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The Factors Governing Corrosion Stiction of Brake Friction Materials to a Gray Cast Iron Disc

Korea Univ.-Jaehyun Gweon, Sanghee Shin, Ho Jang
Hyundai Mobis-Wangyu Lee, Dooyeon Kim, Keeyang Lee
Published 2018-10-05 by SAE International in United States
Corrosion stiction at the contact interface between a brake friction material and a gray iron disc under the parking brake condition was investigated by evaluating the possible parameters that affect the shear force to detach the corroded interface. Using production brake friction materials, comprising non-steel and low-steel types, corrosion tests were carried out by pressing the brake pad onto the gray iron disc using a clamp at various conditions. Results showed that the shear force to detach the corroded interface tended to increase with applied pressure and corrosion time. On the other hand, porosity, acidity, and hydrophobicity of the friction material did not show a reliable correlation to the stiction force. The poor correlation of the stiction force with the friction material properties indicated that the stiction force was not determined by a single factor but governed by multiple parameters including surface contact areas and inhomogeneity of the ingredients. Microscopic observation of the detached disc surface showed adhered fragments that were removed from the friction material surface, thus shedding light on the possible estimation of…
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Numerical Study on Fluid Flow and Heat Transfer Characteristics of a Ventilated Brake Disc Connected to a Wheel

Korea Univ.-Byung Ju Lee, Jin Taek Chung
Hyundai Motor Co.-Hee Yeol Kim
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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Incorporation of Friction Material Surface Inhomogeneity in Complex Eigenvalue Analysis to Improve the Accuracy of Brake Squeal Analysis

Korea Univ.-Byung Soo Joo, Ho Jang
Hyundai Motor Co.-Yoon Cheol Kim, Jaeyoung Lee
Published 2018-10-05 by SAE International in United States
The sliding surface of the brake friction material is not uniform but composed of random contact plateaus with a broad pressure distribution, which are known to closely related to the triggering mechanism of friction induced noise and vibrations. The non-uniform contact plateaus are attributed to the various ingredients in the friction material with a broad range of physical properties and morphology and the size and stiffness of the plateau play crucial roles in determining the friction instability. The incorporation of friction surface inhomogeneity is, therefore, crucial and has to be counted to improve the accuracy of the numerical calculation to simulate brake noise. In this study, the heterogeneous nature of the friction material surface was employed in the simulation to improve the correlation between numerical simulations and experimental results. The distributions of contact stiffness and roughness on the friction material surface were used to represent the surface inhomogeneity in the complex eigenvalue analysis (CEA). The results from the noise simulation with uneven surface contacts minimized the difference between experiments and simulations and shed light on…
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Comparative Evaluation of Engine Control Strategy on Regulated Emissions and Nano-Particle Characteristics of LPG Direct Injection (LPDI) Vehicle During the Cold Start and the Hot Phases in the FTP-75 Cycle

Korea Univ.-Cha-Lee Myung, Simsoo Park
Hyundai-autron-Juwon Kim, JongShin Lee, SeungHyun Rew, Donghyeon Lee
Published 2014-04-01 by SAE International in United States
To evaluate the potential of a dedicated LPG direct injection (LPDI) vehicle, we investigated several engine control parameters that are closely related to the characteristics of mixture preparation and nano-particle emissions. Many researches have pointed out that any amount of particle emissions from GDI vehicles were made during the cold start and cold transient phase. Therefore, in the study, four types of engine control strategies for the LPDI vehicle were applied to evaluate particle number (PN) concentration and regulated emissions in the cold start phase and the hot start phase under the FTP-75 cycle. The reduction rate of the PN concentration with LPG application reached approximately over 99% less than that of the GDI vehicle. The PN level of LPDI vehicle applied various engine control parameters was decreased 60.3% less than that of the LPDI vehicle applied the double split injection (DSI). 73.5% of the total exhausted nanoparticles were emitted during the first acceleration period of phase 1 for the GDI vehicle, whereas those of LPDI vehicles were emitted were 51-78%. A bimodal particle size…
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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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Evaluation of Time-Resolved Nano-Particle and THC Emissions of Wall-Guided GDI Engine

Korea Univ.-Kwanhee Choi, Juwon Kim, Ahyun Ko, Cha-Lee Myung, Simsoo Park
Hyundai Motor Co.-Jongil Park, Seung Kook Han
Published 2011-10-06 by The Automotive Research Association of India in India
A nano-sized PM and THC emission characteristics were investigated according to the fuel injection strategy such as a pressure and timing in the GDI engine. On the part-load condition, the particulate emissions exhibited a strong sensitivity to the injection timing. The fuel injection pressure also had a great association with the nano-particles and THC. A size of PM exhausted from the GDI engine located near 10nm on the part-load. In contrast, accumulation mode particles within 60 - 80nm mainly exhausted during the cold transient start phase. Increment of fuel injection pressure positively affected on the nano-particle and THC emissions during the start of the engine, as well.
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Development of Nano Diamond Polymer Coating on Piston Skirt for Fuel Efficiency

