As a result of brief investigating nuclear fusion among future energy technologies, the following conclusions were drawn. (1) The timing of realization of DT fusion depends on the speed difference with renewable energy technology. (2) Since the fusion reaction is as high as hundreds of millions of degrees K, the destruction of Exergy is unavoidable in converting energy. Therefore, the use of heat cascade is indispensable for high efficiency. For example, a combined cycle system such as "MHD + GT + Rankin". (3) Due to the internal development rules of technology, the full-scale realization of nuclear fusion technology as direct power generation will be realized in the next century.

In the previous paper¹⁾, some items of the innovations in technology in wind turbine for the development of wind industry are clarified. In this paper, the effect of social condition on the technical innovation is further studied based on some historical points of view. As the result of this study, the high-tech wind turbine developed in Germany right after the California wind turbine boom is to be concluded as the indispensable stage of the principal technical innovation.

In recent years, higher thermal efficiency and lower emissions of diesel engine system are essential for complying with stringent fuel economy and emission regulations.

In past research, we investigated the influence of each parameter (fuel injection pressure, pilot injection ratio, fuel temperature, nozzle diameter, distance from nozzle to wall, wall impingement angle) on wall heat loss based by using wall installed a constant volume combustion vessel. According to the results, it was found that the improvement of fuel evaporation reduces the heat loss^（1）. In order to realize the improvement of fuel evaporation that contributed to the reduction of heat loss in an actual engine, the two-component fuel (ML0.8: Mass fraction of Light component n-C5H12: n-C10H22 = 0.8:0.2) was used. As a result, under high-load operating conditions with ML0.8 mixing fuel, it is possible to significantly reduce cooling loss and exhaust loss by forming a compact spray flame and activating late combustion rate compared to JIS #2 diesel oil^（2）. However, the effects of the physical and chemical properties of ML0.8 on the mixture formation process and ignition and combustion characteristics in diesel engines have not been clarified.

In this study, the goal is the clarification of the combustion mechanism with the two-component fuel in diesel engine. In these experiments, JIS #2 diesel oil and the two-component mixed fuel with arbitrarily changed mixing ratios of Light component fuel were used for the test fuel. The spray and combustion characteristics are evaluated through the differences in the physical and chemical properties due to the mixing ratio of the light component fuel. Therefore, we clarified the mixture formation process by analyzing spray images inside a constant volume vessel, and evaluated combustion characteristics with a single cylinder diesel engine. The main conclusions are as follows;

(1)Immediately after the start of injection (tinj=0～ 0.25ms), there was no difference in spray tip penetration and the formation rate of combustible mixture by increasing the mixture ratio of pentane. After 0.25 ms after the start of injection, spray tip penetration decreased and the rate of combustible mixture formation increased by increasing the mixing ratio of n-pentane.

(2)From the combustion experiment using 4 cycle single cylinder diesel engine, by changing the test fuel from the heavy fuel decane to the two- component mixed fuel containing the light component, the break thermal efficiency improves by 3.3 pt. at the maximum and cooling loss is reduced by 3.2pt.at maximum.

This paper reports the spray characteristics of CO₂ gas dissolved fuel. Recent years, the depletion of fossil fuels is becoming an issue, and emission regulations are becoming stricter, and further improvement of thermal efficiency and reduction of emissions are required for internal combustion engines. PM (Particulate Matter) and NOx (Nitrogen Oxides) emissions are a problem in diesel engines, and the process of air mixture formation is important to improve the problem. Rapid atomization and evaporation of spray droplets are necessary for early formation of a lean and uniform mixture. Currently, one of the methods to atomize spray droplets is to use the high pressure injection. It has been reported that high pressure injection is effective to form a lean mixture, because the equivalent ratio in the spray decreases as the fuel injection pressure increase due to the rapid evaporation of well atomized droplets. However, it has also been reported that higher fuel injection pressure provide increased mechanical losses to get higher pressurized fuel, it is leading to lower thermal efficiency. Thus, it is necessary to promote spray atomization by a new method that does not rely on ultra-high pressure fuel injection. Therefore, CO₂ gas dissolved fuel is focused on, which can make the spray highly dispersed by gas effervescence due to depressurization during fuel injection. CO₂ gas dissolved fuel is formed from CO₂ and n-C₁₃H₂₈, and the saturation vapor pressure curve has a two-phase region with a certain width. When CO₂ gas dissolved fuel is injected under the condition of saturated vapor pressure, bubble formation and foaming start. And then, CO₂ gas is expected to be effervesced at an early stage, spreading the spray from the initial stage of injection and forming a highly dispersed spray. However, the spray characteristics in high temperature fields have not been understood in previous studies¹⁾.

