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INVESTIGATION OF THERMAL STRATIFICATION EFFECT ON N-HEPTANE/ISO-OCTANE-AIR MIXTURE HCCI COMBUSTION
임옥택 한국자동차공학회 2013 International journal of automotive technology Vol.14 No.6
The HCCI combustion mode poses its own set of narrow engine operating by knocking. In order to solve this,inhomogeneity method of mixture and temperature is suggested. The purpose of this research is to get fundamental knowledge about the effect of thermal stratification on HCCI combustion of n-Heptane/iso-Octane-Air mixture. The temperature stratification is made by buoyancy effect in combustion chamber of RCM. The analysis items are pressure, temperature of incylinder gas and combustion duration. In addition, the structure of flames using the two dimensional chemiluminescence's images by a framing camera are analyzed. Under stratification, the LTR starting time and the HTR starting time are advanced than that of homogeneous. Further, the LTR period of homogeneous conditions became shorter than that of the stratified conditions. With the case of homogeneous condition, the luminosity duration becomes shorter than the case of stratified condition. Additionally, under stratified condition, the brightest luminosity intensity is delayed longer than at homogeneous condition.
유정에서 선체까지 선박의 액화천연가스 및 해양 연료의 비교 수명주기 평가
임옥택,윤상진 한국수소및신에너지학회 2021 한국수소 및 신에너지학회논문집 Vol.32 No.2
In this study, well to hull was obtained by life cycle assessment (LCA) and the greenhouse gases, regulated emissions, and energy use in transportation model (GREET), which is developed by Argonne National Laboratory to evaluate the environmental impact of marine liquified natural gas (LNG) and marine fuel. This study compared the environmental impact of marine LNG and marine fuels, which were caused by green house gases (GHG) emissions and energy consumption. The effect resulted from well to pump (WTP) process and pump to hull (PTH). Natural gas has the potential to generate more greenhouse gases than liquid fuels due to the amounts of leaks of the gas that were sent out the air during production and processing. Nevertheless, the results showed that the greenhouse gases produced during transportation were enough to reduce the disadvantages of PTH process. The research expects that the results will be in accordance with the environmental policy of South Korea.
EGR 성층화급기에 의한 DME HCCI 연소시의 압력 상승률 저감에 관한 연구
임옥택 한국수소및신에너지학회 2011 한국수소 및 신에너지학회논문집 Vol.22 No.6
Stratified charge has been thought as one of the ways to avoid a sharp pressure rise on HCCI combustion. The purpose of this study is to evaluate the potential of stratified charge for reducing PRR on HCCI combustion. The pre-mixture with thermal, mixing and EGR stratifications is charged in Rapid Compression Machine. After that, the pre-mixture is compressed and in that process, in-cylinder gas pressure and temperature are analyzed. Additionally numerical calculation with multi-zones modeling is run to know the potential of stratified charge for reducing PRR.
HCCI 기관에 있어서의 층상 흡기를 통한 압력 상승률 저감에 대한 단위반응 수치 해석
임옥택(Ock Taeck LIM) 한국가스학회 2009 한국가스학회지 Vol.13 No.6
본 연구의 목적은 온도 성층화와 농도 성층화의 효과가 HCCI 연소에서 압력상승률 저감과 배기가스에 어떤 영향을 미치는지 알아보는 것이다. 2단계 열발생이 생기는 디메틸에테르(Di-Methyl Ether, DME) 연료를 사용하였다. 수치계산은 멀티 존 모델과 상세 화학 반응 스킴을 이용하였다. 수치계산결과, 온도 성층화와 농도 성층화는 연소기간을 길게 하여 압력상승률을 저감시키는 것을 확인하였다. 그러나 농도 성층화의 폭이 너무 커지면 오히려 일산화탄소와 질소산화물이 증가하였으며, 연소효율은 감소하였다. 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.
급속압축장치를 이용한 HCCI기관에서 층상혼합기에 의한 압력상승률의 저감효과에 대한 연구
임옥택(Ock Taeck Lim) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
The introduction of mixture heterogeneity has been considered to be one of the ways to avoid knocking, as it reduces the pressure rise rate in HCCI Combustion. The purpose of this research was to investigate the effects of heterogeneity, in particular thermal stratification and fuel strength stratification, on HCCI Combustion fueled with DME and n-Butane. Thermal stratification is formed in the Combustion Chamber of a Rapid Compression Machine with three kinds of pre-mixture, each with different properties. The stratified charge mixture was adiabatically compressed, throughout which cylinder gas pressure and two-dimensional chemiluminescence images were measured and analyzed.
