• Journal of ILASS-Korea
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• v.15 no.3
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• pp.140-149
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• 2010

The spray-wall impingement in diesel engines is important to mixture preparation, engine performance and pollutant emissions. The purpose of this paper is to study the effects of spray-wall impingement on fuel distribution, combustion and emission characteristics by using both experimental and numerical methods. To investigate the spray-wall impingement process, an impingement-chamber was designed and a visualization experiment system was also developed. The images of impinged spray and free spray were digitally recorded with an intensified CCD camera. To investigate the fuel distribution, combustion and emission characteristics of impinged spray in a real diesel engine, the fuel injection and combustion processes of an engine with impingement-chamber were simulated by CFD software. Equivalence ratio distribution results were obtained to understand the fuel distribution characteristics of the impinged spray. Some combustion and emission characteristics were also acquired and the results showed that ignition delay of impinged spray was shorter than that of free spray; NO emission of the impinged spray was significantly less than that of free spray, but soot emission of impinged spray was more than that of the free spray. This study found that the diesel engine with spray-wall impingement has significant potential to reduce NO emission.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.3
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• pp.458-464
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• 2002

Recently, many researches have been performed to improve performances of the combustion and emission in the D.I.Diesel engine. Especially reduction of the soot formation in tole combustion chamber is the essential to acquire the improvement of the emission performance. These emission of the diesel combustion is effected by the characteristics of air-fuel mixing. Thus, in this study, the distribution of soot in the diesel combustion is measured by LII(laser induced incandescence) and LIS(Laser induced scattering) method. From this experimental results, it is confirmed that the swirl flow intensified by SCV(swirl control valve) is effective on the reduction of soot in the combustion chamber.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.42-53
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• 1999

Two dimensional flame temperature and KL value distribution from the luminous flame containing soot in a DI diesel engine were measured by the tow-color method using tow different wavelengths of the flame image. The combustion chamber of a DI diesel engine was visualized by elongating the piston and cylinder and the flame in the combustion chamber was photographed on a nega-color film using a high speed camera. In this study, color CCD camera was used to digitize the three color density of the film exposed to the flame and standard lamp . The accuracy of the measuring method depends on the calibration line of film made from a high temperature standard tungsten lamp. The formation and oxidization of soot in the diesel engine were studied by observing measured time history of KL factor and flame temperature . Also , effects of various shapes of combustion chamber and fuel injection on flame temperature. Also, effects of various shapes of combustion chamber and fuel injection on flame temperature and KL value distribution were examined.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.115-122
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• 2006

To evaluate the durability characteristics of in-direct injection diesel engine using BDF 20(a blend of 20% biodiesel fuel and 80% diesel fuel in volume), an IDI diesel engine used to commercial vehicle was operated on BDF 20 for 300 hours. Engine dynamometer testing was completed at regularly scheduled intervals to investigate the combustion characteristics, engine performance and exhaust emissions. The engine performance and exhaust emissions were sampled at 1 hour interval for analysis. From the results, the combustion variations such as the combustion maximum pressure($P_{max}$) and the crank angle at which this maximum pressure occurs(${\Theta}_{Pmax}$) were not appeared during long-time dynamometer testing. Also, BSFC with BDF 20 resulted in lower than with diesel fuel. The peak pressure with BDF 20 was higher than that with diesel fuel due to the oxygen content in BDF. And, BDF 20 resulted in lower emissions of carbon monoxide, carbon dioxide, and smoke emissions with a little increase of oxides of nitrogen than diesel fuel. It was concluded that there was no unusual deterioration of the engine, or any unusual change in exhaust emissions during the durability test of an IDI diesel engine using BDF 20.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3019-3025
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• 2008

An experimental study was performed to assess the effect of diesel and JP-8 aviation fuel on the spray characteristics, performance and emissions in a single cylinder optical diesel engine. Both fuels were injected via an 8-hole solenoid-driven injector in a common-rail injection system. For better understanding of spray development, the macroscopic images were captured with high speed camera, offered evidences for the results of performance and emissions. From macroscopic spray images, the spray tip penetration of JP-8 shorter than that of diesel while spray angle of JP-8 was wider than that of diesel. It indicates that the vaporization of JP-8 is superior to that of diesel. The lower cetane number of JP-8 resulted in increased portion of premixed combustion. The IMEP with JP-8 is lower than that of diesel-fueled engine. Especially, using JP-8 has a potential for reducing soot.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.72-77
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• 2011

