DME 예혼합기를 분위기로 하는 디젤 분무의 연소에 관한 연구

임옥택(Ock Taeck LIM),노리마사 이이다(Norimasa IIDA) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

The purpose of the research is to investigate of diesel spray combustion for simultaneously reduce way NOx and PM.The pressure diesel injection were done into intermediates that are generated by very lean DME HCCI combustion using a RCM. The concentration of intermediate could not be directly measured; we estimated it by CHEMKIN calculation. DME HCCI characteristic is surveyed. Validations of the CHEMKIN calculation were confirmed pressure rise of an experiment and pressure rise of a calculation. Using a framing streak camera captured two dimensional spontaneous luminescence images from chemical species at low temperature reaction(LTR) and high temperature reaction (HTR). Also, the combustion events were observed by high-speed direct photography, the ignition and combustion were analyzed by the combustion chamber pressure profiles.

CCI엔진연소의 운전영역확장을 위한 성층화효과에 대한 연구

임옥택(Ock Taeck Lim),표영덕(Young Dug Pyo),정수진(Soo-Jin Jeong) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.41

The purpose of this study is to investigate the mechanism and potential of stratified charge for reducing PRR on HCCI combustion. The numerical calculation with multi-zones model is run to know the potential of stratified charge for reducing PRR. DME is used as a fuel. As a result, following conclusions were obtained. 1) Stratified charge makes the gas temperature difference before reaction start by the differences of initial gas temperature, equivalence ratio and EGR ratio. As a result, the PRR reduction is occurred by the difference of reaction start timing. 2) gain the PRR reduction effect of 50%, temperature difference of 20K in case of thermal stratification, equivalence ratio difference of 0.16 in case of mixing stratification, EGR ratio difference of 15% in case of EGR stratification are needed. 3) When thermal, mixing and EGR stratifications are combined, “in case of relatively rich mixture with high temperature and relatively lean mixture with low temperature” and “in case of relatively rich EGR with low temperature and relatively lean EGR with high temperature” show the greatest potential for reducing PRR.

HCCI엔진연소의 압력상승률 저감의 메카니즘에 대한 이해

임옥택(Ock Taeck Lim),정수진(Soo-Jin Jeong),표영덕(Young Dug Pyo) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11

HCCI engine is able to achieve low NOx and particulate emissions as well as high efficiency. However, its operation range is limited by the knocking at high load, which results from an excessive . To solve the knocking problem, the PRR must be reduced, and stratified charge has been suggested. It is the method to disperse the auto-ignition timing at each local gas in combustion chamber by using thermal, mixing and stratifications. The purpose of this study is to investigate the mechanism and potential of stratified charge for reducing PRR on HCCI combustion. The numerical calculation with multi-zones model is run to know the potential of stratified charge for reducing PRR. DME is used as a fuel. As a result, following conclusions were obtained. 1) Stratified charge makes the gas temperature difference before reaction start by the differences of initial gas temperature, equivalence ratio and EGR ratio. As a result, the PRR reduction is occurred by the difference of reaction start timing. 2) gain the PRR reduction effect of 50%, temperature difference of 20K in case of thermal stratification, equivalence ratio difference of 0.16 in case of mixing stratification, EGR ratio difference of 15% in case of EGR stratification are needed. 3) When thermal, mixing and EGR stratifications are combined, “in case of relatively rich mixture with high temperature and relatively lean mixture with low temperature” and “in case of relatively rich EGR with low temperature and relatively lean EGR with high temperature” show the greatest potential for reducing PRR.

CNG/Diesel 이종연료용 엔진의 성능 및 배출가스 특성에 대한 연구

임옥택(Ock Taeck Lim) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.9

CNG/diesel dual-fuel 엔진은 CNG 를 주 연료로 사용하고 소량의 디젤을 착화제로서 실린더 내에 분사한다. 본 연구에서는 기존의 디젤엔진을 커먼레일직접분사(CRDI)를 통하여 고압으로 디젤을 분사하고, 예혼합을 위하여 CNG 를 흡기포트에 분사하는 CNG/diesel dual-fuel 엔진으로 개조하였다. CNG/diesel dualfuel engine 은 기존의 디젤엔진과 동등한 수준의 토크 및 출력성능을 나타내었다. 또한, CNG 대체율은 CNG/diesel dual-fuel 엔진의 전체 운전영역에 대하여 89% 이상을 만족시켰다. Dual-fuel 엔진의 PM 배출농도는 디젤엔진보다 94% 더 낮게 나타났지만, NOx 배출농도는 더 높게 나타났다. In a CNG/diesel dual-fuel engine, CNG is used as the main fuel and a small amount of diesel is injected into the cylinder to provide ignition priming. In this study, a remodeling of the existing diesel engine into a CNG/diesel dual-fuel engine is proposed. In this engine, diesel is injected at a high pressure by common rail direct injection (CRDI) and CNG is injected at the intake port for premixing. The CNG/diesel dual-fuel engine had an equally satisfactory coordinate torque and power as the conventional diesel engine. Moreover, the CNG alternation rate is over 89% throughout the operating range of the CNG/diesel dual-fuel engine. PM emission by the dual-fuel engine is 94% lower than that by the diesel engine; however, NOx emission by the dual-fuel engine is higher than that by the diesel engine.

