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As the current and future emission regulations become stringent, the research on exhaust manifold with CCC (Close Coupled Catalyst) has been the interesting and remarkable subject. To design of exhaust manifold with CCC is a difficult task due to the complexity of the flow distribution caused by the pulsating flows that are emitted at the exhaust ports. This study is concerned with the theoretical and experimental approach to improve catalyst flow uniformity through the basic understanding of exhaust flow characteristics. Computational and experimental approach to the flow for exhaust manifold of conventional cast type, stainless steel bending type with 900 cell CCC system in a 4-cylinder gasoline engine was performed to investigate the flow distribution of exhaust gases.

A study for improving the resistance to fretting corrosion of SCr 420 pinion gear was conducted. Fretting is the damage to contacting surfaces experiencing slight relative reciprocating sliding motion of low amplitude. Fretting corrosion is the fretting damage to unlubricated contacting surfaces accompanied by corrosion, mostly oxidation that occurs if the fretting occurs in air. Two kinds of conventional heat treatment and a newly designed one suggested for improving the resistance to the fretting corrosion of pinion gear were compared each other to find out what is the main factor for generating fretting corrosion phenomenon. Increased carbon potential at both the heating and diffusing zone and reduced time of tempering was found out to be a solution for improving the resistance to fretting corrosion of forged and heat treated gear steel. On the contrary, modified carbo-nitriding using ammonia gas has been getting worse the fretting corrosion problem.

As the use of diesel engines increases in the transportation industry and emission regulations tighten, the implementation of diesel particulate filter systems has expanded. There are many challenges associated with the design and development of these systems. Some of the key robustness parameters include regeneration, efficiency, fuel penalty, engine performance, and durability. One component of durability in a diesel particulate filter (DPF) system is the filter's ability to resist ring-off-cracking (ROC). ROC is described as a crack caused primarily by thermal gradients, differentials, and the resulting stresses within the DPF that exceed its internal strength. These cracks usually run perpendicular to the substrate flow axis and typically result in the breaking of the substrate into separate halves.

Diesel engines are the most commonly used power train of the freight and public transportations in the world. From the viewpoint of global warming restraint, however, reduction of exhaust emissions from the diesel engine is urgent demand. Stringent emission regulations are being proposed with growing concern on NOx, PM and CO2 emissions. Future emission regulations require advanced emission control technologies, such as SCR(Selective Catalytic Reduction), LNT(Lean NOx Trap) and EGR(Exhaust Gas Recirculation). The EGR is a commonly used technique to reduce emission. In this study, a LP-EGR(Low Pressure Exhaust Gas Recirculation) system was investigated to evaluate its potential on emission reduction and fuel economy improvement, especially for a passenger diesel engine. A 3.0ℓ diesel engine equipped with the LP-EGR system was tested using an in-house control algorithm.

Recently, upon customer’s needs for noise-free brake, carmakers are increasingly widely installing damping kits in their braking systems. However, an installation of the damping kits may excessively increase softness in the brake system, by loosening stroke feeling of a brake pedal and increasing compressibility after durability. To find a solution to alleviate this problem, we first conducted experiments to measure compressibility of shims by varying parameters such as adhesive shims (e.g., bonding spec., steel and rubber thickness), piston’s shapes (e.g., different contact areas to the shims), and the numbers of durability. Next, we installed a brake feeling measurement system extended from a brake pedal to caliper. We then compared experimental parameters with brake feeling in a vehicle. Finally, we obtained an optimized level of brake feeling by utilizing the Design for Six Sigma (DFSS).

Charge boosting strategy plays an essential role in improving the power density of diesel engines while meeting stringent emissions regulations. In downsized two-stage turbocharged engines, turbocharger matching is critical to achieve desired boost pressure while maintaining sufficiently fast transient response. A numerical simulation model is developed to evaluate the effect of two-stage turbocharger configurations on the perceived vehicle acceleration. The simulation model developed in GT-SUITE consists of engine, drivetrain, and vehicle dynamics sub-models. A model-based turbocharger control logic is developed in MATLAB using an analytical compressor model and a mean-value engine model. The components of the two-stage turbocharging system evaluated in this study include a variable geometry turbine in the high-pressure stage, a compressor bypass valve in the low-pressure stage and an electrically assisted turbocharger in the low-pressure stage.