In this study, n-C₁₃H₂₈ and CO₂ gas dissolved fuel were evaluated the spray characteristics using Shadowgraph and Schlieren photography under high temperature ambient. Fig.1 shows spray images. As a result, highly dispersed spray was formed, and equivalence ratio was decreased. The reason was under the ambient condition that flash boiling occurs, bubbles and effervescence were generated after fuel injection. This is thought to have led to a reduction in PM emissions²⁾.

In compression ignition engines, the physical and chemical properties of the fuel are important factors that governed the formation of the air fuel mixture and the subsequent combustion process¹). Our study has proposed a concept of fuel design in which a fuel with a high boiling point is mixed with a fuel with a low boiling point as a spray control method for low emission and combustion control in engine systems. A multicomponent fuel model was proposed to estimate the vapor-liquid equilibrium and physical properties of the mixed fuel, and a two-component fuel spray feature was analyzed using the KIVA code. However, in the previous studies, the maximum fuel injection pressure was set on 15 MPa, and the analysis for high injection pressures in recent diesel sprays has not been performed. In this study, a multicomponent fuel model was used to analyze a two-component fuel spray under high injection pressures, and a large difference was observed between the experimental results of liquid core length and the calculation results. In the analysis, the MTAB model, which models the breakup phenomenon of fuel droplets in low Weber number region, was used as the breakup model, and it is considered necessary to use a breakup model that analyze the breakup behavior in high Weber number region as the fuel injection pressure increases. In this study, the behavior of multicomponent fuel sprays was analyzed by using the WAVE-MTAB model, which models the breakup phenomenon of diesel sprays under high fuel injection pressure conditions²). The spray tip penetration and the spatial distribution characteristics of each component fuel were verified. As a result, as Figure 1 shows that the higher boiling point fuel in a two-component fuel spray injected at high pressure is mainly distributed in the tip of the spray than the lower boiling point fuels.

In recent years, global warming and resource depletion by the large consumption of fossil fuels have become problems. Therefore biomass energy attracts attention as an alternative fuel of fossil fuel. In October, 2020, Japan declared that they aimed at the realization of carbon neutral and decarbonization society in 2050. Consequently, the Ministry of Economy, Trade and Industry (METI) formulated the "Green Growth Strategy with Carbon Neutrality in 2050" (METI, 2020). According to the contents of the formulation, they will introduce renewable energy to the maximum. For diesel engines, biodiesel fuel (BDF) of plant-derived is used as an alternative fuel to diesel oil. The plant is the renewable resource which we can produce every year and absorb CO₂ by the photosynthesis through the growth process. Therefore, the increase of CO₂ emission from the combustion of plant-derived BDF is considered to be “zero” (carbon neutral). Many kinds of the BDF exists, then Fatty Acid Methyl Ester (FAME) which is made from waste cooking oil is used many in Japan. However, FAME is thought to have various damages on engines due to its high kinematic viscosity, low volatility, degradation in lower temperature characteristics and unstable oxidation property. Thus, in these days, Bio Hydrofined Diesel (BHD) has been produced as a new BDF which has the similar fuel properties to conventional diesel oil. BHD has high cetane number, high evaporation property, amelioration in lower temperature characteristics and stable oxidation property. Therefore, BHD is expected as a next-generation BDF to replace FAME.

