• 한국분무공학회지
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• 제17권2호
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• pp.77-85
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• 2012

The CFD simulation of diesel spray tip penetrations were compared with 0-D simulation for experimental data obtained with common rail injection system. The simulated four injection patterns include single, pilot and split injections. The CFD simulation of the spray penetration over these injection patterns was performed using the KIVA-3V code, which was implemented with both the standard KIVA spray and original gas jet sub-models. 0-D simulation of the spray tip penetration with time-varying injection profiles was formulated based on the effective injection velocity concept as an extension of steady gas jet theory. Both the CFD simulation of the spray tip penetration with the standard KIVA spray model and 0-D simulation matched better with the experimental data than the results of the gas jet model for the entire fuel injection patterns.

• Nuclear Engineering and Technology
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• 제42권6호
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• pp.636-655
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• 2010

A thermal-hydraulic code, named CUPID, has been being developed for the realistic analysis of transient two-phase flows in nuclear reactor components. The CUPID code development was motivated from very practical needs, including the analyses of a downcomer boiling, a two-phase flow mixing in a pool, and a two-phase flow in a direct vessel injection system. The CUPID code adopts a two-fluid, three-field model for two-phase flows, and the governing equations are solved over unstructured grids with a semi-implicit two-step method. This paper presents an overview of the CUPID code development and assessment strategy. It also presents the code couplings with a system code, MARS, and, a three-dimensional reactor kinetics code, MASTER.

• Korean Chemical Engineering Research
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• 제50권2호
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• pp.264-269
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• 2012

플라스틱 제품의 다이슬라이드식 사출성형은 기존 사출공법의 부가공정을 삭제하여 제품 생산에 요구되는 비용과 시간을 현저히 줄여준다. 그러나 다이슬라이드식 사출성형은 사출제품의 백화, 수지침투, 기공, 수지넘침 등의 결함들을 해결해야한다. 본 연구에서는 사출성형의 공정파라미터들을 유한요소법과 다구치법을 사용하여 최적화하고자 한다. 사출 성형해석은 Moldflow insight 2010 코드로 해석하며 2차 사출에서는 다단 사출코드를 적용한다. 폴리프로필렌(PP)을 밀폐용기인 냉각수 보조탱크로 성형할 때 사용하는 공정파라미터들은 다구치법의 망소특성과 $L_{16}$ 직교배열을 사용한 실험계획을 통해 최적화된다. 한편 최적값은 유의수준 5% 수준의 분산분석을 통해 타당성을 검증한다. 그리고 최적화 조건에서 성형된 제품과 기존 제품의 치수정확도를 비교한 결과 치수안정성이 5% 이상 개선됨을 확인하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.444-447
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• 2008

Recently, the need of thin-walled injection molding and enhancement of its productivity is greatly increased. In this study, we designed and manufactured a injection molding system, which can mold a part with the thickness of $500{\mu}m$ and 8 cavity. And processing technique for the multi-cavity injection molding system, which is capable of mass productivity on the plastic parts, was considered. The problems of unbalance/imbalance on the molding process for the multi-cavity mold were predicted by numerical analysis using plastic injection molding commercial code. In addition, controllable system of melt front filling was introduced for a balanced filling using the mold temperature sensor on injection mold. It was shown that balanced filling with the suggested injection molding system was possible for $500{\mu}m$ plastic parts with 8 cavity layout.

• 산업기술연구
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• 제22권A호
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• pp.9-17
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• 2002

This analysis is aimed to find out how the conditions of secondary air injection affects the residence time and the turbulence energy of flue gas and flow field in a small incinerator. A commercial code, PHOENICS, is used to simulate the flow field of an Incinerator. The computational grid system is constructed in a cartesian coordinate system In this numerical experiment, an independent numerical variable is the conditions of secondary air injection and dependants are the residence time of flue gas and the mean value of turbulence energy in a primary combustion chamber. The flow field and the distribution of turbulence energy are analysed to evaluate the residence time of flue gas and the turbulence energy The computational results say that the tangential injection of secondary air make the residence time much longer than the radial injection and that the radial injection of secondary make turbulence much stronger than the tangential injection.

