In this research, the effect of higher hydrocarbon and multiple hydrocarbon on oxidation reaction in DOC was investigated, numerically. The oxidation reaction was assumed to occur on the active site where the adsorption also occurred. In the mechanism of oxidation on the active site, the behavior of deactivation was expressed by reduction of empty active site by adsorption. Factors that decrease the oxidation rate are concluded from the oxidation rate and adsorption and desorption rate of each hydrocarbon.

View full abstract

Direct fuel injection gasoline engine has higher thermal efficiency and lower emission than port fuel injection gasoline engine. On the other hand, extremely precise control of air-fuel mixture distribution is indispensable. The purpose of this study is to control air-fuel mixture distribution by fuel heating. In this report, effects of fuel heating on spray and combustion characteristics are observed by using RCEM (Rapid compression expansion machine).

View full abstract

The purpose of this paper is to verify the volumetric efficiency of a screw pump for achieving high efficiency and pressure rising in the low pressure fuel supply system. High efficiency screw pumps require accurate estimation of leakage flow from the discharge to the suction through minute gaps. We constructed simple theoretical estimation and verified it experimentally with an actual screw pump on the market. We conclude that the estimation can be used for design of screw pumps.

View full abstract

The Experiments were carried out to investigate the effects of HC species on Diesel oxidation catalyst deactivation during forced regeneration period.Moreover, to figure out the oxidation reaction mechanism of multicomponent Hydrocarbon (HC), the oxidation phenomena of mixture as 10% hexadecane with 90% decane, 10% eicosane with 90% decane and 10% 1-methylnaphthalene with 90% decane were observed. As a result, it is concluded that the oxidation rate of the initial absorbed HC is dominant factor for deactivation of DOC.

View full abstract

An estimation of heat-loss through the wall from in-cylinder gas is a key to achieve higher thermal efficiency of diesel engines. In the first report of a series of studies, a formula of heat transfer coefficient, which plays a key role in heat-loss processes, was explored by applying ‘‘Similarity of Spray Characteristics’. It was clarified that the dependency of representative velocity on heat transfer coefficient is a half level of that of the conventionally used Woschni formula.

View full abstract

In this study, we devised an experimental model that reproduces sooting characteristics of the in-cylinder pool combustion as a steady phenomenon using an opposed flow burner. Polycyclic aromatic hydrocarbons and the particle volume fraction were measured for binary fuels of iso-Octane and Toluene at 0.1-MPa pressure. Experimental results were compared with numerical results calculated by using the CRECK soot model. As results, it was shown that the experimental values of PVF were the maximum at a slightly lean equivalence ratio of premixture. As the fuel vapor amount increases, the maximum PVF equivalence ratio, _Φmax, transited to the lean side. The numerical results have reproducibility with respect to these tendencies. The experimental values of _Φmax were almost unchanged depending on the mixing ratio of toluene at the same fuel vapor amount. However, numerical results of _Φmax decreases as toluene mixing ratio increases.

View full abstract

We computed the primary soot particle formation in a shock tube with the gasoline surrogate fuel (GSF) of toluene , n‒heptane and iso‒octane mixtures. The model with the method of moment consists of 233 species and 1375 reactions. Soot particle formation in pyrolysis and oxidation conditions (Φ=5, 10) were calculated. Based on our previous studies, we tried to adjust the reaction rate constant of acetylene addition reaction on the surface of soot particles, and optimize the model for gasoline surrogate fuel (GSF model). Further consideration for GSF model would be required about the temporal profile of soot yield.

View full abstract

The potential improvement of SI combustion has been investigated for the alkane fuels with distinguished autoignition properties, that is, the negative octane sensitivities. From the reported RON and MON of pure hydrocarbons, the alkane compounds with negative octane sensitivity were selected and then numerical simulations have been performed by generating the oxidation mechanisms by KUCRS auto-generation tool. As a common features of the negative octane-sensitivity fuels, the prominent NTC (negative temperature coefficient) behaviors were observed. The relationship between the NTC or octane sensitivity and chemical structures of alkanes were discussed. As a general trend, the alkyl substitution decreases the octane sensitivity especially when the substitution was made at third (or larger) position from the edge of the main chain. The replacement of substituent from methyl group to ethyl group significantly decreases the octane sensitivity. The investigation on the pressure and equivalence ration dependences were shown. The autoignition trends have been investigated by varying the compression ratio.

