• 한국수소및신에너지학회논문집
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• 제27권6호
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• pp.727-736
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• 2016

Numerical simulations of n-heptane spray characteristics in a constant volume combustion chamber under diesel engine like conditions with increasing ambient gas density ($14.8-142kg/m^3$) and ambient temperature (800-1000 K) respectively were performed to understand the non-vaporizing and vaporizing spray behavior. The effect of fuel temperature (ranging 273-313 K) on spray characteristics was also simulated. In this simulation, spray modeling was implemented into ANSYS FORTE where the initial spray conditions at the nozzle exit and droplet breakups were determined through nozzle flow model and Kelvin-Helmholtz/Rayleigh-Taylor (KH-RT) model. Simulation results were compared with experimentally obtained spray tip penetration result to examine the accuracy. In case of non-vaporizing condition, simulation results show that with an increment of the magnitude of ambient gas density and pressure, the vapor penetration length, liquid penetration length and droplet mass decreases. On the other hand vapor penetration, liquid penetration and droplet mass increases with the increase of ambient temperature at the vaporizing condition. In case of lower injection pressure, vapor tip penetration and droplet mass are increased with a reduction in fuel temperature under the low ambient temperature and pressure.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.58.2-58.2
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• 2012

Heavy hydrocarbon reforming is a core technology for "Dirty energy smart". Heavy hydrocarbons are components of fossil fuels, biomass, coke oven gas and etc. Heavy hydrocarbon reforming converts the fuels into $H_2$-rich syngas. And then $H_2$-rich syngas is used for the production of electricity, synthetic fuels and petrochemicals. Energy can be used efficiently and obtained from various sources by using $H_2$-rich syngas from heavy hydrocarbon reforming. Especially, the key point of "Dirty energy smart" is using "dirty fuel" which is wasted in an inefficient way. New energy conversion laboratory of KAIST has been researched diesel reforming for solid oxide fuel cell (SOFC) as a part of "Dirty energy smart". Diesel is heavy hydrocarbon fuels which has higher carbon number than natural gas, kerosene and gasoline. Diesel reforming has difficulties due to the evaporation of fuels and coke formation. Nevertheless, diesel reforming technology is directly applied to "Dirty fuel" because diesel has the similar chemical properties with "Dirty fuel". On the other hand, SOFC has advantages on high efficiency and wasted heat recovery. Nippon oil Co. of Japan recently commercializes 700We class SOFC system using city gas. Considering the market situation, the development of diesel reformer has a great ripple effect. SOFC system can be applied to auxiliary power unit and distributed power generation. In addition, "Dirty energy smart" can be realized by applying diesel reforming technology to "Dirty fuel". As well as material developments, multidirectional approaches are required to reform heavy hydrocarbon fuels and use $H_2$-rich gas in SOFC. Gd doped ceria (CGO, $Ce_{1-x}Gd_xO_{2-y}$) has been researched for not only electrolyte materials but also catalysts supports. In addition, catalysts infiltrated electrode over porous $La_{0.8}Sr_{0.2}Ga_{0.8}Mg_{0.2}O_3-{\delta}$ and catalyst deposition at three phase boundary are being investigated to improve the performance of SOFC. On the other hand, nozzle for diesel atomization and post-reforming for light-hydrocarbons removal are examples of solving material problems in multidirectional approaches. Likewise, multidirectional approaches are necessary to realize "Dirty energy smart" like reforming "Dirty fuel" for SOFC.

• 대한기계학회논문집
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• 제18권4호
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• pp.1039-1049
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• 1994

The intermitternt and transient fuel spray have been investigated from the simultaneous measurement of droplet sizes and velocities by using Phase/Doppler Particle Analyzer(PDPA). Measurement have been done on the spray axis and at the edge of the spray near nozzle at various gas-to-liquid density ratios(.rho./sub g//.rho./sub l/) that ranges from those found in free atmospheric jets to conditions typical of diesel engines. Probability density distributions of the droplet size and velocity were obtained from raw data and mathematical probability density functions which can fit the experimental distribations were extracted using the principle of maximum likelihood. In the near nozzle region on the spray axis, droplet sizes ranged from the lower limit of the measurement system to the order of nozzle diameter for all (.rho./sub g/ /.rho./sub l/) and droplet sizes tended to be small on the spray edge. At the edge of spray, average droplet velocity peaked during needle opening and needle closing. The rms intensity is greatly incresed as the radial distance from the nozzle is increased. The probability density function which can best fit the physical breakage process such as breakup of fuel drops is exponecially decreasing log-hypebolic function with 4 parameters.

• 한국분무공학회지
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• 제9권4호
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• pp.38-45
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• 2004

This study describes the analysis results of unsteady cavitating flows behavior inside nozzle of the prototype piezo-driven injector. This piezo-driven injector has been recognised as one of the next generation diesel injector due to a higher driven efficiency than the conventional solenoid-driven injector. The three dimensional geometry model along the central cross-section regarding of one injection hole has been used to simulate the cavitating flows for injection time by at fully transient simulation with cavitation model. The cavitation model incorporates many of the fundamental physical processes assumed to take place in cavitating flows. The simulations performed were both fully transient and 'pseudo' steady state, even if under steady state boundary conditions. We could analyze the effect the pressure drop to the sudden acceleration of fuel, which is due to the fastest response of needle, on the degree of cavitation existed in piezo-driven injector nozzle

• 한국자동차공학회논문집
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• 제22권5호
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• pp.108-115
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• 2014

