• Journal of Navigation and Port Research
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• v.31 no.6
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• pp.485-490
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• 2007

The purpose in having a control rod on a buoy system is to control the motion of it. The system may be composed entirely of a single circular cylinder and a long mooring anchor cable. A control rod has one function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of the effects of mutual interference. then determine the stability characteristics of the body. In this paper, the study of control-rod-attached buoy's 2-dimensional section was accomplished. model tests and numerical simulations had been carried out with different diameters of control rods. and varying the Reynolds number $Re=5,000{\sim}25,000$ based on the cylinder diameter(D=50mm) to predict the performance of the body and the 2 frame particle tracking method Iud been used to obtain the velocity distribution in the flow field. 50mm circular cylinder Iud been used during the whole experiments and measured results had been compared with each other.

• Journal of Power System Engineering
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• v.14 no.2
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• pp.16-21
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• 2010

분사된 연료의 미립화(atomization), 증발(evaporation), 그리고 혼합기형성과정(mixture formation process)이 디젤엔진의 착화 및 연소특성에 영향을 미치기 때문에, 디젤엔진 내에 분사된 연료의 구조해석으로부터 일련의 과정, 즉 고압분사, 분열(breakup), 미립화, 그리고 주위기체의 난류 도입(entrainment)에 관한 연구$^{1-3)}$는 꾸준히 행해져왔다. 본 연구는 증발디젤분무의 구조해석으로부터 디젤충돌분무의 혼합기형성과정을 조사한다. 주위기체의 밀도는 실험변수로서 선택하였고, $5.0kg/m^3$에서 $12.3kg/m^3$까지 변화시켰다. 그리고 소형고속디젤엔진에 있어서 연료분사초기의 상태의 고온 고압 설정이 가능한 정적용기를 사용했다. 주위 온도와 연료분사압력은 각각 700K 및 72MPa로 일정하게 유지했다. 충동증발분무의 액상과 기상의 이미지는 엑시플렉스형광법으로 동시 계측하였다. 실험결과로서 주위기체의 밀도가 높을수록 충돌분무의 선단도 달거리가 주위기체의 항력으로 인하여 감소하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.85-93
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• 2003

Droplet vaporization at various ambient pressures is studied numerically by formulating one dimensional evaporation model in the mixture of hydrocarbon fuel and air. The ambient pressure ranged from atmospheric conditions to the supercritical conditions. The modified Soave-Redlich-Kwong state equation is used to account for the real gas effects in the high pressure condition. Non-ideal thermodynamic and transport properties at near critical and supercritical conditions are considered. Some computational results are compared with Sato's experimental data for the validation of calculations. The comparison between predictions and experiments showed quite a good agreement. The droplet lifetime increases with increasing pressure at temperature lower than the critical temperature, however, it decreases with increasing pressure at temperature higher than the critical temperature. The solubility of nitrogen can not be neglected in the high pressure and it becomes higher as the temperature and the pressure go up.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.7
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• pp.97-104
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• 2006

The spray and breakup characteristics of swirling liquid sheet were investigated by measuring the spray angle and breakup length as the axial Weber number Wel was increased up to 1554 and the ambient gas pressure up to 4.0MPa. As Wel and ambient gas density increased, the disturbances on the annular liquid sheet surface were amplified by the increase of the aerodynamic forces, and thus the liquid sheet disintegrated near from the injector exit. The measured spray angles according to the ambient gas density were different before and after the sheet breaks. Before the liquid sheet breaks, the spray angle was almost constant, but once the liquid sheet started to breakup, the spray angle decreased. And the breakup length decreased because of the increase of the aerodynamic force as the ambient gas density and Wel increased. Lastly, the measured breakup length according to the ambient gas density and Wel was compared with the result by the linear instability theory. We found that the corrected linear instability theory considering the attenuation of sheet thickness agrees well with our experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2075-2080
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• 2013

A Coolant core for Range Extender engine has been developed using CFD technique. Coolant by-pass has been added to the improved model to reduce temperature near and between exhaust valve. Due to the increased coolant flow-rate both around the second cylinder block and between exhaust valves, improved model shows no significant stagnant flow compared with base model. Finally, the improved model shows improved heat transfer coefficients near exhaust valves, and 5% reduced pressure-drop through the coolant core. Reduced pressure-drop may increase the fuel efficiency by reducing the load of a coolant pump.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.5
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• pp.66-71
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• 2011

The spray distribution at high pressure condition was measured by the Tomography method. The constructed spray distribution was compared with the images by Indirect Photography method so that the spray size confirmed and took the boundary of the distribution. It confirmed that the Tomography applies to construct the distribution at high pressure.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.60-68
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• 1996

디젤 엔진의 분사연료를 연소실 내부에 마련된 작은 돌출부에 충돌시켜 액적을 작게 부수고 연료가 연소실 내부에 고루 분포할 수 있도록 하여 여러 가 지 엔진성능향상을 도모한 새로운 디젤 연소실 시스템이 최근 제시되고 있다. 이들 시스템은 피스톤 내부 혹은 엔진헤드 부위에 분사연료 충돌부를 두고 있는데, 여기에서는 이 새로운 시스템 개발에 있어 고려되어야 할 몇 가지 중요 요인들에 중점을 두어 분석하였다. 결과로서 분사압력, 사노즐크기, 주위공기 온도와 압력의 변화가 분무 평균입경과 분무연료의 분포에 미치는 영향을 제시하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.597-600
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• 2010

Cold flow injection test was conducted to investigate the characteristics of cryogenic liquid nitrogen jet at sub to supercritical condition. Single jet injector element was installed in high pressure chamber to investigate the effect of ambient pressure around the jet, injector geometry and flow conditions. Experimental results showed obvious differences between jet characteristics under subcritical and supercritical condition. Effect of injector inlet shape also was investigated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.39-44
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• 2011

This study constructed the spray distribution by the Tomography method at high pressure condition. The constructed spray distribution was compared with the images by Indirect Photography method so that the spray size was confirmed and took the boundary of the distribution. It was confirmed that the Tomography applies to construct the distribution at high pressure.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.21-24
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• 2006

공동 현상은 난류와 이상 유동으로 인해 그 해석에 어려움이 따르게 된다. 따라서 본 연구에서는 Pressure based 알고리즘을 이상 유동 포착 기법 중, volume fraction모델에 Kunz의 공동 현상 모델을 이용, 공동 현상을 해석할 수 있는 코드를 개발하였다. 이를 통해 2차원의 수중익 주위의 정상유동 해석을 통하여 수중익 주위의 압력 분포를 비교, 코드의 검증을 마쳤다. 또한 2차원 수중익 주위의 비정상 해석을 통해 재진입 영역의 발달에 따른 공동의 생성 및 붕괴를 모사하여 실험 결과와 비교하였다.