In our previous study, the mitigating effect of dielectric barrier discharge (DBD) on the intensity of end-gas auto-ignition was observed. In this paper, the mechanism of the effect was investigated through chemical analysis and combustion experiments using a rapid compression and expansion machine (RCEM). Comprehensive GC×GC with time of flight mass spectroscopy (GCxGC-TOFMS) was performed, and the generation of alkyl-hydroperoxide (ROOH) was successfully confirmed for the first time, based on accurate mass analysis. To study the mechanism of the mitigation effect, the influence of ozone was assessed using different fuel-air mixtures, such as primary reference fuel (PRF90) and surrogate gasoline (S5R). The addition of ozone showed the same mitigation effect in the case of PRF90, but a lesser effect in the case of S5R. A characteristic blue light was also observed when ozone was mixed in the end gas prior to auto-ignition. Since ozone is known to promote low temperature oxidation (LTO) reactions, the effect of DBD application likely involves the same mechanism. The difference in effect with the different fuels may be explained in terms of an ozonolysis reaction, because S5R contains olefins and PRF90 does not. Since applying DBD to the fuel-air mixture did not show a difference in effect, between S5R and PRF90, the DBD mitigation phenomena is not induced by ozone, but a plausible candidate is the ROOH. To investigate the precursor phenomena to the blue light emission, planer laser induced fluorescence measurement (PLIF) for formaldehyde (HCHO) was employed in the combustion experiment. Without DBD application, the HCHO distribution in the end gas exhibited gradual homogenization before auto-ignition; whereas, with applied DBD, the characteristic blue flame appeared in the inhomogeneous distribution of HCHO in the end-gas region. This result may support the hypothesis that the mitigating effect is caused by the promotion, by DBD-induced ROOH, of inhomogeneous progress in the end-gas chemical reaction.
This paper discusses a technique for the examination of countermeasures at the early stage of vehicle development to realize efficient enhancement of the engine combustion noise quality. The key point of this technique is to utilize the existing combustion noise quality evaluation method as a simulation technology at the design stage of development. By doing this, the necessary measures can be estimated using the in-cylinder pressures of the newly developed engine measured on the bench and the structure response functions obtained from the previous mass-production vehicle. This process was applied to the new Kei car development and the results demonstrated the effectiveness of above technique.
The purpose of the present research is to enable verification of occupant protection performance, including neck injury, under full-width frontal crash test conditions, using a THOR 5F dummy during the primary phase of automobile development. A THOR 5F neck injury would be considered as important as that of a Hybrid III dummy. To achieve this purpose, a two-dimensional degenerated model was formulated by combining a neck element with a four-rigid-body model consisting of a head, upper body, sternum, and lower body. It was observed that the obtained results were similar to those of the finite element method.
Burning velocity is one of the important properties of premixed turbulent flames. Premixed turbulent flames are, in general, subjected to the thermo-diffusive effects in addition to the increase in the flame front area due to the influence of turbulence. In order to independently evaluate these two effects on turbulent flames and their burning velocity, ethane flames, which have a Lewis number around unity and can therefore be considered insensitive to the thermo-diffusive effects, were examined. Flame front morphologic properties such as a Fractal dimension were obtained by Fractal analysis of flame front tomography, and burning velocity was obtained by Schlieren technique. A novel correlation of turbulent burning velocity with Fractal properties of flame front was proposed.
The structure of the flow field inside a torque converter was quantitatively evaluated using dynamic mode decomposition (DMD). The input time series data in the interference region of the cascade blades were measured using particle image velocimetry (PIV). The spatiotemporal flow field was decomposed by DMD into several modes. Each DMD mode corresponds to the frequency of the flow field fluctuation. The flow field frequency mainly consisted of blade passing frequencies and their harmonics. The flow field was visualized for each DMD mode. Positive and negative vortex structures were generated alternately in the direction of rotation of the impeller and turbine. It was found that the vortex structure became smaller at a lower speed ratio.
To realize an automated driving system which is applicable to community roads, we proposed a lateral localization method focusing on road boundaries. The proposed method extracts road boundary candidates from LIDAR data by focusing on features of each road boundary, and accumulates them in the temporary memory. After traveling a certain distance, the proposed method determines road boundaries on both sides of the road by using the accumulated road boundary candidates; further, the system conducts localization. To evaluate the proposed method, we conducted experiments on community roads, and confirmed that the proposed system correctly estimated self-location.
Narrow tilting vehicles have been proposed to address transportation issues such as traffic congestion, lack of parking space. The investigation of the effects of narrow tilting vehicles on user is insufficient though many methods for improving the stability of those were proposed. The purpose of the present study is to investigate the effects of tilting mechanism of narrow vehicles on psychophysiological states of driver as a fundamental study. Focused on user satisfaction among the components of usability, the hypotheses that a tilting mechanism affects the user’s psychological state, and that the physiological indices such as a frontal alpha asymmetry, beta wave per alpha wave power based on brain activity are valid to evaluate the state were tested. The subjective evaluation of emotional states based on Russell’s circumplex model and the measurement of electroencephalography (EEG) were performed in the experiment using the proposed vehicle with the tilting mechanism. As a result, both the subject evaluation and the physiological indices based on EEG showed a significantly higher value of arousal and valence in the case of the tilting vehicle compared to the control vehicle. These results suggest that both arousal and valence levels of narrow vehicle users can be improved by a tilting mechanism.
This paper describes the development of the finite element (FE) analysis system for comprehensive evaluation of the phenomena occurring during resistance spot welding. The framework underlying this system is FE calculation based on an incrementally coupled electrical-thermal-mechanical simulation procedure. In recent years, evaluation of stress in the spot welding process has been important for elucidating the mechanism of liquid metal embrittlement (LME) crack formation. This analytic system is applied to evaluating the influence of clearance between steel sheets and electrodes on residual stress in the spot welded zone.
Various lane-keeping assist systems have been studied. To avoid collisions, automated lane crossing is sometimes required. In this paper, we propose model predictive steering control with flexible lane crossing for obstacle avoidance. In the proposed method, collision avoidance is guaranteed by hard constraints, and inappropriate lane boundary crossing is suppressed by soft constraints. Experiments show that the proposed controller generates the optimal trajectory for autonomously crossing a lane boundary while suppressing lane deviation and preventing collisions.