View full abstract

Simple but high-accuracy knocking prediction modeling is required to develop and validate innovative combustion control technologies for gasoline engines to achieve higher thermal efficiencies. The Livengood-Wu integral has been widely applied as the simplest and most practical model to predict knocking. But, the scientific nature of this empirical model has been unknown. What is X of the Livengood-Wu integral? In the present study, in-cylinder autoignition prediction using the Livengood-Wu integral was investigated using ignition delay times for a premium gasoline surrogate fuel, computed using a detailed reaction mechanism developed by Miyoshi and Sakai. When autoignition occurs at TDC, ignition delay times near TDC are about 10 times as long as time per crank angle degree every engine speed. Therefore, if only the reciprocal of the ignition delay time is integrated over 10 crank angles near TDC, the integrated value can reach 1 for no scientific reason. Apart from this fact, it was concluded that the true X of the Livengood-Wu integral is the ratio of an integration step out of ignition delay time. Assumed that the profiles of heat release rate along the time normalized by ignition delay times are similar, when the integrated value reaches 1, the parts of a profile of heat release rate can be integrated to be the complete profile. According to this finding, for high-accuracy autoignition prediction using the Livengood-Wu integral, it is significant to express the temperature-, pressure-, and equivalence ratio-dependence of ignition delay time as accurately as possible, and predict the profile of heat release rate.

View full abstract

Schlieren photography is well known as a visualization method of flame propagation. However, in case of spark ignition, the shape or size of initial flame kernel cannot be distinguished due to density variation caused by the plasma or preheating zone. In this paper, the authors attempted to visualize both the discharge channel and the initial flame kernel formation using both a normal high-speed camera and an infrared high-speed camera. In a constant volume combustion chamber, simultaneous visualizations using a CO band filtered infrared and a normal high-speed camera were conducted. A normal high-speed camera was used for schlieren photography and direct imaging of spark channel. As a result, the possibility to distinguish the initial flame kernel from the spark plasma was suggested by using an infrared high-speed camera.

View full abstract

Further improvement of thermal efficiency in gasoline engine is necessary by raising the compression ratio and specific heat ratio. In our previous papers, a new combustion technology to avoid irregular combustion in maximum load condition under ultra-high compression ratio was suggested and validated. This paper investigates fuel consumption performance at partial load by combining lean combustion strategies.

View full abstract

This paper considers machine learning based virtual design process of engine control system, and the demonstration in a diesel engine air path control is shown. This process contains two steps of machine learning. In the first step, a control-oriented forward model that predicts the transient behavior of the engine is learned from detailed engine model by using recurrent neural network (RNN). In the second step, an inverse model that determines the optimal control inputs to follow the references is learned from the numerical computation results of the offline model predictive control (MPC). The forward and inverse models could be used as a state observer and a controller, respectively, in a control system. An experiment of a diesel air path control system designed by the process was conducted using rapid control prototyping (RCP), and its following capability to the reference was demonstrated.

View full abstract

In this paper, we propose a combustion control design scheme of diesel engine with triple fuel injections based on two-degree-of-freedom adaptive output feedback control with a model-based feedforward control. The control system is designed by considering main fuel injection timing and fuel injection quantity of pre-injection as control inputs and in-cylinder peak pressure and peak pressure timing as outputs of the system. The effectiveness of the proposed method is confirmed through engine bench test of steady state.

View full abstract

Gasoline engines have cycle-by-cycle variations which prevent the ignition timing advancing. If the cycle-by-cycle variations can be restricted by some measures, that surely contributes fuel economy. So the contributing factors, flow velocity fluctuation in a cylinder, laminar combustion speed and so on, and their contribution ratios on the cycle-by-cycle variations are detected by a turbulent combustion model considering a combustion zone. Comparing its calculation results with the experimental data, some characteristics of the cycle-by-cycle variations are discussed. In addition, in-cylinder brightness through a bore-scope was also measured to detect the cycle-by-cycle variations, so the results from this measurement are shown here.

View full abstract

The purpose of this study is to discuss the influence of operating condition for Ash deposition in Diesel Particulate Filter (DPF) for construction machinery, based on the experimental results of the long run (non-accelerated) engine bench test. Experimental results show that bulk density of bottom deposited Ash is changed related to regeneration interval. Additionally, results show that it is changed similarly when engine operating condition changed to higher duty ratio. Based on these results, the mechanism of bulk density change of bottom deposited Ash is considered. As a result, it is suggested that the mass balance between Ash load and Soot load at the regeneration is an important parameter to explain the mechanism of bulk density change of bottom deposited Ash.

View full abstract

Ash accumulation in a DPF affects the pressure drop across the DPF and reduces the accuracy of determining the pressure drop caused by the particulate matter loading. It is therefore important to determine the effect of ash on the pressure drop. Herein, we used a used DPF that was installed in a vehicle to investigate the ash distribution within the DPF. In addition, ash samples with different thicknesses were collected from the DPF and the pressure drop was measured across each sample. Furthermore, using scanning electron microscopy, we analyzed the micro structures of the ash layer at several points.

