• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.69-76
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• 2001

VCO nozzle is devised to minimize the HC emission and has been applied on some HSDI diesel engines. But it is not well reported whether VCO nozzle would be advantageous over SAC nozzle in a small HSDI diesel engine. In this paper it is presented that characteristics of VCO and SAC nozzle under common rail fuel injection system and their effects on the performance in a small HSDI diesel engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.28-34
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• 2001

Great attentions are paid to HSDI diesel engine for passenger cars because of its high thermal efficiency. The most interesting research in HSDI diesel engine developments is focused on applying common rail system as a fuel injection equipment. In this study, a series of tests are carried out to investigate the effect of injection pressure variation on the smoke and fuel concluded in a small HSDI diesel engine with common rail system. As a result of this study it is concluded that there is an optimum rail pressure dependent on combustion system such as nozzle type, combustion chamber geometry.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.46-53
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• 2004

Heat release analysis is a very important method for understanding the combustion phenomena inside an engine cylinder. In this study, one-zone heat release analysis was used with the measured cylinder pressures of a HSDI(high speed direct injection) and IDI(indirect injection) diesel engines, Those have benefits of simple equation, fast speed, reliability. The objective of the study is to compare the combustion characteristics between a HSDI and an IDI. The result shoes that the maximum heat release rate of a HSDI is higher than that of an IDI because of long ignition delay period. The heat release curve of an IDI is more linear than that of a HSDI, thus is similiar to that of a SI engine. The combustion efficiency of a HSDI is higher than that of an IDI because of the smaller heat transfer loss of a HSDI. There is a suggestion here that an IDI engine has broad heat transfer area which include two combustion chambers, the connection passage of combustion chambers, etc.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.138-143
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• 2006

Modification of injector, oil ring tension reduction and oil pump rotor re-matching with optimization of relevant engine control parameters could drive fuel consumption reduction of HSDI diesel engine. A 5 holes injector was replaced with a 6 holes with smaller nozzle hole diameter and 1.5 k factor, and evaluated in a view of fuel economy and emission trade-offs. With introducing smaller nozzle hole diameter injector, PM(Particulate Matter) was drastically decreased for low engine load and low engine rpm. Modification of oil pump and oil ring was to reduce mechanical friction and be proved to better fuel economy. Optimization of engine operating conditions was a great help for the low fuel consumption. Influence of the engine operating parameters· including pilot quantity, pilot interval, air mass and main injection timing on fuel economy, smoke and NOx has been evaluated with 14 points extracted from NEDC(New European Driving Cycle) cycle. The fuel consumption was proved to $7\%$ improvement on an engine bench and $3.7\%$ with a vehicle.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2245-2250
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• 2003

Particulate matters(PM) have bad effect on the health. We carried out measurements of diesel PM under $10{\mu}m$ diameter from a HSDI diesel engine with a diesel oxidation catalyst(DOC) by using the ELPI. This paper compares the two results of the smoke level and the PM level of masses and numbers. We also investigated the effect of the DOC. Under high speed and load, HSDI diesel engine exhausts much masses of particulate matters over 100nm diameter, and a number of PM from 7 to 100nm diameters at the same condition. DOC could reduce the total mass of the PM. However, the DOC could increase the number of ultra fine PM. Before light-off of the soot, the DOC absorb the PM and the DOC oxidize the PM after light-off temperature. The fine PM could be made during the oxidation. Therefore, the advanced DOC is needed to reduce the number of the fine PM.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.153-158
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• 2006

To optimize the combustion system in a HSDI diesel engine, a new analysis technology was developed. The in-cylinder 3-D combustion analysis was carried out by the modified KIVA-3V, and the spray characteristics for the high pressure injection system were analyzed by HYDSIM. The combustion design parameters were optimized by coupling the KIVA-3V and the iSIGHT. The optimization procedure consists of 3 steps. The $1^{st}$ step is the sampling method by the Design of Experiment(DOE), the $2^{nd}$ step is the approximation using the Neural Network method, and the $3^{rd}$ step is the optimization using the Genetic Algorithm. The developed procedures have been approved as very effective and reliable, and the computational results agree well with the experimental data. The analysis results show that the optimized combustion system in a HSDI diesel engine is capable of reducing NOx and Soot emissions simultaneously keeping a same level of the fuel consumption(BSFC).

• 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.

• Journal of the korean Society of Automotive Engineers
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• v.23 no.1
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• pp.27-33
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• 2001

• Journal of the korean Society of Automotive Engineers
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• v.23 no.1
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• pp.34-42
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• 2001

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.40-57
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• 2004

The effects of triple (pilot, main and after) injection on combustion and emission characteristics in a HSDI (High-Speed Direct Injection) diesel engine were investigated using a single-cylinder optical diesel engine equipped with a common-rail injection system. The pilot injection affected the spray and combustion evolution of the following main injection. It was found that the pilot injection reduced the ignition delay, which led to lowered NOx (Nitric Oxides) level, and increased IMEP (Indicated Mean Effective Pressure) due to slow combustion pace during an expansion stroke. The after-injection was shown to be effective in reducing PM (Particulate Matter) even when a small amount of fuel was added. The results suggest that a proper combination of individual injection strategy could bring about a good synergetic effect on engine performance and emission.