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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.

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.

The most popular issues nowadays in the automotive industry include reduction of environmental impacts by emission materials from automobiles as well as improvement of fuel economy. This paper deals with development of a ¡mild-hybrid¡ system for a city bus as an effort to increase fuel economy in a relatively reasonable expense. Three different technical tactics are employed; an engine is shut down at an engine idle state, a vehicle kinetic energy when the bus is decelerated is re-saved to a battery in the form of electricity, and finally the radiator cooling fan is operated by an electric motor using the saved electric energy with an optimal speed control. It has been demonstrated through the driving tests in a specific city mode, ¡Suwon city mode¡, that an average fuel economy is improved more than 12%, and the system can be a feasible choice in a city bus running in a city mode experiencing many stop and go¡s.

When unifying the functions of widely used two-fan, engine cooling system into a single fan unit, the noise and power issues must be addressed. The noise problem due to the increased fan radius is a serious matter especially as the cabin noise becomes quieter for sedans. Of the fan noise components, discrete noise at BPF's (Blade Passing Frequency) seriously degrades cabin sound quality. Unevenly spaced fan is developed to reduce the tones. The fan blades are spaced such that the center of mass is placed exactly on the fan axis to minimize fan vibration. The resulting fan noise is 11 dBA quieter in discrete noise level than the even bladed fan system.

In this study a new model is proposed for turbulent premixed combustion in a spark-ignition engine. An independent transport equation is solved for the mean reaction progress variable in a propagation form in KIVA-3V. An expression for turbulent burning velocity was previously given as a product of turbulent diffusivity in unburned gas, laminar flame speed and maximum flame surface density. The model has similarity with the G equation approach, but originates from zone conditionally averaged formulation for unburned gas. A spark kernel grows initially as a laminar flame and becomes a fully developed turbulent flame brush according to a transition criterion in terms of the kernel size and the integral length scale. Simulation of a homogeneous charge pancake chamber engine showed good agreement with measured flame propagation and pressure trace. The model was also applied against experimental data of Hyundai θ-2.0L SI engine.

The efficiency of a gap-type of deflector for suppressing vehicle sunroof buffeting is studied in this work. Buffeting is an unpleasant low frequency booming caused by flow-excited Helmholtz resonance of the interior cabin. Accurate prediction of this phenomenon requires accounting for the bi-directional coupling between the transient shear layer aerodynamics (vortex shedding) and the acoustic response of the cabin. Numerical simulations were performed using a CFD/CAA numerical method based on the Lattice Boltzmann Method (LBM). The well established LBM approach provides the time-dependent solution to the compressible Navier-Stokes equations, and directly captures both turbulent and acoustic pressure fluctuations over a wide range of scales given adequate computational grid resolution. In this study the same gap-type deflector configuration is installed on two different types of vehicles, a SUV and a sedan.

The combustion characteristics of a HSDI diesel engine were analyzed numerically using a reduced chemical kinetics. The reaction mechanism consisting of 26 steps and 17 species including the Zel'dovich NOx mechanism for the higher hydrocarbon fuel was implemented in the KIVA-3V. The characteristic time scale model was adopted to account for the effects of turbulent mixing on the reaction rates. The soot formation and oxidation processes are represented by Hiroyasu's model and NSC's model. The validation cases include the homogenous fuel/air mixture and the spray combustion in a constant volume chamber. After the validation, the present approach was applied to the analysis of the spray combustion processes in a HSDI diesel engine. The present approach reasonably well predicts the ignition delay, combustion processes, and emission characteristics in the high-pressure turbulent spray flame-field encountered in the practical HSDI diesel engines.

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.