View full abstract

In this study, the ash accumulation distribution and density was investigated by observing the ash accumulation site in the DPF using the X-ray CT scanner based on the characteristic that the transmittance of X-rays is proportional to the density of the substance. Quantitative analytical method without DPF destruction was established and the correlation between the ash accumulating condition and ash accumulation site in DPF is discussed in this report from the results of the quantitative analysis.

View full abstract

Accelerated ash accumulation techniques were established by means of diesel particulate generator (DPG) in which engine oil injector is installed. Three diesel particulate filter (DPF) samples with different active regeneration frequency were made by DPG then the ash accumulation distribution was observed nondestructively by X-ray computed tomography (CT). As a result, it was clarified that ash distribution is drastically changed by active regeneration frequency, and soot load is important factor on ash transport during DPF regeneration. Scanning electron microscope (SEM) observations of ash both before and after regeneration were also conducted and it was confirmed that ash particle size grows due to crystallization by ash sintering after regeneration. In addition, from the analysis of change in ash accumulation amount before and after regeneration, it was suggested that ash passing through the DPF may occur during active regeneration.

View full abstract

For exhaust gas regulations of particle matter(PM), it is common to install a diesel particulate filter (DPF) in a vehicle with a diesel engine. To predict a performance includes pressure drop of the DPF, we had developed a physical based model of the DPF. In this study, we focused on the 4 model parameters and searched optimal values to minimize errors between simulations and experiments for some conditions by Fletcher–Reeves conjugate gradient method. And we report the results of the optimization.

View full abstract

In this study, NOx purification characteristics of Cu-zeolite catalyst were analyzed based on the NH₃-SCR reaction mechanism considering Cu redox. Adsorbed NH₃ showed different reactivity with NOx depending on the type of adsorption site and gas compositions. Reactivity of adsorbed NH₃ on Cu sites had changed by the presence of oxidative gas component, and it was shown that NOx was also purified at reaction sites derived from zeolite. We proposed reaction schemes considering these effects and developed the SCR/DPF model incorporating these schemes.

View full abstract

As the high amount of Phosphorus (included in lubricant oil) accumulates in the catalyst washcoat by the long-distance run of the vehicle, the exhaust-gas purification performance of the three-way catalyst decreases substantially. An extensive experiment was conducted to elucidate that mechanism. As a result of XRD analysis, it was clarified that Phosphorus and Cerium (included in oxygen storage components) formed CePO₄ after the severe aging. Some collapse of the CeO₂-ZrO₂ structures by CePO₄ formation causes the degradation of oxygen storage capacity (OSC) which affects NOx conversion efficiency. Furthermore, the addition of phosphorus trapper materials into the top catalyst layer demonstrated the suppression of the purification performance deterioration.

View full abstract

For realizing a model-based control system of a diesel engine, a control oriented model with three-stage fuel injections has been developed by authors. In this study, the model is expanded to treat four-stage fuel injections and its accuracy is evaluated by comparing with experimental results. Furthermore, its scalability of a modularly-structured calculation method to predict the spray shape, the ignition timing and the combustion for one fuel injection is discussed.

View full abstract

The present study shows how the power is transmitted from driving to driven pulleys under fluctuated torque for metal V-belt CVT. The applied torque amplitude is periodically greater than a half of the mean torque for every one rotation. Consequently, the torque applied to the smaller pitch diameter pulley is often enough to cause sliding slip for every rotation. However, the experimental results confirmed that no sliding slip macroscopically occurred while partial slip called micro sliding slip occurred when the maximum torque exceeded the critical torque for a given thrust. The micro sliding slip reduces the power transmitting efficiency, and probably gives additional damage to pulleys and elements of the belt. When we applied a periodically altered thrust synchronized to the fluctuating torque, the efficiency appreciably increased, suggesting that the metal V-belts drives were more widely applicable to reduced size and cylinders engines.

View full abstract

An electric motor driven fuel cell garbage truck was developed to reduce CO2 emissions of a conventional diesel engine garbage truck. A fuel cell power plant bench test was performed to confirm the fuel cell power plant performance and to develop a simulation model. Based on the simulation model result, hydrogen consumption and each component losses were compared by two different fuel cell system types and output control methods for weight reduction during a garbage collection route driving of one day in the Shunan City, Yamaguchi Prefecture. The recent mass production of fuel cell system and battery pack were considered for the weight reduction fuel cell systems.

