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It is known that SEA is a rapid and simple methodology for analyzing complex vibroacoustic systems. However, the SEA principle is not always valid and one has to be careful about the physical conditions at which the SEA principle is acceptable. In this study, the appropriate damping loss factor of the vehicle interior cavity is studied in the viewpoint of the modal overlap factor of the cavity and the decay per mean free path (DMFP) of the cavity. Virtual SEA tests are performed with an FE model combination, which is suggested by a previous study of Stelzer et al. for the simulation of the sound transmission loss (STL) of vehicle panel structure. The FE model combination is consisting of the body in white (BIW), an acoustical-excited hemisphere-shaped exterior cavity, and the interior cavity. It is found that the DMFP of the interior cavity is appropriate between 0.5 ~ 1 dB for applying SEA principle.

High-voltage battery system plays a critical role in eco-friendly vehicles due to its effect on the cost and the electric driving range of eco-friendly vehicles. In order to secure the customer pool and the competitiveness of eco-vehicle technology, vehicle electrification requires lowering the battery cost and satisfying the customer needs when driving the vehicles in the real roads, for example, maximizing powers for fun drive, increasing battery capacities for achieving appropriate trip distances, etc. Because these vehicle specifications have a critical effect on the high-voltage battery specification, the key technology of the vehicle electrification is the appropriate decision on the specification of the high-voltage battery system, such as battery capacity and power. These factors affect the size of battery system and vehicle under floor design and also the profitability of the eco-friendly vehicles.

Fuel sloshing noise is involved with flow motion inside fuel tanks as well as structural characteristics of vehicles. Therefore it is necessary to introduce Fluid-Structure Interaction (FSI) analysis to predict sloshing noise phenomena more accurately. Purposes of this paper are to verify the reliability of the FSI method and suggest new CAE analysis processes to predict fuel sloshing noise. The vibration of floor panels induced by sloshing impact is evaluated through FSI analysis. A series of tests is carried out to validate simulation results. The numerical optimization of parameters is also carried out to reduce computation time. In addition, effects of sloshing noise factors are discussed based on simulation and test results. Lastly, a method to predict fuel sloshing noise by exerting sloshing load on a vehicle is suggested.

Passenger fatigue during long distance driving is greatly influenced by the comfort performance of the seat. Seat comfort performance is determined by the appropriate contour of the seat and the appropriate pad with sufficient thickness. The height of vehicle has been lowered to enhance car styling, and battery for electric vehicle applied to the underbody of the vehicle, reducing the package space of the seat in the vehicle. These external factors eventually lead to a reduced pad thickness of the seat cushion and compromise one of the important components in the seat cushion compartment, creating an uncomfortable cushioning problem when driving long distances. To improve the cushion composition of the seat within a limited package, air bladders are applied to the underside of the cushion pad. In addition, the function to support the buttocks using the air bladders of the lower cushion, similar to lumbar support for the back, was implemented to improve cushion comfort performance.

In order to understand the automotive PEM fuel cell system, mathematical system modeling is conducted and the model is implemented and simulated by using the Matlab®/Simulink®. The components such as fuel cell stack, air supplier, and radiator are modeled individually and integrated into a system level. The PEM fuel cell system operation control includes thermal management, air supply control, hydrogen supply control, fuel cell stack protection control, and load following control. In the thermal management, the inlet and outlet temperature of coolant are controlled to operate the fuel cell stack in desired temperature range and to prevent flooding inside the fuel cell stack. In air supply control and hydrogen supply control, the flow rates of air and hydrogen are controlled not to starve the fuel cell stack according to the output current. A control structure for the system is developed and confirmed by using the developed simulation model.

Adopting the Spray-guided Gasoline Direct Injection (SGDI) concept, a new multi-cylinder engine has designed. The engine has piezo injectors at the central position of its combustion chamber, while sparkplugs are also at the center. The sparkplug location is designed so that the spark location is at the outer boundary of the fuel spray where the appropriate air-fuel mixture is formed. A few important operating parameters are chosen to investigate their effects on the combustion stability and fuel consumption. The final experimental results show a good potential of the SGDI engine; the fuel consumption rate was much less than that of the base Multi Port Injection (MPI) engine at various engine operating conditions.

For a complete automotive HVAC system, it is desirable to keep good air quality control for the interior vehicle cabin. This experimental study for evaluating the CO2 concentration levels in a vehicle cabin was done on the roads in South Korea. Increasing levels of CO2 can cause a passenger to become tired, sleepy and cause headaches or discomfort. The study results shows that CO2 and fine dust concentration is a result of the number of passengers,_driving condition and HVAC user settings. The result from this investigation can be used to establish a development guide for air quality in a vehicle cabin.

Recently, high speed direct injection (HSDI) diesel engines are rapidly expanding their application to passenger cars and light duty commercial vehicles in western European market and other countries such as Korea and Japan. These movements are strongly backed by the technological innovations in the area of air charging and high pressure fuel injection systems. Variable geometry turbine (VGT) turbocharger, which could overcome the typical weak point of the existing turbocharged engine, and the common rail fuel injection system, which extended the flexibility of fuel injection capability, became two of the most frequently referred keywords in recent HSDI technology. In this paper some aspects of VGT potential as a full load torque and power modulator will be discussed. Possibility to utilize the portion of full load potential in favor of part load emissions and fuel economy will be investigated.

