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This paper examines the effect of pulse-and-glide (PnG) driving strategies on the fuel efficiency when applied on parallel HEVs. Several PnG strategies are proposed, and these include the electrical, mechanical, and combined PnG strategies. The electrical PnG strategy denotes the hybrid powertrain control tactics in which the battery is charged or discharged according to the power demanded while maintaining the constant vehicle speed. On the other hand, the mechanical PnG strategy denotes the powertrain control tactics in which the vehicle accelerates or decelerates according to the power load while minimizing the battery usage. The combined PnG strategy involves both electrical and mechanical strategies to find a balanced point in between them. Here, a tradeoff relationship between the fuel efficiency and the vehicle drivability related to the tracking performance of the desired target speed is revealed.

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.

Tuning the size and position of the cooling water holes in the head gasket during engine cooling system development is generally positioned at the final stage of the cooling system hardware design. Until now, the gasket hole tuning operation was dependent on the case study through repetitive CFD analysis. In this process, there was a difference in the optimization level by know-how and expertise of the person in charge. In this study, a gasket hole tuning technique was developed using optimization algorithms to improve the level of optimization. First, select factors and perform screening using the DOE(Design Of Experiments) method, and then find the optimal gasket hole size and arrangement through the optimal design process based on the results of the CFD analysis planned by DOE.

Hydroforming process is an emerging manufacturing technology which allows engineers to use continuous closed section without flange for spot weld in a given package envelope. In this research, Hydroforming is applied to a front pillar and a roof side rail for improvement of obstruction angle, body stiffness and roof crush resistance. In addition, the joints of front / center pillar that were integrated into the hydroforming part and structure of package tray were improved. As a result, front pillar width is reduced by 23%, body torsional stiffness is increased by 45% and roof crush resistance is improved by 35%.

Impact resistance of plastic underbody parts was studied using simulated injection-molded specimen which can be tested according to different types of material used, injection molding variants like position and number of injection molding gates, and features of ribs. Material applied was glass fiber reinforced polyamide which can be used in underbody parts. Test was performed using several combinations of injection molding gates and rib types. From the test result, optimal design guide for plastic underbody parts was determined. Also, new high impact resistant plastic material made of glass fiber reinforced polyamide 66 (PA66) and polyamide 6 (PA6) alloy was developed and the material properties useful for CAE were determined. As a case study, oil pan and muffler housing were designed following the optimal design guide and CAE. And the reliability of the sample muffler housing designed was verified.

Aerodynamic simulation results are most of the time compared to wind tunnel results. It is too often simplistically believed that it suffice to take the CAD geometry of a car, prepare and run a CFD simulation to obtain results that should be comparable. With the industry requesting accuracies of a few drag counts when comparing CFD to wind tunnel results, a careful analysis of the element susceptible of creating a difference in the results is in order. In this project a detailed 1:4 scale model of the Hyundai Genesis was tested in the model wind tunnel of the FKFS. Five different underbody panel configurations of the car were tested going from a fully paneled car to a car without panels. The impact of the moving versus static ground was also tested, providing over all ten different experimental results for this car model.

This research addresses the pressing need for reducing vehicle aerodynamic resistance, with a specific focus on mitigating wheel and tire resistance, which constitutes approximately 25% of the overall vehicle drag. While the prevailing method for reducing resistance in mass production development involves wheel opening reduction, it inadvertently increases wheel weight and has adverse effects on brake cooling performance. To overcome these challenges, novel complementary resistance reduction methods that can be employed in conjunction with an appropriate degree of wheel opening reduction are imperative. In this study, we introduce symmetrical wheels with a fan-like shape as a solution. The fan configuration influences the surrounding flow by either drawing it in or pushing it out, depending on the direction of rotation. Application of these fan-type wheels to a vehicle's wheels results in the redirection of flow inwards or outwards during high-speed driving due to wheel rotation.

A comparative study was carried out to investigate the DTV (disk thickness variation) behavior according to the types of brake disks (gray iron grade 250 and high-carbon gray iron grade 200, 170) with two typical friction materials (non-steel and low-steel friction materials). To evaluate DTV generation and recovery characteristics, a parasitic drag mode simulating highway driving (off-brake) and a normal braking mode simulating city traffic driving (on-brake) were used with an inertia brake dynamometer. Results showed that DTV and BTV were strongly affected by the microstructure, hardness level and distribution of the gray cast iron with the friction material types. The BTV was reduced in the friction two pairs using non-steel friction materials with high carbon grade disks and low-steel friction materials with high-carbon, low hardness disk. In particular, the pair of low-steel friction materials and high-carbon, low-hardness brake disks was more effective on DTV recovery.

Optimizing fuel injection spray is essential to comply with stringent future emission regulations for hybrid vehicles and internal combustion engine vehicles, and the spray characteristics and geometry must be robust for various engine operating conditions. This study presents experimental and numerical assessments of spray for lateral-mounted gasoline direct injection (GDI) sprays with different plume arrangements to analyze collapse characteristics, which can significantly deteriorate the geometry and characteristics of fuel sprays. Novel spray characterization methods are applied to analyze complex spray collapse behaviors using LED-based diffusive back-illuminated extinction imaging (DBIEI) and 3D computed tomographic (CT) image reconstruction. High-fidelity computational fluid dynamics (CFD) simulations are performed to analyze the detailed spray characteristics besides experimental characterization.

