Torsion beam axle system design with a multidisciplinary approach

This research proposes an automatic torsion beam axle optimization process with a multidisciplinary approach and generates the optimal torsion design parameters, such as thickness and shape. In order to construct an automatic analysis process, multidisciplinary analysis models, such as modal analysis, roll mode dynamic analysis, and fatigue analysis, were applied in batch mode. To understand the design space, a parametric study using the torsion beam thickness and shape was performed. Considering roll durability and K&C characteristics, the torsion beam axle could be optimized. For the automated design process, a PIDO tool called PIAnO was used. In conclusion, a reduction in the computer-aided simulation time was achieved, and the durability and K&C characteristics of the torsion beam were enhanced by optimizing the thickness and shape.     

Development of quantitative measuring technique to find critical flow conditions for preventing soot deposit accumulated in the diesel exhaust system using main muffler composed of three chambers

If a vehicle that meets emission regulations operates sufficiently for a long time under low speed and low load conditions, soot contained in the exhaust gas is accumulated on the inner surface of the exhaust system. This soot deposition problem occurs frequently in all diesel cars. However, when a vehicle is placed under the conditions of sudden start and sudden acceleration after city mode driving for a long time, the deposited soot is abruptly blown up with the soot produced during fuel combustion. In the present study, the main cause of the abrupt outburst of deposited soot is investigated to overcome this adverse phenomenon. First, we developed a method to quantify the amount of the exhausted soot particles (or the accumulated soot particles) by measuring the opacity that represents the contamination level of the exhaust gas due to soot particles. Using this measuring scheme for deposited soot, we found the critical conditions for engine speeds and load conditions at which soot particles are emitted into the air without accumulation in the exhaust system using main muffler composed of three chambers. In order to meet these critical conditions and thus to drastically reduce soot accumulation, the exhaust system using the main muffler applied in this study must be designed to ensure that the flow velocity of the exhaust gas is higher than 62 m/s when the back pressure at the exit of the turbocharger is under 0.08 bars.     

Light duty gasoline vehicle emission factors at high transient and constant speeds for short road segments

Vehicle emissions estimates are needed at high spatial and temporal resolution to estimate near-roadway air quality and human exposures. The MOBILE6 emission factor model is based on transient test cycles of less than 65 mph. Correction factors for high speed and constant speed are developed based on vehicle-specific power-based modal models for light duty gasoline vehicles, using data from portable emission measurement systems. At 80 mph versus 65 mph, the estimated average emission rates are greater by 30%, 20%, 80%, and 10% for NO_x, HC, CO, and CO₂. The ratio of constant to average of transient speed emission rates range from 0.49 to 0.94 for NO_x at speeds of 20 mph and 80 mph. The high speed and constant speed correction factors are applied to estimate vehicle emissions for a freeway segment that includes vehicle cruising speeds between 65 and 80 mph. The potential error for not accounting for constant speed operation on a short segment of highway could be 49% at moderate speed and 24% at high speed.     

Simplified Technique for Predicting Offshore Pipeline Expansion

In this study, we propose a method for estimating the amount of expansion that occurs in subsea pipelines, which could be applied in the design of robust structures that transport oil and gas from offshore wells. We begin with a literature review and general discussion of existing estimation methods and terminologies with respect to subsea pipelines. Due to the effects of high pressure and high temperature, the production of fluid from offshore wells is typically caused by physical deformation of subsea structures, e.g., expansion and contraction during the transportation process. In severe cases, vertical and lateral buckling occurs, which causes a significant negative impact on structural safety, and which is related to on-bottom stability, free-span, structural collapse, and many other factors. In addition, these factors may affect the production rate with respect to flow assurance, wax, and hydration, to name a few. In this study, we developed a simple and efficient method for generating a reliable pipe expansion design in the early stage, which can lead to savings in both cost and computation time. As such, in this paper, we propose an applicable diagram, which we call the standard dimensionless ratio (SDR) versus virtual anchor length (L_A) diagram, that utilizes an efficient procedure for estimating subsea pipeline expansion based on applied reliable scenarios. With this user guideline, offshore pipeline structural designers can reliably determine the amount of subsea pipeline expansion and the obtained results will also be useful for the installation, design, and maintenance of the subsea pipeline.     

用于预报离岸管线膨胀的简化技术（英文）

In this study, we propose a method for estimating the amount of expansion that occurs in subsea pipelines, which could be applied in the design of robust structures that transport oil and gas from offshore wells. We begin with a literature review and general discussion of existing estimation methods and terminologies with respect to subsea pipelines. Due to the effects of high pressure and high temperature, the production of fluid from offshore wells is typically caused by physical deformation of subsea structures, e.g., expansion and contraction during the transportation process. In severe cases, vertical and lateral buckling occurs,which causes a significant negative impact on structural safety, and which is related to on-bottom stability, free-span, structural collapse, and many other factors. In addition, these factors may affect the production rate with respect to flow assurance, wax, and hydration, to name a few. In this study, we developed a simple and efficient method for generating a reliable pipe expansion design in the early stage, which can lead to savings in both cost and computation time. As such, in this paper, we propose an applicable diagram, which we call the standard dimensionless ratio(SDR) versus virtual anchor length(LA) diagram, that utilizes an efficient procedure for estimating subsea pipeline expansion based on applied reliable scenarios. With this user guideline,offshore pipeline structural designers can reliably determine the amount of subsea pipeline expansion and the obtained results will also be useful for the installation, design, and maintenance of the subsea pipeline.     

