• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.948-955
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• 2005

A three-dimensional computation was conducted to understand effects of the inlet boundary layer thickness on the internal flow in a low-speed axial compressor operating at the design condition($\phi=85\%$) and near stall condition($\phi=65\%$). At the design condition, the flows in the axial compressor show, independent of the inlet boundary layer thickness, similar characteristics such as the pressure distribution, size of the hub comer-stall, tip leakage flow trajectory, limiting streamlines on the blade suction surface, etc. However, as the load is increased, the hub corner-stall grows to make a large separation region at the junction of the hub and suction surface for the inlet condition with thick boundary layers at the hub and casing. Moreover, the tip leakage flow is more vortical than that observed in case of the thin inlet boundary layer and has the critical point where the trajectory of the tip leakage flow is abruptly turned into the downstream. For the inlet condition with thin boundary layers, the hub corner-stall is diminished so it is indistinguishable from the wake. The tip leakage flow leans to the leading edge more than at the design condition but has no critical point. In addition to these, the severe reverse flow, induced by both boundary layer on the blade surface and the tip leakage flow, can be found to act as the blockage of flows near the casing, resulting in heavy loss.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.10 no.4
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• pp.81-93
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• 2015

The research was conducted with awareness of cultural uniqueness in each country and similarities and universality among countries. On that account, it raised questions about the idea that social well-being can be achieved only materialistic consumption and its cultural symbolism can lead to incongruity in social hierarchy and then dysfunctions in a counter way. On the other hand, the value of well-being can be achieved by many different ways and within one's limited budget as well as material consumption. This paper provides basic information about the development of essential wellbeing products and strategies for building market segmentation in the industry. The research also provides policy makers with the direction of welfare policy in our society to establish a foundation of creating conditions for true well being. This paper will be helpful in fulfilling well-being in our whole society.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.7
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• pp.20-28
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• 2002

In this paper, the aerodynamic performance prediction of a 30kW counter-rotating (C/R) wind turbine system has been made by using the momentum theory as well as the two-dimensional quasi-steady strip theory with special care on the wake and the post-stall effects. In order to take into account the wake effects in the performance analysis, the wind tunnel test data obtained for a scaled blade are used. Both the axial and rotational inductions behind the auxiliary rotors are determined through the wake model. In addition, the optimum chord and twist distributions along the blades are obtained from the Glauert's optimum actuator disk model considering the Prandtl's tip loss effect. The performance results of the counter-rotating wind turbine system are compared with those of the conventional single rotor system and demonstrated the effectiveness of the counter-rotating wind turbine system.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.36-41
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• 2005

The aerodynamic characteristics of the oscillating airfoil(NACA0012) were measured by experimental methods by using the airfoil oscillating test rig installed at KARI 1m wind tunnel. The chord of the airfoil is 0.2m and the span is 0.75m. The lift and pitching moments were calculated by integrating the surface pressure measured by strain-gage type pressure sensors. The test condition is like this : the reduced oscillating frequency(k) < 0.1, Re ~ 820,000, Mach < 0.25. The test results were compared with the reference data published by other facilities.

• The KSFM Journal of Fluid Machinery
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• v.11 no.6
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• pp.54-63
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• 2008

A study on the flow characteristics in a 4-stage axial compressor and the behavior of rotating stall was experimentally performed at the third-stage rotor and stator rows in order to investigate its performance and instability of the compression system. The pressure losses generated due to the leakage flow at a tip clearance and a shroud seal clearance and the wake flow near the trailing edge of a blade were taken into consideration to estimate the causes of performance drop of the low speed research compressor(LSRC) in Seoul national university. In addition, the measurement of rotating stall was conducted with hot-wire probes and the existence and propagation of stall cell could be confirmed through fast Fourier transform and cross-correlation analysis.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.744-750
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• 2001

In now a days, the concern to environment and energy saving problem is increased worldly. So many countries are developing the wind power system as clean energy system. In our country, Cheju local government has the plan of the Cheju Island wind farm and 600kW class 2 wind turbines, 660kW class 2 turbines, 225kW class 1 turbine and 750kW class 2 turbines has been operated at Hangwon. In this paper the field operation data of the wind turbines was analyzed and was compared with the characteristics & performance of each turbines. As the results, we would find the possibility of wind turbine in domestic and suggest the direction of developing technology.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.1
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• pp.75-84
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• 2000

Performance and flow characteristics of a small forward swept propeller fan for home refrigerators are studied experimentally. An unusual discontinuity is observed in the performance curve of the fan. Mean flow fields measured with as-hole Pitot probe reveal that the flow is axial at the high flow rate and radial at the low flow rate. The flow structure changes abruptly across the discontinuity. Unsteady flow measurements with a set of hot-wire probes indicate that near the discontinuity a single-cell stall rotates at 40% speed of the fan speed, while away from the discontinuity the flow shows periodic variation corresponding to the blade passage frequency. Phase-lock averaged flow fields measured with a triple-sensor hot-wire probe show that there appears radially inward flow over the pressure side of the blade and the outward passage flow over the tip.

• 한국전산유체공학회:학술대회논문집
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• 2000.10a
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• pp.176-182
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• 2000

This paper presents methods for dynamic stall control utilizing an optimization approach. Unsteady aerodynamic sensitivity code is developed using a direct diffentiation method from a discrete two-dimensional unsteady compressible Navier-Stokes code including a two-equation turbulence model. Dynamic stall control is conducted by minimizing an objective function defined at an instant instead of integrating a response for a period of time. Unsteady sensitivity derivative of the objective function is calculated by the sensitivity code, and optimization is conducted using a linear line search method at every physical time level. Examples of dynamic stall control utilizing airfoils nose radius or maximum thickness variation show very satisfactory results.

• The KSFM Journal of Fluid Machinery
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• v.5 no.3 s.16
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• pp.46-53
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• 2002

This paper reports an experimental investigation on a centrifugal compressor with the adjustable inlet guide vane. The compression system is composed of a radial impeller, a vaneless diffuser, and an IGV. The results have shown that surge line on the performance map is affected by the amount of prewhirl and the prewhirl has an effect on transient region between rotating stall and surge. The surge lines have been shifted toward the lower flow region with the increased positive prewhirl and the higher flow region with the increased negative prewhirl. During the unsteady performance test, it was also found that the transient region was reduced with the increased negative prewhirl, and weak signals of rotating stall were detected just before surge as the positive prewhirl was increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.5 s.236
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• pp.639-646
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• 2005

As the internet communication is prevalent in recent years, it becomes quite possible to monitor and control some mechanical plants from the remote place through the TCP/IP communication. Such a concept is expected to be applied to many industrial systems fur easy maintenance and trouble shooting as well as various kinds of expensive test equipments fo. sharing. Synthetic jet actuate.(SJA) is a kind of high-lifting device to prevent flow separation at high angle of attack and its use for flow control has received a great amount of attention. In this research, remote control and data monitoring system for SJA wind tunnel test is implemented by TCP/IP communication with DSP as a embedded web server. From the tests performed with embedded server, it showed the possibility of reliable remote control system design utilizing the internet communication.