http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
LPG 예혼합 압축 착화 엔진의 배기가스 및 연소 특성
염기태(Kitae Yeom),장진영(Jinyoung Jang),배충식(Choongsik Bae) 한국자동차공학회 2006 한국 자동차공학회논문집 Vol.14 No.4
This paper investigates the steady state combustion characteristics of LPG homogeneous charge compression ignition (HCCI) engine with variable valve timing (VVT) and di-methyl ether (DME) direct injection, to find out the benefits in exhaust gas emissions. VVT is one of the attractive ways to control HCCI engine. Hot internal residual gas which is controlled by VVT device, makes fuel is evaporated easily, and ignition timing is advanced. Regular gasoline and liquefied petroleum gas (LPG) were used as main fuel and di-methyl ether (DME) was used as ignition promoter in this research. Operating range and exhaust emissions were compared LPG HCCI engine with gasoline HCCI engine. Operating range of LPG HCCI engine was wider than that of gasoline HCCI engine. The start of combustion was affected by the intake valve open (IVO) timing and the λTOTAL due to the latent heat of vaporization, not like gasoline HCCI engine. At rich operation conditions, the burn duration of the LPG HCCI engine was longer than that of the gasoline HCCI engine. CAD at 20% and 90% of the mass fraction burned were also more retarded than that of the gasoline HCCI engine. And carbon dioxide (CO2) emission of LPG HCCI engine was lower than that of gasoline HCCI engine. However, carbon oxide (CO) and hydro carbon (HC) emission of LPG HCCI engine were higher than that of gasoline HCCI engine.
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 성층화 상태가 DME HCCI 연소에 미치는 영향에 관한 수치해석 연구
정동원(Dongwon Jeong),Soyol-Erdene,권오석(Oseock Kwon),임옥택(Ockteack Lim) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
It has been known from numerical analysis that HCCI combustion can be significantly affected by thermal and fuel stratification of the in-cylinder gas. With the same combustion timing (CA50), large thermal and fuel stratification tends to prolong the combustion duration and lower down the in-cylinder pressure-rise rate that make HCCI engines be operated at high load. Numerical analysis on pre-mixture having 40K thermal width with 0.15 fuelling width is presented for predicting the change of Pressure-rise rate and IMEP in four cases. Furthermore, comparing pressure traces of four cases with those of thermal stratification and fuel stratification. The fuel used, Di-Methyl-Ether (DME) which indicates two-stage auto-ignition has less cycle-to-cycle variation so that potentially can help effects of thermal and fuel stratification to expand operating range in DME HCCI engine.
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.
예혼합 기의 초기 온도 및 초기압력이 HCCI엔진연소에 미치는 영향에 관한 수치해석연구
임옥택(Ocktaek LIM),윤상진(Sangjin Yoon) 한국자동차공학회 2011 한국자동차공학회 지부 학술대회 논문집 Vol.2011 No.4
In HCCI combustion, sometimes there are two stage heat release; low temperature heat release (LTHR) and high temperature heat release (HTHR). Some experimental results clearly show pressure also is very important in determining whether we get LTHR or not. For instance, we found that if we run the engine with boosted intake pressure and low temperature, we could see LTHR but LTHR disappears if the same fuel is run with low intake pressure and high intake temperature. Thus whether you see LTHR in HCCI tests depends very much on the operating conditions. The purpose of this study is to evaluate the elementary reaction path affected by an initial Pressure and Temperature. The influence of the fuels between high octane number and low octane number fuels are also considered. For this reason, n-Heptane (PRF0) that has large heat release in LTHR and iso-Ocatne (PRF100) that has small heat release in LTHR were used as test fuels. The method of calculate the contribution of each elementary reactions and chemical species are also considered.
Multi zone Modeling 을 이용한 흡기관내의 과급이 온도성층화를 갖는 예혼합압축자기착화엔진에 미치는 영향에 관한 연구
권오석(O Seok kwon),임옥택(Ock Taeck Lim) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.4
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, a pressure rise rate is a major limitation for high load range and power reduction. Recently, we were able to reduce the pressure rise rate using thermal stratification. Nevertheless, this was insufficient to produce high power. In this study, the reduction of the pressure rise rate using thermal stratification was confirmed and the HCCI engine power was increased using the boost pressure. The rate and engine power were produced by CHEMKIN and modified SENKIN. As a result of increasing the boost pressure, a higher IMEP was attained while the pressure rise rate increased only slightly in the HCCI with thermal stratification.