Mechanical and Aerospace Engineering
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Effect of flow residence time on the flame-retardant performance of fluorine-based flame retardant: Comparison of blowoff limits of CH₂F₂ and CH₄
The article investigates the combustion characteristics of hydrofluorocarbon (HFC) and hydrocarbon (HC) fuels to understand the increased flammability of fluoropolymers like ETFE under microgravity. Key findings: CH₂F₂ exhibits minimal sensitivity of blowoff limit to oxygen, unlike CH₄. CH₂F₂ flames have lower temperatures and suppressed H and OH radical formation, due to dominant HF-producing pathways inhibiting radical chain reactions. Despite susceptibility to blowoff, CH₂F₂ maintains high adiabatic flame temperature, allowing combustion at low oxygen if sufficient residence time is provided.
Yusuke Konno, Ayuto Ota, Nozomu Hashimoto, and Osamu Fujita
Mechanisms underlying the dynamic strength of cancellous bone based on the impact strength of individual trabeculae and microarchitecture
Osteoporotic fractures occur in cancellous bone due to even minor impacts. In addition to bone mass, the impact strength of individual trabeculae and the microarchitecture are hypothesized to determine the dynamic strength of cancellous bone. This study aims to experimentally clarify these mechanisms and apply the findings to further improve the control of dynamic fracture risk.
Satoshi Yamada, Tomohiro Shimizu and Kazuhiro Fujisaki
Grant-in-Aid for Scientific Research(B) 2025.4.1～2028.3.31
Development of a 3D-printable head protection material with superior impact absorption and durability using biomimetic porous structures
We are developing a novel 3D-printable head protection material using a biomimetic structure inspired by cancellous bone architecture. This offers excellent multi-impact absorption capabilities. Its high three-dimensional isotropy enables it to absorb impacts from any direction. The porous design can be freely tailored to meet specific shape and performance requirements. In addition to head protection, the material shows strong potential for applications in body protection gear and cushioning materials for transporting precision equipment.
Satoshi Yamada, Yuelin Zhang, and Keita Kawashima
Adaptable and Seamless Technology transfer Program through Target-driven R&D (A-STEP) 2024.12.1～2027.3.31
Investigation of Single Ammonia Droplet Evaporation Characteristics Under High Temperature and Pressure Conditions
Ammonia is a promising alternative fuel for significantly reducing CO₂ emissions. However, to utilize it efficiently, it is necessary to develop technologies that enable direct spray combustion of liquid ammonia. In this study, we clarified—for the first time in the world—the evaporation characteristics of ammonia droplets under high-temperature and high-pressure conditions. Furthermore, we obtained essential droplet evaporation data necessary for the development of ammonia spray combustion technology.
Leang So Khuong, Nozomu Hashimoto, Yu Ito, Nobuto Nakamichi, Yusuke Konno, and Osamu Fujita
Spatiotemporal mode extraction for fluid–structure interaction using mode decomposition
We proposed a method to extract the spatiotemporal modes of structural deformation obtained from fluid-structure interaction analysis using Dynamic Mode Decomposition (DMD). By applying this method, it becomes possible to identify the dominant structural deformation modes in systems where fluid forces induce significant structural changes, such as flexible aeroshells.