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Chung, Jin Taek
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Numerical Study on Fluid Flow and Heat Transfer Characteristics of a Ventilated Brake Disc Connected to a Wheel

Hyundai Motor Co.-Hee Yeol Kim
Iljin Global-Yunho Jung, Honglae Kim, Seungpyo Lee
Published 2018-10-05 by SAE International in United States
The role of a brake disc is to convert the kinetic energy of automobiles into thermal energy caused by friction between the brake pads and disc surfaces. The braking performance of an overheated disc is decreased due to hot judder and fade. Hence, the cooling technology of a brake disc is one of the most important issues related to automobile safety. In the present study, the fluid flow and heat transfer analysis of a ventilated brake disc are conducted numerically. Some geometries of automotive parts such as bearings, hubs and wheels are considered in this study. The commercial code ANSYS CFX is used to simulate the fluid flow and the conjugate heat transfer which includes conduction and convection. To evaluate the cooling performance in each case, the results, including the flow patterns of cooling air inside the wheel and the heat transfer coefficient distribution at the disc surfaces, were investigated and compared for various disc-hub combinations.
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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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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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