• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.67-70
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• 2010

Spandex yarn requires a twisting process during winding and unwinding processes at the textile industry. The air-twist nozzle is widely used as part of the winding and unwinding. This paper describes computational approach to design the geometry of the air-twist nozzle. The nozzle has circular yarn-channel and the air-inlet which is perpendicularly connected to the yarn-channel with yarn-loading slit. The air-inlet of the nozzle is designed while measurements of the yarn-channel are fixed. The airflow inside the air-twist nozzle is simulated by using Computational Fluid Dynamic model. The Ansys CFX was used to perform steady simulations of the airflow for the air-twisting process. The vortical structure and the airflow pattern such as velocity streamline, vorticity, velocity of the air-twist nozzle are discussed. Computational results are compared with experimental results in this paper.

• 한국수산과학회지
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• 제19권3호
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• pp.274-280
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• 1986

대, 소조기에 마산만에서 연속관측한 자료를 사용하여 만구 단면의 유속 변동특성을 구명하기 위하여 net velocity와 RMS속도의 등양선 및 순 유출입량을 계산하여 검토하였다. 최강유속은 수도 중앙과 서부의 4m 이하의 표층에서 나타나고, 최대 유입속도 24cm/sec 최대 유출속도는 15 cm/sec이다. 최강유속 시간임에도 불구하고 4m 이심에서는 유속이 약하여 $0{\sim}2cm/sec$에 불과하다. 만구 단면의 가장자리의 상층에 역류가 존재한다. net velocity는 비가 오지 않은 대조기의 경우 유출유속은 만구단면 서부에서 나타나며, 유입유속은 단면 동부에서 나타난다. 비온 직후의 소조기에는 이와 정반대로 흐른다. RMS속도의 최대 세기는 대조기에 $11.3{\sim}15.0cm/sec$, 소조기에 $7{\sim}10.3cm/sec$로서 단면 서부의 표층에 있으며, 매 조석주기마다 거의 동일위치에서 계속 존재한다. 순 통과유량은 건기에 $-39.7m^3/sec$, 우기 $-170m^3/sec$로서 유출이 탁월하다. 항유성분은 건기에는 조석잔차류가 우세하지만, 소조기의 강우시에는 밀도류가 우세한 것으로 추리된다.

• 대한환경공학회지
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• 제22권4호
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• pp.639-650
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• 2000

여과집진장치의 중요 문제점 중의 하나인 높은 압력손실을 해결하기 위해 하부유입식 원심 여과집진장치의 특성을 실험적으로 분석하는 것이 본 연구의 주목적으로, 실험은 원심 여과집진장치의 집진효율과 압력손실(특히, 여과포 압력손실) 특성을 일반 여과집진기와 비교 분석하기위해 유입유속, 유입농도 및 선회영역의 변화 등과 같은 다양한 파라메터들에 대해 수행하였다. 실험 결과, $1{\mu}m$ 이하의 서브마이크론 입자들에 대해서 접선유입식이 중앙유입식의 경우 보다 높은 집진효율을 보였으며, 총괄집진효율은 99% 이상을 나타내었다. 유입농도 $100mg/m^3$에서, 압력손실 감소율은 유입유속에 따라 large bag의 경우 15~38%인 반면, small bag의 경우 선회영역의 증가에 의해 30~48%이었다.

• 대한기계학회논문집B
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• 제29권9호
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• pp.971-978
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• 2005

Effects of inlet distorted flow on performance, stall and surge are experimentally investigated for a high-speed centrifugal compressor. Tested results for the distorted inlet flow cases are compared with the result of the undistorted one. The performance of compressor is slightly deteriorated due to the inlet distortion. The inlet distortion does not affect the number of stall cell and the propagation velocity. It also does not change stall inception flow rate. However, as the distortion increases, stall starts at the higher flow rate for low speed and at the lower flow rate for high speed. For 50,000 rpm stall occurrs as the flow rate decreases, however disappears fur the smaller flow rate. This is due to the interaction of surge and stall. After the stall and surge interact, the number of stall cell decreases.

• International Journal of Fluid Machinery and Systems
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• 제9권3호
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• pp.277-286
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• 2016

The development of heavy-duty process pumps, usually based on various design criteria, depends on the pump's application. The most important criteria are Q-H, efficiency and NPSH characteristics. Cavitation due to inlet recirculation is not often one of the design criteria, although many problems in pump operation appear because of inlet recirculation, when the operation range is from 0.5-0.8 $Q_{opt}$. The present paper shows that steady state CFD analysis of inlet recirculation can give quite good results for the design of new hydraulic shapes, which have been developed to expand operating range and to minimize the harmful influence of recirculation at part load. In this paper, the structures of inlet recirculation are presented, as well as detailed shapes of vortices between the blades for various operating regimes, axial velocity distribution at the impeller inlet, the experimental results of NPSH and efficiency characteristics of an existing and newly designed pump.

• 소음진동
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• 제8권5호
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• pp.807-813
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• 1998

Transmission loss of the simple expansion chamber with multiple inlet and outlet ports is obtained. Transfer matrices which represent the relation between the power variables(pressure and velocity) of inlets and outlets depend on the input relatons as well as the acoustic system parameters(i.e. geometry of the chamber, wall admittance, etc.). The analysis has been performed analytically, including the effects of higher order modes for the 2-inlet/1-outlet, 1-inlet/2-outlet and 2-inlet/2-outlet systems. This study yeilds that phase difference between the inlet ports can significantly increase the transmission loss in low frequency range.

• 한국유체기계학회 논문집
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• 제12권6호
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• pp.7-12
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• 2009

This paper presents a numerical study on the design of side-suction inlet geometry which is used for multi stage centrifugal pumps or inline centrifugal pumps. In order to achieve an optimum inlet geometry and to explain the interactions between the different geometric configurations, the three dimensional computational fluid dynamics and the design of experiment methods have been applied. Geometric design variables describing the cross sectional area distribution through the inlet were selected. The objective functions are defined as the non-uniformity of the velocity distribution at the passage exit which is just in front of the impeller eyes. From the 2k factorial design results, the most important design variable was found and the performance of the side suction inlet was improved compared to the base line shape.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.81.1-81.1
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• 2005

• 한국연소학회지
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• 제13권2호
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• pp.1-6
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• 2008

An experimental study of the flame response in a turbulent premixed combustor has been conducted with room temperature, atmospheric pressure inlet conditions using premixed natural gas. The fuel is premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. Therefore the observed flame response is only the result of the imposed velocity fluctuations, which are produced using a variable speed siren. Measurements are made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results are analyzed to determine the phase and gain of the flame transfer function as a function of the modulation frequency. Of particular interest is the effect of flame structure on the flame response predictions and measurements. The results show that both the gain and the phase of flame transfer function are closely associated with the flame length and structure, which is dependent upon the upstream flow perturbation as well as equivalence ratio in the current study.