예혼합기의 열적성층화가 PRF연료의 예혼합압축자기착화에 미치는 영향

임옥택(Ocktaeck LIM),이이다 노리마사(Norimasa IIDA) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

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 PRF -Air mixture. The temperature stratification is made by buoyancy effect in combustion chamber of RCM. The analysis items are pressure, temperature of in-cylinder 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.

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.

이차원발광화상계측에 의한 예혼합압축자기착화연소의 연소실내 혼합기의 불균질성에 관한 연구

임옥택(Ocktaeck Lim),노리마사 이이다(Norimasa Iida) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.12

HCCI엔진에는 농도성층화와 열적성층화가 존재하고, 이것들은 착화와 연소과정에 영향을 미치고 있다. 본 연구에서는 예혼합기의 불균질성이 HCCI연소과정에 미치는 영향에 대해서 조사하였다. 우선 4행정광학엔진을 이용하여 잔류가스가 있는 경우와 급속압축장치를 이용하여 잔류가스가 없는 경우의 예혼합기의 불균질성에 대하여 비교분석하였다. DME를 연료로 이용하고 프래밍카메라를 사용하여 2차원화학발광이미지를 취득하였다. 그 결과, 잔류가스가 있는 불균질 한 경우에 4행정엔진실험에서는 연소현상이 공간적으로 연소현상의 시간차이가 발생하였다. 잔류가스가 없는 급속압축장치의 실험에서는 4행정기관의 결과에 비해서 더 적은 공간적인 변화가 존재하는 것을 알 수 있었다. Fuel stratification and thermal stratification occur in the HCCI combustion chamber on a microscopic scale. They affect the ignition and combustion processes. In this study, the effect of the inhomogeneity in the mixture gas on the HCCI combustion process was investigated. Two-dimensional chemiluminescence images were captured using a framing camera to evaluate the flame structure. DME was used as the test fuel. First, the effect of inhomogeneity in the fuel distribution in the premixture was investigated for the four-stroke optically accessible engine. Then, by comparing the combustion of the homogeneous mixture in the rapid compression machine, which does not contain any residual gas, with the combustion in the four-stroke engine, the effect of inhomogeneity in temperature due to the residual gas was analyzed. The results showed that a time lag appears spatially in combustion under inhomogeneous conditions in the four-stroke engine. The spatial variation in the combustion without the residual gas in the rapid compression machine is less than that in the combustion in the four-stroke engine.

예혼합기의 열적성층화가 PRE연료의 예혼합압축자기착화에 미치는 영향

임옥택(Ocktaeck LIM),이이다 노리마사(Norimasa IIDA) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

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 PRF -Air mixture. The temperature stratification is made by buoyancy effect in combustion chamber of RCM. The analysis items are pressure, temperature of in-cylinder 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.

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.

냉시동시 압축착화 조건의 상관관계에 관한 수소 HCCI 기관의 실험적 연구

이광주,이종구,안병호,이종태 한국수소및신에너지학회 2012 한국수소 및 신에너지학회논문집 Vol.23 No.6

It was found that the pure hydrogen-air pre-mixture was self-ignited at a high compression ratio without any assisting method in room temperature, thus refuting the preconception that compression ignition of hydrogen engine was impossible. Therefore, in order to analyze the correlation of compression ignition condition at cold start with hydrogen HCCI engine clearly, the possibility of compression igniting compression ratio is investigated with the change of equivalence ratio and engine speed, experimentally. As the results, it is confirmed that the possibility of compression-igniting compression ratio at cold start was decreased by increasing equivalence ratio due to decreasing auto-ignition temperature. In addition, it is grasped that the possibility of compression-igniting compression ratio at cold start is decreased around 14.9% by increasing engine speed at same supply energy.

DME 예혼합 자기착화 연소중의 디젤분무연소에 관한 연구

임옥택(Ock Taeck LIM) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.4

The purpose of the research is to investigate of diesel spray combustion for simultaneously reduction way of NOx and PM.The 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, so we estimated it by CHEMKIN calculation. Two dimensional spontaneous luminescence images which are created by chemical species reaction at low temperature reaction (LTR) and high temperature reaction (HTR) are captured by using a framing streak camera. Also,combustion events were observed by high-speed direct photography. The ignition and combustion events were analyzed by pressure profiles and the KL values and flame temperatures were analyzed by the two-color method.

예혼합기의 열적성층화가 PRF연료의 예혼합압축자기착화에 미치는 영향

임옥택(Ocktaeck Lim) 한국자동차공학회 2008 한국 자동차공학회논문집 Vol.16 No.5

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.

급속압축 장치를 이용한 불균일 예혼합기가 HCCI연소에 미치는 영향에 관한 연구

임옥택(Ock Taeck Lim) 한국자동차공학회 2009 한국 자동차공학회논문집 Vol.17 No.3