• 소음진동
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• 제7권6호
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• pp.909-918
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• 1997

Combustion oriented noise is a part of engine noise, which is mainly determined by the in-cylinder pressure profile and the structure attenuation of an engine. A numerical model for predicting the in-cylinder pressure profile and the resultant combustion noise developed by the use of a commercial code. The model is experimentally validated and updated based on the performance as well as the noise by considering the fuel injection timing, the fuel injection rate, Cetane number, intake temperature, and compression ratio. For providing a design guide of a fuel injector for a low combustion noise engine model, the optimal parameters of injection pressure profile, injection rate profile, and injection timing are determined, which gives the 5 dBA noise reduction.

• 한국분무공학회지
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• 제25권1호
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• pp.1-7
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• 2020

In the common rail fuel injection system, which is the core of diesel high efficiency and NO_X reduction, injection strategies such as high pressure injection of fuel, accurate injection rate control, and multistage injection are important to increase fuel atomization. In this study, the bypass type piezo injector for the electronic control based common rail injection system applied to diesel fuel vehicle was studied. In particular, the injection rate and internal fuel flow characteristics of the high-pressure injector according to the piezo stacking number and applied voltage were analyzed by theoretical numerical method. When the applied voltage changes, it is determined that additional fuel flow through the bypass compensates for the reduced valve driving force due to the change in the driving voltage.

• 산업기술연구
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• 제20권B호
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• pp.45-53
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• 2000

A numerical study is done on the thrust vector control using gaseous secondary injection in the rocket nozzle. A commercial code, PHOENICS, is used to simulate the rocket nozzle flow. A $45^{\circ}-15^{\circ}$ conical nozzle is adopted to do numerical experiments. The flow in a rocket nozzle is assumed a steady, compressible, viscous flow. The exhaust gas of the rocket motor is used as an injectant to control the thrust vector of rocket at the constant rate of secondary injection flow. The injection location which is on the wall of rocket is chosen as a primary numerical variable. Computational results say that if the injection position is too close to nozzle throat, the reflected shock occurs. On the other hand, the more mass flow rate of injection is needed to get enough side thrust when the injection position is moved too far from the throat.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2965-2970
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• 2008

Effects of split injection and oxygen-enriched air on soot emissions in a DI diesel engine were studied by the KIVA-3V code. When split injection is applied, the second injection of fuel into a cylinder results in two separate stoichiometric zones which increases soot oxidation. As a result, soot emissions are decreased with split injection. When oxygen-enriched air is applied together with split injection, higher concentration of oxygen helps secondary combustion which results in a higher temperature in the cylinder. The increased temperature promotes growth reaction of acetylene with soot but doesn't improve the acetylene formation during the second injection of fuel. As more acetylene is consumed in the growth reaction of acetylene, the net acetylene mass in the cylinder is decreased, which leads to a decrease of soot formation. With an increase of soot oxidation caused by split injection, the soot emissions are decreased significantly. However, to avoid excessive NOx emissions with increased oxygen concentration, the level of oxygen concentration should be lower than 22% in volume.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.164-173
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• 2006

In the electro-hydraulic injector for the common rail Diesel fuel injection system, the injection nozzle is being opened and closed by movement of a injector's needle which is balanced by pressure at the nozzle seat and at the needle control chamber, at the opposite end of the needle. In this study, the piezo actuator was considered as a prime movers in high pressure Diesel injector. Namely a piezo-driven Diesel injector, as a new method driven by piezoelectric energy, has been applied with a purpose to develop the analysis model of the piezo actuator to predict the dynamics characteristics of the hydraulic component(injector) by using the AMESim code. Aimed at simulating the hydraulic behavior of the piezo-driven injector, the circuit model has been developed and verified by comparison with the experimental results. As this research results, we found that the input voltage exerted on piezo stack is the dominant factor which affects on the initial needle behavior of piezo-driven injector than the hydraulic force generated by the constant injection pressure. Also we know the piezo-driven injector has more degrees of freedom in controlling the injection rate with the high pressure than a solenoid-driven injector.