• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.305-307
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• 2012

This study was computationally explored how the fuel autoignition reactivity was affected by operating parameters such as fuel, pressure, intake temperatures, engine speed and EGR compositions for HCCI combustion. This is done for DME and CHEMKIN-PRO was used as a solver. At first, influence of the operating parameters and EGR compositions were showed. And then, in order to clarify the mechanism of them on autoignition reactivity, data-sets of kinetic were analyzed to investigate the elementary reaction path for heat release at transient tempeatures by using contribution matrix.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.3
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• pp.8-14
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• 2009

Effect of heterogeneity of combustion chamber has been thought as one of the way to avoid dramatically generating heat in HCCI Combustion. The purpose of this research is to investigate the effect of heterogeneity, especially thermal stratification and fuel strength stratification on HCCI Combustion fueled with DME and n-Butane. Thermal stratification is formed in Combustion Chamber of Rapid Compression Machine with 3 Kinds of pre-mixture has different properties. The stratified charge mixture is adiabatic compressed and on that process, in cylinder gas pressure and two-dimensional chemiluminescence images are measured and analyzed.

• 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.

• 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.

• Journal of ILASS-Korea
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• v.11 no.3
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• pp.140-146
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• 2006

The objective of this work is to analyze the atomization and evaporation characteristics of dimethyl ether(DME) fuel for the application of HCCI diesel engine. In order to investigate the spray behavior of DME fuel, the macroscopic and microscopic characteristics were investigated in terms of spray development, spray tip penetration, impingement time, SMD, and axial mean velocity under the various injection timing and ambient conditions. For the illumination of spray, the spray visualization system was composed of a Nd:YAG laser and an ICCD camera and laser-sheet method was used. The atomization characteristics of DME fuel are analyzed by using phase Doppler particle analyzer (PDPA) system It was reveal that the spray development of DME is slower and rapidly disappeared as elapsed time after start of injection at the same injection duration. The impingement timing of diesel fuel was fester than that of DME fuel. The comparison of spray atomization characteristics in both fuels shows that diesel fuel has a large SMD value that DME.

• Journal of Hydrogen and New Energy
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• v.24 no.6
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• pp.573-579
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• 2013

Hydrogen engine with homogeneous charged compression ignition can achieve high efficiency by high compression ratio and rapid chemical reaction rates spatially. However, it needs to expansion of the operation range with over-all load conditions which is very narrow due to extremely high pressure rise rate. The adoption of the lean boosting in a HCCI $H_2$ engine is expected to be effective in expansion of operation range since minimum compression ratio for spontaneous ignition is decreased by low temperature combustion and increased surround in-cylinder pressure. In order to grasp its possibility by using lean boosting in the HCCI $H_2$ engine, compression ratio required for spontaneous ignition, expansion degree of the operation range and over-all engine performance are experimentally analyzed with the boosting pressure and supply energy. As the results, it is found that minimum compression ratio for spontaneous ignition is down to the compression ratio(${\varepsilon}$=19) of conventional diesel engine due to decreased self-ignition temperature, and operation range is extended to 170% in term of the equivalence ratio and 12 times in term of the supply energy than that of naturally aspirated type. Though indicated thermal efficiency is decreased by reduced compression ratio, it is over at least 46%.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.451-458
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• 2009

This experimental study was conducted to investigate macroscopic characteristics of the flash boiling spray with tow component mixing fuel. Homogeneous Charge Compression Ignition (HCCI) is a newer combustion method for internal combustion engines to reduce nitrogen oxide and particulate matter simultaneously. But it is difficult to put this combustion method to practical use in an engine because of such problems as instability of combustion in low load operating conditions and knocking in high load operating conditions. In HCCI, combustion characteristics and exhaust emissions depend on conditions of air/fuel mixture and chemical reactions of fuel molecules. The fuel design approach is achieved by mixing two components which differ in properties such as density, viscosity, volatility, ignitability and so on. We plan to apply the fuel design approach to HCCI combustion generated in a real engine, and examine the possibility of mixture formation control using the flash boiling spray. Spray characteristics of two component fuel with a flash boiling phenomenon was investigated using Shlieren and Mie scattering photography. Test fuel was injected into a constant volume vessel at ambient conditions imitated injection timing BTDC of a real engine. As a result, it was found that a flash boiling phenomenon greatly changed spray structure, especially in the conditions of lower temperature and density. Therefore, availability of mixture formation control using flash boiling spray was suggested.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.83-90
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• 2014

The main purpose of the study is to investigate the ideal manner and ratio to inject gasoline and DME simultaneously into intake port, and moreover to confirm the characteristics of combustion and emission of engine. Experimental conditions are 1200 rpm, compression ratio 8.5, intake air temperature (383 K). Internal cylinder pressure was collected to confirm the characteristics of combustion in order to calculate the heat release rate in the cylinder. In addition, HORIBA (MEXA 7100) which was possible analyzing emissions (NOx, CO, HC) was used. Vanguard gasoline engine (23HP386447) was used in this experiment. The result show that fuel design (DME-Gasoline) leads to the decrease of low temperature heat release, which is a benefit for higher-load on the HCCI engine. Also, IMEP and the indicated thermal efficiency increase with combustion-phasing retard, and these observations can be explained by considering the control of low temperature oxidation of DME.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.182-189
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• 2005

In order to investigate the effect of premixed gasoline, diesel fuel, and n-heptane charges on the combustion and exhaust emission characteristics in a direct injection (DI) diesel engine, the experimental studies are performed. The premixed fuels are injected into the premixing chamber that installed upstream of the intake port in order to minimize the inhomogeneity effect of premixed charge. The injection nozzle for directly injected fuel is equipped in the center of the combustion chamber. The air temperature control system is equipped in the intake manifold to examine the effect of air temperature. The experimental results of this study show premixing fuel is effective method to reduce the NOx and soot emissions of diesel engine. NOx emissions are linearly decreased with increasing premixed ratio for the three kinds of premixed fuels. The heating of intake air $(80^{\circ}C)$ reduced the deterioration of BSFC in high premixed ratio, because it promotes evaporation of premixed diesel droplet in the premixing chamber.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.8-14
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• 2007

Compression ignition of homogeneous charges in IC engines indicates possibilities of achieving the high efficiency of DI diesel engines with low level of NOx and particulate emissions. The objectives of this study are to further understand the characteristics of the HCCI(Homogeneous charge compression ignition) combustion and to find ways of extending the rich HCCI operation limit in an engine-like environment. DME fuel is supplied either in the form of premixture with air or directly injected in the combustion chamber of a rapid compression and expansion machine under the conditions of various equivalence ratio and injection timing. The cylinder pressure is measured and the rate of heat release is computed from the measured pressure for the analysis of the combustion characteristics. The experimental data show that the RCEM can operate without knock on mixtures of higher equivalence ratio, when DME is directly injected in the combustion chamber than introduced as a fraction of a perfect or nearly perfect premixture. Very early fuel injection timings usually employed in HCCI operation are seen to have only insignificant effects in control of ignition timing.