Interannual variation of the Polar Front in the Japan/East Sea from summertime hydrography and sea level data

The Polar Front in the Japan/East Sea separates the southern warm water region from the northern cold water region. A merged TOPEX/POSEIDON and ERS-1/2 altimeter dataset and upper water temperature data were used to determine the frontal location and to examine the structure of its interannual variability from 1993 to 2001. The identified frontal location, where sea surface height gradient has a maximum about 10–20 cm over the horizontal distance of 100 km, corresponds well to the maximum subsurface horizontal temperature gradient. The front migrates more widely (36°N–41°N) in the western part of the sea than in the eastern part. The interannual migration induces large variability in upper water temperatures and sea surface height in the western region. Responsible physical mechanisms were studied using a reduced-gravity model. Differences between inflow and outflow change the total volume of warm water, and total warm water volume change in the warm water region uniformly pushes the front in the meridional direction across its mean position in the model simulation. Interannual variation of wind stress causes relatively wide migration of the modeled front in the western part.     

Numerical investigation of a DI diesel spray flame using a detailed chemical reaction mechanism

Emission standards have grown increasingly stricter, consequently triggering greater interest in issues surrounding environmental pollution. In particular, soot and NOx released from DI diesel vehicles is considered to be the main source of air pollution in urban environments. However, the mechanics of fuel spray formation and the influence of the operating parameters on the resulting spray flame are not yet fully understood. In this study, the original KIVA code was modified to incorporate a detailed chemical reaction mechanism involving various species and multiple reaction steps to better understand the spray characteristics. n-Heptane, C₇H₁₆, was used as the representative fuel for diesel fuel, and the reaction mechanism for this fuel was composed of 66 species and 274 elementary reaction steps. The accuracy of the predicted results was demonstrated primarily by a comparison with experimental results. The numerical prediction of a specific operating condition for the parametric investigation correlates well with the experimental results.     

A comparative study on the power characteristics and control strategies for plug-in hybrid electric vehicles

A comparative study was performed on two types of plug-in hybrid electric vehicles (PHEVs): the GM Volt and the Toyota Prius Plug-in Hybrid. First, the powertrain models of the two vehicles were derived. Based on the dynamic models, a detailed component control algorithm was developed for each PHEV. Specifically, a control algorithm was proposed for motor generator 1 (MG1) and MG2 to achieve optimal engine operation. Additionally, an energy management strategy for selecting the operation mode was developed from the viewpoint of fuel economy, battery state of charge and vehicle velocity. Using the dynamic model of the control algorithm for each PHEV, simulations were performed, and the simulation results were verified by comparing them with those obtained using the Powertrain System Analysis Toolkit simulator for the plug-in Prius. Based on the simulation results, a comparative study was performed, and it was found that the role and capacity of MG1 and MG2 and the mode selection algorithm must be determined depending on the configuration of the PHEV.     

Shape optimization of rubber isolators in automotive cooling modules for the maximization of vibration isolation and fatigue life

Rubber isolators are mounted between a cooling module and a carrier to isolate the car body from vibration due to the rotation of the cooling fan. The isolators should be durable against fatigue loads originating from fan rotation and road disturbance. Thus, the design of rubber isolators is required to maximize both vibration isolation and fatigue life. In this study, the shapes of the rubber isolators are optimally designed using a process integration and design optimization (PIDO) tool that integrates the various computer-aided engineering (CAE) tools necessary for vibration and fatigue analyses, automates the analysis procedure and optimizes the design solution. In this study, we use CAE models correlated to the experimental results. A regression-based sequential approximate optimizer incorporating Process Integration, Automation and Optimization (PIAnO), a commercial PIDO tool, is employed to handle numerically noisy responses with respect to the variation in design variables. Using the analysis and design procedure established in this study, we successfully obtained the optimal shapes of the rubber isolators in two different cooling modules; these shapes clearly have better vibration isolation capability and fatigue lives than those of the baseline designs used in industry.     

Numerical modeling of journal bearing considering both elastohydrodynamic lubrication and multi-flexible-body dynamics

This study uses an elastohydrodynamic lubrication model coupled with multi-flexible-body dynamics (MFBD) to analyze dynamic bearing lubrication characteristics, such as pressure distribution and oil film thickness. To solve the coupled fluid-structure interaction system, this study uses an MFBD solver and an elastohydrodynamics module. The elastohydrodynamics module passes its force and torque data to the MFBD solver, which can solve general dynamic systems that include rigid and flexible bodies, joints, forces, and contact elements. The MFBD solver analyzes the positions, velocities, and accelerations of the multi-flexible-body system while incorporating the pressure distribution results of the elastohydrodynamics module. The MFBD solver then passes the position and velocity information back to the elastohydrodynamics solver, which reanalyzes the force, torque, and pressure distribution. This iteration is continued throughout the analysis time period. Other functions, such as mesh grid control and oil hole and groove effects, are also implemented. Numerical examples for bearing lubrication systems are demonstrated.