Emissions regulations are becoming more severe, and they remain a principal issue for vehicle manufacturers. Many engine subsystems and control technologies have been introduced to meet the demands of these regulations. For diesel engines, combustion control is one of the most effective approaches to reducing not only engine exhaust emissions but also cylinder-by-cylinder variation. However, the high cost of the pressure sensor and the complex engine head design for the extra equipment are stressful for the manufacturers. In this paper, a cylinder-pressure-based engine control logic is introduced for a multi-cylinder high speed direct injection (HSDI) diesel engine. The time for 50% of the mass fraction to burn (MFB50) and the IMEP are valuable for identifying combustion status. These two in-cylinder quantities are measured and applied to the engine control logic.

As environmental problems such as global warming are emerging, regulations on automobile exhaust gas are strengthened and various exhaust gas reduction technologies are being developed in various countries in order to satisfy exhaust emission regulations. Exhaust gas recirculation (EGR) technology is a very effective way to reduce nitrogen oxides (NOx) at high combustion temperatures by using EGR coolers to lower the combustion temperature. This EGR cooler has been mass-produced in stainless steel, but it is expensive and heavy. Recently, high efficiency and compactness are required for the EGR cooler to meet the new emission regulation. If aluminum material is applied to the EGR cooler, heat transfer efficiency and light weight can be improved due to high heat transfer coefficient of aluminum compared to conventional stainless steel, but durability is insufficient. Therefore, the aluminum EGR cooler has been developed to enhance performance and durability.

Non-Asbestos Organic (NAO) disc pads and Low Steel Lomet disc pads were subjected to high and low humidity conditions to discover how humidity affects these two classes of formulations for physical properties, friction, wear and noise characteristics. The 2 classes of formulations show similarities and differences in response to increasing humidity. The humidity effect on deformation of the surface microstructure of the gray cast iron disc is also investigated. Humidity implications for pad quality control and brake testing are discussed.

For the lightweight and compact cylinder block, new cast iron liner was developed, which has counter spiny form on the out side of the liner. Additionally, the outer surface was spray-coated with Aluminum in order to enhance the heat conductivity and to increase the grip force between the liner and the block. Without any redesign of cylinder block or crankshaft, the displacement of the engine could be increased from 1.25ℓ to 1.4ℓ by adapting this new liner only. This liner enabled to expand the engine displacement without both great dimension changes and production facility changes.

An engineering strategy to develop a new 27-ton dump truck is introduced in the process of design and analysis. Main engineering concerns in development of the new dump truck are focused on reducing weight as much as 180kg without deteriorating structural strength and fatigue life of its upper body - deck and subframe. To achieve this goal, a stress analysis and a fatigue life prediction based on CAE technique are employed at the early stage of design process. A finite element model of the full vehicle was constructed for the strength analysis. Then the fatigue life was predicted through the strength analysis and an S-N curve of high strength steel. The S-N curve for welded structures made of high strength steel was used along with a prototype vehicle's endurance test in order to set strength targets. As a result, the upper body was successfully developed without any fatigue issues.

In order to cope with new exhaust emission regulations, automotive industry is interested in research and development of HSDI (High Speed Direct Injection) diesel engines with common rail systems. Since HSDI diesel engine operates under highly loaded condition due to increased power output, cylinder head of HSDI diesel engine is susceptible to high cycle fatigue cracks. In this study, FE analysis was used to find the mechanism of high cycle fatigue crack in the HSDI diesel cylinder head. In order to improve the durability of HSDI diesel cylinder head, the modifications of cylinder head and head bolt pre-load were investigated. Experiments were performed to prove the existence of residual stress created during the heat treatment of cylinder head. The results of experiments showed that residual stress can affect the durability of HSDI diesel cylinder head.

Environmental standards concerning Suspended Particulate Matter (SPM) are continuously becoming stricter. The light-duty diesel passenger car market is rapidly increasing due to performance improvements and the economic advantages of the diesel engine. To meet EURO 4 diesel passenger car emission regulations, regeneration experiments of a catalyzed particulate filter (CPF) system have been performed with 2.0L common-rail diesel engine. For effective regeneration of the CPF system, we investigated the effects of various regeneration conditions on the system. Conditions such as exhaust gas temperature, oxygen/hydrocarbon concentrations, gas compositions, etc. were investigated. We found that the regeneration efficiency was improved when the exhaust gas temperature increased to more than 700°C during CPF regeneration using engine post injection. An additional amount of post injection increased the exhaust gas temperature and residual hydrocarbon content.

SUS exhaust manifold is weaker than cast iron in aspect of high temperature vibration. So as to improve reliability of SUS exhaust manifold and get over gas temperature limit, exhaust manifold vibration mode and level has to be decreased. And because of error and limit of conventional modal analysis, we measured vibration mode and level of SUS exhaust manifold directly in engine firing condition. To measure vibration of hot parts(600∼800°C) in engine, we used special cooling device at base of accelerometer. Thus we developed analysis method of SUS exhaust manifold crack mechanism. We came to know the accurate vibration mode and level of SUS exhaust manifold in hot condition. Besides, we found out in proportion as vibration level increases endurance life decreases.

