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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.

A combined experimental and computational study of 3-D unsteady compressible flow in exhaust manifold and CCC system was performed to understand the flow characteristics and to improve the flow distribution of pulsating exhaust gases within monolith. An experimental study was carried out to measure the velocity distribution in production exhaust manifold and CCC under engine operating conditions using LDV (Laser Doppler Velocimetry) system. Velocity characteristics were measured at planes 25 mm away from the front surface of first monolith and between two monolithic bricks. To provide boundary conditions for the computational study, velocity fields according to crank angle were also measured at the entrance of exhaust manifold. The comparisons of exhaust gas flow patterns in the junction and mixing pipe between experimental and computational results were made.

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.

The primary purpose of using a plastic material instead of conventional aluminum cast for intake manifold is to reduce its weight and cost. Moreover, the use of plastic for intake manifold is regarded as a key for further development of so called an “intake modular system”. As a secondary effect, the engine power can be increased with the help of improved interior surface roughness and lowered air temperature. With regard to NVH, however, plastic intake manifold is considered somewhat negative since it is less rigid and less dense than aluminum one. In this paper, the mechanism that plastic intake manifold affects the performance and NVH of in-line 4 cylinder gasoline engine is presented. In connection with engine performance, air flow efficiency of not only intake manifold itself but also other components of intake system and also cylinder head is evaluated.

Most of car makers nowadays produce Cylinder Head Cover with Thermoplastic to get the benefit of weight and cost reduction. The production of Cylinder Head Cover with Thermoplastic brings a number of benefits such as enhancement in productivity, design freedom, integration with other parts and reduction in weight. However, NVH characteristics, sealing performance issues possibly caused by design of cover and gasket and loss of properties of materials when used for long-term period still remain as critical tasks to be solved. Especially in case of car OEMs strongly insist that we have to meet their severe specifications requirements so as to satisfy their customers' growing demand. Sealing performance is one of the core factors, which require continuous effort and studies to meet the OEM's specifications.

The purpose of this paper is to investigate the air/fuel mixture formation and combustion characteristics in a spray-guided GDI engine using a commercial code, STAR-CD. This engine adopted the outwardly opening injector located in the center of cylinder head, which forms a hollow cone spray. The spray injection was modeled arranging multiple points using random function along the ring-shaped nozzle exit. To predict the breakup of spray, Reitz-Diwakar's breakup model was used, and the model constants were calibrated against published experimental data in a constant volume chamber. The validated spray models were applied to the analysis of spray behavior and mixture formation process inside the engine combustion chamber under operating condition of ultra-lean mixture (λ ≈ 4). To predict the combustion process, the modified eddy breakup combustion model was applied.

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.

This paper presents two closed-loop control methods for monitoring and improving the combustion behavior and the combustion noise on two 4-cylinder diesel engines, in which an in-cylinder pressure and an accelerometer transducer are used to monitor and control them. Combustion processes are developed to satisfy the stricter and stricter regulations on emissions and fuel consumption. These combustion processes are influenced by the factors such as engine durability, driving conditions, environmental influences and fuel properties. Combustion noise could be increased by these factors and is detrimental to interior sound quality. Therefore, it is necessary to develop robust combustion behaviors and combustion noise. For this situation, we have developed two closed-loop control methods. Firstly, a method using in-cylinder pressure data was developed for monitoring and improving the combustion noise of a 1.7L engine. A new index using the values calculated from the data was proposed.

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.

The purpose of this paper is to identify and reduce a knocking noise from a rear suspension. First, the characteristics of a knocking noise are analyzed experimentally in the frequency domain. It was found that the knocking noise of a passenger room and vibration at a lower arm, a subframe and a floor are strongly correlated. Second, the knocking noise sensitivity is strongly dependent on suspension dynamics characteristics. Moreover, the improvement of ride comfort and noise was achieved simultaneously based on simulation analysis, principle vehicle testing. A design parameter study shows that the trailing arm bush stiffness, shock absorber bump/rebound damping characteristics, floor stiffness and shock absorber insulator bushing are one of the most sensitive parameter to affect the suspension knocking noise. Finally, this paper shows how the suspension knocking noise and ride comfort can be improved considering handling performance.

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.

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.

In order to align with net-zero CO2 ambitions, automotive OEMs have been developing increasingly sophisticated strategies to minimise the impact that combustion engines have on the environment. Intelligent thermal management systems to actively control coolant flow around the engine have a positive impact on friction generated in the power cylinder by improving the warmup rate of cylinder liners and heads. This increase in temperature results in an improved frictional performance and cycle averaged fuel consumption, but also increases the piston to liner clearances due to rapid warm up of the upper part of the cylinder head. These increased clearances can introduce piston slap noise and substantially degrade the NVH quality to unacceptable levels, particularly during warmup after soak at low ambient temperatures. Using analytical techniques, it is possible to model the thermo-structural and NVH response of the power cylinder with different warm up strategies.