EVS27를 다녀와서

임옥택(Ock Taeck Lim) 한국자동차공학회 2014 오토저널 Vol.36 No.1

급속압축장치를 이용한 노말헵탄,이소옥탄 혼합연료의 HCCI 연소특성에 대한 연구

임옥택 ( Ock Taeck Lim ) 한국분무공학회 2011 한국액체미립화학회지 Vol.16 No.4

The HCCI engines have been known with high efficiency and low pollution and can be actualized as the new internal combustion engines. However, As for(??) the ignition and combustion depend strongly on the oxidation reaction of the fuel, so it is difficult to control auto-ignition timing and combustion duration. Purpose of this paper is creating the database for development of multi-dimensional simulation and investigating the influence of different molecular structure. In this research, the effect of n-heptane mole ratio in fuel (XnH) on the ignition delay from homogeneous charge compression ignition (HCCI) has been investigated experimentally. By varying the XnH, it was possible to ascertain whether or not XnH is the main resource of ignition delay. Additionally, the information on equivalence ratio for varying XnH was obtained. The tests were performed on a RCM (Rapid Compression Machine) fueled with n-heptane and iso-octane. The results showed that decreasing XnH (100, 30, 20, 10,0), the ignition delays of low temperature reaction (tL) and high temperature reaction (tH) is longer. And the temperature of reaction increases by about 30K. n-heptane partial equivalence ratio (fnH) affect on tL.and TL. When φnH was increased as a certain value, tL was decreased and TL was increased.

엔진회전속도의 변화가 HCCI엔진연소에 미치는 영향에 관한 수치해석 연구

임옥택 ( Ock Taeck Lim ) 한국액체미립화학회 2011 한국액체미립화학회지 Vol.16 No.3

In HCCI Engine, combustion is affected by change of compression speed corresponding to engine speed. The purpose of this study is to investigate the mechanism of influence of engine speed on HCCI combustion characteristics by using numerical analysis. At first, the influence of engine speed was shown. And then, in order to clarify the mechanism of influence of engine speed, results of kinetics computations were analyzed to investigate the elementary reaction path for heat release at transient temperatures by using contribution matrix. In results, as engine speed increased, in-cylinder gas temperature and pressure at ignition start increased. And ignition start timing was retarded and combustion duration was lengthened on crank angle basis. On time basis, ignition start timing was advanced and combustion duration was shortened. High engine speed showed higher robustness to change of initial temperature than low engine speed. Because of its high robustness, selecting high engine speed was efficient for keeping stable operation in real engine which include variation of initial temperature by various factors. The variation of engine speed did not change the reaction path. But, as engine speed increased, the temperature that each elementary reaction would be active became high and reaction speed quicken. Rising the in-cylinder gas temperature of combustion start was caused by these gaps of temperature.

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.

화학반응수치해석을 이용한 HCCI기관의 예혼합기의 성층화성이 연소시의 압력 상승률에 미치는 영향

임옥택(Ock Taeck Lim) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.5

HCCI 엔진은 고효율, 저공해를 실현할 수 있는 차세대 내연기관이다. 그러나 HCCI 엔진이 상용화되기 위해서는 몇 가지 문제점들이 해결되어야 한다. 그 중에서 가장 큰 문제점은 과도한 압력 상승률이 노킹을 발생시키기 때문에 운전영역이 제한되는 것이다. 이번 연구의 목적은 HCCI 엔진에서 압력상승률 저감을 위하여 온도 성층화와 농도 성층화 효과를 조사하는 것이다. 그리고 Multi-zone 모델을 이용한 화학반응 수치해석을 통하여 연소 및 배기가스 특성에 미치는 영향을 알아보았다. 수치해석에서 2 단계 열발생을 가지는 DME와 1단계 열발생을 가지는 메탄을 사용하였다. 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.

A study on ignition delay of compression ignition engine with a rapid compression expansion machine

Ock Taeck Lim(임옥택),Myung Taeck Lim(임명택) 한국자동차공학회 2017 한국자동차공학회 부문종합 학술대회 Vol.2017 No.5