• Journal of the Korean Institute of Gas
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• v.24 no.1
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• pp.23-32
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• 2020

It is not easy to fully fuel high pressure(70 MPa) hydrogen in a hydrogen vehicle tank quickly. This is because the temperature inside the tank rises rapidly due to heat caused by the Joule-Thomson effect, etc. So fueling protocols such as SAE J2601 in the U.S. and JPEC-S 0003 in Japan appeared. However, there is a problem with these protocols that a number assumption are introduced and the content is too complex and limited in scope. This study was conducted to develop a new protocol based on complete real-time communication. In this study, the hydrogen fueling simulation program were used to examine how the pressure ramp rate affects the temperature and pressure rise in the tank and the fueling flow rate. The results confirmed that the first parameter to be considered in determining the pressure ramp rate is the temperature of the tank.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.449-456
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• 2010

The HCCI engine is a prospective internal combustion engine with which high diesel-like efficiencies and very low NOx and particulate emissions can be achieved. However, several technical issues must be resolved before HCCI engines can be used for different applications. One of the issues concerning the HCCI engine is that the operating range of this engine is limited by the rapid pressure rise caused by the release of excessive heat. This heat release is because of the self-accelerated combustion reaction occurring in the engine and the resulting engine knock in the high-load region. The purpose of this study is to evaluate the role of thermal stratification and fuel stratification in reducing the pressure rise rate in an HCCI engine. The concentrations of NOx and CO in the exhaust gas are also evaluated to confirm combustion completeness and NOx emission. The computation is carried out with the help of a multizone code, by using the information on the detailed chemical kinetics and the effect of thermal and fuel stratification on the onset of ignition and rate of combustion. The engine is fueled with dimethyl ether (DME), which allows heat release to occur in two stages, as opposed to methane, which allows for heat release in a single stage.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.3
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• pp.60-66
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• 2006

Notable are the burning rate characteristics of solid propellant burning at extremely high pressure(10000-20000 psia). The burning rate test using closed bomb shows the discontinuous increment around 4000 psia so that the exponent of burning rate(n) is almost double, from 0.4 to 0.8. The pressure-increasing rate of the test motor is about 300 times as high as that of the motor operating at the conventional pressure, less than 2000 psia, is, therefor the burning rate is augmented about 5-50 times. The performance prediction reflecting the pressure-change-rate effect are fairly comparable with the test data at various test conditions.

• Journal of the Korean Institute of Gas
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• v.13 no.6
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• pp.21-28
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• 2009

The purpose of this study is to gain a better understanding of the effects of thermal stratification and partial fuel stratification on reducing the pressure-rise rate and emission in HCCI combustion. The engine is fueled with Di-Methyl Ether(DME) which has unique 2-stage heat release. Computational work is conducted with multi-zones model and detailed chemical reaction scheme. Calculation result shows that wider thermal stratification and partial fuel stratification prolong combustion duration and reduce pressure rise rate. But too wide partial fuel stratification increases CO and NOx concentration in exhaust gas, and decreases combustion efficiency.

• The Optical Journal
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• s.173
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• pp.38-44
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• 2019

올해 국내 실물경기는 수출 증가세가 점차 둔화되고, 내수도 소비의 둔화와 투자의 감소 전환 등의 영 향으로 완연한 하락세를 보였다. 내수는 설비투자와 건설투자가 크게 감소하면서 급속한 조정 양상을 보이고 있으며, 소비도 연 2%대 증가율로 떨어지면서 둔화세를 기록하고 있다. 수출은 물량의 증가세가 유지되고 있으나, 단가는 기저효과로 인한 유가상승 폭의 축소 등의 영향으로 상승률이 떨어지면서 증가세가 둔화되었다. 2019년 세계경제는 선진권의 경기둔화와 개도권의 성장률 정체가 예상되는 가운데 하방 리스크 요인으로 인해 제한적 성장이 예상된다. 선진권은 미국경제의 성장률 하락이 예상되는 한편, 일본과 유로권도 전년보다는 약간 낮은 성장률이, 중국은 연 6%대 초반까지 성장률 하락이 예상된다. 국제유가는 글로벌 경기 둔화에 따른 원유의 수요 감소와 미 달러화의 가치 상승 등 금융 요인이 하방 압력으로 작용하나, OPEC의 감산 지속과 지정학적 불안정성이 상승 요인으로 작용하면서 연평균 보합이 예상된다. 환율은 미 달러화의 강세기조가 2019년 상반기까지 이어질 것으로 예상되지만, 하반기에는 유럽 등지의 통화긴축 전환과 미국경기 둔화 등의 영향으로 달러화가 약세로 전환하면서 연평균 기준 소폭 상승할 것으로 기대된다. 2019년 국내경제는 수출과 투자가 글로벌 경기 둔화 등의 영향으로 소폭 증가에 그치고, 소비가 전년대비 둔화세를 보이면서 2018년보다 약간 낮은 2.6%의 성장률이 예상된다. 소비는 실질소득 감소와 고용 부진 등이 예상되고, 대외 불확실성으로 인한 체감경기 약화로 증가세가 둔화되나, 보건 복지 고용의 지출 확대, 유류세 인하 등 정부 정책은 실질구매력 제고에 긍정적 요인으로 작용할 전망이다. 설비투자는 대외 불확실성과 대내 구조적 취약성 등의 영향으로 인해 제한적인 증가세가 예상되며, 건설투자도 정부의 부동산시장 안정화 대책과 SOC예산 감축 등의 영향으로 감소세가 이어질 전망이다. 수출은 세계경기의 성장세 둔화로 인해 수출물량이 소폭 증가에 그치고, 반도체의 가격 하락과 국제유가의 횡보 전망 등으로 수출단가도 하락 압력이 커지면서 2018년 보다 낮은 3.7%의 증가율이 예상된다.