In this study, BHD and FAME produced from waste cooking oil were used as the test fuel, and diesel oil was used as the reference fuel. The fuel properties are shown in the table1. The experimental devices were used a constant volume vessel. In addition, using the single-cylinder diesel engine (bore stroke: φ 85 96.9 mm, displacement: 550 and compression ratio: 16.3).

In this report, basic spray characteristic were investigated by spray photography in the evaporation field. Then, based on the knowledge of the spray characteristics, the combustion characteristics of BDF with different fuel properties were investigated by using single-cylinder diesel engine. Furthermore, the entire life cycle CO₂ emission of BHD and FAME was also evaluated by using Life Cycle Assessment.

The main conclusions from this experimental study are as follows:

(1)BHD, which has high cetane number, high evaporation, low penetration and high dispersion, promotes mixing with ambient air and reduces ignition delay.

(2)BHD is a non-oxygen biodiesel fuel, but its emission is improved by forming a lean and homogeneous spray.

(3)The ignition delay is reduced by high injection pressure, but the fuel property is dominant, and the ignition delay of BHD is shorter than that of diesel oil and FAME.

(4)The fuel properties of BHD and high injection pressure can simultaneously reduce NOx and smoke while maintaining brake power.

Stringent emission regulation, such as Euro 6, have forced manufacturers of diesel vehicles to implement exhaust aftertreatment systems. Among these, selective catalytic reduction (SCR) system has been established as an effective measure to reduce nitrogen oxides (NO_x). Automotive SCR system is based on the injection of a liquid urea-water-solution (UWS) into the exhaust system, and the water evaporates and the remaining urea decomposes to ammonia (NH₃). NH₃ vapor is used as the reduction agent for NO_x in a catalytic converter, located downstream of the injection position. The spray behavior injected in tail-pipe can be divided into the regime of a free spray, a spray impingement, an evaporation of liquid film and droplets separation and UWS dispersion. Then, in each regime, after evaporation of H₂O in UWS completely, NH₃ is generated by thermolysis reaction of gaseous, liquid or solid urea. However, intermediate products such as biuret (C₂H₅N₃O₂) and cyanuric acid (C₃H₃N₃O₃) may be generated without NH₃ being generated, which may cause deposit. From the above reasons, UWS spray behavior before and after impingement and the chemical reaction process are very complicated. Therefore, the purpose of this research is to reveal the spray behavior before and after impingement and chemical reaction process of urea, and to construct the model capable of predicting those accurately. In this report, we have introduced another chemical reaction process via gaseous urea to CFD and modified the reaction rate. Also it is compared and verify with NH₃ concentration values in experimental results⁽¹⁾. As a result, the prediction accuracy of NH₃ concentration values could be greatly improved. In the numerical calculation, FIRE2017.1 from AVL is used as CFD code. The main conclusions are as follows;

(1)Under this experimental conditions, most of the NH₃ produced went through the liquid film, and the numerical results showed a similar trend.

(2)With the introduction of another chemical reaction process of urea that can reproduce real phenomena and modifying the reaction rate, the prediction accuracy of NH₃ concentration values can be greatly improved.

The occurrence of LME cracking has been reported when resistance spot welding is applied to galvanized steel sheets. Stress and temperature are two of the factors that contribute to LME cracking. In this study, the effect of welding parameters on temperature and stress distribution on the surface of resistance spot welded high-strength steel sheets was investigated using 3-D numerical simulation. In particular, the current value and the contact angle of the electrodes were examined as welding parameters. To summarize the results, the increase in current value and contact angle increases the surface temperature. And, the compressive plastic strain increases with the increase of the current value and the contact angle. Furthermore, the tensile stress generated by the compressive plastic strain increases.

