• Title/Summary/Keyword: 연료성층화

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An Investigation on the Effect of Fuel Stratification of DME/n-Butane mixture on Reduction of Pressure Rise-Rate in HCCI Combustion (DME/n-Butane 혼합 연료의 농도 성층화에 의한 HCCI엔진연소의 압력 상승률 저감에 관한 연구)

  • Lim, Ock-Taeck;Park, Kyu-Yeol
    • Journal of the Korean Institute of Gas
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    • v.15 no.3
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    • pp.39-46
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    • 2011
  • This study investigates the effects of the DME and n-Butane mixture and of the stratification on combustion characteristics of HCCI engine by chemical reaction calculation. First, the existing DME reaction scheme and n-Butane is combined to make new chemical reaction model, then validating the effectiveness of new scheme. Furthermore, this study verify the HCCI combustion characteristics according to the changes of DME and n-Butane mixture ratio, which shows different auto ignition characteristics. Finally, it confirms the effects of stratification of mixture fuel on the reduction of pressure rise rate.

Potential of Thermal Stratification and Partial Fuel Stratification for Reducing Pressure Rise Rate in HCCI Engines (HCCI 기관에 있어서의 층상 흡기를 통한 압력 상승률 저감에 대한 단위반응 수치 해석)

  • Lim, Ock-Taeck
    • Journal of the Korean Institute of Gas
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    • v.13 no.6
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    • pp.21-28
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    • 2009
  • 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.

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Numerical Analysis of Effect of Inhomogeneous Pre-mixture on Pressure Rise Rate in HCCI Engine by Using Multizone Chemical Kinetics (화학반응수치해석을 이용한 HCCI기관의 예혼합기의 성층화성이 연소시의 압력 상승률에 미치는 영향)

  • Lim, Ock-Taeck
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.5
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    • pp.449-456
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    • 2010
  • 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.

Fuel Stratification Process in a Lean Burn Internal Combustion Engine by Using Planar Laser Induced Fluorescence (PLIF를 이용한 희박연소엔진에서의 연료 성층화에 관한 연구)

  • 정경석
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.3
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    • pp.7-12
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    • 2003
  • Mixture formation in the cylinder of a lean bum engine has been observed by Laser Induced Fluorescence technique. XeCl laser (308nm) was used to produce a laser sheet. 3-pentanone has been added to iso-octane fuel to produce fluorescence, the intensity of which is proportional to the concentration of the fuel. The laser sheet was introduced through the piston window and the fuel distribution in the vertical plane was observed through a side window. Comparison has been made for the cases of selected fuel injection timing as 0, 360, 405, and 450 CA. For the case of 0 and 360 CA injection, uniform fuel distribution in the combustion chamber has been obtained at the ignition time which is favorable for the high load mode. And the late injection cases, 405 and 450 CA, revealed the stratified formation of rich mixture around the spark plug. That extends the lean misfire limit and reduces cyclic variation in the low load mode.

Study on the Effect of Thermal Stratification on DME/n-Butane HCCI Combustion (열적성층화가 DME/n-Butane 예혼합압축자기착화연소에 미치는 영향에 관한 연구)

  • Lim, Ock-Taeck
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.12
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    • pp.1035-1042
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    • 2010
  • 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.

Research about Thermal Stratification Effect on HCCI Combustion Fueled with Primary Reference Fuel (예혼합기의 열적성층화가 PRF연료의 예혼합압축자기착화에 미치는 영향)

  • Lim, Ock-Taeck
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.5
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    • pp.157-163
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    • 2008
  • 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.

Fuel stratification by multiple injection in DME HCCI engine combustion (DME 예혼합 압축착화 엔진에서 다단분사를 통한 연료 성층화)

  • Yoon, Hyeonsook;Bae, Choongsik
    • 한국연소학회:학술대회논문집
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    • 2012.11a
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    • pp.311-312
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    • 2012
  • Homogeneous charge compression ignition combustion with multiple-injection strategy using dimethyl-ether was investigated in a single cylinder direct-injection compression-ignition engine. The combustion performance and exhaust emissions were tested by varying the post injection conditions. The experiments were carried out under low load and low speed conditions. By the late post injection near the top dead center, the combustion phase was retarded and lengthened, and the fuel conversion efficiencies improved without the drawbacks of exhaust emissions increment.

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Numerical Analysis for Booster Effect in DME HCCI Engine with Fuel Stratification (연료의 불균질성을 갖는 DME HCCI엔진에서 과급의 효과에 관한 수치해석)

  • Kwon, O-Seok;Lim, Ock-Taeck
    • Transactions of the Korean Society of Automotive Engineers
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    • v.18 no.3
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    • pp.19-25
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    • 2010
  • The purpose of this study is to gain a better understanding of the effects of fuel stratification on reducing the pressure-rise rate at high load in HCCI combustion. It was found that fuel stratification offers good potential to achieve a staged combustion event and reduced pressure-rise rates. The engine is fueled with Di-Methyl Ether (DME) which has unique 2-stage heat release. Numerical analysis is conducted with single and multi-zones model and detailed chemical reaction scheme is done by chemkin and senkin. Calculation result shows that proper fuel stratification prolongs combustion duration and reduce pressure rise rate. Besides IMEP, combustion efficiency and indicated thermal efficiency keep constant. However, too wide fuel stratification increases pressure rise rate and CO and NOx emissions in exhaust gas.

Laminar Burning Velocities of Propane and Iso-Octane Fuels for Stratified Charged Combustion Modeling (성층화 혼합기 연소 모델링을 위한 프로판 및 이소옥탄 연료의 층류 화염 속도)

  • Pae, Sang-Soo;Kim, Yong-Tae;Lim, Jae-Man;Min, Kyoung-Doug
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.704-709
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    • 2000
  • Laminar burning velocities of propane- and iso-octane-air mixtures have been numerically modelled over a wide range of equivalence ratio, pressure and temperature. These correlations are applicable to the modelling of stratified charged combustion like that of lean bum and GDI engine combustion. The numerical models are based on the results calculated by PREMIX code with Sloane's detailed chemical reaction mechanism for propane and FlameMaster code with Peters' for iso-octane. Laminar burning velocity for two fuels showed a pressure and temperature dependence in the following form, in the range of $0.1{\sim}4MPa$, and $300{\sim}1000K$, respectively. $S_L={\alpha}\;{\exp}[-\xi({\phi}-{\phi}_m)^2-{\exp}\{-{\xi}({\phi}-{\phi}_m)\}-{\xi}({\phi}-{\phi}_m)]$ where ${\phi}_m=1.07$, and both of ${\alpha}$ and ${\xi}$ are functions of pressure and temperature. Compared with the results of the existing models, those of the present one showed the good agreement of the recent experiment data, especially in the range of lean and rich sides. Judging from the calculated results of the stratified charged combustion by using STAR-CD, the above modelling prove to be more suitable than the other ones.

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