• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.78-82
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• 2003

The cooling mechanism for a regenerative cooling liquid rocket engine of 10tf-thrust using kerosene as a fuel was studied from the viewpoint of curtain cooling. Based on the concept of a highly-stratified gas flow in the combustion chamber, the cross section of the combustion chamber was spilt into 2 independent parts, core and exterior part. Additional fuel is injected into the exterior section and gas temperature can be reduced in the exterior section. Consequently, the heat flux into the coolant and wall temperature are reduced and the thermal stability of a liquid rocket engine could be improved.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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• pp.538-545
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• 2006

Stratified charge compression ignition (SCCI) combustion, also known as HCCI(homogeneous charge compression ignition), offers the potential to improve fuel economy and reduce emission. In this study, SCCI combustion was studied in a single cylinder gasoline DI engine, with a direct injection system. We investigated the effects of air-fuel ratio, intake temperature and injection timing such as early injection and late injection on the attainable SCCI combustion region. Injection timing during the intake process was found to be an important parameter that affects the SCCI region width. We also find it. The effects of mixture stratification and fuel reformation can be utilized to reduce the required intake temperature for suitable SCCI combustion under each set of engine speed and compression ratio conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.121-126
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• 2006

A gasoline-fueled stratified charge compression ignition (SCCI) engine with both direct fuel injection and intake temperature and compression ratio was examined. The fuel was injected directly by using the high temperature resulting from heating intake port. With this injection strategy, the SCCI combustion region was expanded dramatically without any increase in NOx emissions which were seen in the case of compression stroke injection. Injection timing during the intake temperature was found to be an important parameter that affects the SCCI region width. The effect of mixture stratification and the effect of fuel reformation can be utilized to reduce the required intake temperature for suitable SCCI combustion under each set of engine speed and compression ratio conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.10
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• pp.66-72
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• 2003

The cooling mechanism for a liquid rocket engine of 10tf-thrust using kerosene as a fuel was studied from the viewpoint of both the regenerative and curtain cooling. Based on the concept of a highly-stratified gas flow in the combustion chamber, the cross section of the combustion chamber was spilt into 2 independent parts, core and exterior part. Additional fuel is injected into the exterior section and gas temperature can be reduced in the exterior section. Consequently, the heat flux into the coolant and wall temperature are reduced and the thermal stability of a liquid rocket en g i.ne could be improved.

• International Journal of Automotive Technology
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• v.7 no.5
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• pp.585-593
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• 2006

The effect of the shape of the side wall on vaporization and fuel mixture were investigated for the impinging spray of a direct injection(DI) gasoline engine under a variety of conditions using the LIEF technique. The characteristics of the impinging spray were investigated under various configurations of piston cavities. To simulate the effect of piston cavity configurations and injection timing in an actual DI gasoline engine, the parameters were horizontal distance from the spray axis to side wall and vertical distance from nozzle tip to impingement plate. Prior to investigating the side wall effect, experiments on free and impinging sprays for flat plates were conducted and these results were compared with those of the side wall impinging spray. For each condition, the impingement plate was located at three different vertical distances(Z=46.7, 58.4, and 70 mm) below the injector tip and the rectangular side wall was installed at three different radial distances(R=15, 20, and 25 mm) from the spray axis. Radial propagation velocity from spray axis along impinging plate became higher with increasing ambient temperature. When the ambient pressure was increased, propagation speed reduced. High ambient pressures tended to prevent the impinging spray from the propagating radially and kept the fuel concentration higher near the spray axis. Regardless of ambient pressure and temperature fully developed vortices were generated near the side wall with nearly identical distributions, however there were discrepancies in the early development process. A relationship between the impingement distance(Z) and the distance from the side wall to the spray axis(R) was demonstrated in this study when R=20 and 25 mm and Z=46.7 and 58.4 mm. Fuel recirculation was achieved by adequate side wall distance. Fuel mixture stratification, an adequate piston cavity with a shorter impingement distance from the injector tip to the piston head should be required in the central direct injection system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.335-342
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• 2012