新幹線のブレーキディスク用パッドには，開業時から銅焼結のリジッドパッド（Fig.1(a)）が用いられてきた．リジッドパッドは高速からの制動時にブレーキディスクがミリオーダーで熱変形すると，パッド面とディスク面とが局部摺動により，スポット状の高温域を生じてディスクき裂の発生やブレーキ性能の低下を招く．新幹線は高速化とブレーキ距離短縮ニーズがあるが，従来のリジッドパッドではこれに対応できなかった．このことから日本製鉄とJR東海では，熱変形したディスクに摩擦材が追従可能なばね構造を有する新型ブレーキパッドの開発に着手し，長期間に及ぶラボ，そしてフィールドテストの結果から改良を重ね，高機能で信頼性の高い新型ブレーキパッド（Fig.1(b)(c)）の開発に成功した．

日本製鉄は新幹線用ブレーキディスク設計メーカであることから，ブレーキの熱変形挙動を詳細に解析することが可能である．これを生かし，ディスク形状に最適化されたばね構造と摩擦材配置のブレーキパッドを検討することができた．具体的にはディスクブレーキ制動時の摩擦によるディスクの温度分布の測定技術開発および測定した温度分布に基づく制動時のディスクの熱変形と連成させたブレーキ制動面圧の解析を実施．これにより制動時の熱変形にも追従して制動面圧を均一化することができ，さらに繰り返しブレーキングで変形が蓄積したディスクに対しても制動初期から後期まで安定して制動面圧を均一化できる等圧構造を有するパッドを開発した．これによって，営業運転速度からの緊急停止や通常運転での減速に必要なブレーキングでの摩擦力は維持しつつ，制動時のディスクの局所的発熱を従来のリジッドパッドよりも100℃以上低減し（Fig.2），ディスクに生じる熱き裂の発生を抑え耐久性を向上した．

新型ブレーキパッドはばね構造を有するため，当然従来品よりコストUPとなるが，摩擦材1ブロックに対し皿ばね2枚という極めてシンプルな構造を採用することで，コストUPを最小限に抑えている．また省スペースのばね構造を実現したことから，現行車両にも搭載することができ，採用に際し，投資を最小限に抑えることができる．新幹線の高速化に際し，既に現状のリジッドパッドでは適用できない領域に達している．高速化における利用者の利便性改善は言うまでも無く非常に大きい．またブレーキ距離短縮に関しては特に地震時における短縮ニーズが高く，その安全性向上による効果は図ることができないほど大きなものである．

新型ブレーキパッドは2017年にデビューした東海道新幹線N700A・3次車に採用された．またN700A・3次車だけでなく既存のN700A系車両も随時新型ブレーキパッドへ交換され，最新のN700S系車両にも更なる改良型が継続採用されている．現在では東海道新幹線全ての車両が新型ブレーキパッド搭載車両となっている．

Researches on crash boxes for automobiles are being carried out to reduce occupant damage caused by traffic accidents. We have been studying a crash box consisting of many cells with an elliptical hole for the purpose of improving energy absorption by increasing the amount of displacement during crushing. Our previous studies have showed that the tapers on the side plane of the crash box reduces load fluctuations, however the densification comes from middle part of the crash box. In this study, models that crushed from the impact face of the crash box were examined to reduce damage to the side members connected to the crash box. In addition, by comparing the performance of a crash box model consisting of cells with a circular hole and a crash box model with an elliptical hole, it was clarified that the crash box consisting of cells with elliptical holes had a large crushing displacement and was excellent in impact energy absorption.

Automobiles are highly convenient and indispensable as a means of transportation in our lives, however traffic accidents are an important issue and casualties must be significantly reduced. Technology for automobile safety is required to reduce casualties caused by traffic accidents, and impact energy absorbing members, such as a crash box and a side member, are used to protect occupants in the event of an accident. These members are required to be lightweight in order to improve running distanse and be required to absorb more impact energy. The crash box requires the ability to suppress load fluctuations, and has high strength and large deformation to improve the impact energy absorption performance. In this study, the shapes of lattice structure imitating Miura-ori, which is a kind of origami, were examined with the aim of increasing the amount of impact energy absorbed by increasing the amount of deformation. From results obtained by the impact crushing analysis, it was found that lattice structures imitating Miura-ori with appropriate strut angles and diameters have small load fluctuations and excellent impact energy absorption performance.

