• Journal of Advanced Marine Engineering and Technology
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• 제39권3호
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• pp.238-242
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• 2015

다중 효용 해수 담수화 설비에 적용되는 증기이젝터 진공장치에 대한 수치해석적 연구를 수행하였다. 본 연구의 목적은 해수 담수화 과정을 위한 증기이젝터 진공장치의 성능특성에 대한 수치적 검토를 수행하는 데에 있다. 증기이젝터 내부의 유동특성을 보다 잘 파악하고 최적의 설계를 도모하기 위하여, 노즐 사이즈 및 디퓨저 축소각의 변화와 같은 설계변수의 변화가 증기이젝터의 성능에 미치는 영향에 대해서도 논의하였다. 해석결과는 실험결과와 전반적으로 잘 일치함을 알 수 있으며, 목부에서의 shock train 현상도 잘 재현하고 있음을 알 수 있다.

• 한국압력기기공학회 논문집
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• 제11권1호
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• pp.53-60
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• 2015

This study was investigated to develop process technology of laser cladding with austenite stainless steel for Weld Inlay repair of dissimilar metal weld in reactor vessel in/outlet nozzles. Weld Inlay experiments were performed by laser cladding repair system consisting of common manipulator, laser apparatus and welding process scheduler, etc. Single pass welding experiments were conducted in order to obtain the optimum welding process parameters for filler wires of ER309L and Alloy 52M before multi-layer laser cladding. Based on the above obtained results, multi-layer laser cladding experiments were carried out, and welding qualities for weld specimens were estimated by PT, OM, SEM and EDS analysis. Consequently, it was revealed that multi-layer laser cladding on austenite stainless steel using filler wires of ER309L and Alloy 52M could be possible to meet ASME Code standard without any weld defect.

• 한국가스학회지
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• 제25권6호
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• pp.22-28
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• 2021

발전용 가스터빈에 사용되는 이중 콘형 예혼합 연소기의 성능 개선 및 검증을 위하여 기존 노즐에서 연료 분사 특성을 개선한 노즐(분사구 직경 증가, 분사구 수 감소, 총 분사면적 유지)을 이용하여 고압 및 다중화염 조건에서 실험 연구를 수행하였으며 배기가스 특성을 기존 노즐과 비교하였다. 실험 결과로는 노즐의 연료 직경을 크게 한 경우 연소용 공기로 연료의 침투 거리가 증가하기 때문에 콘 내부에서 연료와 공기의 혼합특성이 개선되어 상압뿐만 아니라 압력 상승 시 NOx 배출 농도는 감소하며 다중 화염의 경우 화염간 연소영역의 중첩이 감소하게 되어 NOx 배출은 감소하지만 화염 안정성은 저하된다. 연료 분사구를 개선한 노즐의 발전 플랜트 실증 결과는 실험 결과와 같이 기존 노즐에 비하여 NOx 농도가 낮게 배출되었다.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.613-624
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• 2013

Multi-dimensional two-phase phenomena occur in many industrial applications, particularly in a nuclear reactor during steady operation or a transient period. Appropriate modeling of complicated behavior induced by a multi-dimensional flow is important for the reactor safety analysis results. SPACE, a safety analysis code for thermal hydraulic systems which is currently being developed, was designed to have the capacity of multi-dimensional two-phase thermo-dynamic phenomena induced in the various phases of a nuclear system. To validate the performance of SPACE, a two-dimensional two-phase flow test was performed with slab geometry of the test section having a scale of $1.43m{\times}1.43m{\times}0.11m$. The test section has three inlet and three outlet nozzles on the bottom and top gap walls, respectively, and two outlet nozzles installed directly on the surface of the slab. Various kinds of two-dimensional air/water flows were simulated by selecting combinations of the inlet and outlet nozzles. In this study, two-dimensional two-phase void fraction profiles were quantified by measuring the local gap impedance at 225 points. The flow conditions cover various flow regimes by controlling the flow rate at the inlet boundary. For each selected inlet and outlet nozzle combination, the water flow rate ranged from 2 to 20 kg/s, and the air flow rate ranged from 2.0 to 20 g/s, which corresponds to 0.4 to 4 m/s and 0.2 to 2.3 m/s of the superficial liquid and gas velocities based on the inlet port area, respectively.