A need to develop a cooling method with high cooling performance like jet impingement is increased as high power of an inverter is required. Jet Impingement on the dimpled plate would increase thermal performance than that of flat plate. Many previous researchers have dealt with the multi jet impingement on flat plate and some results of the study on dimpled plate evaluate the effect on heat transfer coefficients on several limited cases, making it difficult to apply them to inverter designs. Therefore, in this paper, heat transfer performance, pressure drop, and robustness at micro-scale of jet impingement on the dimpled plate were investigated in detail and the correlations of each performance were proposed. Finally, the optimal design was presented. The cooling performance was influenced by the jet array and the effect of depth and width of the dimples.

The use of light-weight materials in automotive engine components has increased in order to achieve better fuel efficiency and engine performance. In this study, Al alloy (AI5056) valve spring retainer can reduce a weight by 63% in comparison to steel and improve the upper limit of engine speed by about 500rpm. The Al valve spring retainer was fabricated by cold forging and coated with hard anodizing, DLC (diamond like coating), cold spray and thermal spray for better wear resistance and durability. We conclude that among these materials the DLC coating improves the wear resistance of Al valve spring retainer and has a sufficient durability after endurance testing.

A module based IPS (Intelligent Power Switch) evaluation system is proposed in this paper. As the IPS is gradually replacing the conventional relay and fuses, the stability and reliability of power system depends more on these IPS. The proposed IPS evaluation system outperforms the conventional manual evaluation in terms of speed and efficiency. This paper will introduce the structure of hardware and software of the IPS evaluation system. The system is placed between the module and cable connector to evaluate the module in an operating car without changing the cables. The control and signal processing is carried out by personal computer which is connected to the evaluation system by USB (Universal Serial Bus). The load resistance can be switch from actual load to arbitrary value using relay circuitry and DC electric load controlled by GPIB (General Purpose Interface Bus). CAN (Controller Area Network) circuits were added to control the IPS mounted inside the module.

Most bucket type valvetrain engines use DLC coated tappet for low friction and fuel efficiency. However the requirements on coating robustness have been increased as the tribological environments have become more severe by use of low viscosity oil or higher engine output. In order to obtain higher coating efficiency and improved wear resistance, 5∼9 at.% Si doped DLC (Si-DLC) coated tappet has been developed using PACVD process. Thermal stability and wear resistance of Si-DLC were improved impressively than those of DLC, although mechanical properties such as hardness and adhesion were degradated. It seems that Si suppresses a graphitization of DLC and thin SixOy film on coating surface acts as a barrier to oxidation or flash heat.

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.

We analyzed the in-cylinder flow fields of an optical-access single cylinder diesel engine with the PIV and STAR-CD CFD code. The PIV analysis was carried out in the bottom and side view mode during a compression stroke (ATDC 220°-340°) at 600 rpm. The flow pattern traced by the streamlines, the location of vortex center, the generation and disappearance of tumble, and the squish effect agreed well, as visualized by the PIV and CFD. Vorticity and spatial fluctuation intensities abruptly increased from ATDC 310, reflecting more complicated flow pattern as approaching TDC. In a quantitative sense, the velocity magnitudes obtained from the PIV were, on an average, higher than those from the CFD by 1 m/s approximately and the difference in velocity magnitude between them was about 26 %. In the CFD analysis, the standard high Reynolds κ-ε and RNG k-ε model were adopted for calculation with tetra and hexa or their hybrid meshes, to determine the turbulence model dependencies.

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 present study focused on CrN-Cu nanocoatings composed of nano-meter grains with CrN, Cr and Cu functioning low-friction, anti-wear and heat resistance. The coatings were synthesized by hybrid PVD including metal arc source, magentron sputter source and ion-gun source. Although Cu has low hardness, the hardness of CrNCu is not declined because it was composed of below 20nm sized grains of CrN, Cr, and Cu. However, CrN-Cu had lower friction than CrN owing to Cu’s low shear strength. CrN-Cu films optimized using the Reaction Surface Method (RSM) showed the excellent tribological behavior and low coefficient of friction compared with DLC. The tribological properties of the Cr-Cu-N demonstrated superior wear resistance and low friction at normal and high temperature conditions. The CrN-Cu nanocoatings can be used for the downsizing automotive engines working at severe tribological conditions.

The Representative Interactive Flamelet(RIF) concept has been applied to numerically simulate the combustion processes and pollutant formation in the direct injection diesel engine. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the RIF concept has the capabilities to predict the auto-ignition and subsequent flame propagation in the diesel engine combustion chamber as well as to effectively account for the detailed mechanisms of soot and NOx formation. In order to account for the spatial inhomogeneity of the scalar dissipation rate, the Eulerian Particle Flamelet Model using the multiple flamelets has been employed. Special emphasis is given to the turbulent combustion model which properly accounts for vaporization effects on turbulence-chemistry interaction.

Since the introduction of the DrivAer in 2012 this model has become the standard generic aerodynamic benchmark and aerodynamic research model used by automotive OEMs, software vendors and researchers. In 2017, the relevance of the DrivAer has been furthered by the inclusion of a simplified engine bay. Whilst the DrivAer has become the popular standard, the availability of detailed wind tunnel test data, a key enabler for more sophisticated aerodynamic benchmarking and research, remains limited. This paper presents a comprehensive set of wind tunnel test data of the notchback version of the Ford Open Cooling DrivAer, including aerodynamic force measurements, detailed surface pressure measurements and flow field measurements at 3 cross-sections in the vicinity of the model. In addition, the paper will discuss the sensitivity of the experimental data to wind tunnel repeatability and facility-to-facility variations.

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.