In this study, experimental approaching method was applied under and single-cylinder engine to research the performance of direct needle-driven piezo injector (DPI) for CR direct-injection. As key-point factor of this DPI that relies on direct-acting operating of injector needle, unlike conventional hydraulic-servo, its nozzle needle can be directly driven by piezo actuator. Thus, effect of direct-acting injection of DPI on diesel combustion and emission characteristics was investigated under common-rail single-cylinder direct-injection engine, equipped with three different driving mechanism, including indirect-acting solenoid, piezo and DPI system. As main results, it found that a direct-acting piezo injector has higher of IMEP. And it has higher heat release rate during premixed combustion and mixing controlled combustion phase due to its higher heat release, even though nitrogen oxide (NOx) formations were increased slightly.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.135-144
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• 2005

The Effects of intake swirl and combustion parameters on the performance and emission characteristics in a V8 type turbocharged intercooler D.I. diesel engine of the displacement $16.7\iota$ were studied experimentally in this paper. Generally the swirl in the combustion process of diesel engine promotes mixing of the injection fuel and the intake air. Also, TCI diesel engine is put to practically use intercooler in order to increase boost efficiency which is cooled boost air. As a result of steady flow test, when the swirl ratio is increased, the mean flow coefficient is decreased, whereas the Gulf factor is increased. And through engine test, its can be effected to meet performance and emission by optimizing the main parameters; the swirl ratio is 2.25, compression ratio is 17.5, combustion bowl is re-entrant $8.5^{\circ}$, nozzle hole diameter is $\phi0.33^{\ast}3+\phi0.35^{\ast}2$, injection timing is BTDC $12^{\circ}CA$ and turbocharger is T02 model which are compressor 0.6A/R+46trim and turbine 1.0A/R+57trim.

• 에너지공학
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• 제13권2호
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• pp.118-127
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• 2004

본 연구는 배기량이 16.7ι인 V8형 터보차져 인터쿨러 직접분사식 디젤기관에서 흡기포트의 선회유동과 연료분사계 및 과급기가 기관성능 및 배출가스특성에 미치는 영향을 실험적으로 고찰하며 성능을 개선하는데 있다. 일반적으로 기관의 출력을 높이기 위하여 과급기 및 인터쿨러를 장착하여 과급공기를 냉각시켜 과급효율을 더욱 높인 TCI디젤기관이 보편화되고 있다 본 연구의 결과로서 흡기포트의 선회비가 2.25인 경우에서 압축비 17.5, re-entrant 8.5$^{\circ}$ 형 연소실, 노즐분공경 $\Phi$0.33*3+$\Phi$0.35*2, 노즐돌출량 3.18mm, 분사시기 BTDC 12$^{\circ}$CA, 과급기 T042(압축기 0.6A/R+46Trim, 터빈 1.0A/R+57Trim)경우가 기관성능 및 NO$_{x}$ 농도의 배출특성을 고려할 때 운전영역에서 가장 우수하여 흡기포트, 분사계 및 과급기에 대한 각 인자를 적정화할 수 있었다.

• 한국해양환경ㆍ에너지학회지
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• 제7권4호
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• pp.174-179
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• 2004

현재 국내 엔진 제작사에서 주로 이용하는 NOx 저감 기술은 low NOx fuel nozzle과 연료분사시기 조정과 같든 엔진 개량방법이지만, 향후 NOx에 대한 규제가 강화될 것을 대비하여 고효율의 NOx 제거기술(EGR, Dn, SCR 등) 도입과 정책적 지원이 요구된다. 또한, THC, PM, CO 등에 대한 추가 규제가 예상되므로 기타 대기오염물질을 제거할 수 있는 DPF/CDPF DOC, HCC 등의 기술을 선박에 도입하기 위한 연구가 이루어져야 한다. 선박에서 발생하는 대기오염물질을 규제하기 위한 법률의 제ㆍ개정시에는 내륙에서 운항되는 유람선 등에 대한 규제가 동시에 이루어져야 할 것이다.

• 한국자동차공학회논문집
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• 제19권6호
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• pp.140-147
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• 2011

The injection nozzle of an electro-hydraulic injector for the common rail Diesel fuel injection system 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 slenoid actuator was considered as a prime movers in high pressure Diesel injector. Namely a solenoid-driven Diesel injector with different driving current types, as a general method driven by solenoid coil energy, has been applied with a purpose to develop the analysis model of the solenoid actuator to predict the dynamics characteristics of the hydraulic component (injector) by using the AMESim code. Aimed at simulating the hydraulic behavior of the solenoid-driven injector, the circuit model has been developed as a unified approach to mechanical modeling in this study. As this analytic results, we know the suction force and first order time lag for driving force can be endowed in solenoid-driven injector in controlling the injection rate. Also it can predict that the input current wave exerted on solenoid coil is the dominant factor which affects on the initial needle behavior of solenoid-driven injector than the hydraulic force generated by the constant injection pressure.

• 대한기계학회논문집B
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• 제35권10호
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• pp.1025-1031
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• 2011

자발화 특성은 디젤 및 PCCI 엔진의 설계에서 중요한 인자이다. 특히, 디젤분무화염은 자발화현상에 의해서 형성되어 노즐에서 부상된다. 노즐과 부상화염 사이의 영역에서 분무된 디젤의 중앙으로 주위 공기의 유입이 발생하기 때문에, 그 부상된 화염은 매연 생성에 영향을 준다. 본 연구에서 간단한 모델로써 동축류 제트를 적용하였고, 점화지연시간에 대한 자발화 과정에서 발생하는 열손실의 영향을 확인하였다. 메탄($CH_4$), 에틸렌($C_2H_4$), 에탄($C_2H_6$), 프로핀($C_3H_6$), 프로판($C_3H_8$), 및 노말 부탄(n-$C_4H_{10}$)의 연료들을 고온의 공기로 분사하였으며 자발화된 부상화염의 높이를 측정하였다. 그 결과로 자발화된 부상화염의 높이와 열손실을 고려한 점화지연시간과의 상관관계를 결정하였다.