Nowadays, automobile manufacturers are focusing on the reduction of exhaust-gas emissions because of the harmful effects on humans and the environment, such as global warming by greenhouse gases. Gasoline direct injection (GDI) combustion is a promising technology that can improve fuel economy significantly compared to conventional port fuel injection (PFI) gasoline engines. In the present study, ultra-lean combustion with an excess air ratio of over 2.0 is realized with a spray-guided-type GDI combustion system, so that the fuel consumption is improved by about 13%. The level of exhaust-gas emissions and the operation performance with the multiple injection strategy and exhaust-gas recirculation (EGR) are examined in comparison with the emission regulations and from the point of view of commercialization.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.4
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• pp.24-30
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• 2004

As the environmental pollution becomes serious global problem, the regulation of emission exhausted from automobiles is strengthened. Therefore, it is very important to know how to reduce the NOx and PM simultaneously in diesel engines, which has lot of merits such as high thermal efficiency, low fuel consumption and durability. By this reason, the new concept called as Homogeneous Charge Compression Ignition(HCCI) engines are spotlighted because this concept reduced NOx and P.M. simultaneously. However, there is trade off between output and NOx in a HCCI engine. In this study, output and emission characteristics for a gasoline direct injection type HCCI engine were investigated to clarify the effects of intake air temperature, injection time and mixture formation. From these experiments, we found that the smoke was not produced when the fuel was injected earlier than BTDC 90$^{\circ}$. In addition, the output was increased because of delay of ignition time and NOx emission was decreased because of homogeneous charge of first injection in case of split injection.

• International Journal of Automotive Technology
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• v.7 no.6
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• pp.675-680
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• 2006

In the direct injected gasoline engine, atomized spray is desired to achieve efficient mixture formation needed to good engine performance because the injection process leaves little time for the evaporation of fuels. Therefore, substantial understanding of global spray structure and quantitative characteristics of spray are decisive technology to optimize combustion system of a GDI engine. The combustion and emission characteristics of gasoline-fueled stratified-charge compression ignition(SCCI) engine according to intake temperature and compression ratio was examined. The fuel was injected directly to the cylinder under the high temperature condition resulting from heating the intake port. With this injection strategy, the SCCI combustion region was expanded dramatically without any increase in NOx emissions, which were seen in the case of compression stroke injection. Injection timing during the intake temperature was found to be an important parameter that affects the SCCI region width. The mixture stratification and the fuel reformation can be utilized to reduce the required intake temperature for suitable SCCI combustion under each set of engine speed and compression ratio conditions.

• Journal of the Korean Society of Combustion
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• v.18 no.1
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• pp.7-12
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• 2013

A quasidimensional program is developed for a four stroke cycle homogeneous GDI (Gasoline Direct Injection) engine. It includes models for spray, burning rate and chemistry to predict knock and emissions. With early injection a homogeneous GDI engine goes through spark ignited, turbulent premixed combustion as in PFI (Port Fuel Injection) engines. The cylinder charge is divided into unburned and burned zone with the latter divided into multiple zones of equal mass to resolve temperature stratification. Validation is performed against measured pressure traces, NOx and CO emissions at different load and RPM conditions. Comparison is made between an empirical knock model and predictions by the chemistry model in this work.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.10-18
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• 2004

It is well known that the stratified charge combustion has many kind of advantages to combustion characteristics, such as higher thermal efficiency and less CO, NOx levels than conventional homogeneous mixture combustion. Although this combustion can be caused low fuel consumption, it is produced the high unburned hydrocarbon and soot levels because of different equivalence ratio in the combustion chamber. Moreover it has a lot of possibility of low output and misfire if the mixture gas would not be in existence around the spark plug. In this paper, fundamental studies for stratified combustion were carried out using a constant volume combustion chamber. The effect of locally mixture gas distribution according to control the direct injection and premixed injection in the chamber were examined experimentally. In addition, the effects of turbulence on stratified charge combustion process were observed by schlieren photography.