SAE International Journal of Engines

Korea Univ.-Tae-Suek Kan, Joonsung Park
Hyundai Motor Company-Yoolkoo Kim, Hyundal Park, Jeong Uk An
  • Journal Article
  • 2011-01-1401
Published 2011-04-12 by SAE International in United States
Various polymer-based coatings are applied on piston skirt to reduce friction loss between the piston skirt and cylinder bore which is one of main factors of energy loss in an automotive engine system. These coatings generally consist of polymer binder (PAI) and solid lubricants (graphite or MoS₂) for low friction property. On the other hand, the present study found that PTFE as a solid lubricant and nano diamond as hard particles can be used to improve the low friction and wear resistance simultaneously. In the process of producing coating material, diamond particles pulverized to a nano size tend to agglomerate. To prevent this, silane (silicon coupling agent) treatment was applied. The inorganic functional groups of silane are attached to the nano diamond surface, which keep the diamond particles are apart. In addition, the organic functional group in the silane has property to combine with polymer like PAI or PTFE in the coating solution which improves the bonding energy between nano diamond and the polymer. To find a coating of optimal properties, nano diamond and silane…
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Time-Resolved Emission Behavior of SI Engine under Transient Throttle Operating Conditions during Start Phase

Korea Univ.-Hyungmin Lee, Cha-Lee Myung, Simsoo Park
Hyundai Motor Co.-Hyuk Im, Seungkook Han, Wootae Kim
  • Technical Paper
  • 2008-08-0272
Published 2008-05-21 by Society of Automotive Engineers of Japan in Japan
This work was investigated on the time-resolved regulated emission such as THC, NOx, and smoke behaviors emitted from the tailpipe of a gasoline engine under different throttle movement ramp rates with the fuel injection pressure during transient phase. Throttle ramp rates were classified into three patterns such as very fast (0.1s), mild (0.5s), and slow throttle gradient (1.0s) transient operation. Simultaneously measuring THC and NOx with fast response gas analyzers, a high sensitivity opacimeter for full flow type was used for smoke. To verify the emission formation mechanism during transient phase, various sensors and actuating signals were accurately diagnosed.
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Effect of Intake Charge Motion Control on Combustion Phenomena with Cyclic HC and NOx Formation Characteristics in CVVT Engine

Korea Univ.-Kwanhee Choi, In Goo Hwang, Cha-Lee Myung, Simsoo Park
Sunchon National Univ.-Kyung-Hwan Lee
  • Technical Paper
  • 2008-08-0271
Published 2008-05-21 by Society of Automotive Engineers of Japan in Japan
It is known that swirl and tumble effects are strengthening charge motions within cylinder, and in consequence, improve combustion stabilities through stratifying the mixture of a perimeter of the spark plug as well as intensifying the mixing of air and fuel. In this study, enhanced charge motions were induced by a gasket type port masking scheme with a variety of shapes and ratios. The purpose of this investigation is to analyze the effects of intake flow motions on combustion phenomena and characteristics of cyclic THC and NOx exhaust emissions with various intake openings in CVVT system.
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Examination on Fuel Leakage Mechanism of LPi Vehicle to Meet the ULEV Regulation

Korea Univ.-Seongwon Choi, Hochul Kwak, Cha-lee Myung, Simsoo Park
  • Technical Paper
  • 2006-05-0346
Published 2006-10-22 by Society of Automotive Engineers of Japan in Japan
Liquid Phase LPG injection (LPi) system has several advantages of precise fuel metering and higher engine performance comparing to those of conventional mixer system. However leakage problem of LPi system at the injector tip is a main obstacle for meeting more stringent future emission regulations because it produces excessive amount of THC emission during cold and hot restart phase. The main focus of this paper is the development of leakage fuel recirculation system with activated carbon canister to eliminate the leaked fuel at intake system. The leaked fuel level was quantified using Fast Response Flame Ionization Detector (FRFID). Finally, to confirm the adsorption efficiency of recirculation system in LPi vehicle, THC emission level is measured through the phase 1 of FTP-75 mode. The result of vehicle test that duty control makes stable engine operation with various operation engine condition and recirculation system is an effective method to meet the SULEV standard of the LPi engine.