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Kim, Ho Young
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A Numerical Investigation of Mixing Characteristics of a Direct-Injection (DI) Engine with Liquefied Petroleum Gas

Korea University-Jae Seong Lee, Juhyeong Seo, Ho Young Kim, Simsoo Park
Published 2013-03-25 by SAE International in United States
Mixing characteristics of a Direct-Injection engine with liquefied petroleum gas were numerically investigated using a 3D unsteady Eularian-Lagrangian two-phase model. Numerical results were validated to the experimental data of heat release rate, pressure and mass flow rate of air. The numerical results and experimental data were in a good agreement. Simulations were conducted with various engine operation conditions to investigate the effects of supercharging on the mixing characteristics of the DI engine with LPG. The results showed that the fuel uniformities and evaporation rates of LPG are higher than them of gasoline. Fuel consumption rates and maximum cylinder temperatures of LPG were also higher than them of gasoline.
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Numerical Studies on the Combustion and Liquid Fuel Films Characteristics with the Dependence on Injection and Spark Timing of GDI Engine

Korea Univ.-Ju Hyeong Seo, Ho Young Kim, Jin Woo Bae, Jin Taek Chung
Published 2011-10-06 by The Automotive Research Association of India in India
GDI (gasoline direct injection) engine can be one of the solutions to increase the fuel efficiency and reduce NOx (nitrogen oxide) emissions. The LFF (liquid fuel film) formation within the engine cylinder due to direct injection is an impediment to both fuel efficiency and environment problems. To achieve the proper operating conditions, liquid fuel film formation and combustion characteristics in the cylinder of GDI engine must be investigated.The numerical simulations for the characteristics of GDI engine including the effect of both fuel injection and spark timing have been carried out to optimize the liquid fuel film phenomenon and combustion characteristics. In this study, 3D unsteady Eularian-Langrangian two-phase model was used to obtain an optimal operating condition of a GDI engine by using S/W STAR-CD (CD-adapco). The κ-ε/RNG model was used as a turbulence model. Simulation results indicate the flow field and mixture distribution inside the cylinder to obtain subsequent combustion and emission characteristics. Moreover, conditions minimizing the amount of LFF within cylinder have been suggested.
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Analysis of Flow and Mixing Characteristics of Caiengine for the Various Exhaust Valve Timing

Hyundai Motors Co.-Hyung Lee, Woo Tae Kim
Korea University-Ho Young Kim, Jin Nam Kim, Sam S. Yoon
  • Technical Paper
  • 2006-05-0251
Published 2006-10-22 by Society of Automotive Engineers of Japan in Japan
To efficiently control autoignition of CAI engines, intake-air temperature is increased using the recycled exhaust gases, called internal EGR. Because the distribution of the internal EGR affects the mixture formation as well as the overall mean temperature inside a combustion cylinder, the method to control the intake and exhaust valve timing is often used to achieve the negative valve overlap condition. In the present study, transient numerical simulations have been carried out to predict the mixing characteristics and flow field inside the cylinder with respect to the variation in the valve timing: The 3D unsteady Eulerian-Lagrangian two-phase model is used for the interaction between the intake-air with the remaining internal EGR during the under-lap operation while varying the EVO/EVC timing. Computational results show that retarding EVC motion is more effective than advancing EVO to control the pressure, temperature and distribution of the internal EGR. When the EVC timing is retarded, the mean pressure inside the cylinder during the under-lap period is decreased because of the following two reasons: First, less amount of residual gas remains…

Enhancement of the Sensitivity of Hot Film Type Air Flow Sensor in Throttle Upstream Flow

Daewoo Heavy Industries & Machinery Ltd.-Youngjin Cho
Hyundai Motor Co.-Woo Tai Kim
  • Technical Paper
  • 2004-05-0344
Published 2004-05-23 by Society of Automotive Engineers of Korea in South Korea
In current spark ignition engines, the air-fuel ratio is usually controlled by ECU (Electronic Control Unit) and variable sensor signals contribute to ECU for feedback control. Because HFM (Hot film Flow Meter) offers a primary data of air mass flow rate to ECU, the measurement errors of HFM deteriorate the engine performance (e.g., volumetric efficiency, exhaust emission). The heat capacity of HFM as well as the characteristic of the gas exchange processes (e.g., fluctuation, reverse flow, velocity distribution in the cross-sectional area of air duct) causes the measurement errors of HFM. Thus, the reduction of HFM measurement errors contributes to the feedback control of the electronic fuel injection system. To reduce the measurement errors of HFM, this study investigated the effect of intake system geometry (e.g., intake duct length & angle, Helmholtz resonator geometry).
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Flow Analysis and Catalytic Characteristics for the Various Catalyst Cell Shapes

Hyundai Motor Co.-Kum Jung Yoon
Korea Univ.-Simsoo Park, Ho Young Kim, Young Jin Cho, Sun Youp Lee
Published 1999-05-03 by SAE International in United States
The shape of unit cell of catalytic converter has great influence on the conversion efficiency and pressure drop characteristics. Therefore, the properties of design parameters of catalyst monolith were analyzed and the parameters of various cell shapes of catalyst were compared.Also, the numerical study of a three dimensional compressible flow in a Close-coupled Catalyst Converter (CCC) system was performed to investigate the flow characteristics and the flow distribution of exhaust gases. Unsteady flow analysis shows that severe interferences of each pulsating exhaust gas flow as well as geometric factors (junction, mixing pipe, cell shape etc.) influence greatly on the flow uniformity and flow characteristic in substrate. The results can be applied for the catalytic converter design.
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Effects of Gas Composition on the Performance and Hydrocarbon Emissions for CNG Engines

Korea University-Byoung Hyouk Min, Ki Hon Bang, Ho Young Kim, Jin Taek Chung, Simsoo Park
Published 1998-08-11 by SAE International in United States
Natural gas is considered to be an alternative fuel for passenger cars, truck transportation and stationary engines that can provide both good environmental effect and energy security. However, as the composition of fuel natural gas varies with the location, climate and other factors, such changes in fuel properties affect emission characteristics and performance of CNG (Compressed Natural Gas) engines. The purpose of the present study is to investigate effects of difference in gas composition on engine performance and hydrocarbon emission characteristics. The results show that THC decreases with an increasing WI (Wobber Index) and MCP (Maximum Combustion Potential) of natural gas. The power is shown to be proportional to the total heat value of the actual amount of gas entering the cylinder. There is 20% power variation depending on the composition of gas when the A/F ratio and spark timing are adjusted and fixed for a specific gas.
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