• Journal of the Korean Institute of Gas
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• v.14 no.6
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• pp.7-14
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• 2010

This study investigated the effect on reducing the pressure rise rate(PRR) in HCCI Engine by the variation of mixing ratio in the pre-mixture of DME and n-Butane that has different auto-ignition characteristics. In addition to measure of gas pressure in the engine cylinder, chemiluminescence image using the optical accessible engine and numerical analysis with multi-zones model were used to assess the combustion at each local area in the combustion chamber. The maximum PRR changes depending on mixing condition of DME and n-Butane. When DME is stratified and n-Butane is distributed uniformly, maximum PRR becomes lowest which is about 0.25MPa/ms and it corresponds to 5deg. retarding of CA50.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1433-1438
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• 2009

The purpose of this study is to investigate how the ignition spark timing conversion influences the engine performance of LPG/Gasoline Bi-Fuel engine. We propose the control system which can advance the ignition spark timing in LPG fuel mode more than used in gasoline fuel mode. In order to investigate the engine performance during combustion, engine performance are sampled by data acquisition system, for example cylinder pressure, pressure rise rate and heat release rate, while change of the rpm(1500, 2000) and the ignition timing advance($5^{\circ}$,$10^{\circ}$,$15^{\circ}$,$20^{\circ}$) As the result, between 1500rpm and 2000rpm, the cylinder pressure and pressure rise rate was increased when the spark ignition was advanced but pressure rise rate at $20^{\circ}$was smaller value. Also, the heat release rate at 1500rpm was increased but it was lower around $20^{\circ}$at 2000rpm.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.4
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• pp.32-39
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• 2009

The HCCI engine is a next generation engine, with high efficiency and low emissions. The engine may be an alternative to SI and DI engines; however, HCCI's operating range is limited by an excessive rate of pressure rise during combustion and the resulting engine knock in high-load. The purpose of this study was to gain a understanding of the effect of only initial temperature and thermal stratification for reducing the pressure-rise rate in HCCI combustion. And we confirmed characteristics of combustion, knocking and emissions. The engine was fueled with Di-Methyl Ether. The computations were conducted using both a single-zone model and a multi-zone model by CHEMKIN and modified SENKIN.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.2
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• pp.1-7
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• 2003

This paper proposes a method to detect misfired cylinders by the exhaust pressure ascent rate. The misfire is generated by faults of electric system or faults of fuel delivery system. It is one of the abnormal combustions. Therefore, it increases the unburned hydrocarbon and the carbon monoxide and affects a bad influence to the 3-way catalyst. The misfire causes to decrease the power of the engine and increase the consumption of the fuel. Early detection and correction of the misfired cylinders can prevent these unusual phenomena. The misfired cylinders can be detected by the comparison of exhaust pressure ascent rate during each cycle. The exhaust pressure ascent rate is defined as pressure rise per time. Our experimental results showed that the proposed method is effective in the detection of the misfired cylinders on a gasoline engine regardless loads and revolutions of the engine.

• Journal of the Korean Institute of Gas
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• v.15 no.3
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• pp.39-46
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• 2011

This study investigates the effects of the DME and n-Butane mixture and of the stratification on combustion characteristics of HCCI engine by chemical reaction calculation. First, the existing DME reaction scheme and n-Butane is combined to make new chemical reaction model, then validating the effectiveness of new scheme. Furthermore, this study verify the HCCI combustion characteristics according to the changes of DME and n-Butane mixture ratio, which shows different auto ignition characteristics. Finally, it confirms the effects of stratification of mixture fuel on the reduction of pressure rise rate.