Partial oxidized fuel in the residual gas is thought to affect the auto-ignition timing. However, the accurate composition of the residual gas cannot be determined by computer simulation even using detailed chemical reaction models. In order to clarify the composition of the residual gas, a comprehensive two-dimensional gas chromatograph equipped with a time-of-flight mass spectrometer was used to analyze the exhaust gas components emitted from spark-ignited engines as a model of residual gases. In this study, n-heptane, isooctane and diisobutylene were used as the model fuels. The main reaction paths for the low temperature oxidation of n-heptane, isooctane are different each other, suggesting that the low temperature oxidation of the saturated hydrocarbons depends on their chemical structure. However, the types of compounds detected as reaction products (the number of carbon atoms and oxygen atoms) differed depending on the fuel used. Notably, the several products detected in this study are not existed in the detailed chemistry model of lowtemperature oxidation.

View full abstract

In previous work, we have proposed a soot mass prediction model applicable for design calculations of internal combustion engines. In this study, we expanded this model and developed a new model which can predict the soot particle size distribution. The model was validated for experimental results measured by using burner stabilized stagnation flames for iso-octane/n-heptane/toluene blended fuels. As a result, it was shown that the proposed model can reproduce the particle formation characteristics with changes in the fuel mixing ratio, the residence time, and the equivalence ratio. On the other hand, it was found that there is room for improvement in the polycyclization and soot growth process for pure iso-octane and n-heptane flames.

View full abstract

A Multi-material structural member for Automobile which absorb the crash energy by deforming in the automotive body collision were developed by sandwiching a small amount of resin between an ultra-high strength steel structural parts and a resin fixing plate made of a thin steel. When this structure was applied to 980MPa grade steel parts, the energy absorption in the bending was improved over 45%, and the weight was reduced by 6% in comparison with the parts of the same performance, and vibration characteristic by hammering test were improved.

View full abstract

Millimeter-wave radome, a key component supporting autonomous driving, has often been decorated with indium films with island structures. In order to further understand relationships between millimeter-wave transmittance and structural parameters of the indium films, we thoroughly characterized the indium films prepared by DC magnetron sputtering under various conditions. We found that the millimeter-wave transmittance of indium films strongly depends on the coefficient of variation of the island area rather than the commonly used parameters such as film thickness and island area.

View full abstract

To establish an evaluating method of fluctuating aerodynamic noise, the active turbulence generator was fabricated, and wind tunnel experiments were conducted. A side-view mirror model was set in several flow conditions, and fluctuating noises and flow velocities were measured by a microphone and an anemometer, respectively. The analysis with modulation power spectra indicated that it is possible to express the differences of fluctuating aerodynamic noise with the power of the modulation frequency band. The correlation analysis of the auditory evaluation revealed that the expressions corresponding to the different amplitudes of the fluctuating aerodynamic noises were “unstable sound” or “uneven sound”.

View full abstract

The purpose of this study is to acquire a practical prediction formula for easily obtaining an air entrainment flow rate in the initial design phase of a filler tube. An air entrainment phenomenon is modeled based on the similarity to the working principle of a jet pump, and a theoretical formula of the air entrainment flow rate is derived. However, it is difficult to specify the mixed fluid density and the mixing completion position to solve the theoretical formula. Therefore, the prediction formula is constructed by multiple regression analysis that considers the major design variables. Finally, an example of the application of the prediction formula in the initial design phase of an actual vehicle is reported.

View full abstract

In direct injection spark ignition engines, PM reduction under cold conditions is important, and controlling liquid film adhesion by spray wall interaction is a key issue. In this study, to control the amount of liquid film adhesion by wall impinging spray, fuel film analysis method was developed applying the total internal reflection laser induced fluorescence (TIR-LIF) method, which can estimate the film thickness and the film temperature those change unsteadily during the film formation process. Decrease in fuel temperature and wall temperature increases the We number of spray droplets, which increases the amount of splash by droplet impingement and decreases the amount of film adhesion. However, the effects of fuel spray and fuel film temperature on the film formation process of impinging wall spray under low temperature conditions is not clear. In this paper, the spray droplets impinging on the wall were set in the same condition by changing the wall temperature only. The effect of the temperature change on the film formation process was estimated by measuring the film temperature and thickness of the spray droplets while their impingement on the wall. It is found that as the liquid film temperature decreased, the amount of droplet adhesion to the liquid film decreases because the amount of splash increases when droplets imping on the film.

