogen compression system Numerical analysis was conducted. General information about an internal gas flow is presented by numerical analysis approach. Relating with hydrogen compressing system, which have an important role in hydrogen energy utilization, this should be a useful tool to observe the flow quickly and clearly. Flow characteristic analysis, including velocity, pressure and turbulence kinetic energy distribution of hydrogen gas going out from the cylinder to discharge-path line are presented in this paper. Discharge-passage model is designed based on real model of hydrogen compressor. Pressure boundary conditions are applied considering the real condition of operating system. The result shows velocity, pressure and turbulent kinetic energy are not distributed uniformly along the passage of the Hydrogen system. Path line or particles tracks help to demonstrate flow characteristics inside the passage. The existence of vortices and flow direction can be precisely predicted. Based on this result, the design improvement might be done.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1436-1444
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• 2001

Stall inception in a high-speed centrifugal compressor has been examined. The main objective was to find stall precursor and to develop a reliable stall warning method. Eight equally spaced fast-response pressure transducers in the inducer detected the spatial structure of small amplitude perturbations, via spatial Fourier transform, as stall is approached. Near the stall inception point, the phase of spatial courier coefficients increased linearly with the speed of impeller relation for several impeller revolutions at all test speeds, and the spectrum at impeller frequency increased as stall is approached. These are the clear evidences that the impeller frequency participates in the stalling process.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.191-198
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• 2002

Oil-free turbo-compressor supported by compliant foil bearings which remove oil-contamination by elimination of the conventional ball bearing and oil lubrication systems is presented. Turbo-compressor makes two individual air compression with two impellers at operating speed, 39,000rpm. In this study, the rotordynamic effects caused by aerodynamic instability were investigated with variable mass flow rate. Correlation between frequencies of pressure fluctuation in two diffusers and those of excitation forces on rotor were clearly developed in aerodynamic unsteady region. Thus, these results show that it is beneficial to design high speed rotating turbomachinery considering coupling effect between aerodynamic instability and rotordynamic force.

• The KSFM Journal of Fluid Machinery
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• v.7 no.3 s.24
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• pp.23-31
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• 2004

An experimental study on the performance and instability development characteristics of a centrifugal compressor equipped with an adjustable inlet guide vane has been performed with varying guide vane angles. The test was conducted at the design speed of 20,800 rpm for 6 guide vane angles : $-30^{\circ},\;-20^{\circ},\;10^{\circ},\;0^{\circ},\;10^{\circ},\;20^{\circ},\;30^{\circ}$. Unsteady pressures were measured using high-frequency pressure transducers at the inducer to investigate the instability phenomena such as rotating stall and surge inside the compressor. From the unsteady measurements, it is found that the transient process from rotating stall to surge was mainly affected by inlet guide vane angles. The results of the present study can be applied to the instability control of the centrifugal compressors using a adjustable inlet guide vane.

• The KSFM Journal of Fluid Machinery
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• v.6 no.2 s.19
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• pp.62-69
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• 2003

An oil-free turbo-compressor supported by compliant foil bearings which remove oil-contamination by elimination of a conventional ball bearing and oil lubrication systems is presented. Turbo-compressor makes two individual air compressions with two impellers at a operating speed of 39,000 rpm. In this study, the rotordynamic effects caused by aerodynamic instability were investigated with variable mass flow rates. Correlations between frequencies of pressure fluctuation in two diffusers and those of excitation forces on rotor were clearly observed in an aerodynamic unsteady region. Thus, these results show that it is beneficial to design high-speed rotating turbomachinery by considering coupling effect between aerodynamic instability and rotordynamic force.

• The KSFM Journal of Fluid Machinery
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• v.11 no.1
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• pp.33-39
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• 2008

Hybrid power generation systems combining a solid oxide fuel cell and a gas turbine is promising due to their high efficiency. In the pressurized hybrid system, the operating condition of the gas turbine may play a critical role in designing the hybrid system. In particular, prevention of surge of the compressor can be a critical issue. The existence of fuel cell between the compressor and the turbine may cause an additional pressure loss and thus compressor operating points tend to approach the surge if the original turbine inlet temperature is pursued. In this study, bypassing some of the turbine inlet gas directly to the turbine exit side is simulated. Its effects on suppressing the surge problem and change in performance characteristics are discussed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.939-944
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• 2004

The numerical methods including the performance analysis and the noise prediction of the centrifugal compressor impeller are coupled with the optimization design skill, which consists of response surface method, statistical approach, and genetic algorithm. The flow-field Inside of a centrifugal compressor is obtained numerically by solving Wavier-Stokes equations. and then the propagating noise is estimated from the distributed surface pressure by using Ffowcs Williams-Hawkings formulation. The quadratic response surface model with D-optimal 3-level factorial experimental design points is constructed to optimize the impeller geometry for the advanced centrifugal compressor. The statistical analysis shows that the quadratic model exhibits a reasonable fitting quality resulting in the impeller blade design with high performance and low far-field noise level. The influences of selected design variables, objective functions, and constraints on the impeller performance and the impeller noise are also examined as a result of the optimization process.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.227-233
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• 2002

For the purpose of high outlet pressure, compactness and low vibration and noise, modem reciprocating air compressors are tend to have a multi-stage W-type or V-type cylinder arrangement. An effective counter weight calculation method is presented for reducing the inertia forces of the compressor. This calculation method is using the complex representation and verified its validity. A design program for the counter weight of W-type or V-type air compressor was presented to the manufacturer, A designed counter weight was attached to the W-type or V-type air compressor. Vibration test results gave us improved performance.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.533-539
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• 2004

The rotary compressor is widely used for the air conditioner because it is efficient and compact. In recent, the need for silent and efficient compressors is much stronger than the past. The new type muffler was invented to reduce noise level and to improve efficiency. The new type muffler that has two side discharge holes and dome shape represents much lower overall noise level, especially noise levels around 1kHz than the old type one that has one center discharge hole In acoustic spectra. Also it has higher air conditioner efficiency by lower oil discharging amount of a compressor than old type one that has rectangular shape and two side discharge holes. The noise reduction and efficiency improvement effects of the new type muffler were verified by tests for rotary compressors and air conditioners.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.476-481
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• 2003

In this paper, the effect of circumferential inlet distortion on performance and stall has been experimentally investigated in a high-speed centrifugal compressor, comparing distorted cases with undistorted one. The performance of compressor was slightly deteriorated by defect of inlet static pressure which is caused by the circumferential inlet distortion. As stall was fully developed the inlet distortion did not affect the number of stall cell and the propagation velocity. It also did not affect stall inception at 40,000 and 50,000 rpm. However stall occurred at the lower flow rate for distorted flow at 60,000 rpm. For 50,000 rpm a unexpected phenomenon occurred : stall occurred first and then it disappeared.