The engine indicated torque is not delivered entirely to the wheels, because it is lowered by losses, such as the pumping, mechanical friction and front auxiliary power consumption. The front auxiliary belt drive system is a big power consumer-fueling and operating the various accessory devices, such as air conditioning compressor, electric alternator, and power steering pump. The standard fuel economy test does not consider the auxiliary driving torque when it is activated during the actual driving condition and it is considered a five-cycle correction factor only. Therefore, research on improving the front end auxiliary drive (FEAD) system is still relevant in the immediate future, particularly regarding the air conditioning compressor and the electric alternator. An exertion to minimize the auxiliary loss is much smaller than the sustained effort required to reduce engine friction loss.

The success of improved fuel economy is the proper integration of thermal management components which are appropriately performed to reduce friction and wasted energy. The thermal management systems of vehicle are able to balance the multiple needs such as heating, cooling, or appropriate operation within specified temperature ranges of propulsion systems. Since the propulsion systems of vehicle have changed from a single energy source based on conventional internal combustion engine to hybrid system including more electrical system such as full type of hybrid electric vehicle or plug-in hybrid electric vehicles, a new transition associated with vehicle thermal management arises. More efficient thermal management systems are required to improve the fuel economy in the hybrid electric vehicles because of the driving of electric traction motor and the increase of engine off time. The decrease of engine operation time may not sustain the proper temperature ranges of engine and gearbox.

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.

This paper investigated the influence of the injector nozzle geometry on fuel consumption and exhaust emission characteristics of a light-duty diesel engine with 250 MPa injection. The engine used for the experiment was the 0.4L single-cylinder compression ignition engine. The diesel fuel injection equipment was operated under 250MPa injection pressure. Three injectors with nozzle hole number of 8 to 10 were compared. As the nozzle number of the injector increased, the orifice diameter decreased 105 μm to 95 μm. The ignition delay was shorter with larger nozzle number and smaller orifice diameter. Without EGR, the particulate matter(PM) emission was lower with larger nozzle hole number. This result shows that the atomization of the fuel was improved with the smaller orifice diameter and the fuel spray area was kept same with larger nozzle number. However, the NOx-PM trade-offs of three injectors were similar at higher EGR rate and higher injection pressure.

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.

A fractional recirculation of cabin air was proposed and studied to improve cabin air quality by reducing cabin particle concentrations. Vehicle tests were run with differing number of passengers (1, 2, 3, and 4), four fan speed settings and at 20, 40, and 70 mph. A manual control was installed for the recirculation flap door so different ratios of fresh air to recirculated air could be used. Full recirculation is the most efficient setting in terms of thermal management and particle concentration reduction, but this causes elevated CO₂ levels in the cabin. The study demonstrated cabin CO₂ concentrations could be controlled below a target level of 2000 ppm at various driving conditions and fan speeds with more than 85% of recirculation. The proposed fractional air recirculation method is a simple yet innovative way of improving cabin air quality. Some energy saving is also expected, especially with the air conditioning system.

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.

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.

Generally, the HVAC system of a vehicle is composed of Blower unit assembly and Heater unit assembly, and is located on the driver’s side of the dash panel. However, electric vehicles have far fewer parts than conventional internal combustion engine vehicles, so electric vehicles have large space in the engine room. This allows HVAC, which occupies large volume in the interior side, to be pushed in the direction of the engine room altogether, or by placing a part inside the engine room to make a slim cockpit and expand the interior space. However, this new structure, called the Split HVAC System, is mounted through the dash, allowing noise to pass through relatively easily. Since this adversely affects the NVH of an electric vehicle, it needs to be developed in terms of noise transmission. Therefore, in this paper, a study was conducted to predict the sound transmission loss of Split HVAC through an analytical method.

In this paper, an application process is studied at which the insertion loss (IL) test data of sound insulating parts or noise control treatments are utilized for the sound transmission loss (STL) simulation of the trimmed dash structure. The considered sound barrier assemblies were composed of a felt layer, a mass layer, and a decoupler layer. Flat samples of sound barrier assemblies with several different thicknesses were prepared, and ILs of them were measured by using a sound transmission loss facility. Flat samples were assumed to have mass-spring-mass resonance frequencies. The mass was set as the area mass of the sound barrier layer of the felt layer and the mass layer. The spring constant of the decoupler layer was assumed as the multiplication of that of an air spring and a spring correction factor.

In this study, two-phase flow simulations have been performed for the intake system of a commercial truck. The intake duct, which is the first component in heavy-duty engine, is located in the upper side of a cabin. The flow in the intake system is a typical two-phase flow with the air as the continuous phase and the water as the dispersed phase during rainy weather. The numerical two-phase simulation is performed by using the Largrangian model as implemented in STAR-CD. The influence of the water droplets on the airflow as well as droplet break-up and interactions of the droplets with the walls can be taken into account. Two and three cyclone model inside the intake system have been investigated by numerical simulations. The computational results can be used to get a better understanding of the physics of the flow inside the intake system and to optimize the water separation.

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.