View full abstract

In direct injection spark ignition (DISI) engines, strict control of pollutant emissions at cold start is required to comply with new emission regulations. To clarify the effect of the impingement distance between the nozzle and the wall on the film formation process under low temperature conditions and the relationship between heat transfer and evaporation characteristics of the fuel film in an actual engine, total internal reflection laser induced fluorescence (TIR-LIF) method was applied to visualize the fuel film formation process. The parameters are 14mm, 28mm, 42mm, and 57 mm in wall impingement distance and the wall surface temperatures are 253 K and 293 K. As a result, the wall impingement distance increases, the momentum of the spray droplets just before impingement on the wall is smaller and it follows the gas flow in the spray more easily, resulting in a decrease in the amount of fuel adhesion on the wall. At a wall impingement distance of 14 mm, the amount of dispersion from the fuel film increases due to the large momentum of the spray droplets. In DISI engines, the fuel film easily residual in the intake process due to the reduction of heat transfer from gas to liquid and increase in heat require for evaporation of the fuel film at the earlier injection timing.

View full abstract

The unburned components that do not contribute to combustion exhausted from internal combustion engines should be significantly reduced. In this study, enhancement of fuel evaporation under cold conditions was investigated by controlling the in-cylinder gas properties of a directinjection gasoline engine equipped with a variable valve system. It was confirmed by controlling the degree of superheat for liquid fuels allows the reduction of unburned hydrocarbons and particulate numbers in cold conditions. Late intake valve opening (LIVO) has achieved lower emissions and superior combustion stability under extremely cold conditions by effectively utilizing the energy of the intake air flow.

View full abstract

In order to comply with increasingly stringent emission regulations, including EURO7, it is necessary to enhancement of fuel evaporation under cold start, when fuel vaporization and atomization are insufficient, and to significantly reduce unburned components that do not contribute to combustion. It has been shown that controlling the in-cylinder gas properties to be equivalent to that at high temperature, fuel vaporization can be accelerated and emission at cold start can be reduced. In this study, the mechanism of cold emission reduction was clarified through high-speed exhaust gas measurements on an actual engine, PN particle size distribution measurements, and combustion observations on a visualized engine.

View full abstract

Dynamic wireless power transfer (DWPT) has been proposed to solve the issues of a short cruising range and Green House Gas emissions in manufacturing electric vehicles. Both the durability of the road structure and the transmitter coils of DWPT are important for the implementation of DWPT system on public roads. On the other hand, it is important to thin road structure on the coils to improve the transmitting efficiency. To realize both high durability and the high transmitting efficiency, the precast coil that has the transmitter coils in the high-performance fiber reinforced cement composite is proposed. This paper presents the evaluation method and the measured results of the durability of the precast coil as the road structure.

View full abstract

Due to the tightening of CO2 regulations for automobiles, it is required to significantly improve fuel efficiency, and reduce the weight of the car body. On the other hand, the demand for improving crash safety performance is increasing, and achieving both weight reduction and crash safety performance are a major issue in future automobile body development. Therefore, it is necessary to improve the strength and weight reduction of the frame that constitutes the car body. In this study, we assume an automobile structure that receives multiple axial loads, and perform multipurpose optimization of the cross-sectional shape. For the purpose of improving strength and reducing mass under the conditions of multiple axial loads, optimized cross-sectional shape. The design variable was the XY coordinates of the vertices of the cross section. Objective function was maximize torsional strength, maximize bending strength and mass minimization. As a result of the optimization, We not only get a lightweight cross-section, but also revealed that transition of the cross-sectional shape on the Pareto line of torsional strength and bending strength is existed. In addition, the mechanical validity was verified from the viewpoint of buckling.

View full abstract

Our previous researches show that the generation of piston-connecting-rod coupled vibration in engines affects the vibration characteristics on the engine outer surface, but the effect of the coupled vibration was not reproduced in the engine outer surface vibration in the numerical simulation. This study numerically investigated the effect of the vibration transmission characteristics by changing the joint models around the small end of the connecting-rod from a non-linear sprig to elastic-hydrodynamically lubricated joint.

View full abstract

In this study, using human finite element models with various body sizes and postures, it was shown that the belt-ASIS overlap and the pelvis-belt angle are effective parameters to predict submarining using logistic regression. The two indices were applied to the anthropometry of 40 participants wearing the lap belt measured using CT systems in various postures, and submarining occurrence was calculated. It was found that the probability of submarining was high due to small initial belt-ASIS overlap and low pelvis-belt angle in the reclining posture and the slouching seating posture.

View full abstract

Changing lanes on busy roads requires interacting with surrounding vehicles, which is difficult for autonomous driving. In this study, we separated the process of changing lanes during congestion into the following steps: (1) identification of entry position, (2) display of intention, and (3) judgment of entry possibility. On actual congested roads, we measured the driving behavior of multiple skilled drivers changing lanes and clarified qualitative and quantitative characteristics of each step.

View full abstract

Engine coolant temperature prediction utilizes Conjugate Heat Transfer (CHT) analysis. However, identifying the combustion chamber walltemperature based on actual measurements is a time-consuming process. The purpose of this paper is to develop a surrogate model that canpredict the combustion chamber wall temperature faster than conventional methods. We propose that a surrogate model utilizing multipleregression analysis and deep learning can achieve high explanability and high efficiency.

View full abstract