In case of cooling module rotated by belt, many sources (vehicle’s vibration, belt’s tension and thrust force by rotated fan) are acting on it. Because it is not easy to analyze them individually, there were no rig test modes for pre-validation while developing a new vehicle. In this study, we correlated the strain gauges signal to belt’s tension and fan’s thrust force, and measured acceleration of a vehicle and cooling module by driving a vehicle on the several test roads. In that case of measured acceleration data, we could analyze it by using PDF and construct the representative rig test modes considering vibrational fatigue characteristics by using the FDS. These modes can be utilized while developing a new vehicle without measuring anymore. Also, we could understand each load’s characteristics. It is confirmed that the factors affecting the fatigue were not only the vehicle’s vibration but also the belt’s installation tension.

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.

The purpose of this paper is to investigate the mixture formation and optimize the operating conditions under cold start in a stoichiometric (λ=1) GDI engine with wall-guided piston using a 3D commercial code, STAR-CD [8]. For GDI engine under cold start, it can be difficult to carry out the optimization of operating conditions by engine test alone without the understanding of mixture formation inside the combustion chamber. In this study, three cold start conditions of the catalyst heating mode with split injection, the cranking under freezing temperature and acceleration before engine warm-up which causes oil dilution were calculated. In particular, injection strategy for each cold start condition were optimized and compared to the engine test data. The previously validated spray models [6] were applied to the analysis of the spray formation and mixing process inside the combustion chamber.

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.

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 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.

Conventional combustion models are suitable for predicting flame propagation for a wrinkled flamelet configuration. But they cannot predict the burned gas composition. This causes the overestimation of burned gas temperature and pressure. A modified method of combustion simulation was established to calculate the chemical composition and to investigate their ultimate fate in the burned gas region. In this work, the secondary products of combustion process, like CO and H2, were considered as well as the primary products like CO2 and H2O. A 3-dimensional CFD program was used to simulate the turbulent combustion and a zero dimensional equilibrium code was used to predict the chemical composition of burned gas. With this simple connection, more reasonable temperature and pressure approaching the real phenomena were predicted without additional time costs.

Hyundai Motor Company developed its second-generation fuel cell hybrid electric vehicle (FCEV) based on its small Tucson SUV. Compared to Hyundai's first generation fuel cell vehicle, the Santa Fe FCEV, the Tucson FCEV has an extended driving range plus cold weather starting capability. It incorporates numerous technical advances including a fuel cell that operates at sub-zero temperatures and a new high voltage lithium ion polymer battery. Using both a fuel cell and a high voltage battery as sources for driving energy, the Tucson hybrid system provides optimum driving conditions, which ensures high tank to wheel efficiency. The Tucson FCEV's power plant has been located in the front - under the front hood - unlike its predecessor Santa Fe FCEV, which featured an under-floor installation. More importantly, Tucson FCEV's driving range has been extended to 300km thanks to its 152-liter hydrogen storage tanks.

Recently, automobile manufacturers are interested in the development of battery electric vehicle (BEV) having a longer mileage to satisfy customer needs. The BEV with high efficiency depends on the temperature of the electric components. Hence it is important to study the effect of the cooling system in electric vehicle in order to optimize efficiency and performance. In this study, we present a 1-D vehicle thermal management (VTM) simulation model. The individual vehicle subsystems were modeled including cooling, power electric (PE), mechanical, and control components. Each component was integrated into a single VTM model and it would be used to calculate energy transfer among electrical, thermal, and mechanical energy. As a result, this simulation model predicts a plenty of information including the state of each component such as temperature, energy consumption, and operating point about electric vehicle depending on driving cycles and environmental conditions.

Bad weather conditions such as torrential rain, heavy snow, and thick fog frequently occur worldwide. Vehicle accidents in such bad weather conditions account for a significant portion of all vehicle accidents, and the level of damage is relatively severe compared to other accidents that occur in clear weather. This paper analyzes the driver's driving stability in bad weather conditions, which has such a significant meaning, in various ways through experiments on the inconvenience experienced by the driver. In this study, three levels of bad weather conditions were implemented in a driving simulator environment to evaluate driver inconvenience for six activities. Through driving experiment, quantitative bio-signals and vehicle signals were analyzed in each weather condition. The SD survey was used to assess the driver's inconvenience level for activities performed while driving and analyze the ranking of inconvenience.

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.