• Journal of ILASS-Korea
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• v.21 no.1
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• pp.7-12
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• 2016

In this study, to research in-cylinder flow characteristics of spark-ignited engine with intake valve closing timing change for Miller cycle. 3D simulation study were used 6 different intake valve profile with $CAD10^{\circ}$ gap for retard intake valve closing timing. Comparison of In-cylinder flow pattern characteristic were accompanied between Base and LIVC. And the efficiency of volume and the work of compression were analyzed with simulation study. When intake valve closing angle was retarded in $CAD50^{\circ}$, the pressure in cylinder was decreased about 12~13 bar and volume efficiency was reduced about 16%. The efficiency of volume and the work of compression were reduced on LIVC.

• Journal of ILASS-Korea
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• v.20 no.3
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• pp.141-148
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• 2015

In order to research engine characteristics of spark-ignited engine with intake valve closing timing change for Miller cycle, two cam for LIVC(Late Intake Valve Closing) were designed and fabricated an prototype valvetrain. And intake valve closing timing were adjusted to build low compressing and high expansion cycle for HEV. In experimental study, it were investigated with different engine speed, spark timing and air-fuel ratio to compare base cam and LIVC cam type. It was found that the volumetry efficiency and effective work of compression process were decreased in case of LIVC cam. When compared with the existing results, the maximum pressure in the cylinder was reduced about 12~13 bar and the volumetric efficiency was reduced about 16%.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1698-1703
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• 2004

To understand the high expansion effects by adopting intake closing time in the cases of compensating intake air-mass and effective compression ratio simultaneously, fundamental study was carried out by using RICEM realizing Atkinson cycle. Intake air-mass and effective compression ratio were compensated by increasing supercharged pressure and geometric compression ratio. The results showed that the increasing rates of expansion ratio and expansion-compression ratio were increased by compensating both a intake air-mass and effective compression ratio the same tendencies were obtained with the increases of compression ratio and cut off ratio It was also found that LIVC has more advantages in expansion ratio and effective work than those of EIVC under above conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.24-29
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• 2001

Adaptive valve timing control is one of the promising techniques to accomplish the optimized mixture formation and combustion depending on the load and speed, which is needed to meet the future challenges in reducing fuel consumption and exhaust emissions. The behavior and the effect of adaptive valve timing control system has been investigated by computer simulation, which simulates the gas dynamics in engines. Improved fuel economy can be achieved by reduction of pumping loss under low and mid load conditions. EIVC(Early Intake Valve Closing) strategy turns out to be superior to LIVC(Late Intake Valve Closing) strategy in reducing fuel consumption. Deterioration of combustion quality can be overcome by introducing LIVO(Late Intake Valve Opening) strategy, which increases turbulent intensity in cylinders. Furthermore, LIVO can reduce HC emission by decreasing the required amount of fuel to be injected during cold start.

• Journal of ILASS-Korea
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• v.27 no.3
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• pp.117-125
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• 2022

This study examines whether engine fuel efficiency is improved by optimization of the exhaust valve timing in a state where the intake valve timing has been optimized in a small turbo gasoline engine that has intake cams and exhaust cams with fixed valve opening periods. When the exhaust valve is opened late, the expansion stroke is longer, and the efficiency can be improved. A 2-cylinder turbo gasoline engine with 0.8 liters of displacement and an MPI (Multi Point Injection) fuel system was used. The engine was operated at 1,500 and 3,000 rpm, and the load conditions included a partial load of 50 N·m and a high load of 70 N·m. Data was recorded as the exhaust valve timing was controlled, and this was used to calculate the efficiency of combustion using a heat release, the fuel conversion efficiency, and the pumping loss. Results and the hydrocarbon concentrations in the exhaust gas were compared for each condition. Experiment results confirmed that additional fuel efficiency improvements are possible through exhaust valve timing control at 1,500 rpm and 50 N·m. However, in other operating conditions, fuel efficiency improvements could not be obtained through exhaust valve timing control because cases where the pumping loss and fuel/air mixture slip increased when the exhaust valve timing changed and the fuel efficiency declined.

• Journal of ILASS-Korea
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• v.15 no.1
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• pp.1-7
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• 2010

As world attention has focused on global warming and air pollution, high efficiency diesel engines with low $CO_2$ emissions have become more attractive. Premixed diesel engines in particular have the potential to achieve the more homogeneous mixture in the cylinder which results in lower NOx and soot emission. Early studies have shown that the operation conditions such as the EGR, intake conditions, injection conditions and compression ratio are important to reduce emissions in a PCCI (Premixed Charge Compression Ignition) engine. In this study a modified cam was employed to reduce the effective compression ratio. While opening timing of the intake valve was fixed, closing timing of the intake valve was retarded $30^{\circ}$. Although Atkinson cycle with the retarded cam leads to a low in-cylinder pressure in the compression stroke, the engine work can still be increased by advanced injection timing. On that account, we investigated the effects of various injection parameters to reduce emission and fuel consumption; as a result, lower NOx emission levels and almost same levels of fuel consumption and PM compared with those of conventional diesel engine cam timing could be achieved with the LIVC system.

• Journal of ILASS-Korea
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• v.22 no.1
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• pp.22-28
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• 2017

In this study, the effects of intake valve closing timing by using Cam-in-Cam system on combustion and emission characteristics for diesel engine were investigated under GT-POWER simulation environment. As a result, it was found that volumetric efficiency and effective compression ratio were decreased as the intake valve closing(IVC) timing is retarded due to its backflow effect. Also, we found that in-cylinder pressure, heat release rate and NOx emission were decreased as IVC timing was retarded. These show that the LIVC(late intake valve closing) can be effective to control AFR and mixing rate in diffusion combustion of diesel engine.

• Journal of ILASS-Korea
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• v.19 no.1
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• pp.25-32
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• 2014

For reduction of $CO_2$ emission emitted from combustion engine, the developed nations have been focused on R&D of hybrid electric vehicle. Further more, many automobile companies are researching on various techniques related to engine used in HEV to enhance fuel economy. One of key techniques is miller cycle that control a valve timing to reduce compression stroke for saving energy and increase expansion stroke for high power. In this study, it was investigated the in-cylinder flow characteristics of miller cycle with variable intake valve timing by using the ANSYS simulation code. For simulation, the key analytic parameter defined as intake valve closing timing and cam profile. As main results, it was shown that LIVC cause a lower pressure inside cylinder and had better control turbulence intensity.