HCCI 기관에 있어서의 층상 흡기를 통한 압력 상승률 저감에 대한 연구
임옥택(Ock Taeck LIM) 한국가스학회 2010 한국가스학회지 Vol.14 No.6
본 연구에서는 자착화특성이 다른 DME와 n-Butane을 이용하여 다양한 흡기공급방식에 따른 HCCI엔진연소에서 압력상승률의 저감특성에 대하여 조사하였다. 연소실내부의 가스압력측정, 광학측정용 엔진을 이용한 화학발광법의 측정 그리고 화학반응수치계산을 통하여 연소실내부에서 각 국소부분의 연소특성을 파악하였다. 최대압력상승률은 DME와 n-Butane의 혼합 상태에 의해 결정되어진다. DME가 성층화되고 n-Butane이 균일하게 분포되진 조건에서 가장 많이 감소되는데 두 연료가 균일한 경우에 비해서 최대압력상승률은 0.25㎫/㎳ 로 저감되었고 CA50도 5deg 지각되었다. 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 0.25㎫/㎳ and it corresponds to 5deg. retarding of CA50.
소형 세라믹 리니어엔진을 이용한 RE-EV용 파워팩의 설계에 관한 연구
임옥택(Ock Taeck Lim),김남열(Nam Yuer Kim),김강출(Gang Chul Kim),김진복(Jin Bok Kim) 한국자동차공학회 2010 한국자동차공학회 지부 학술대회 논문집 Vol.2010 No.12
A current rechargeable battery for EV cannot provide high energy density and the operational durations required. In this study, we develope a linear engine and generator for portable power pack for RE-EV. To increase the efficiency and endurance, we made a piston and cylinder sleeve by ceramic materials. Efficiency is relatively high because linear engine don’t have crank mechanism compared with rotary engine. We made prototype engine and had experiments to know moving characteristic about the Linear Engine. It was possible to operate velocity at 50 ㎐ at the firing and pressure in cylinder was 16bar.
HCCI엔진연소에서 엔진회전수의 영향에 대한 수치해석연구
임옥택(Ocktaeck Lim),윤상진(Sangjin Yoon),박규열(Kyuyeol Park) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
HCCI combustion offers both high efficiencies and very low NOX and particulate emissions. However, operating range of HCCI engines is limited by an excessive pressure rise rate(PRR) during combustion in high load region which will lead engine knock. HCCI combustion is controlled by chemical reaction depending on thermal properties and fuel composition. Besides, engine speed also has significant effects on ignition timing, since it relates to the speed of compression. The engine speed is related to combustion robustness in expansion stroke because of changing expansion speed. The objective of this study is to investigate the influence of engine speed on combustion characteristics such as in-cylinder gas temperature, pressure at combustion start, combustion duration and combustion efficiency by using numerical analysis. Then, In order to investigate the mechanism of influence of engine speed, contribution matrix has been used. In results, DME which has negative temperature coefficient and methane which has not negative temperature coefficient were used as fuels.
화학반응수치해석을 이용한 HCCI기관의 예혼합기의 성층화성이 연소시의 압력 상승률에 미치는 영향
임옥택(Ocktaeck LIM),박규열(Kyuyoel Park),백영순(Youngsoon Baek),표영덕(Youngduk Pyo) 한국가스학회 2009 한국가스학회 학술대회논문집 Vol.2009 No.4
The HCCI engine is prospective internal combustion engine, which is capable of providing both high diesel-like efficiencies and very low NOx and particulate emissions. However, several technical issues must be resolved before an HCCI engine can be used as widespread application. One of issues is that its operating range is limited by an excessive pressure rise rate which is caused by excessive heat release because of its self-accelerated combustion reaction and the resulting engine knock in high-load region. The purpose of this study is to evaluate the potential of thermal and fuel stratification for reducing pressure rise rate in an HCCI engine. The concentration of NOx and CO in exhaust gas is also evaluated to confirm the combustion completeness and NOx emission. The computational work is conducted using a multi-zone code with detailed chemical kinetics, including the effects of thermal and fuel stratification on the onset of ignition and the rate of combustion.