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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.
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.
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.
열적성층화가 DME/n-Butane 예혼합압축자기착화연소에 미치는 영향에 관한 연구
임옥택(Ocktaeck Lim) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.12
HCCI 엔진연소에서 열적성층화 효과는 노킹을 회피하는 수단으로서 생각되고 있다. 본 연구에서는 DME 와 n-Butane 을 연료로 하는 HCCI 엔진연소의 열적성층화 효과를 조사하였다. 예혼합기가 연소실내부에 투입되고 부력의 효과를 이용하여 연소실 내부에 열적성층화를 형성한다. 그 뒤에 피스톤의 압축에 의해서 단열압축 시킨 후 연소실압력과 2 차원화학발광법을 계측하여 해석하였다. 열적성층화가 존재하는 경우에는, 저온산화반응과 고온산화반응의 시작시기가 균질한 경우에 비해서 진각되었고 연소기간은 길어졌다. 발광의 시작은 온도가 높은 곳에서부터 시작하여 온도가 낮은 곳으로 전파 되는 것을 확인하였고 발광기간도 길어짐을 확인하였다. The thermal stratification effect has been thought as one of the way to avoid dramatically generating the heat from HCCI combustion. We investigate the effect of thermal stratification on HCCI combustion fueled by DME and n-Butane. The thermal stratification occurs in a combustion chamber of a rapid compression machine with premixture by buoyancy effect that is made of fuel and air. The premixture is then adiabatically compressed, and during the process, the in-cylinder gas pressure is measured and two-dimensional chemiluminescence images are prepared and analyzed. Under the thermal stratification, the LTR starting time and the HTR starting time are advanced than that of homogeneous case. Further, the LTR period and the luminosity duration under homogeneous conditions are shorter than the corresponding quantities under stratified conditions. Additionally, under stratified conditions, the brightest luminosity intensity is delayed longer than that of homogeneous condition.
DME/Diesel 듀얼 퓨얼 엔진의 연소 및 배출특성에 관한 연구
임옥택(Ocktaeck Lim),박규열(Kyuyeol Park),표영덕(Youngduck Pyo),이영재(Youngjae Lee) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Nowadays we are more concerned about emissions that are harmful in our environment, so at once an increasing of importance to think about clean diesel. One of the alternative technologies covers in this study that is preceded by dual-fuel combustion which is controlling combustion by using two fuels with different auto-ignition values. For dual-fuel combustion, here used two fuels such as DME and diesel. Both of them have different characteristics of evaporation and auto-Ignition. In the current work, we focus on understanding the characteristic of combustion and emissions under single cylinder engine and ignition is done by compression ignition. Pre-mixture is formed by injecting low-pressure DME into an intake manifold and high-pressure fuel (diesel or DME) is injected directly into the cylinder. Both direct diesel injection and port fuel injection reduced the significant amount of Soot, CO and NOx in the homogeneous charge compression ignition engine due to present of oxygen in DME as well having diesel engine like thermal efficiency. In addition, when direct DME injecting in cylinder with port DME injection, there is no changes in emissions and energy consumption rate even causing homogeneous charge compression ignition.