Abnormal combustion that includes preignition and knocking is a big issue in the development of the hydrogen engine for carbon neutrality. Thus, it is necessary to clarify the peculiar combustion mechanism of hydrogen with visualization. In this paper, we tried combustion visualization with our supercharged direct injection hydrogen test engine.

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Appropriate fuel properties can be expected to further improve thermal efficiency and exhaust gas emissions, compared to conventional diesel fuel. However, the effects of each fuel property on compression ignition combustion and emission characteristics have not yet been revealed, since each fuel property interacts with others, resulting in the difficulty of identifying them separately. Evaluating the independent effects of each fuel property could help in designing preferable fuels for a future carbon-neutral society. This study investigates the effects of synthetic fuels with different properties on combustion characteristics and exhaust emissions.

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This study investigates the impact of synthetic fuel properties on improving the combustion and emissions of high-compression-ratio (CR) heavy-duty diesel engines. Diesel, DP2b (diesel + C6H14: 6:4 vol%), and DP3b (diesel + nC7H16: 6:4 vol%) fuels are tested in a single-cylinder CR=23 engine. A 3D-CFD model was calculated using CHEM-KIVA4 and Waseda’s phenomenological soot model. The results showed that the use of mixed fuels reduced Soot under each operating conditions. Comparison between experiments and calculations confirms that the reasons why soot is reduced with mixtures fuels are promotion of spray atomization and suppressing for soot particle neucleation and surface growth processes.

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In this study, an electrically heating catalyst (EHC) is installed upstream of the SCR catalyst in a diesel engine exhaust system to raise the exhaust gas temperature. This allows the SCR catalyst to be activated early by electric heating in the low-temperature region below the active temperature, thereby improving NOx conversion efficiency. A numerical model has been developed to calculate the required power of the EHC for setting the target temperature of exhaust gas entering the SCR catalyst based on exhaust gas flow rate, exhaust gas composition, and exhaust gas temperature at the EHC inlet.

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Brake chambers used in transport trucks are the most important parts in terms of safety. However, they are prone to deterioration due to internal corrosion caused by rust, which makes visual inspection difficult. Therefore, by using machine learning to learn about the operating conditions of trucks, we aim to develop a predictive model that estimates the risk of brake chamber failure and use it as a criterion for deciding whether to perform expensive disassembly and inspection.

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Ammonia burning velocity is small and it makes stable operation of a spark ignition engine fueled with ammonia/hydrogen mixture difficult. To improve this, discharge energy is increased, and the effect on the operating characteristics is investigated. With the increase in ammonia equivalence ratio, the effect of change in molar number increases. However, with the increase in ammonia equivalence ratio, the effect of degree of constant volume and combustion efficiency decreases around the operation limit. Indicated thermal efficiency has a peak about ammonia equivalence ratio of 0.88. Discharge energy enhancement contributes to keeping degree of constant volume and combustion efficiency high.

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This study evaluates the effectiveness of Ni filler wire in laser welding between cast iron and carbon steel used in automotive differential gears, by comparing with the joint strength without filler wire. Micro-tensile tests were used to measure the tensile strength of weld metals and heat-affected zone. Micro-tensile testing proved effective for small weld areas even in materials with large grain sizes like cast iron. Results show that without Ni filler wire, the weld metal’s strength is lower than that of the base metals and showed the brittle fracture behavior. Using Ni filler wire improves weld metal strength higher than base metals, enabling non crack welding without additional heat treatment. The findings show that welding quality and cost benefits in automotive production are possible.

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In our previous research, we discovered that gasoline-derived deposits hardened at room temperature when formed at temperatures exceeding 110 ℃. In this study, we found that repeated heating and cooling between 100 ℃ and room temperature also led to hardening, accompanied by a gradual increase in molecular weight. Chemical analysis revealed that the deposits mainly consisted of hydrocarbons containing hydroxyl and carboxyl groups. However, no significant compositional changes were observed before and after thermal cycling. We identified the strong polarity and intermolecular forces of these functional groups as key factors contributing to the hardening behavior.

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