• 대한기계학회논문집B
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• 제26권8호
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• pp.1115-1122
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• 2002

The present experiment investigates the effects of pore density f of aluminum foam heat sinks, the jet-to-jet spacing X and the nozzle plate-to-target surface spacing H of 3$\times$3 square impinging arrays on the averaged Nusselt number. The performance of the aluminum foam heat sinks and the rectangular plate heat sink is evaluated in terms of the enhancement factor. /equation omitted/. The multiple impinging jet with X/d=4.0 displays higher Nusselt numbers than single impinging jet for 12.0$\leq$H/d$\leq$20.0. With the variation of the jet-to-jet spacing, the aluminum foam heat sink of 10 PPI show higher Nusselt numbers than the 20 and 40 PPI aluminum foam heat sinks. Further, the 10 PPI aluminum foam heat sink demonstrates 26% higher enhancement factor than the rectangular plate heat sink in the range of 7000$\leq$Re$\leq$11000.

• 한국분무공학회지
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• 제15권2호
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• pp.83-93
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• 2010

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle inside feedwater heater installed downstream of the turbine extraction stream line. At that point, the extract steam from the turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows to reverse direction after impinging the impingement baffle, the shell wall of feedwater heaters may be affected by flow-accelerated corrosion. In this paper, to compare degree of shell wall thinning mitigation rate to squared type with mitigation rate of other type baffle plate, four different types of impingement baffle plate-squared, curved, mitigating type and multi-hole type-applied inside the shell. With these comparison data, this paper describes operation of experiments and numerical analysis which is composed similar condition with real feed water heater. And flow visualization is operated for verification of experiments and numerical analysis. In conclusion, this study shows that mitigating type and multi-hole type baffle plate are more effective than other baffle plate about prevention of pressure concentration and pressure value decrease.

• 한국레이저가공학회지
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• 제2권3호
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• pp.11-18
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• 1999

This paper describes the weldability of carbon steel and stainless steel using 5㎾ $CO_2$ laser system with nearly multi-mode beam and a parabolic focusing mirror. In the laser welding of steels, major welding parameters are focal point, travel speed, beam power, shield gas and gap tolerance, etc.. Two kinds of gases(Ar, He) were used as a assist gas and supplied through the external nozzle. It is very important for optimum condition to remove plasma plume which absorbs laser beam and to obtain deep penetration and sound weld bead. Bead-on-plate welding tests were carried out for the experiments. Penetration data were obtained with various welding parameters and the effects of welding parameters were discussed. Butt welding tests were performed with various conditions. Only the optimum laser parameters assured good weld quality As a result of this study, We achieve the fundamental weldabilities using a high power $CO_2$ laser for carbon steel and stainless steel.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.881-888
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• 2017

일반적으로 다단 축류 터빈은 높은 압력비에서 유동 가속으로 인하여 특정 단에서 초킹 현상이 발생하게 된다. 초킹의 경우 유량 변화 없이 압력비만 증가하게 되며, 이러한 특성을 입구 유량 경계조건을 사용하는 일반적인 평균반경해석법을 이용하여 예측하는데 한계가 있다. 본 연구에서는 이러한 문제점을 해결하기 위해 초킹 영역에서의 성능을 예측하는 알고리즘을 재안하였다. 초킹 지점 이후에는 초킹이 발생하는 노즐 혹은 로터 출구 유동이 팽창하는 특성을 반영하여 고정된 유량 조건에서 압력비가 변할 수 있도록 알고리즘을 구성하였다. 이러한 결과를 다단 축류 터빈 전산해석 결과 및 실험결과와 비교하여 신뢰성을 확인하였다.

• 한국추진공학회지
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• 제22권2호
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• pp.20-28
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• 2018

일반적으로 다단 축류 터빈은 높은 팽창비에서 유동 가속으로 인하여 특정 단에서 초킹 현상이 발생하게 된다. 입구 유량 경계조건을 사용하는 일반적인 평균반경해석법을 사용하는 경우 유량 변화없이 팽창비만 증가하게 되는 초킹 현상을 예측하는데 한계가 있다. 본 연구에서는 이러한 문제점을 해결하기 위해 초킹 영역에서의 성능을 예측하는 알고리즘을 제안하였다. 초킹 지점 이후에는 초킹이 발생하는 노즐 혹은 로터 출구 유동이 팽창하는 특성을 반영하여 고정된 유량 조건에서 팽창비가 변할 수 있도록 알고리즘을 구성하였다. 계산된 결과를 다단 축류 터빈 전산해석 결과 및 실험결과와 비교하여 신뢰성을 확인하였다.

• 설비공학논문집
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• 제27권4호
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• pp.201-206
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• 2015

The MVR was theoretically modeled by performing the polytropic process, and the polytropic coefficient was estimated by using the performance curve provided by the manufacturers. The TVR was investigated by applying the conservation equations to the movement of fluids inside the TVR. The size of the nozzle and diffuser was determined. Theoretical MVR and TVR modeling was verified by comparing the results of the model with the available design data. Besides, the effects of multi-staging of the MVR on power consumption, and the effects of suction and primary pressure on the sizing of TVR were investigated.