As the markets require a more environmentally friendly and high fuel consumption vehicle, we have to satisfy bilateral target. Though many new after-treatment techniques like LNT, SCR are investigated to meet both strong emission regulations and low fuel consumption, high cost of these techniques should be solved to adopt widely. This paper describes how to optimize the dual loop EGR as a tool to reduce CO₂ emission of a HSDI diesel engine in the passenger car application. Focus is not only on the optimization to obtain the maximum CO₂ reduction but also on how to assess and overcome various side effects. As a result of careful optimization, as much as 6% CO₂ reduction was achieved by introduction of low pressure EGR loop, maintaining the same boundary conditions as those with high pressure EGR loop only.

Brake judder caused by corrosion of gray iron disks was investigated. In this study, the microstructure of the gray iron disks and the friction film developed on the disk surface by commercial friction materials were examined to find the root cause of the corrosion induced brake torque variation. Corrosion of the disk was carried out in an environmental chamber, simulating in-vehicle disk corrosion. Moisture content and acidity of the friction materials were also taken into account for this investigation and brake tests to examine torque variation during brake applications were performed using a single-end brake dynamometer. Results showed that the friction film developed on the disk surface strongly affected the amount of corrosion, while graphite morphology of the gray iron had little effect on the corrosion.

In the era of electric vehicles(EVs), the need for weight reduction of the vehicle body is increasing in order to maximize the driving distance of the EV. Accordingly, there is an increasing need for research to efficiently apply lightweight materials, such as aluminum and CFRP, to the EV body parts. In this study, design methodologies and optimization measures to increase lightweight efficiency when applying lightweight materials to EVs will be discussed. Based on theoretical basis and basic performance of each part of the EV, the “Material Substitution Method” of replacing existing parts of a steel body with aluminum materials will be defined, and the optimal design process on how to overcome performance trade-off caused by material characteristics will be addressed. In applying the “Material Substitution Method” to the actual EV body design process, it was possible to convert 93% of the components from steel to aluminum and reduce the overall weight of the body by 23%.

The controlled rolling process has been introduced to increase strength and toughness of alloy steels for the application of transmission gear. Cr-Mo alloy steel containing 0.02% Nb was controlled rolled in the temperature range of 870-970°C, showed fine austenite grain size, about ASTM No.11, resulted from the effects of recrystallization and Nb(C,N) precipitation. To investigate the effects of grain refinement on mechanical properties, several tests were conducted for the newly developed controlled rolled steel and conventional Ni-Cr-Mo alloy steel after carburizing. The new steel showed 2.1 times higher pitting resistance than the conventional steel. Fatigue limits of new and conventional steels were 950 and 930 MPa respectively. Charpy impact energy of new steel was improved about 35% compared with the conventional steel. Consequently, the pinion gear from the new steel instead of conventional one showed enhanced performance, especially pitting resistance, in dynamometer test.

The weight reduction of the car suspension parts has a direct influence on the ride and handling. However, the application of nonferrous metal materials, such as aluminum and magnesium, which results in a lighter weight of the suspension can lead to an increase in manufacturing costs compared to cast iron. In this study, vertical type high-pressure die casting using by electro-magnetic stirring (EMS) with A356 alloy in the sleeve was used to control the fine microstructure. Process optimization and part development, as well as unit product and automotive assessment were carried out for electro-magnetic stirring methods. Without making the slurry, the mechanical properties were obtained through optimization of process variables UTS 320MPa, YS 239MPa, EL 13.3%. It also succeeded in mass production with minimum cost increase of aluminum suspension components.

In diesel engine development, the new technology is coming out to meet the stringent exhaust emission regulation. The regulation demands more eco-friendly vehicles. Euro6c demands to meet not only WLTP mode, but also RDE(Real Driving Emission). In order to satisfy RDE mode, the new technology to reduce emissions should cover all operating areas including High Load & High Speed. It is a big challenge to reduce NOx on the RDE mode and a lot of DeNOx technologies are being developed. So the new DeNOx technology is needed to cover widened operating area and strict acceleration / deacceleration. The existing LNT(Lean NOx Trap) and Urea SCR(Selective Catalytic Reduction) is necessary to meet the typical NEDC or WLTP, but the RDE mode demands the powerful DeNOx technology. Therefore, the LNT & Urea SCR on DPF was developed through this study.