An energy absorbing member called a crush box is mounted on automobiles to absorb shocks in the event of an accident. These members are required to suppress an extraordinarily high load at an initial stage of collision, to have a high energy absorption capacity, and to be lightweight. In this study, we focused on the crush box with the lattice structure as the energy absorbing member. Then, the impact crushing analysis was performed on four types of structures based on the crystal structure and polyhedral shape. As a result, it was found that the lattice structure was suitable as an energy absorbing member, becuase the extraordinarily high load at an initial stage of collision was not generated and load fluctuation during crushing was small. Furthermore, it was found that the FCC structure had the best impact absorption characteristics, and the amount of energy absorption could be increased by increasing the aspect ratio of the unit cell. In addition, from comparison with the conventional tubular models, the FCC lattice structure is excellent in reducing damage of the occupants. Additionally, we conducted impact compression tests on AlSi12 lattice structure and heat-treated AlSi12 lattice structure and examined their crushing charactaristics and the validity of the analysis method. As a result, it was found that the lattice structure could be used as a energy absorbing member by performing heat treatment.

In recent years, space debris has been on the increase. Space debris orbits around the earth at a maximum speed of 15 km/s(1). If space debris collides with a space station, it will cause enormous damage. Therefore, countermeasures against space debris collisions are indispensable for advancing space development. The purpose of this study is to clarify how the defending performance of the bumper shield can be improved to reduce damage to the space structure. Reimerdes et al.(4) showed that it was advantages to halve the thickness and install two bumpers than to install one bumper. In this study, the defending performance of the bumper shield in which one bumper was divided into plural bumpers in the thickness direction and those bumpers were arranged was examined by using SPH analysis. In addition, the bumpers with protrusions were examined to scatter fragments of debris and bumpers. From analysis results, it was found that the defending performance of the bumper shield was improved as the number of bumpers increased. The method of scattering fragments of debris and bumpers was effective for improving the defending performance. It was also found that the defending performance of the bumper with protrusions depended on the place where debris collided with the bumper. Therefore, it is considered that bumpers with protrusions are less reliable than flat bumpers. It is necessary to consider an effective method for scattering debris.

In the design of industrial products, CAE analysis such as drop impact simulation has been conducted to ensure the soundness of those products. In this study, tension tests were carried out using specimens of SPCC, SS400 and FCD450, which are used for various parts of industrial products subjected to impact loading, in a wide range of strain rates from 10^-2 to 10² s^-1 to obtain their stress – strain relationships with strain rate dependence. Furthermore, the material constants of Tanimura – Mimura model, which can deal with the response of viscoplastic material subjected impact loading, were determined for each material based on the experimental data. Numerical simulations were also performed to reproduce the tension tests using the constructed material models, and the calculated results were compared with those of the experiments. The results of numerical simulations showed that the calculated flow stress in true stress – plastic strain relationship was slightly underestimated compared to that of the corresponding experiment.

PIV measurements are performed for turbulent channel flows over rib-roughened permeable walls changing the rib-pitch. In order to understand the combined effects of the wall permeability and roughness on turbulence, the friction coefficient is evaluated and the von Karman constant, the zero-plane displacement and the equivalent roughness height of the logarithmic mean velocity profile are examined. As the wall permeability increases, the difference in values of the friction coefficient decreases despite the structural roughness. For scaling parameters of the logarithmic mean velocity, it is found that the zero-plane displacement is linearly correlated with the equivalent roughness height. We discuss these parameters to estimate the log-law mean velocity from wall properties.

It is known that fluid properties such as the viscosity and the density are dependent on the fluid temperature. Although such properties are assumed to be constant in most numerical simulations of incompressible turbulent flows, effects of variable properties on the flow fields are often significant. In this study, we thus develop a wall-function which can consider the effect of the viscosity variation depending on the fluid temperature. Using this model, we conduct Large Eddy Simulations (LES) of turbulent flows with temperature dependent viscosity. The simulated results show that the proposed model well describes the effect of the variable viscosity in flow fields.