This study is to investigate the effect of the distillation temperature in ultra low sulfur diesel fuel on exhaust emissions in the low-temperature diesel combustion with 1.9L common rail direct injection diesel engine. Low temperature diesel combustion was achieved by adopting an external high EGR rate with a strategic injection control. The engine was operated at 1500 rpm 2.6 bar BMEP. The 90% distillation recovery temperature (T90) was $270^{\circ}C$ and $340^{\circ}C$ for the respective cetane number (CN) 30 and 55. It was found that there exists no distinctive discrepancy on exhaust emissions with regards to the different T90s. The high CN (CN55) fuels follow the similar trend of exhaust emissions as observed in CN30 fuels' except that high T90 fuel (CN55-T340) produced higher PM compared to low T90 fuel (CN55-T270). This may come from that high T90 plays an active role in aggravating the degree of fuel-air mixture preparedness before ignition.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.5
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• pp.124-129
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• 2010

The direct injection (DI) diesel engine has become a prime candidate for future transportation needs because of its high thermal efficiency. However, nitrogen oxides (NOx) increase in the local high temperature regions and particulate matter (PM) increases in the diffusion flame region within diesel combustion. Therefore, the demand for developing hybrid system consist of exhaust gas recirculation (EGR) and aftertreatment system as well as diesel particulate filter (DPF) or lean NOx trap (LNT) should be applied. The variation of EGR rate due to the malfunction of EGR valve can affect not only the combustion stability of engine but also the performance of aftertreatment system. In this research, 2.0 liter 4-cylinder turbocharged diesel engine was used to investigate the combustion and emission characteristics for various operating conditions with EGR. While the fuel consumption was increased with increase of EGR rate, NOx emission was improved by maximum 90% at low speed, low load operating condition. To achieve combustion stability and reliability of aftertrearment system with minimum penalty in fuel consumption and emissions, the fault diagnosis of EGR malfunction must be employed.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.202-206
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• 2007

Plasma assisted combustion is an old subject for the combustion society, but recently, the subject is refocused partly because techniques for non-thermal plasmas are progressed significantly, and partly because there are lots of applications which need to be overcome by a new reaction technology. In the present study, we have developed plasma assisted burner (plasma burner), which can be used as a heating source in a diesel particulate filter system. The burner can bum 20 - 60 cc/min of diesel fuel with 50 lpm of fresh air in an exhaust pipe of 2.0 liter diesel engine. Using 20 cc/min of diesel fuel, an exhaust temperature for 2.0 liter disel engine can be raised up to around $600^{\circ}C$ for the range of engine speeds is idle - 3,000 rpm. The characteristics of the plasma burner are reported, and the possible operating mechanism of it will be discussed based on the effects of an electric field and a plasma on flames.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.97-103
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• 2010

The four combustion stages in a diesel engine have close correlation among them. Especially, the ignition delay period has significant effect on the following combustion stage. And the period is also one of inevitable combustion processes in the diesel engine. For example, the diesel knocking is a well-known phenomenon due to the long ignition delay period. The interval of the ignition delay period is affected by the mixture formation process in the cylinder. However, in the case of the D.I. diesel engine, the available duration to make the mixture formation of air-fuel is very short. In addition, the means of the mixture formation mainly depends on the injection characteristics and properties of the fuel. It is difficult to make complete mixture. Therefore, an early stage of combustion is violent, which leads to the weakness of noise and vibration. In this study, using the visible engine, we measured the ignition delay period by photo sensor which detect occurrence of flame and presented the factors of the injection characteristics such as kinds of injection system, the injection pressure and the injection timing. The relation between the ignition delay period and cylinder pressure diagram which was concurrently obtained was also estimated.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3300-3305
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• 2007

Ignition delay of second injection of HSDI diesel engine was usually much shorter than that of first injection. It is due to the interaction between radicals generated during the combustion process, and mixed gas of second injection. In this paper, To analyze combustion phenomena of multiple injection mode in HSDI diesel engine effectively, two-dimensional flamelet combustion model was modified. To reduce calculation time, two-dimensional flamelet equations were only applied near stoichiometric region. If this region was ignited, species and temperature of other region were changed to the steady-state solutions of one dimensional flamelet equations. By this method calculation time for solving flamelet equations was reduced to 20 percents, thought the results were almost same. Modified flamelet combustion model was coupled to commercial CFD code interactively using user subroutine.