Development of a semi-empirical program for predicting the braking performance of a passenger vehicle

Since the invention of automobiles, the need to know the braking performance of vehicles has been acknowledged. However, because there are numerous design variables as well as nonlinearities in the braking system, it is difficult to predict the performance accurately. In this paper, a computational program is developed to estimate the braking performance numerically. This synthetic braking performance program accounts for pedal force, pedal travel and deceleration of braking parts, such as master cylinder, booster, valve, brake pad, rotor, and hoses. To improve the accuracy of program, a semi-empirical model of a braking system is introduced by using the empirical test data of pad compression, hose expansion and the friction coefficient between the pad and rotor. The accuracy of the estimation is evaluated by comparing it to the actual vehicle test results. The developed program is easy for the brake system engineers to manipulate and it can be used in the development of new vehicles by incorporating the graphical presentations.     

Structural design of an outer tie rod for a passenger car

This study proposes a structural design method for an outer tie rod installed in a passenger car. The weight of the outer tie rod is optimized by using the aluminum alloy Al6082M, which is developed as a steel-substitute material, and applying structural optimization techniques. The high strength aluminum with improved mechanical properties was developed to reduce the weight of the outer tie rod. The newly developed aluminum alloy Al6082M is applied as the material of the outer tie rod. The static strength due to inertia force, durability and buckling performances are considered in the structural design of the outer tie rod. At the proto design stage of a new outer tie rod, it is cost-effective to utilize FE (finite element) analysis to predict each of these performances. In addition, the current trend in the structural design of automobile parts is to use optimization techniques to reduce the weights of the parts. First, for an arbitrary base design, the static strength, the life cycle and the buckling load are calculated to check whether the design satisfies its criteria. Then, the critical performance is selected so as to include its loading condition only in the optimization process. In this study, the metamodel based optimization process using kriging is adopted to obtain the minimum weight satisfying the critical design requirement. Then, the feasibility of the determined optimum shape is investigated against the other performances. Finally, the optimum design of outer tie rod is modified by considering forging efficiency. The performances of the final design are investigated through simulation and experiment.     

Development of a hardware in the loop simulation system for electric power steering in vehicles

In this paper, a hardware-in-the-loop simulation (HILS) system was developed before the development of an electric power steering (EPS) system in a vehicle. This study was focused on the establishment of the HILS system. Driving conditions are simulated with the HILS system. The actual steering input parameters are confirmed on the monitor while driving the HILS system. The steering forces observed in the simulation with the developed HILS system are similar to those in real vehicle tests. The developed HILS system can be applied in the development of various types of EPS systems.     

Experimental evaluation of SOF effects on EGR cooler fouling under various flow conditions

An experiment was conducted to characterize the effects of SOF on EGR cooler fouling. A removable singletube test rig combined with a soot generator was developed to represent an EGR cooler and diesel exhaust gas. The use of a soot generator, which controlled the size and concentration of soot particles, enabled independent variables to be completely controlled. Either n-dodecane or diesel lube oil as substitute SOFs were vaporized and injected into the test rig to evaluate their effects on the growth of PM deposits and the degradation performance of the EGR cooler. Coolant temperature, which seemed to be associated with SOF content, was chosen as an independent variable, and PM deposit mass per unit area and the effectiveness drop versus time increased as the coolant temperature decreased. The PM deposit mass per unit area and effectiveness drop had maximum values at a coolant temperature of 40°C for every n-dodecane injection rate. For substitute SOFs tested in this experiment, the deposit mass increased when either n-dodecane or diesel lube oil was injected, but the effect of lube oil was more significant. Diesel lube oil seemed to have a stronger effect on the reduction of thermal conductivity by filling pores in the deposits. When diesel lube oil was injected, the deposit mass per unit area increased 127% compared to dry soot without injection. The effectiveness drop after 10 hours increased only 12.5%.     

Road identification in monocular color images using random forest and color correlogram

This paper presents a system to identify road and non-road regions from monocular color images of paved and unpaved roads. Despite being a single object, the road in these images is subject to large changes in appearance due to environmental effects and track materials. This condition has challenged the practical application of road identification. The proposed system combines random forest with color correlogram to overcome such conditions and offers a classifier for road and non-road regions in traffic images. As a color feature, the color correlogram depicts the spatial correlation of color changes in an image. Using random forest, road identification is formulated as a learning paradigm. The combined effects of color correlograms and random forest create a robust system capable of identifying roads even in variable situations in real time. This combination is more effective than other combinations, such as a color histogram plus random forest, a color correlogram plus neural network, or a color histogram plus neural network.     