View full abstract

The relation between the stiffness increase of a structure and the Ustar (U*) value of stiffener location was theoretically formulated. In the formula, U^* from the loading point (U^*_A) is not included, although the effect of U^* from the support point (U^*_B) is dominant. As an example, the stiffness increase ratios of passenger car bodies caused by stiffeners at the strut tower top for the lateral force were quantitatively predicted using the obtained formula. The predicted values using U^* corresponded well with the stiffness increase obtained from a FEM computer simulation model of an actual sedan body.

View full abstract

The index Ustar (or U^*) to express the load transfer in structures was previously developed by the authors. In order to realize lightweight vehicle bodies with high stiffness for reduction of CO₂ emissions, in the present study, we developed a structural optimization method using U^*. We focused on the local structure (front suspension tower) for the design space, and load path U^* calculation is applied. The difference between the load transfer paths from the loading point and the supporting point was improved by iterative calculations. An actual optimization shows that the specific torsional stiffness was improved by 10.2%.

View full abstract

In order to study deformation mode control, three-point bending analysis of the hat member with the strength distribution was carried out. As a result, it was found that a desired deformation mode can be obtained by optimizing the material strength difference and the plate thickness difference. Furthermore, it was found that the material strength difference required to control the deformation mode becomes larger as the plate thickness of the member becomes thinner.

View full abstract

To investigate the biofidelity of the thorax response of the next-generation frontal crash test dummy THOR, a series of thorax compression CAE analysis from various locations and directions was performed in comparison with Hybrid III and human body FE models. As a result, although the chest response of THOR was closer to human body than that of Hybrid III, it was found that the response discrepancy in oblique direction in which rib fractures occur frequently becomes large.

View full abstract

Human body FE models containing muscle controllers were developed for occupant injury analyses with body sizes of AM50, AM95, and AF05. Muscle activation can be controlled as to maintain occupant postures and simulate braced drivers pushing on a steering wheel and a brake pedal. After the models without muscle activations were validated against cadaver test data on side impacts, the models were applied to side collision analyses. We investigated how muscle activation conditions and body sizes of occupants would affect the kinematics and injury outcomes during side collisions.

View full abstract

The purpose of this study was to examine the mechanisms of thoracic injury in seatbelt restrained occupants. The fracture locations and fracture patterns were analyzed using CT images and were derived from injured occupants in our in-depth traffic accident database. The results of our analysis showed that some fractures occur along the seatbelt path, however, the majority of fractures occurred in the lateral thoracic region, away from the seatbelt path. For drivers(seated in the right front position), break fractures occurred predominantly in the upper right part of the thoracic region while crack fractures and bend fractures occurred predominantly in the lower left part of the thoracic region. Drivers aged 65 years and over had twice as many rib fractures compared to drivers under the age of 65 years.

View full abstract

Portable emissions measurement systems (PEMS) are attracting attention because of requirements for measurement of vehicle emissions under real driving conditions. Solid particle number (PN) emission is one of measurement component defined by a European light-duty regulation. Because of difference in calibration procedures between conventional stationary PN measurement systems and PN-PEMS, measurement difference of PN emissions by these systems are concerned. Influence of particle size distribution is evaluated in this study. Moreover, feasibility of on-board small particle measurement down to 10 nm by extending the detection efficiency of PN-PEMS to small particles is discussed.

View full abstract

In in-use hybrid electric vehicles (HEV) of 100,000km or more driving, fuel economy performance would change due to the deterioration of hybrid batteries. If a life cycle CO₂ emission from HEV is estimated, the deterioration of fuel economy performance of HEV should be considered. So we conducted fuel consumption measurements of JC08 mode 60km/h constant driving with a HEV of 187,000km driving, and the performance of battery cells were investigated also. From the results, though the deterioration of battery capacity was 20-30%, fuel economy of JC08 mode changed about 2.5%.

View full abstract

This paper describes the modeling technique of carbon fiber reinforced plastics (CFRP) using shell elements. The in-plane characteristics were represented by shell elements while the out-of-plane properties were defined in cohesive elements. The material properties were determined based on coupon tests. The laminated CFRP model was validated to a drop test of crash box and to a three-point bending test of double hat-shaped member. The results suggested the possibility to reduce calculation time with shell elements.

View full abstract

12V battery replacement interval prediction model is presented. This prediction model mainly consists of two parts. One is training part, and the other is prediction part. In the training part, clustering procedures are carried out by Self-Organizing Map (SOM) which is one of the unsupervised machine learning techniques. On the other hand, in the prediction part, pattern matching between clustering results and observed connected car data is performed. In this paper, the effectiveness of prediction model has been verified using car dealers’ actual maintenance data and connected car data.

View full abstract