High specific power, additional hardware and mapping optimization was done to achieve reduction of fuel economy for current engine in this study. 2 stage turbocharger with serial configuration was best candidate not only for high specific power at high engine speed but also for increase of low end torque for current engine. This increase of low end torque is important for development of transient characteristic of vehicle. DoE and efficient EGR Cooler was applied for optimization of fuel economy. DoE was useful for optimization of fuel consumption affected by various fuel injection parameters. This DoE was also efficient for matching optimal fuel economy after change of engine hardware. Performance improvement of engine with 2 stage turbocharger VGT was evaluated and additional development of fuel economy was performed in this study.

We developed new single coated Pd/Rh three-way catalysts (TWC). Several Pd/Rh single layered catalysts were prepared by changing the precious metal (PM) fixation method and adding new base metal oxides (BMO). These samples were compared with double-coated catalyst by using model gas activity test, BET test, XRD test and vehicle emission test. It is found that the performance of the single coated catalyst is as good as that of commercialized double-coated catalyst. The oxygen storage capacity of the single coated catalyst is better than that of double-coated catalyst. Moreover, manufacturing the single coated catalyst enables us to eliminate the unnecessary coating process which is essential to the conventional one. Our test results demonstrate that the developed catalyst has sufficient activity and durability of OSC to meet emission and OBD-II regulations.

High speed natural light motion picture records synchronized with head gasket ionization probe and in-cylinder pressure data have been made in the transparent engine of different combustion chamber configurations. For knocking cycles, the head gasket ionization current method simultaneously taken with pressure data was able to find the location of knocking occurrence. To investigate the effects of combustion chamber configurations, the flame propagation experiments for pent-roof combustion chamber with center ignition ( Modified Type I engine ) and modified pent-roof ( Type II engine ) combustion chamber were performed with high speed natural light photography technique. The flame propagation of Modified Type I engine represents more uniform patterns than that of Type II engine. The investigation of knocking combustion was also made possible by observing flame propagation with the measuring techniques that use head gasket ionization probe and in-cylinder pressure data.

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.

A study of unsteady compressible flow for two types of exhaust manifold and CCC (Close-Coupled Catalyst) systems attached to a 4-cylinder DOHC gasoline engine was carried out to investigate the flow distribution of exhaust gases and finally to make the conversion efficiency of catalyst better. An experimental study was conducted, using LDV technique, to measure the velocity distributions inside exhaust manifolds and CCC under practical engine conditions. In this study, through experiment and calculation, the effects of geometric configuration of exhaust manifold on flow maldistribution in monolith were mainly investigated to understand the exhaust flow structure in terms of flow uniformity and to improve the conversion efficiency. As a result of this fundamental study, the modified exhaust manifold (Type B) was designed and manufactured. Full load performance tests and vehicle emission tests were performed to see the effects of flow characteristics on engine performance and emission.

Improved Lean NOx Trap (LNT) catalysts with enhanced NH3 generation feature were developed for the small diesel engine. The next generation LNT system needs to perform good NOx conversions over the wide temperature range including below 200°C for urban driving and above 400°C for motorway of real road driving. However, the extended use of BaO, a component of LNT known to be very effective for high temperature NOx storage, results in the decrease of low temperature NOx conversion due to the degradation of NO oxidation associating with sulfur over time. The improvement of the low-temperature LNT performance is a key requirement for the real driving emission control as the best operation temperature for urea-SCR is above ~250°C. In this study, our next generation LNT with new washcoat architecture has demonstrated improved NOx removal efficiencies under the wider operation temperature window than the current production technology.

Hyundai's new engine is developed which optimize the cooling efficiency for knocking improvement and friction reduction. The cooling concepts for this purpose are 1) equalizing the temperature among cylinders by flow optimization, 2) cooling the required area intensively, 3) adopting ‘active flow control’ and 4) enlarging fuel economy at high speed range. In order to realize the cooling concept, 1) cross-flow, 2) compact water jacket & exhaust cooling, 3) flow control valve and 4) cylinder head with integrated exhaust manifold are considered. Improvement of knocking and friction reduction by increased cooling water temperature makes fuel efficiency possible. On the other hand, in order to strengthen the cooling around the combustion chamber and to reduce the deviation among the combustion chamber of cylinders, it is required to design the head water jacket shape accordingly.