Study of n-C<Subscript>12</Subscript>H<Subscript>26</Subscript> reforming over DFC catalyst in a simulated diesel exhaust

In lean-DeNOX catalysis reactions, hydrogen is a good reducing agent in PGM catalysts as well as an effective promoter in selective catalytic reduction reactions over base metal oxide catalysts. However, such a lean-DeNOX system, which uses hydrogen, requires an on-board fuel reforming system applicable to internal combustion engines. In this study, catalytic partial oxidation (CPOx) performance was tested in a laboratory for various reactants and hydrocarbon conditions. Volume concentrations of 5–10% oxygen and 0-5% water vapor were used to simulate diesel exhaust, and n-C₁₂H₂₆ was used as the feedstock for the reforming reaction. In the CPOx of n-C₁₂H₂₆, the highest hydrogen selectivity was 64% and was achieved at 100,000 h-1 GHSV. Additionally, the C/O ratio was less than unity in the absence of water vapor. However, as the water concentration was increased to 2.5 and 5.0 vol. % in the n-C₁₂H₂₆ CPOx reactions, the maximum hydrogen selectivity was increased from 64% in the absence of water to 70% and 75%, respectively. This effect is a consequence of the water-gas shift reaction over the catalyst bed. Regarding oxygen concentration effects, hydrogen selectivity slightly increased with increasing oxygen concentration from 10% to 15%. It was also found that the CPOx reaction of n-C₁₂H₂₆ can be ignited at temperatures below 300 C. Accordingly, it can be concluded that CPOx is a useful and feasible device for promoting diesel DeNOx catalysis in terms of hydrogen productivity and reaction initiation.     

Establishment of an installation process of a valve seat to a cylinder head using the cae technique

Valve seats press-fitted in the cylinder head function to hold exhaust gas inside the ignition chamber and to transfer heat to the coolant moving in the water jacket of the head. The press-fitting of the valve seats to the head at ambient temperature has been widely spread out due to its many advantages over pressing with frozen valve seats or with a heated head. The benefits include lower equipment costs, lower running costs, and fewer installation faults during the press-fitting. Nevertheless, a systematic approach for pressing at ambient temperature (ATP; ambient temperature press-fitting) has not been studied and analyzed to date. A technique to check the reliability of the press-fitting by measuring hoop strain inside the valve seat and the FEM procedure to simulate ATP is developed in this study. The FEM procedure of ATP developed here exhibits a concurrence with experimental results. Utilizing the DOE (Design of Experiments) technique, we determined the effects of various geometric parameters and the optimal shapes of the valve seat and cylinder head. The optimal shapes have been successfully applied in an actual engine and varified in a running-engine test.     

Simplified dynamics model for axial force in tripod constant velocity joint

Tripod constant velocity (TCV) joints are common components in automotive and mechanical applications. The benefits of the TCV joint are its high plunge capacity and high torque capacity. During power transmission, the friction inside the joint generates an axial force according to the kinematics. This force causes noise and vibration problems. In this study, a simplified multi-body dynamic model based on a phenomenological TCV joint friction model is developed. This model considers the generated axial force (GAF) of a TCV joint with different lubricate conditions. The efficiency and accuracy are verified by comparison with other prediction models and experiments. Thus, this model can be used to design and control the manufacture process of TCV joints.     

Combustion characteristics of LPG and biodiesel mixed fuel in two blending ratios under compression ignition in a constant volume chamber

This study aims to investigate the combustion characteristics of mixed fuel of liquefied propane gas (LPG) and biodiesel under compression ignition (CI) in an effort to develop highly efficient and environmentally friendly mixed fuelbased CI engines. Although LPG fuel is known to be eco-friendly due to its low CO₂ emission, LPG has not yet been widely applied for highly efficient CI engines because of its low cetane number and is usually mixed with other types of CI-friendly fuels. In this study, a number of experiments were prepared with a constant volume chamber (CVC) setup to understand the fundamental combustion characteristics of mixed fuel with LPG and biodiesel in two weight-based ratios and exhaust gas recirculation (EGR) conditions. The results from the current investigations verify the applicability of mixed fuel of LPG and biodiesel in CI engines with a carefully designed combustion control strategy that maximizes the benefits of the mixed fuel. Based on the results of this study, ignition is improved by increasing the cetane value by using higher blending ratios of biodiesel. As the blending ratios of biodiesel increased, CO and HC decreased and CO₂ and NO_x increases.     

Analytical study of pressure pulsation characteristics according to the geometries of the fuel rail of an MPI engine

In a conventional MPI engine, a pulsation damper is usually mounted on the fuel rail to diminish undesirable noise in the vehicle cabin room; however, pulsation dampers are quite expensive. Therefore, several studies have focused on reducing fuel pressure pulsation by increasing the self-damping characteristics of the fuel rail. This paper details the development of a fuel rail that reduces pulsation using a self-damping effect. Using an oil hammer simulation technique, pressure pulsation characteristics were investigated with respect to the aspect ratio of the cross-section, wall thickness, and fuel rail material. Increasing the aspect ratio and decreasing the wall thickness efficiently reduced the pressure pulsation. In addition, the pressure pulsation characteristics were investigated with respect to the resonant engine speed and injection period. These simulated data can be used to reduce the pressure pulsation peak and to avoid the resonant point in the design stage during the development of a fuel rail.