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To get a better understanding of the characteristics of the high pressure gasoline sprays impinging on a wall, a fundamental study was conducted in a high-temperature high-pressure constant volume vessel under the simulated engine conditions of in-cylinder pressures, temperatures, and wall temperatures. The injection pressure was varied from 20 to 120 MPa. The spray tip penetration, vapor mass distribution, and vaporization rate were quantitatively measured with the laser absorption-scattering (LAS) technique. The velocity fields of the wall-impinging sprays under vaporizing conditions were measured with the particle image velocimetry (PIV) technique using silicone oil droplets as tracers. The effects of injection pressure and spray/wall interactions on spray characteristics were investigated. The results showed that the increased injection pressure improved penetration, vaporization, and turbulence of the sprays.

A road vehicle’s cornering motion is known to be a compound motion composed mainly of forward, sideslip and yaw motions. But little is known about the aerodynamics of cornering because little study has been conducted in this field. By clarifying and understanding a vehicle’s aerodynamic characteristics during cornering, a vehicle’s maneuvering stability during high-speed driving can be aerodynamically improved. Therefore, in this study, the aerodynamic characteristics of a vehicle’s cornering motion, i.e. the compound motion of forward, sideslip and yaw motions, were investigated. We also considered proposing an aerodynamics evaluation method for vehicles in dynamic maneuvering. Firstly, we decomposed cornering motion into yaw and sideslip motions. Then, we assumed that the aerodynamic side force and yaw moment of a cornering motion could be expressed by superposing linear expressions of yaw motion parameters and those of sideslip motion parameters, respectively.

Combustion behavior in Rotary Engine (RE) is quite different from that in conventional reciprocating engines. Therefore, it is important to observe the combustion in RE. In the previous studies, an optical RE was developed, which enabled the observation of the flame propagation in the rotor rotating direction (side view). In the present study, modification was made to the optical RE so that the observation of the flame propagation in the rotor width direction (bottom view) became possible. By using two high-speed cameras, the combustion in RE was observed by bottom view and side view simultaneously. Consequently, it was found that the flame propagation in the rotor width direction is also important for better engine performance as well as that in the rotor rotating direction.

The present study investigated the aerodynamic pitching stability of sedan-type vehicles under the influence of A- and C-pillar geometrical configurations. The numerical method used for the investigation is based on the Large Eddy Simulation (LES) method. Whilst, the Arbitrary Lagrangian-Eulerian (ALE) method was employed to realize the prescribed pitching oscillation of vehicles during dynamic pitching and fluid flow coupled simulations. The trailing vortices that shed from the A-pillar and C-pillar edges produced the opposite tendencies on how they affect the aerodynamic pitching stability of vehicles. In particular, the vortex shed from the A-pillar edge tended to enhance the pitching oscillation of vehicle, while the vortex shed from the C-pillar edge tended to suppress it. Hence, the vehicle with rounded A-pillar and angular C-pillar exhibited a higher aerodynamic damping than the vehicle with the opposite A- and C-pillars configurations.

An experimental and numerical study was conducted on the spray and mixture properties of a hole-type injector for direct injection (D. I.) gasoline engines. The Laser Absorption Scattering (LAS) technique was adopted to simultaneously measure the spatial concentration distributions and the mass of the liquid and vapor phases in the fuel spray injected into a high-pressure and high-temperature constant volume vessel. The experimental results were compared to the numerical calculation results using three-dimensional CFD and the multi-objective optimization. In the numerical simulation, the design variable of the spray model was optimized by choosing spray tip penetration, and mass of liquid and vapor phases as objective functions.

Seat lumbar support is thought to be essential for seating comfort as it plays important role in the driver's fatigue during long term driving. We tried to evaluate the lumbar support performance objectively with Seat Pressure Distribution. First, the tolerance in the measurement was eliminated by application of ASPECT manikin that reproduced a human seating torso posture [1, 2]. Second, an analysis method to visualize the seat support balance on the human back was developed. Third, a hypothesis for the optimal support balance to minimize the fatigue was proposed according to the fatigue growing mechanisms. Examining the deviation of each seat result from the optimal support, the performances were quantitatively evaluated. In addition to that, the effect of the lumbar support adjuster was taken into consideration to predict the market evaluation more precisely.

In the previous study of the authors, it was found that some benefits for the mixture preparation of DI gasoline engines can be offered by splitting the fuel injection, such as the phenomenon of high density liquid phase fuel piling up at the leading edge of the spray can be circumvented. In a further analysis, the vapor quantity in the “stable operating” range (equivalence ratio of vapor ϕv in a range of 0.7≤ϕv≤1.3) was significantly increased by the split injection compared to the single injection. In this work, the mechanism of the effect of the split injection on the mixture formation process was studied by combining the laser-sheet imaging, LIF-PIV and the LAS (Laser Absorption Scattering) technique. As a result, it is found that the spray-induced ambient air motion can help the formation of the more combustible mixture of the split injection whereas it played a minus role of diluting the spray by the single injection.

Mixture formation processes play a vital role on the performance of a D.I. Gasoline engine. Quantitative measurement of liquid and vapor phase concentration distribution in a D.I. gasoline spray is very important in understanding the mixture formation processes. In this paper, an unique laser absorption scattering (LAS) technique was employed to investigate the mixture formation processes of a fuel spray injected by a D.I. gasoline injector into a high pressure and temperature constant volume vessel. P-xylene, which is quite suitable for the application of the LAS technique, was selected as the test fuel. The temporal variations of the concentration distribution of both the liquid and vapor phases in the spray were quantitatively clarified. Then the effects of injection pressure and quantity on the concentration distributions of both the liquid and vapor phases in the spray were analyzed.

To reduce real world fatal/serious/minor injuries, factors causing such injuries should be investigated in depth from wider perspectives. The aim of this paper is to clarify the factors based on Japanese accident database compiled by ITARDA (Institute for Traffic Accident Research and Data Analysis). ITARDA database has data for injury rates, seatbelt use rate of driver and age of driver involved in crashes, etc. by vehicle model. As a result of an elaborate statistical analysis, the most influential and essential factors on all injuries including fatality were quantitatively found to be seatbelt use rate and vehicle weight. The increase by 1% in seatbelt use rate makes injury rate decrease by 7%. The influence of vehicle weight is 1.7 times higher than seatbelt use rate. Multiple regression analysis on these two parameters was also conducted. The present analysis successfully predicted all injury rates by model per 10,000 units.

Collision warning systems are expected to be an effective countermeasure to reduce traffic accidents; however there have been relatively few studies on the effects of such warning systems on the driver's collision avoidance behavior. In this study, a driving simulator which had a large motion system was used, and 45 subjects experienced crash imminent situations in which the preceding cars suddenly decelerated while the subject looked off the road. Analyzing the subjects' collision avoidance behaviors, it was found that the braking response time and the number of simulated collisions were substantially decreased with collision warnings. Furthermore, potential reduction of rear-end collisions on the road was estimated by modeling the driver's braking response.

Three-dimensional flows around a vehicle-like bluff body (Ahmed's body) in ground proximity were computed by directly integrating the governing unsteady, incompressible Navier-Stokes equations. A well-established finite-difference procedure was used. The basic equations were formulated in a generalized coordinate system. A third-order upwind scheme was applied to discretize the equations, and the numerical solutions were acquired without any explicit turbulence models. Computations were performed at a high Reynolds number, Re=106 (based on the body length). In order to investigate the influence of the base slant angle, computations were performed for three base slant angles, i.e., 12.5 °, 25 °and 30 °. Extensive flow visualizations, using state-of-the-art computer graphics, were carried out. The present numerical results were found to be in broad agreement with the experiments of Ahmed.